Saturday, May 20, 2017

Yes, they Really Were Worried About Global Cooling in the '70's.

One of the newest trends in political discourse today is to rewrite history.  Snowflake advocates are demanding that public displays in the South of the confederacy be demolished, that Confederate soldier war memorials be removed, because the South seceded over slavery.  They ignore the act of congress that made Confederate soldiers US veterans, thus making Confederate war memorials into US veteran memorials. They seek to rewrite history, erase the labyrinth of politics of the day in order to teach an easier to understand sound byte that doesn't do justice to history.

In a likewise fashion, anthropogenic global warming (AGW) fanatics apologists are trying to rewrite the history of climate science.  This was spurned on by President Trump making reference to an internet meme that compared the thinking then to the thinking now:

This was debunked as a photoshopped cover.  There never was any such cover.  Here is the real cover from the Apr. 9, 2007, cover of TIME:

So, yeah, it's a clever meme, but fake. The AGW folks even call it a hoax, because, well they're snowflakes and unable to process disagreement without feeling threatened. But the propaganda machine goes further than that, and, in typical modern fashion, seeks to actually rewrite history by saying there was no consensus in the 1970's that the world was cooling, and even going so far sometimes to say there were no scientific papers to that effect.  Never mind that there is no consensus that AGW is real today, no matter what Al Gore said in his propaganda movie (10,257 earth scientists were surveyed, 3,000 responded, of which only 77 were peer-reviewed climate scientists, and of those 75 thought human activity is a significant contributing factor in changing mean global temperatures).

Never mind that  ". . .more than 31,000 American scientists from diverse climate-related disciplines, including more than 9,000 with Ph.D.s, have signed a public petition announcing their belief that “…there is no convincing scientific evidence that human release of carbon dioxide, methane, or other greenhouse gases is causing or will, in the foreseeable future, cause catastrophic heating of the Earth’s atmosphere and disruption of the Earth’s climate.” - Forbes, July 17, 2012.

Sorry, I was there.  I remember this, and unfortunately for those who seek to rewrite history, facts are stubborn things. The world was all lathered up because the temperature measurements showed a cooling trend from 1940 through the then-present 1970's, and guess what? It was all man's fault, then, too!  The arrogance. . .

There were many papers that promoted this, for anyone who's willing to dig just a little and do their own research and seek primary sources. And yes, even Time Magazine weighed in on it in their Jun. 24, 1974 issue. Russian climate scientists were even advocating massive projects to redirect ocean currents to promote global warming and melt arctic ice to stave off the coming cold spell, as related in Battan, 1970 and Borisov, 1969. Scientists were aware of the issue with CO2, but mostly dismissed it as irrelevant, correctly pointing out that water vapor is the dominant greenhouse gas, beside which CO2's contribution is insignificant. The thing that modern AGW believers don't mention - or even know - is that measuring CO2 is easy. Measuring small changes in water vapor and cloud cover is hard. Guess which gas gets more study? Guess which change actually affects the climate more?

The many papers presented below agree that the global temperature fell from 1940 until sometime in the 1970's.  The papers that deal with CO2 loading admit that  all during this time CO2 levels were rising. The general consensus, therefore is that CO2 levels were not a significant factor in climate modeling. This is born out by the physics of CO2 absorption. These conclusions are something that AGW advocates find embarrassing, and so they wish them out of existence by denying the scientific world openly accepted the possibility that we were on the verge of a major cooling cycle - as we may still be.

But hey, this is just a whacky right-wing, Christian oriented, anti-Islamic blog.  So don't take my word for it.  See for yourself. Below are nearly 200 peer-reviewed papers that admitted, considered and discussed the implications of the cooling trend prominent in the '60's.  Will you find a smoking gun here?  No, Scientists then tended to be more objective, self-critical and less hysterical than now. There also wasn't the heavy handed influence of corporate funding driving the agenda, because whether you agree with it or not, Anthropogenic global warming alarmism is big money.  Examine how Al Gore has gotten rich off this, and wonder if maybe he's as objective as a scientist should be. What you will find here is an unquestioned consensus that the planet cooled after 1940, and a refreshing willingness among scientists to admit that they don't really know - something you rarely hear today, which should be setting off alarm signals for anyone who has made a living in applied science, as I have.

Kondratiev and Niilisk, 1960: “The dependence of atmospheric heat radiation on CO2 and H2O contents and also on temperature vertical distribution is investigated with the help of the radiation chart. It is shown that the heat radiation of the atmosphere almost doesn’t depend on variations of carbon dioxide content in the atmosphere.”

Kaplan, 1960: “Although PLASS (1956 b) realized that the existence of clouds would decrease the effect of changing CO2, concentration on temperature, his clear sky estimate of 3.8° C for a halving of the CO2, content was used in his discussions of the influence of CO2, changes on climatic change (PLASS, 1956 b, 1956 c, 1959). It now appears that this number is too high by more than a factor of two, and perhaps by as much as a factor of three. It would seem, therefore, that CO2, variations could not play a major role in the ice-age cycle unless the CO2 changes were by an order of magnitude. It is also found from Table 4, with the same reasoning, that a change of 10 % in CO2 content should result in a change of not more than one-fourth of a degree in the surface temperature. The magnitude of this change does not seem to be large enough to account for the secular increase in European temperatures that was observed in the beginning of this century.”

Manabe and Möller, 1961: “According to our computation of radiative heat budget, in the stratosphere, net heating effects include the absorption of solar radiation by water vapor, carbon dioxide (not negligible around the tropopause), and ozone and the atmospheric radiation due to the 9.6 μ band of ozone; net cooling effects include the long wave radiation by water vapor and carbon dioxide. Summing all these contributions we obtain a very weak heating in low latitudes and a rather strong cooling in the lower stratosphere at high latitudes. This cooling is too large to be considered as the product of uncertainties involved in the computation and must be compensated for by heat processes other than radiation. (7) [T]he study of various processes contributing to the heat of the layer around the 18-krn. level, where the observed temperature sharply increases with latitude, was performed. The long wave radiation by water vapor has a tendency to maintain the existing latitudinal gradient. The effects of ozone have the same tendency in low latitudes but not in high latitudes. The long wave radiation by carbon dioxide has a strong tendency to destroy the existing latitudinal increase of the temperature. The net effect of these radiative processes could barely maintain the stratospheric temperature approximately constant with latitude and hardly explains the sharp latitudinal temperature increase observed in the stratosphere. “

Lamb, 1961: “The carbon dioxide changes obviously cannot account for various decades and longer periods of climatic cooling in historical and recent times.”

Lamb et al., 1962: “Jan Mayen [glaciers] appears as a somewhat localized exception to a general cooling of the Arctic surface temperatures by 1° C. or rather more from the 1940’s to 1950’s”

Meier and Post, 1962: “At about 1945 a climatic change occurred in western Washington, leading to more winter precipitation and cooler summers.  The first observed glaciological evidence of this change was a thickening of ice on Nisqually Glacier detected by Johnson in 1946 (Johnson 1949, 1960). By 1955 many of the glaciers in the Northern Cascade Range were advancing in a rather spectacular fashion (Hubley, 1956, p. 671).”

Benson, 1962: “A revised estimate for the balance of the ice sheet gives a slightly positive balance which is interpreted to mean that the Greenland ice sheet is essentially in equilibrium with present-day climate.”

Möller, 1963: “The numerical value of a temperature change under the influence of a CO2 change as calculated by Plass is valid only for a dry atmosphere. Overlapping of the absorption bands of CO2 and H2O in the range around 15 μ essentially diminishes the temperature changes. New calculations give ΔT [temperature] = + 1.5° when the CO2 content increases from 300 to 600 ppm. Cloudiness diminishes the radiation effects but not the temperature changes because under cloudy skies larger temperature changes are needed in order to compensate for an equal change in the downward long-wave radiation. The increase in the water vapor content of the atmosphere with rising temperature causes a self-amplification effect which results in almost arbitrary temperature changes, e.g. for constant relative humidity ΔT = +10° in the above mentioned case. It is shown, however, that the changed radiation conditions are not necessarily compensated for by a temperature change. The effect of an increase in CO2 from 300 to 330 ppm can be compensated for completely by a change in the water vapor content of 3 per cent or by a change in the cloudiness of 1 per cent of its value without the occurrence of temperature changes at all. Thus the theory that climatic variations are affected by variations in the CO2 content becomes very questionable.”

Kamb, 1964: “Intensive study of the energy budgets and mass budgets of glaciers in relation to meteorological variables shows that radiation balance (solar and sky radiation) is the dominating energy factor but that no single climatic variable is responsible for the changing mass balance, even though a general correlation has been established between increasing mean summer temperature and glacier retreat. … Detailed application of these ideas has not been made to the well-known general retreat of mountain glaciers throughout the world, which has gone on over the past 50 years or at a rate of 5 to 20 meters per year. Correlation with climatic trends suggest the retreat may be about to reverse itself, and recently there has been standstill or moderate-to-strong glacier advance in places, notably in the Pacific Northwest and on the island of Jan Mayen in the northern Atlantic.”

Lamb, 1966: “The investigation here reported of some of the gross features of world climatic behaviour since 1960 apparently discloses an abrupt return to conditions as they were before the well-known warming of climates in the early 20th century–indeed a reversal of the change of behaviour of the large-scale wind circulation that took place about 1895.”

Gebhart, 1967: “Hitherto absorption of solar radiation has completely been disregarded when investigating how a CO2 increase of the atmosphere modifies the earth’s climate. It can be shown that shortwave and longwave influence of a higher CO2 concentration counteract each other. The temperature change at the earth’s surface is ΔT=+1.2°C when the present concentration is doubled.”

Tangborn, 1967: “The balance trend for the higher altitude Thunder Creek glaciers shows a major change occurring about 1944, from generally negative balances between 1920-44 to a gain in glacier mass between 1945-65The glaciers in the Thunder Creek basin lost mass steadily during the period 1920-44 at an average rate of 0.9 m of water per year. During the period 1945-65 a gain in glacier mass occurred at the rate of 0.2 m per year (fig. 4). Several pronounced advances of glaciers in the North Cascades have been observed since the late 1940’s and early 1950’s. Most high elevation glaciers have been unusually active and many have advanced or increased in size (Bengson, 1956; Harrison, 1956; Hubley, 1956; Johnson, 1954). A distinct change in climate, which was conducive to glacier growth, undoubtedly occurred in the Pacific Northwest in the mid-forties. On the basis of this rather approximate hydrologie method of determining glacier mass balances, a significant change from a negative to positive trend in the mass balances of the high elevation Thunder Creek glaciers occurred at the same time. The reliability of the hydrologie method of measuring approximate glacier mass balances is supported, therefore, by this recent evidence of glacier growth.”

Lauzier, 1967: “Here it is our intention to emphasize the temperature fluctuations during the past 17 years, 1951-1966, in the Subarea 4. This means all overlap from the previous studies (to 1962), but a necessary one to assure continuity and to cover the entire recent cooling period. The cooling period is also given its proper perspective with respect to the previous fluctuations.  … The cooling trend experienced in Subarea 4, from the early fifties, is still continuing in the middle sixties. The average rate of cooling during the last 15 or 16 years is of the order of 0.19°C/year. The St. surface temperature variations are representative of bottom temperature variation over a large segment of the Scotian Shelf”

McCormick and Ludwig, 1967: “Theoretical considerations and empirical evidence indicate that atmospheric turbidity, a function of aerosol loading, is an important factor in the heat balance of the earth-atmosphere system. Turbidity increase over the past few decades may be primarily responsible for the decrease in worldwide air temperatures since the 1940’s”

Fletcher, 1968: “Since the “little ice age” of 1650-1840, which climaxed the cooling trend from about 1300, a new warming trend predominated which seems to have reached a climax in the 1920’s, followed by cooling since about 1940, at first irregularly but then sharply since about 1960.  … [T]he sharp global cooling of the past decade indicates that other factors are more influential than increasing CO2. For example, Moller (1953) estimates that a 10% change in CO2 can be compensated by a 3% change in water vapor or a 1% change in mean cloudiness.  Moreover, the oceans have an enormous capacity to absorb CO2, which also varies with temperature; that is, colder oceans can store more CO2. Thus, warming oceans could be a primary cause of increasing CO2 in the atmosphere.  In summary, it appears that, other factors being constant, CO2 from human activity could cause important changes of global climate during the next few decades.  But , of course, other factors are not constant, and in recent years have apparently been more influential than the CO2 increase.”

Wahl, 1968: “A comparison of climatic data for the eastern United States from the 1830’s and 1840’s with the currently valid climatic normals indicates a distinctly cooler and, in some areas, wetter climate in the first half of the last century. The recently appearing trend to cooler conditions noticed here and elsewhere could be indicative of a return to the climatic character of those earlier years [1830s, 1840s].

This penultimate climatic episode, called the “Neoboreal” by Baerreis and Bryson (1965) and also frequently referred to as the “Little Ice Age” (Brooks, 1951) apparently started during the middle of the 16th century at a time of glacial advances both in Europe and North America. It continued as a distinctly cooler, and, in some regions, wetter period well into the 19th century. Following it was a warming trend that between 1880 and 1940 to 1950 became quite pronounced in very many regions of the Northern Hemisphere. During the last two decades there appears to be some evidence that this warming trend of the last 100 yr. has changed over recently to a distinct new deterioration of the climate, leading to conditions that in the 1960’s appear to approach those which were generally found around the turn of the century or even earlier, i.e. a return to the climatic character of the 19th century.”

Thorarinsson, 1969: “The glacier surges that have occurred in Iceland since 1890 are listed, and the largest ones, those of Brúarjökull in 1890 and 1963–64, are described. The glacier area affected by the surges of Brúarjökull is about 1400 km2 , the volume of ice and firn affected is about 700 km3, and the total advance of the glacier front 8-10 km. The maximum rate of advance of the glacier front in 1963 was at least 5 m/hour. Brúarjökull’s surges seem to occur with an interval of 70-100 years.”

Stanley, 1969: “For part of 1966, Steele Glacier in the Icefield Ranges, Yukon Territory, Canada, made a spectacular advance at a rate exceeding 500 m per month. The main part of the surge continued for two years, but by early 1968 the advance had slowed to less than one tenth of the maximum rate.”

Flecher, 1969: “The post-glacial warming culminated in the “climatic optimum” of 4000-2000 BC, during which world temperatures were 2-3°C warmer than they are now …Since the “little ice age” of 1650-1840, which climaxed the cooling trend from about 1300, a new warming trend predominated which seems to have reached a climax in this century, followed by cooling since about 1940, at first irregularly but more sharply since about 1960.”

Curry, 1969: “At least four major periods of increased mean snowfall and cooler, cloudier summers during the last 10,000 years resulted in four periods of multiple glacial advance in the Sierra Nevada. These occurred [1] between 6000 and 7000 years ago, [2] between 2000 and 2600 years ago, [3] around 1000 years ago, and [4] between 650 years ago and the present. The latest major period of net accumulation and advance in all cirques that are presently occupied by residual glaciers occurred between 1880 and 1908 with a peak from 1895 to 1897.”

[By including the last 650 years to the present, the authors strongly imply that the present 1960s-era climate had not sufficiently warmed enough to be distinguished from the post-1400 AD Little Ice Age.]

Budyko, 1969: “To answer the question of in what way the climate will change in the future, it is necessary to establish the causes of Quaternary glaciations initiation and to determine the direction of their development. Numerous studies on this problem contain various and often contradictory hypotheses on the causes of glaciations.  … [A] rise in temperature that began at the end of the last century stopped in about 1940, and a fall in temperature started. The temperature in the northern hemisphere that increased in the warming period by about 0.6oC then decreased by the middle of the fifties by 0.2oC.  “

Newell and Dopplick, 1970: “The greenhouse theory as usually discussed puts such a “heating” interpretation on the CO2 changes even though the actual effect of a CO2 increase is to diminish the cooling rate. It is well to stress that the conditions here are such that all other items are unchanged. The term greenhouse is of dubious applicability because the greenhouse glass leads to higher temperatures by reducing turbulent eddy heat losses, rather than by a radiative influence (Kondratyev, 1965). To place the CO2 contribution to temperature change in perspective it is compared with other radiative components at two levels in Table 2. Clear skies are assumed. Carbon dioxide is secondary to water vapor in the troposphere as noted by others (e.g., Rodgers and Walshaw, 1966) and dominant in the lower stratosphere under the conditions assumed here. When looking for a potential influence of global pollution on the tropospheric temperature it would be therefore wise to pay careful attention to the water cycle and its possible modification, particularly as it enters also through the effect of latent heat.”

Libby, 1970: “Item: American Scientist, January-February 1970, p. 18, “Though dire effects on climate of an increase in CO2 have been predicted, they are far from being established. The cycle is not really understood; carbon dioxide may well prove to be the least objectionable or the only beneficial addition to the atmosphere from industrial sources … Atmospheric CO2 is the source of almost all the carbon of organic compounds in our bodies. It is likely that CO2 from industrial sources has actually increased the productivity of terrestrial vegetation since 1900, and that as fossil fuels are exhausted and industry goes to atomic power there will be a decrease, possibly ten percent, in agricultural yields….”

Budyko, 1970; Orvig, 1970: “Recent studies of the Antarctic ice budget seem to indicate that the ice budget is slightly positive at present [1970], with an annual gain of perhaps a little Iess than 600 km3 water. Greenland has, probably a small net annual loss of a little less than 100 km3 water. The net result should be a lowering of the sea level of approximately 1.5 mmlyear. It should be remembered that Antarctic information is very recent-since the I. G. Y. in 1957-58.

“Recent times have seen a relatively stable sea level-a rise of about 20 cm for the fifty years ending in 1940 [+4 mm/yr for 1890-1940], but a decrease to about half of this rate of rise since then.  Perhaps the various figures would be comparable if data were compared for the last 10 years. It does seem that the great ice caps are now more or less in equilibrium.”

Reid Jr., 1970: “Except for a period of about five years (1928 to 1933), the weather before 1942 was warmer and wetter than since that time

Mitchell, 1970: “Although changes of total atmospheric dust loading may possibly be sufficient to account for the observed 0.3°C-cooling of the earth since 1940, the human-derived contribution to these loading changes is inferred to have played a very minor role in the temperature decline.”

Fletcher, 1970: “[F]rom about 1890 to 1940 the general but irregular trend was toward growing strength of the global atmospheric circulation, northward displacement of the polar fronts in both the atmosphere and the ocean, northward displacement of ice boundaries in both the arctic and antarctic, weaker development of anticylones over the continents and more northward cyclone paths. These dynamic changes were reflected by a dramatic warming of the arctic and of the North Atlantic, and aridity in the south central parts of North America and Eurasia.  Conversely, recent decades have exhibited opposite trends: weakening planetary circulation, southward shifts of ice boundaries and cyclone paths and sharp cooling and different rainfall patterns over continents. … Less than 20,000 years ago the Wisconsin ice sheet covered North America from the Atlantic to the Pacific and was up to two miles thick.  Most of this vast ice mass melted during the only a few thousand years, raising the level of the world ocean by several hundred feet.  This warming culminated in a “climatic optimum” from about 4000-2000 B.C., during which world temperatures were four to five degrees warmer than they are now and rainfall patterns were very different.  … [T]he secondary “climatic optimum” around 1000 A.D. [was] a period characterized by a relatively dry, warm and storn-free North Atlantic which permitted the great viking colonization of Greenland and Newfoundland.  The decline, from about 1300 A.D., with one partial recovery from about 1400 to 1550, continued to about 1750, culminating in the “little ice age” of 1650-1840.  During the cooling period, North Atlantic ice boundaries advanced and the Viking colonies were extinguished. The warming since the cooling climax of the 1700s continued irregularly up to the 1940s, when renewed cooling seems to have set in.

Wahl and Lawson, 1970: “Lamb (1966) had already suggested that it appears likely that we have passed the height of the warming episode in the first half of this century and are now reverting to a pattern characterized by lower zonal flow and intensification of the trough/ridge systems, essentially a reestablishment of the climatic character of the last century.”

Hughs, 1970: “Convection in the Antarctic Ice Sheet Leading to a Surge of the Ice Sheet and Possibly to a New Ice Age. [A] surge of the ice sheet appears likely.”

Benton, 1970: “Climate is variable. In historical times, many significant fluctuations in temperature and precipitation have been identified. In the period from 1880 to 1940, the mean temperature of the earth increased about 0.6°C; from 1940 to 1970, it decreased by 0.3-0.4°C. Locally, temperature changes as large as 3-4°C per decade have been recorded, especially in sub-polar regions.”

Eichenlaub, 1970: “Evidence suggests that lake effect snowfall has significantly increased during the past several decades, particularly in Southern Michigan and Northern Indiana. While the observed changes cannot be definitively ascribed to any single factor, it seems likely that a general cooling of winter temperatures may be partially responsible for this climatic change. [M]any of the snowfall time-series curves for the lake stations show downward trends during the 1920’s and 1930’s, at the height of the recent warm period, and the more recent snowfall increase has coincided with a general world-wide cooling which has occurred in the last several decades [1940s-1970s]. Recent evidence derived from [isotope] analysis of ice core samples on the Greenland ice cap indicates a continuance of this cooling trend for another 20 or 30 years [through the 1990s].”

Rasool and Schneider, 1971: “It is found that, although the addition of carbon dioxide in the atmosphere does increase the surface temperature, the rate of temperature increase diminishes with increasing carbon dioxide in the atmosphere.

It is found that even an increase by a factor of 8 in the amount of CO2, which is highly unlikely in the next several thousand years, will produce an increase in the surface temperature of less than 2°K. However, the effect on surface temperature of an increase in the aerosol content of the atmosphere is found to be quite significant. An increase by a factor of 4 in the equilibrium dust concentration in the global atmosphere, which cannot be ruled out as a possibility within the next century, could decrease the mean surface temperature by as much as 3.5°K. If sustained over a period of several years, such a temperature decrease could be sufficient to trigger an ice age!”

Bray, 1971: “Increased atmospheric carbon dioxide content was concluded to have had an ambiguous climatic influence and may be less important than sometimes considered. Several studies have suggested increased turbidity has produced a recent global cooling trend. An examination of some climatic effects of volcanic eruption was made in relation to the prediction that the effect of 500 supersonic transport aircraft would be comparable over the North Atlantic to the amount of stratospheric injection from the 1963 Mount Agung eruption. World glacial advance over the past three centuries was shown to be synchronous with volcanic eruption (p <0.01) and with poor harvests (p <0.001) and lower world temperatures were significantly related to volcanism (p <0.01). These relationships support the results of a previous study and suggest that the effects of 500 supersonic transport aircraft may lead to reduced surface temperatures and possibly an intensification of alpine glaciation.”

Barrett, 1971: “Changes in concentration of those atmospheric constituents which contribute to the planetary albedo can give rise to climatic alterations. … These computations show that substantial depletions of irradiance can result from moderate to heavy particulate loadings, and that an increase in man-made particulate emissions by a factor of 50 or more could give rise to a general cooling of serious magnitude.”

Eichenlaub, 1971: “Evidence derived from the carefully screened temperature record at Eau Claire, Mich., and from radiosonde data at Sault Ste. Marie, Mich., supports the conclusion of Wahl and Lawson that a return to the temperature and circulation features of the early and mid-19th century in the eastern United States may be underway. Cooling trends at Eau Claire during the most recent decades have been accompanied by progressive lowering of the 700-mb surface at Sault Ste. Marie, and increased cold air advection into the southern Great Lakes area.

“Definite cooling tendencies appeared in summer and winter, particularly during seasonal extreme months of July and January. Figure 2 shows 10-yr moving averages of monthly temperatures for June, July, and August. All 3 mo[nths] show temperature declines since the height of the recent climatic optimum during the 1930s. July temperatures have decreased about 3.5°F since the decades beginning with the early 1930s, and August temperatures have decreased about 3°F since the decades beginning with the late 1930s and early 1940s. … winter temperatures have decreased markedly since the late 1940s and early 1950s.”

Mitchell, 1971: “Turning to the presumed effect of such large-scale background aerosol increases, a number of authors have called attention to the coincidence between these increases and a systematic decline of worldwide average temperature in the past two or three decades, and have considered the possibility of a causal connection between the two phenomena (McCormick and Ludwig, 1967; Bryson, 1968; Budyko, 1969; Bryson and Wendland, 1970; Mitchell, 1970).  … With particular regard to the recent cooling trend of worldwide climate, the attribution of this cooling (or any significant part of it) to secular increases in atmospheric particles from human activities now appears unlikely, not merely on quantitative grounds (see Mitchell, 1970) but on qualitative grounds as well.”

Hare, 1971: “The rise between 1880 and 1940 was much greater than the computed carbon dioxide effect, and since 1940 temperatures have actually fallen as the rise in [CO2] mixing ratio accelerated.”
Hays and Perruzza, 1972: “The carbonate curves are interpreted to indicate a pronounced increase in wind stress and probable climatic deterioration after the beginning of the last interglacial (post-Eemian). This is also reflected in the carbonate curves for the previous major climatic cycle. If the Holocene warm period is analogous to the Eemian (Barbados Terrace III) then we may expect a pronounced climatic deterioration [cooling/glaciation] in the next few thousand years.”

Sancetta et al., 1972: “If the Eemian is taken as the analog of the present interglacial, a point in time 116,000 YBP becomes the historical model for today’s ocean, and the North Atlantic is now approaching a time of severe cooling.”

McIntyre and Ruddiman, 1972: “Samples representing the post-Eemian cool interval (approx 110,000 yr BP) were taken from 15 cores on the eastern flank of the mid-Atlantic Ridge from 42°N to 61°N lat. The floral-faunal assemblages in these samples characterize the surface paleooceanography which we consider a possible analog to the cooling expected to follow the present warm interval. The derived paleooceanographic map indicates at least a 16° lat southward displacement of cooled water masses from today. The present position of the Transitional water mass which gives N. Europe its equitable climate was then occupied by Subpolar water while the Polar Front extended south of Iceland. The result was a drop in annual temperature of the NE Atlantic surface water by at least 5°C.”

Richmond, 1972: “Correlation of the timing of the regional glacial-interglacial record for the past 140,000 yr with the record of major sea level changes and with the calculated changes in the earth’s insolation suggest that the present interglacial may be completed within a few millenia and that it may be followed by a significant cooling of the climate.”

Emiliani, 1972: “Oxygen isotopic analysis and absolute dating of deep-sea cores show that temperatures as high as those of today occurred for only about 10% of the time during the past half million years. The shortness of the high temperature intervals (“hypsithermals”) suggests a precarious environmental balance, a condition which makes man’s interference with the environment during the present hypsithermal extremely critical. This precarious balance must be stabilized if a new glaciation or total deglaciation is to be avoided.”

Absolon, 1972: “The present assemblages of Ostracods in Central Europe resemble the assemblages known from the earliest phases of Holocene. This observation supports the view that the termination of the present warm interval is to be expected in the near future.”

Lentfer, 1972: “Mitchell (1965) states that world climate during the past century has been characterized by a warming trend from the 1880’s to the 1940’s. Thereafter, the warming trend appears to have given way to a cooling trend that has continued to at least 1960 with some evidence that it was continuing in 1965.”

Kukla and Kukla, 1972: “An insolation chronology is introduced here, which is based entirely on astronomic factors (on the so called Milankovitch mechanism of Earth orbital elements). It is independent of any geologic or geochronologic dating systems. Two alternating units comprise the insolation chronology. The positive insolation regime (PIR) is an episode defined by progressively increasing winter irradiation in the Northern Hemisphere, whereas the negative insolation regime (NIR) is an episode of progressively decreasing winter irradiation. … It is observed that the positive insolation regime designated as PIR 110, which started at 11,000 YBP, has ended recently. The new negative insolation regime, NIR 0/ + 8, will last for the next 8000 yr. Inasmuch within the last radiometrically dated 150,000 yr no NIR is known to correlate with generally warm interval, the prognosis is for a long-lasting global cooling more severe than any experienced hitherto by civilized mankind.”

Sancetta et al., 1972: “If the Eemian is taken as the analog of the present interglacial, a point in time 116,000 YBP becomes the historical model for today’s ocean, and the North Atlantic is now approaching a time of severe cooling.”

Andrews et al., 1972: “Mean summer temperatures have declined throughout the 1960s to a level cooler than for approximately 40 yr.  … On a regional basis, winter precipitation has increased by more than 30% over the last 10 yr. Both the winter-warming trend and the increased precipitation are presumably related to a change in the frequency of southerly airflow types advecting warm moist air into the region. The net effect has been for heavier falls of snow in winter and with lower summer temperatures and therefore less melting (Jacobs et al, 1972), resulting in notably increased glacierization. … Recent field observations and comparisons with aerial photographs taken late in the ablation seasons of 1949 and 1960 provide verification of a recent climatic deterioration.  Snowbanks decreased from 1949 to 1960 and expanded during the next 10 yr.  In one case, a permanent snowbed overlay 25 mm thalli of the lichen Alectoria minuscula which indicate seasonally snowfree surface for the previous 40 ± 10 years.  Additionally, at least two corries snowfree in 1960 are presently occupied by incipient glaciers. …  The present Neoglacial ice is nearly as extensive as the late glacial stade (Figs. 2 and 3).”

Mörner, 1972: “We are now living under interglacial climatic conditions, the Present Interglacial of Flandrian Interglacial Age. It will certainly be followed by the Future Ice Age. The major cold/warm changes seem to have a cyclicity of 10,500 years. We have been in the 2nd cycle (characterized by a cooler climate) after the Last Ice Age for 2200 yr and will continue to be so for another 8300 yr. … ADDENDUM BY AUTHOR Several articles in this volume provide material strongly in favor of Alternative II of Fig 1.  This would mean we are now rapidly approaching a future situation equivalent to the “Pre-Brörup Stadial” (cf. Fig. 2), characterized by continental glaciation over Fennoscandia and the Kolar Peninsula and tundra or park-tundra conditions in most of the rest of Europe (the”Pre-S. Pierre Stadial” of North America was similarly characterized by continental glaciation over northeastern North America and alpine glaciations in the mountain regions of the West Coast).”

Schultz, 1972: “The nine-banded armadillos (Dasypus novemcinctus) have been moving northward in the Great Plains region from the late 1800s to the 1950s but now seem to be retreating from their lately acquired northern range. The armadillos have a nontypical homoiothermic blood system which makes them fairly vulnerable to cold climates. Many other adjustments of animal ranges have taken place in the Holocene, even during the past few centuries and evidence indicates that in many cases climate changes played an important role.”

Kukla, 1972: "A new glacial insolation regime, expected to last 8000 years, began just recently. Mean global temperatures may eventually drop about 1oC in the next hundred years."

Wright, 1972: “The Holocene has already run a course of at least 10,000 yr. If it is like earlier interglacials, it will end soon, giving way to gradually developing cold conditions, which may not lead to glacial maxima for tens of thousands of years.”

Bradley and Miller, 1972: “The climatic warming trend since the 1880s, which seems to have been global in extent and was manifested by an upward trend in mean annual (and particularly mean winter) temperatures, seems to have given way since the 1940s to a cooling trend, which is most marked in higher latitudes.”

Fairbridge, 1972: “Within any given cycle there is an Interglacial, Anaglacial, Pleniglacial and Kataglacial phase, characteristics of which are repeated on a small scale in minor cycles. Their timing is variable in a latitudinal sense, apparently steered by radiation changes that first affect the tropics. Interglacials are defined in their classical stratotype areas of NW Europe, by sedimentary sequences characterized by the pollen of deciduous forests, pointing to climates at least as warm as those of the present time. The present cycle began ca. 10,000 YBP, with the start of the Holocene epoch, and the contemporary warm phase is seen as a typical interglacial stage. Such warm peaks characteristically last about 10,000 yr. Symptoms of the expected ensuing glaciation range from a global fall in temperature since mid Holocene, to tropical desiccation (growth of deserts) and high latitude retreat of tree lines.”

Bradley, 1973: “A number of studies in recent years have been concerned with climatic fluctuations on a global or hemispheric basis (Putz 1971; Treshnikov and Borisenkov 1971 ; Mitchell 1961, 1963). A notable feature of these studies is the general conclusion that in the Northern Hemisphere the regions of greatest Warming from the 1880s to the 1930s or later have been in higher latitude zones. Similarly, areas of greatest cooling over the last 30 years have also been in these regions. Treshnikov and Borisenkov (1971), for example, note that the mean increase in annual temperatures 1881-1920 to 1921-60 for stations between 67°30’ and 77°30’N., and 72°30’ and 88°30’N. was 0.88 degrees C. and 1.11 degrees C. respectively. Flohn (1971) using data from Putz (1971) also shows data, 1961-70, for 10° latitude belts as deviations from the 1931-60 normals. These indicate that the largest negative changes occurred in higher latitudes (> 60°N.), suggesting that a return to conditions of the late nineteenth century is under way. Both the early twentieth century warming trend and the subsequent cooling have been most marked in “winter” months (December, January, and February), a fact also noted by Mitchell 1963. The studies indicate that the arctic and subarctic regions are extremely sensitive to climatic fluctuations and may be considered indicators of hemispheric trends”

Griggs, 1973,1975: “In fact, there has been a decrease in the mean annual air temperature since about 1945 at mid latitudes, suggesting that the aerosol pollution effect is greater than that of the CO2 increase. However, the effects of aerosols and CO2 are more complex than suggested above, so that their effects on climate are not readily predicted. For instance, Robinson points out that the earth may self-regulate its temperature by the variation of cloud amount: the higher temperatures, due to the CO2 greenhouse effect, lead to a higher water content in the lower atmosphere, which may increase the cloud amount; this increases the albedo, thereby decreasing the temperature. Robinson concludes there is no justification for forecasting a final equilibrium temperature due to an increase in CO2 content, until atmospheric models are significantly improved to include the cloud cover as a variable.”

Palmer, 1973: “Recent downward trends in the average surface temperature of the biosphere has led some scientists to conclude that albedo increases due to the effect of aerosol backscatter is the causative mechanism. While there is evidence for and against this hypothesis, this paper emphasizes that albedo changes due to aerosol modification of cloud cover may be a more significant mechanism for explaining temperature trends.”

Starr and Oort, 1973: “Between May 1958 and April 1963 the mean temperature of the atmosphere in the northern hemisphere fell by about 0.60° C.”

Bodhaine and Pueshel, 1973: “The effect of the atmospheric aerosol load on the earth’s climate has been of great concern during the past decade.  McCormick and Ludwig (1967), Bryson (1968) and Mitchell (1970) suggested an increase of particulate loading would lead to a decrease in incoming solar radiation that would, in turn, lead to a general cooling of the earth’s temperature as observed during the past 30 years. Subsequently, other investigators (Charlson and PIlat, 1969; Mitchell, 1971)  have suggested that the inclusion of the absorption effects of tropospheric  aerosols could very well lead to a warming at the earth’s surface .  It is generally agreed that stratospheric aerosols would lead to surface cooling, whereas uncertainty prevails about the consequences of an increase in tropospheric particulate loading. … Solar radiation has been monitored at Mauna Loa Observatory, Hawaii … since 1957. Since then there has been no significant change at Mauna Loa attributable to anthropogenic sources (Ellis and Pueschel, 1971).”

Denton and Karlén, 1973: “Should this pattern continue to repeat itself, the Little Ice Age will be succeeded within the next few centuries by a long interval of milder climates similar to those of the Roman Empire and Middle Ages.”

[The use of future tense in the statement that the Little Ice Age “will be succeeded within the next few centuries by a long interval of milder climates” similar to the Medieval and Roman Warm Periods strongly implies that the authors did not agree that modern (1970s) climate had sufficiently emerged from the Little Ice Age to yet qualify as a warm interval , and that it might be a “few centuries” before this warm period might commence.]

Lister and Lemon, 1974: “Increased CO2 levels cause an increase in tropospheric and surface temperature due to absorption of long-wave radiation in bands centered around 4 µm and 15 µm. Assuming fixed relative humidity, the temperature effect of a 10% increase in CO2 concentration would cause a warming of about 0.3°C. However, normal variations in the present cloud and synoptic weather patterns could easily override the quantitative effects of CO2 on the radiation budget. [N]one of the present models simulates the interaction of clouds and aerosol layers and almost none considers thermal radiation; thus at best they can only be considered quite speculative.”

Willett, 1974: “The recent climatic fluctuations are examined as to amplitude and pattern, as a necessary prerequisite to explanation and predictive extrapolation. Two quite distinct hypothesis, that of atmospheric pollution and that of cyclical solar-climatic interaction, are considered as possible causes of the recent fluctuations and accordingly as predictors of the climatic changes to come, notably with respect to the imminence of an Ice Age. The solar-climatic hypothesis gains the strong preference of the author.”

Johnson, 1974: “I suspect that we are witnessing the recovery in recent years of Boreal faunas which were reduced in diversity sometime prior to the census of 1940, perhaps by the deleterious environmental effects of the relatively warm-dry period of the 1930s. It is tempting to hypothesize that the recent period of global cooling, which reversed the warm trend of the 1940s (Kukla and Matthews 1972), has gradually improved montane environments in the Southwest for the occupancy of additional Boreal species.”

Stockton and Boggess, 1979: “Van Loon and Williams (1976) suggest that regional trends in surface temperature are indeed connected with long wave circulation changes, that the greatest variations appear above 500 N. latitude, but that the changes may be compensated for in other regions. For example, during 1942-1972 there appears to have been a change of -1.4°C in the mean temperature above 600 N. latitude but this appears to have been offset by a +0.20°C change over the area between 300 N. to 300 S. latitude. Budyko and Asakura (in NAS, 1975) show that for the period 1880-1969, average temperature for the northern hemisphere attained a maximum around 1940 and decreased until 1969. More recent records, however, indicate the decrease has leveled off and during the last 5 years and there has actually been little change. Budyko-Asakura’s average temperature data for the northern hemisphere (Figure 2) shows the range of change between 1880 to 1940 to be approximately 1.1°C.”

Reitan, 1974: “Mean monthly temperatures for the Northern Hemisphere were determined for the years 1955 through 1968 following the same procedures used by H. C. Willett and J. M. Mitchell, Jr., in their studies of long-term trends. It was found that the downward trend they reported starting in the 1940s continued, though interrupted, into the 1960s. The temperature data when combined with radiation data and other components of the hemispheric energy budget led to the formulation of the response ratio, the relationship between change in incoming solar radiation and change in temperature. When this response ratio was applied to the reported trends in direct solar radiation and to the decrease in direct solar radiation following the eruption of Agung in 1963, a probable cause-effect relationship was suggested.”

Schneider and Dickinson, 1974: “ [A]bout 1000 years ago a relatively mild period permitted Viking exploration of the North Atlantic region. Several hundred years later, at the onset of the ‘little ice age,’ the Norse colonies in Greenland were wiped out, and the historical chronicles tell of long harsh winters that brought suffering and deprivation to Europe. Milder climate has returned in modern times, but the optimum (warmest) condition occurred in the 1940’s, and since then, there has been a fairly rapid cooling in the high latitudes of the northern hemisphere. The relatively benign climate that we have taken for granted in the latter half of the twentieth century is not characteristic of all periods since the retreat of the ice age. … Climate-induced famine is even more serious today. Already, 6 consecutive years of drought have ravaged large populations in parts of central Africa known as the ‘Sahel.’ The drought has left millions of people near starvation, and the number of deaths approaches hundreds of thousands. There are hints that the situation may yet worsen [e.g., Winstanley, 1973; Bryson, 1973].”

Sanchez and Kutzbach, 1974: “A review of selected literature on latitudinal climatic shifts and atmosphere-ocean interaction suggests some similarities between the patterns of climate in the 1960s and the climate of the Little Ice Age.

Cimorelli and House, 1974: "... between 1880 and 1940 a net warming of about 0.6°C occurred, and from 1940 to the present our globe experienced a net cooling of 0.3°C."

Kalnicky, 1974: “The mean temperature for the Northern Hemisphere had a warming trend from 1890 to 1950 and a cooling trend since 1950. The eastern and central United States had colder temperatures in 1961–1970 than in 1931–1960. The temperature changes were associated with an adjustment of hemispheric circulation from more frequent zonal flow between 1900 and 1950 to more frequent meridional flow since 1950. Regional variations in magnitude and direction of the change were largely related to position in relation to the upper air westerly wave pattern. Time series of individual circulation indices tend to resemble the step function model of climatic change.

 Ellsaesser, 1974: "Since 1945 there has been a cooling trend and we are now nearly back down to the averages of the early 19th century. None of the calculations of which I am aware found that the man augmented CO2 could have contributed more than a small fraction of the warming up to 1940."

NOAA, 1974; “ Some climatologists think that if the current cooling trend continues, drought will occur more frequently in India—indeed, through much of Asia, the world’s hungriest continent. … Some climatologists think that the present cooling trend may be the start of a slide into another period of major glaciation, popularly called an “ice age.””

Haber, 1974: “A meteorologist and Director of the Institute for Environmental Studies at the University of Wisconsin, Dr. Bryson believes that the Earth is moving toward an inevitable climate change; the consequences, he says, are already being felt – tragically – in the drought-plagued belt of West Africa called the Sahel. The global climate will become cooler, Bryson predicts, the pattern of rainfall will change, and a southward movement of the subtropical deserts will take place.”

U.S. Central Intelligence Agency,1974 : “A number of meteorological experts are thinking in terms of a return to a climate like that of the 19th century. This would mean that within a relatively few years (probably less than two decades, assuming the cooling trend began in the 1960’s) there would be brought belts of excess and deficit rainfall in the middle-latitudes; more frequent failure of the monsoons that dominate the Indian sub-continent, south China and western Africa; shorter growing seasons for Canada, northern Russia and north China.  Europe could expect to be cooler and wetter. … [I]n periods when climate change [cooling] is underway, violent weather — unseasonal frosts, warm spells, large storms, floods, etc.–is thought to be more common.

Flohn, 1974: “Since about 1945 [to 1974], global cooling, on a scale of -0.01°C/yr [-0.3°C total], has reversed the warming trend of the first decades of our century. The bulk of these changes is probably not man-made, but of natural origin. … A large majority of the participants of the symposium concluded that the present warm epoch has reached its final phase, and that—disregarding possible man-made variations are comparable in scale with the effects–the natural end of this interglacial epoch is “undoubtedly near.””

U.S. Central Intelligence Agency, 1974: “Early in the 1970s, a series of adverse climatic anomalies occurred:

* The world’s snow and ice cover had increased by at least 10 to 15 percent.

* In the eastern Canadian area of the Arctic Greenland, below normal temperatures were recorded for 19 consecutive months. Nothing like this had happened in the last 100 years.

. . . It has become increasingly imperative to determine whether 1972 was an isolated even or – as the climatologists predicted – a major shift in the world’s climate.”

Schneider, 1974: “In the last century it is possible to document an increase of about 0.6°C in the mean global temperature between 1880 and 1940 and a subsequent fall of temperature by about 0.3°C since 1940. In the polar regions north of 70° latitude the decrease in temperature in the past decade alone has been about 1°C, several times larger than the global average decrease (see Fig. 3.8 in the SMIC Report)”

Zdunkowski et al., 1975: “It is found that doubling the carbon dioxide concentration increases the temperature near the ground by approximately one-half of one degree [0.5°C] if clouds are absent. A sevenfold [700%] increase of the present normal carbon dioxide concentration increases the temperature near the ground by approximately one degree. Temperature profiles resulting from presently observed carbon dioxide concentration and convective cloudiness of 50% or less are compared with those resulting from doubled carbon dioxide concentrations and the same amounts of cloud cover. Again, it is found that a doubling [100% increase] of carbon dioxide increases the temperature in the lower boundary layer by about one-half of one degree.”

Williamson, 1975: “Since about 1958 the reduced heat transport via the warm air sectors of the depressions has permitted an increase in pack-ice off northern and eastern Iceland to a condition comparable with the 1880s, and Polar Bears Thalarctos maritimus have been able to cross from Greenland for the first time for half a century (Marshall 1968). This relapse from warmth continued into the 1970s with one winter, 1962/63, as devastating over the English Midlands and south as anything experienced since 1740 (Manley n.d., Lamb 1966, Booth 1968). People asked, are we on the threshold of another long climatic recession?”

Lamb, 1975: “The history of climatic change since 1970 is also an interesting one. To anyone living in Europe, where there have been four or five notably mild winters in a row, it is probably surprising to learn that the global cooling seems to have continued. The 5-year mean ocean surface temperature averaged for all the North Atlantic weather ships fell by 0°- 5°C from 1951-55 to 1968-72. The North Pacific has also become colder, and Canada and the Canadian Arctic have become colder than before.”

Harshvandahn and Cess, 1975: “A significant fraction of the aerosol population of the stratosphere is believed to consist of sulfate, presumably in the form of sulfuric acid. An increase in stratospheric aerosols could modify global climate by augmenting reflection of sunlight as well as enhancing the atmospheric greenhouse, two competing mechanisms with regard to changing the global surface temperature. Assuming that the aerosols consist of supercooled 75 % aqueous sulfuric acid, we present a first-order estimate as to the effect of aerosol concentration upon global surface temperature. The model calculations illustrate that the increase in reflected sunlight constitutes the dominant contribution by aerosols; the normal aerosol concentration reduces the global surface temperature by roughly 0.7 K, and a doubling of concentration would provide a further decrease by the same amount. Increased aerosol concentration further results in heating of the stratosphere through absorption of infrared radiation emitted by the earth-atmosphere system. The model indicates that stratospheric temperature at 20 km could be raised by as much as 9 K, consistent with Southern Hemisphere observations following the eruption of Mt. Agung.

“Stratospheric aerosols can modify global climate in one of two ways. Reflection of solar radiation enhances the planetary albedo, reducing the global surface temperature, whereas the infrared opacity of the aerosol layer augments the greenhouse effect and increases the surface temperature. There has been considerable debate as to which of these two competing mechanisms dominates, although recently Coakley & Grams (1975) have presented a simple but convincing argument that the albedo modification is most important, so that an increase in aerosol concentration would produce a global cooling trend. … Volcanic activity during the 1960’s could, however, contribute in part to what appears to be a global cooling trend since 1940 (e.g. Budyko, 1969).”

Nelson et al., 1975: “Even with the temperature corrections included, Indiana June, July and August mean temperatures showed a decrease of approximately 3°F [-1.7°C] from 1930 to 1976.”

Douglas, 1975: “Since 1940, however, the temperature of the Northern Hemisphere has been steadily falling: Having risen about 1.1 degrees C. between 1885 and 1940, according to one estimation, the temperature has already fallen back some 0.6 degrees, and shows no signs of reversal. . . . According to the academy  report on climate, we may be approaching the end of a major interglacial cycle, with the approach of a full-blown 10,000-year ice age a real possibility.”

King and Willis, 1975: “Starr and Oort (1973) have made a comprehensive study of meteorological temperatures, using about 10 million individual measurements of temperature, to derive the average temperature of the bulk of the atmospheric mass in the northern hemisphere for each of the 60 months between May 1958 and April 1963. If the mean seasonal variation is subtracted from the monthly values to yield the residual temperatures, it is found that the spatially averaged temperature fell by about 0.60° C during the 5 years. A comparison of the temperatures with the monthly mean sunspot numbers during the same period suggests that the declining temperature trend may be associated with the decline in solar activity. This suggestion is supported by the fact that smoothed variations of temperature and sunspot number are both relatively flat during the first and last years of the 5-year period. Alternatively, it appears that Earth’s magnetic dipole is moving slowly into the northern hemisphere (Nagata, 1965) and the magnetic field is, on the average, gradually increasing there; this behavior may lead, in some unknown way, to the decrease of northern hemisphere meteorological temperatures.”

Thompson, 1975: “ The cooling and shrinking of the atmosphere at the higher latitudes is believed to have brought the subtropical anticyclones nearer to the tropical rainbelt and have caused a shifting of the monsoon belt. The regions that would be most severely affected by a continuation of the cooling trend to the year 2000 would be the higher latitudes (above 50 degrees) where spring wheat is grown and the warm band below 30 degrees latitude where rice is the principal grain crop. . . .Even if the weather does trend toward the coolness of a century ago yields will not be reduced significantly unless the weather becomes more variable.”

Potter et al., 1975: “Of the various mechanisms suggested by which man might change the planetary climate, the removal of tropical rain forests to increase arable acreage seems to be one of the more imminent. For this reason we selected this as one of the first problems to be tested in our recently updated climate model. Bearing in mind the fallibility of computer simulations, we find overall global cooling and a reduction in precipitation: a larger tropical reduction being almost balanced by a subtropical increase.”

Collis, 1975: “It is not clear how such favorable and relatively consistent conditions are related to the higher temperatures in this century or the peaking of temperatures around 1940. The reversal of this warming trend, however, could mark the beginning of a new ice age as some climatologists have indicated. It should be noted, though, that even if we are in fact heading for another ice age, many years or decades will elapse before this will become apparent”

Ghil, 1975: “ There has also been a concern about a possible climatic catastrophe [global cooling] being imminent because of the increase in the quantity of industrial pollutants in the atmosphere (Rasool and Schneider, 1971).”

Gribbin, 1975: “over the period from 1951 to 1972 there was a decline corresponding “to a return of about one-sixth of the way to full ice age.”The observed cooling corresponds to a re-establishment of the ‘Little Ice Age’ which persisted for several hundred years up to the end of the nineteenth century; it may be that all that has happened since 1950 is that the unusually mild spell of the first part of this century has ended.”

Ellsaesser, 1975: “In recent years there have appeared a rash of papers claiming an upward trend in airborne particulates, which is presumed to have already reversed the alleged CO2 induced heating of the atmosphere observed between the 1880’s and 1940’s and to pose the further threat of inducing another ice age. Allusions to the trend have become so common that many authors now cite it as an accepted reality requiring neither qualification nor attribution by reference.”

National Academy of Sciences, 1975 “A striking feature of the instrumental record is the behavior of temperature worldwide. As shown by Mitchell (1970), the average surface air temperature in the northern hemisphere increased from the 1880’s until about 1940 and has been decreasing thereafter.  Starr and Oort (1973) have reported that, during the period 1958-1963, the hemisphere’s (mass-weighted) mean temperature decreased by about 0.6 °C. . . .There seems little doubt that the present period of unusual warmth will eventually give way to a time of colder climate, . . . there is a finite probability that a serious worldwide cooling could befall the earth within the next hundred years. …  If the end of the interglacial is episodic in character, we are moving toward a rather sudden climatic change of unknown timing, although as each 100 years passes, we have perhaps a 5 percent greater chance of encountering its [the next glacial’s] onset.”

Singer, 1976: “The distribution of the radiating gases is largely responsible for the layering of the Earth’s atmosphere. The troposphere extends from sea level up to approximately 12 km at which point the temperature has dropped to approximately -60°C. Water vapor is about 10 times more important than carbon dioxide, both for radiative heating by absorbing solar radiation and for radiative cooling. In the stratosphere, however, radiative heating by the absorption of solar radiation by ozone is dominant.”

Hays et al., 1976: “[T]he longterm trend over the next 20,000 years is toward extensive Northern Hemisphere glaciation and cooler climate.

Bach, 1976: “It appears that major ice ages seem to occur every 100,000 yr and that after an interglacial interlude we are on the brink of a period of colder climate. It has been estimated that the mean temperature of the planetary atmosphere in its surface layers has decreased by about 0.3°C since the 1940’s despite an 11% increase of CO2 above the nineteenth century preindustrial level of 290 ppm. It appears that the natural climatic cooling trend is roughly 3 times more powerful than the present influence of CO2.”

Dunbar, 1976: “[T]he past history of the present interglacial has been much the same as in the sea, predictably. The trend since the climatic maximum of 5000 years B.P. has been downward, involving a retreat southward of the treeline by some 500 km, a global drop in mid-latitude air temperatures of some 2.5°C, and increasing aridity in the tropics (Fairbridge 1972). And there has been the same recent upswing to 1940 and same subsequent cooling to about 1970, followed by the suggestion of a reversal of the cooling trend in the past five years, possibly or probably a temporary reversal only.

I find it difficult to believe that either carbon dioxide in the atmosphere, water vapour, freon, or any other substance, produced by man’s efforts, is going to compete seriously with Nature in changing our climate. . . .Rasool and Schneider (1971) conclude that an increase in the carbon dioxide content of eight times the present level would produce an increase in surface temperature of less than 2°C, and that if the concentration were to increase from the present level of 320 parts per million to about 400 by the year 2000, the predicted increase in surface global temperature would be about 0.1°C. … Johnsen et al. (1969), on the basis of ice-cap measurements in Greenland, expect the present cooling trend to continue for one or two decades with subsequent warming reaching a maximum in about 40 or 50 years. Winstanley (1973) does not expect a change in the cooling trend for another 60 years.”

Oliver, 1976: “A period of several decades existed (~1915-1945) in which volcanic activity was unusually light and, as mentioned earlier, the temperatures were higher than the preceding [1880s to 1910s] or, in fact, the subsequent (current) [1960s-1970s] period. … Numerous possible causes of climate change have been discussed in the literature, including both anthropogenic and natural factors. Two principal anthropogenic sources are often considered: changes in atmospheric carbon dioxide and changes in tropospheric dust. … The possible effects due to changes in CO2 are perhaps most readily subject to analysis, for good data do exist on atmospheric CO2 and its increase over recent decades. Thus, according to Reitan (1971), based on calculations by Manabe and Wetherald (1967), the increase in CO2 between the 1880’s and the 1960’s could have caused a mean temperature increase of 0.3°C. Unfortunately, however, such computations are based on assumptions of constant cloudiness, and possible changes in cloud cover are exceedingly important. Manabe and Wetherland (1967) show, for example, that a 1% increase in low cloudiness would cause an 0.8°C decrease in mean temperature; thus, a 0.3° warming could be compensated by a change of about 0.4% in low cloudiness. A change of 0.4% in low cloudiness would obviously be exceedingly difficult to detect. … Mitchell (1975) concluded that neither tropospheric particulates [anthropogenic pollution] nor atmospheric CO2, in concert or separately, could have accounted for the major part of the observed temperature changes of the past century.”

Zirin et al., 1976: “In the past 100 years, meteorological records indicate that the world underwent a relatively small variation of temperature, of amplitude about 0.5°C, with lowest temperatures in the 1880’s and highest in the 1940’s. A cooling trend has been dominant in many parts of the world, especially in the arctic and sub-arctic, since the 1940’s.”

Gates, 1976: “Recorded data show that from 1940 to the early 1970s the average temperature in the Northern Hemisphere slowly decreased, with a net cooling of approximately 1°F [-0.55 °C] over the continents and less cooling over the oceans. We also know that during the period from about 1890 to 1940 the air over at least the continents of the Northern Hemisphere underwent a gradual warming of over 1.5°F [+0.83°C]. … Whether such fluctuations are primarily the result of man’s activities or are only natural climatic variations remains an open question.”

Allen et al., 1976: “In recent decades, however, a general cooling has been apparent in high latitudes. In northeast Greenland this appears to have been of the order of 0.3°C for the period 1940 to 1959”

Landsberg, 1976: “Howard A Wilcox (1975) [in his book] Hothouse Earth, has both polar ice caps melting as a result of heat rejection from human energy consumption; the second [book], by Nigel Calder (1975), The Weather Machine, warns of an imminent ice age.  That leaves us where we were before; both cannot  be right. … The basic model Wilcox adopts is the Budyko-Sellers radiation equilibrium concept, slightly modified.  He discounts feedbacks, has no concept of the role of the oceans, and leaves out all transport and eddy dissipation effects.  Where the climatologists have cautiously and conservatively made tentative calculations with 1-2% changes in the solar “constant,” Wilcox regales us to an energy rejection equal to the present solar energy income by about the year 2200. He generously omits the evidently minor concomitant CO2 effects [as a factor affecting warming].  Perturbingly, there are nowhere real error limits placed on any of the estimates.

Calder’s book takes us to the other extreme. He gives a composite word picture that inexorably leads to an ice age. Mr. Calder is a science writer, who bases his views essentially on talking to scientists and reading literature selectively. Thus the book essentially is a review.  … Calder’s vivid portrayal of catastrophic weather events are a tribute to him as a writer, but the conclusions he draws from them are very shaky. Of course, we are all very distressed by the human consequences of such events as the Sahel drought or the damages wrought by hurricane Agnes, but are they really indications of climatic change [global cooling]?  … [I]n talking about the Indian monsoons he clearly advocates that these have become weaker and will be further weakened by a cooling of the earth; he then disparagingly quotes the Indian Meteorological Service stating that there are no trends in rainfall in the subcontinent corresponding to global warming or cooling.He also reads from the record of the cores that ice caps can swoop down on us suddenly.  For this he coins the term “snowblitz,” a rapid extension of the snow cover that will not melt in the summer. So we shall be frozen out at latitude 50°N, by his own calculations (without error limits), in the next century or two.”

Ratcliffe, 1977: “A steady increase in mean temperature in the British Isles during the first part of the century was reversed around 1940-50 and the last three decades have been marked by a steady fall in mean temperature.”

Paterson et al., 1977: “An oxygen-isotope climatic record from the Devon Island Ice Cap Arctic Canada. Figure 4a-shows 10-yr mean [temperature] values from AD 1200 to present. Prominent features are brief warm periods with peaks at 1240 and-1380, cold peaks at 1430, 1520 and  1560, the ‘Little Ice Age’ continuously cold from 1680 to 1730 and with another temperature minimum at 1760, a pronounced warming at about 1910 with relatively warm temperatures until about 1960 and a marked cooling thereafter.”

Wendland, 1977: “The cooling from about 1950 to 1974 is ~0.3°C (Brinkmann, 1976). Moran (1975) suggests that the recent drought of peninsular Florida is largely due to decreased frequencies of tropical storms, associated with the general atmospheric and oceanic cooling since about 1940 (Wahl and Bryso, 1975).”

Kukla, 1977: “Indicators of large-scale climate developments show that the oscillatory cooling observed in the past 30 yr in the Northern Hemisphere has not yet reversed. This conclusion was reached by updating our data on the month-to-month, season-to-season, and year-to-year variations of selected zonally averaged meteorological parameters.”

Paterson, 1977: “Figure 4a shows 10-yr mean [temperature] values from AD 1200 to present [Arctic Canada]. Prominent features are brief warm periods with peaks at 1240 and 1380, cold peaks at 1430, 1520, and 1560, the ‘Little Ice Age’ continuously cold from 1680 to 1730 and with another temperature minimum at 1760, a pronounced warming at about 1910 with relatively warm temperatures until about 1960 and a marked cooling thereafter … [T]he cooling trend over the past 5,000 yr has probably been more than 1°.”Norwine, 1977: “Around 1900, a radically different climate stage set in, probably worldwide, one of warming (see Figure 1). … Well, all that was nice while it lasted, but a substantial cooling phase of deterioration has characterized the last 25 to 30 years”

Angell and Korshover, 1977: “Between 1958 and 1965 there was a significant cooling averaging about 0.3°C over much of the globe, but since 1965 the temperature variations have been small.”

Bryson and Ross, 1977: “The authors of this paper show, based on some examples from climatic history, that climate can change rapidly and that these changes can have drastic effects on world food production, as well as on other aspects of economic and cultural life. The historical examples are the Arctic expansions of around 1900 B.C. and A.D. 1200. The authors also describe a presently occurring Arctic [ice] expansion and its world-wide effects on climate to date.”

Barry, 1977 The Greenland temperature records are of considerable interest (Figures 1 and 2). Winter (September through May) temperatures rose intermittently from about 1890 to 1930-1940 resulting in an overall increase of 4 to 5°C. The warming was especially pronounced in the 1920s. Some cooling has occurred since 1930-1940 although temperatures in the 1960s are still approximately 3°C above those of the 1880s. “

Thompson, 1977: “Recent theoretical studies (Pollack and others, 1976) and empirical evidence (Newell, 1970) indicated that variations in the concentration of particles in the atmosphere is an important component in the heat balance of the earth-atmosphere system.   Some investigators (McCormick and Ludwig, 1967; Bryson, 1968; Rasool and Schneider, 1971) attributed the decrease in mean air temperatures of the northern hemisphere since the 1940’s to an increase in the atmospheric aerosol load. It is generally agreed that the effect of high altitude aerosols, such as stratospheric dust veils of volcanic origin, is theoretically one of surface cooling; however, the role of aerosols concentrated in the lower troposphere in the radiation budget is still open to speculation. Neumann and Cohen (1972) predicted net cooling as the end result, while Charlson and Pilat (1969) predicted net warming. … Mitchell (1975) found a correlation between an increase in the quantity of volcanically-injected stratospheric material and a decrease in mean temperatures in the northern hemisphere for the period since 1880 A.D.

Yamamoto et al., 1977: “  By Willett’s method, Mitchell presented the trend of the global mean of the surface air temperature, which shows a warming from the decade of 1880 to that of 1940, and afterwards cooling. A similar trend for the Northern Hemisphere was also given by Budyko, using maps of temperature anomaly, although the manner of constructing the maps was not described in his paper. Reitan shows a similar trend of the North Hemisphere temperature until the middle of the decade 1960, with the use of Willett’s method.”

Moran and Morgan, 1977: “In Wisconsin, the growing season became cooler and shorter from 1958 into the mid-1960s. These trends accompanied a pronounced drop in the mean annual tropospheric temperature of the Northern Hemisphere. Although Northern-Hemispheric—tropospheric temperatures continued to fall (albeit at a lesser rate) from the mid-1960s through 1973, the growing season in Wisconsin showed a general trend toward lengthening and warming.”

Denton and Karlén, 1977: “Here, the ages of Little Ice Age moraines suggest fluctuating glacier expansion between ad 1500 and the early 20th century. Much of the 20th century has experienced glacier recession, but probably it would be premature to declare the Little Ice Age over.”

Geist, 1978: “Introduction: Denton and Karlén (1973) found a periodicity of about 2500 years for minor glaciations that correlated with a regular variation in the solar corpuscular activity (Bray, 1971); about 900 years coincide with the expansion of glaciers and 1600 with their retreat. In recent years weather patterns have changed as the mean earth temperature has begun to decline, so that there is an increase in snowfall and cold temperatures of the northern hemisphere, and an increase in snowfall and cold temperatures over the old epicenters of glaciation such as the Rocky Mountains, Hudson Bay, Labrador, Scandinavia, and the Alps, as well as an increase in aridity in the major deserts, which may indicate a return to glacial conditions.”

Hustich, 1978: “The climatic ‘improvement’ of the late 1930’s had, as was expected, given way to a colder trend in the 1950’s and 1960’s … Dunbar (1976, p. 190) writes that he finds it “difficult to believe that either Carbon dioxide in the atmosphere, water vapour, freon, or any other substance produced by man’s efforts is going to compete seriously with Nature in changing our climate”.  … Heino’s diagrams illustrate the exceptional nature of the climatic improvement experienced in the 1930’s, but they also show clearly the slow deterioration which set in in the 1950’s. The 1960’s constituted climatically a rather unfavourable decade from man’s point of view”

Lamb and Mörth, 1978: “After many decades in which it was generally assumed – and taught – that climate could for practical purposes be treated as constant, it was Ahlmann who in this journal (Geogrl J. 112 (1949)) drew widespread public attention to the fact that a very significant warming of world climate had been going on more or less throughout the first half of this century, particularly from 1920 to 1940. The reversal of this trend [cooling] that followed, particularly between 1955 and 1965, and the remarkable incidence since 1960 of many kinds of extreme weather in many parts of the world, going beyond the statistical expectations based on the data of the so-called climatic ‘normal’ periods between 1900 and 1960, have created concern amongst planners in agriculture, industry, and trade.”

Bulatov and Zakharov, 1978: “The authors investigate the impact of the cooling trend that has prevailed since the early 1940’s on certain aspects of sea ice conditions in the Soviet Arctic: specifically changes in the average concentration of old ice, i.e., older than one year, between the decades 1946–55 and 1956–65, and changes in the position of the southern boundary of the old ice. Both criteria show differences between the Western Arctic and the Eastern Arctic, with the dividing line at approximately 160°E. West of this meridian, concentrations increased by up to 3 tenths (in a zone north of Severnaya Zemlya and New Siberian Islands), while the southern boundary of old ice was up to 100 miles farther south to the west of the divide, and up to 100 miles farther north to the east. The significance of these changes with regard to navigation conditions is selfevident.”

Zakharov, 1978: “The author utilizes ice data from Arctic stations and from ice reconnaissance flights to investigate the impact of the cooling trend that began in the early 1940’s on sea ice conditions in the Soviet Arctic.”

Petersen and Larsen, 1978: “An attempt is made to identify a stochastic model that makes the best fit to a generalized temperature curve covering the last 700,000 years. A search is made for the model within the family of auto-regressive, integrated, moving average models. All the models presented forecast a decline in temperature during the next 5000 years.”

Chi-chun and Pen-hsing, 1978: “Research on glacier fluctuations shows that the Little Ice Age was also experienced here [Chinghai-Tibet Plateau] with maxima occurring during the 19th century. This was followed by a strong retreat from the 1930s with recent signs of the initiation of a new period of glacier advance.  … Our on-the-spot investigations, documental records and information local residents all tell us that, beginning in the thirties, the glaciers in Tibet underwent a period of strong retreating. The air temperature began to fall after the fifties. From meteorological records, we know that the temperature in the sixties was universally 0.7°C or so lower than in the fifties, but the precipitation increased by 5-27 per cent.”

Angell and Korshover, 1978: “Based on a network of 63 well-spaced radiosonde stations around the world, the global temperature within the surface to 100 mb layer was lower in 1976 than in any year since commencement of the record in 1958, and the 1976 surface temperature equated the global record for the lowest temperature set in 1964; but even so the trend in global temperature since 1965 has been small compared to the 0.5°C decrease during 1960–65. Between 1958 and 1976 the surface to 100 mb temperature in north extratropics decreased by about 1°C, with the decrease twice as great in winter as in summer, and in 1976 this region was 0.2°C lower than in any previous year of record.

One other attribute of the CO2 trend should be emphasized. Between 1958 and 1968 the rate of increase of CO2 at Mauna Loa averaged about 0.7 ppm per year-1, whereas between 1968 and 1973 the increase averaged about 1.4 ppm per year-1, and even between the periods of augmentation 1.2 ppm per year-1.  In contrast to this near doubling of the rate of increase of CO2, the [anthropogenic] CO2 input into the atmosphere only increased by about 30% between the periods 1961-67 and 1967-74 (Baes et al., 1976), so that factors other than [anthropogenic] emissions rates appear to be involved in the overall CO2 growth rate.”

Miles, 1978: “The cooling of the Northern Hemisphere since 1940 has been variously interpreted as the overture to the next Ice Age, the effect of industrial pollution in the atmosphere or of a decline in the solar output. Are we in a position to judge between these various interpretations and to make a prediction for the next few decades? The link with the next Ice Age may be dismissed as a confusion of timescales; the explanation in terms of atmospheric pollution merits careful examination but seems unlikely to be adequate on its own. Natural fluctuations must also be considered.”

Williams, 1978: “It has been suggested that the Laurentide Ice Sheet originated with extensive perennial snow cover, and that the snow cover affected climate so as to aid ice-sheet development. In this study, a large increase in extent of October 1st snow cover in the Canadian Arctic from 1967–1970 to 1971–1975 is compared to changes in October means of other climate variables. Over the area of snow-cover expansion, mean surface air temperature decreased by up to 3°C, mean 500-mbar height was lowered by over 60 m, and precipitation was increased by up to a factor of two. These effects, if applied to the entire summer, together with the temperature change computed by Shaw and Donn for a Northern Hemisphere summer insolation minimum (the Milankovich effect), can account for glacierization of the Central Canadian Arctic.”

Ya-feng et al., 1978: “Conclusion (last paragraph): Since the fifties the decline of temperature and the increase of precipitation have been the predominant trend in the western part of China. According to the dendroclimatological data obtained from several places, the declining temperature trend will continue till the end of this century or the beginning of the next [late 1990s to early 2000s]. From this we predict that the number of advancing glaciers may increase considerably in the days to come. But the relation between the fluctuations of glaciers and the changes of climate is very complex. The law ruling the fluctuations of glaciers is still left to a considerable extent to the systematic study and observation of us all.

Shultz and Hillerud, 1978: “Kukla and associates (1977) presented “new data on climatic trends” and showed that during the last 30 years in the Northern Hemisphere, the oscillatory cooling has not yet reversed.”

Schneider, 1978: “In the short term (left) the temperature has risen by about 1/2 degree Celsius since the 1880s, and from the middle 1940s to the middle 1960s it dropped about 1/4 degree. What’s wrong with this picture is that there should be large error bars on it, because there are still vast regions of oceans not covered by thermometers. But the main point is that the range of variation is only on the order of 1/2 degree, and that’s probably been significant enough to cause important local changes.”

Miles, 1978: “The cooling of the Northern Hemisphere since 1940 has been variously interpreted as the overture to the next Ice Age, the effect of industrial pollution in the atmosphere or of a decline in the solar output. Are we in a position to judge between these various interpretations and to make a prediction for the next few decades? The link with the next Ice Age may be dismissed as a confusion of timescales; the explanation in terms of atmospheric pollution merits careful examination but seems unlikely to be adequate on its own. Natural fluctuations must also be considered.”

Robock, 1978: “Northern Hemisphere annual mean temperature has risen about 1°C from 1880 to about 1940 and has fallen about 0.5 °C since then (Figs. 1-3). Various attempts to simulate this temperature record (Schneider and Mass, 1975; Pollack et at., 1976; Bryson and Dittberner, 1976) have all focused on external causes, such as volcanic dust, solar constant variations and anthropogenic effects. It is possible, however, that even in the absence of any external forcing a unique climate may not exist. Climate change may be a natural internal feature of the land-oceanic-atmosphere (climate) system.”

Imbrie and Imbrie, 1979: “The Coming Ice Age. What of the future? Does the fact that ice ages have occurred many times in the past mean that another one lies ahead?  Unless there is some fundamental and unforeseen change in the climate system, most scientists who have examined the evidence agree that the world will experience another age of ice.  … An analysis of deep-sea cores (Figure 40) shows that no Pleistocene interglacial has lasted more than about 12,000 years and that most have lifespans of about 10,000 years.  Statistically speaking, then, the present interglacial is already on its last legs, tottering along at the advanced age of 10,000, and can be expected to end within the next 2000 years. … [From] readings made at a worldwide network of weather stations, Mitchell was able to show that global climate has been cooling since 1940 (Figure 44).”

Sagan et al., 1979: “Observations show that since 1940 the global mean temperature has declined by ~0.2 K, despite an accelerated increase in the carbon dioxide content of the atmosphere. Extrapolation of present rates of change of land use suggests a further decline of ~1 K in the global temperature by the end of the next century, at least partially compensating for the increase in global temperature through the carbon dioxide greenhouse effect, anticipated from the continued burning of fossil fuels.”

Hoyt et al., 1979: “Conclusions: The trends in [anthropogenic] atmospheric transmission at the three locations examined in this paper are very small, perhaps nonexistent, and generally not statistically significant. If the trends in atmospheric transmission and hence anthropogenic aerosols are small near their presumed sources, then the global increase in aerosols must be very small indeed. Consequently, the effects of anthropogenic aerosols on climate is probably negligible.

There now appear to be two schools of thought concerning anthropogenic aerosols. One school argues that their increase has caused much of the observed cooling of the Northern Hemisphere since 1940. Some proponents of this viewpoint are Bryson and Dittberner (1976) and Budyko (1969).  The other school of thought contends that there is no evidence for an increase in anthropogenic aerosols on a global scale and hence they are unlikely to be important climatically.  Proponents of this viewpoint include Ellsaesser (1975), Dyer (1974) and Landsberg (1975).  The results of this paper support the views of the latter.  A recent study by Jones and Jiusto (1980) also indicates the impact of urban areas on climate is undetectable in most cases.”

Post, 1979: “Concern over the vulnerability of a heavily populated world to climatic fluctuations affecting harvests and world food supply has emerged only recently. This concern has been stimulated by anomalous weather patterns beginning with the colder winters in Europe and North America in the 1960s, the Indian monsoon failures and droughts in the Soviet and Chinese grainlands in that decade and since, and the drought which continued for many years in Africa and brought chaos to the Sahel and Ethiopia.  But, despite the computer revolution in meteorology, no generally accepted theory of climatic change to inform the future exists at this time.”

Brinkmann, 1979: “Concern about the impact of the recent downward trend in the average surface temperature for the ‘Northern Hemisphere’ (Reitan, 1974; Angell and Korshover, 1975) on the world food supply has led to an increasing interest in possible changes in the length of the growing season (NRC, 1976; NRC, 1977).”

Idso, 1980: “The mean global increase in thermal radiation received at the surface of the earth as a consequence of a doubling of the atmospheric carbon dioxide content is calculated to be 2.28 watts per square meter. Multiplying this forcing function by the atmosphere’s surface air temperature response function, which has recently been determined by three independent experimental analyses to have a mean global value of 0.113 K per watt per square meter, yields a value of ≤ 0.26 K for the resultant change in the mean global surface air temperature. This result is about one order of magnitude less than those obtained from most theoretical numerical models, but it is virtually identical to the result of a fourth experimental approach to the problem described by Newell and Dopplick. There thus appears to be a major discrepancy between current theory and experiment relative to the effects of carbon dioxide on climate. Until this discrepancy is resolved, we should not be too quick to limit our options in the selection of future energy alternatives.”

Bryson and Goodman, 1980: “Since the measured values of direct solar radiation decreased about 5 percent during the 1945 to 1975, the surface mean temperature should have decreased 6 to 10 K during this time if only the solar constant varied. This is clearly much larger than the 0.3 K or so [of cooling] that was observed.  … From 1945 to 1970, the annual eruption numbers roughly doubled from 16 to 18 per year to 37 to 40 per year. During the same interval, the aerosol optical depth also roughly doubled. This is in good agreement with the observations of Hammer, who reported a doubling in the amount of nonorganic impurities deposited on the Greenland Ice Sheet between times of low and high volcanic activity based on ice core analysis for the past 300 years.”

Chaston, 1980: “Much of the Northern Hemisphere experienced a dramatic upsurge in snowfall during the 1970s as compared with the previoius decades. … Whether the “Snowy Seventies” heralded the dawn of a major cooling trend or is merely a temporary anomaly is highly debatable. One may ask fifty meteorologists for his/her opinion on climatic change and inevitably receive fifty differing opinions. This is why meteorology is so exciting: even with relatively advanced computer programs and the complete set of equations of motion of the atmosphere, we are far from truly understanding the mechanics of Mother Nature. What we do know is that, anomalous or not, the 70s saw a small fall in global temperature accompanied by a dramatic increase in Northern Hemisphere snowfall.”

Kotlyakov, 1980: “His latest results (Kukla et al., 1977) indicate clearly a cooling of most of the Northern Hemisphere in the period from 1950 to 1975, reaching 0.1-0.2°C per decade (Fig. 3).”

Gordon, 1980: “Recent climatic trends in the Arctic have been characterized by a general cooling between the mid-1950s and the late-1960s, followed by a return to warmer conditions in the early 1970s (refs 1,2). Throughout the Canadian Arctic Archipelago and at Thule in north-west Greenland a marked decrease in summer temperature occurred after 1963, and winter precipitation increased. These changes were accompanied by a lowering of the average July freezing level height by as much as 500 m (ref. 5), decreased glacier mass loss and increased glaciation. Here I report similar climatic trends in West Greenland and demonstrate different glacier responses, in particular an advance of cirque and small valley glaciers since about 1968, contrasting with a simultaneous retreat of larger valley and icefield outlet glaciers.”

Agee, 1980: “Evidence has been presented and discussed to show a cooling trend over the Northern Hemisphere since around 1940, amounting to over 0.5°C, due primarily to cooling at mid- and high latitudes. Some regions of the middle latitudes have actually warmed while others, such as the central and eastern United States, have experienced sharp cooling. A representative station for this latter region is Lafayette, Ind., which has recorded a drop of 2.2°C in its mean annual temperature from 1940 through 1978. The cooling trend for the Northern Hemisphere has been associated with an increase of both the latitudinal gradient of temperature and the lapse rate, as predicted by climate models with decreased solar input and feedback mechanisms. … Observations and interpretation of sunspot activity have been used to infer a direct thermal response of terrestrial temperature to solar variability on the time scale of the Gleissberg cycle (90 years, an amplitude of the 11-year cycles). Measurements at the Greenwich Observatory and the Kitt Peak National Observatory, as well as other supportive information and arguments, are presented to hypothesize a physical link between the sunspot activity and the solar parameter. On the time scale of the Gleissberg cycle when the mean annual sunspot number exceeds 50 it is proposed that global cooling may be initiated due to the decreased insolation. This is also supported by umbral-to-penumbral ratios computed and interpreted by Hoyt (1979a).”

Magill, 1980: “There is no way of determining, however, whether or not the world is entering into another major ice age or if the present cooling of temperatures is simply a pause in the warming trend that began in the mid1800s.  At present, insufficient knowledge is available on the delicate balance among the various interacting factors controlling climate to determine precisely the future course of climate.”

Jones et al., 1981: “There is evidence that the long-term cooling that characterized the 1940’s, 1950’s and 1960’s has ended. Warming began in the mid to late 1960’s in winter and spring, in the mid 1970’s in autumn and later in summer. Year-to-year variability has been particularly pronounced during the 1970’s. For example, 1972 was the coldest winter since 1918, yet 1980 and 1981 were among the five warmest winters during the last 100 years. There is, as yet, no statistical reason to associate the recent warming with atmospheric CO2 increases.”

Kukla and Gavin, 1981: “Autumns in the Northern Hemisphere during the 1974–78 pentad were substantially cooler than in the pentad ending in 1938 [1934-’38].  Zonally averaged surface air temperature in October along latitude 80°N was 4.8°C lower, while summers were 0.6°C warmer. The recent pentad is cooler between 20 and 80°N in all seasons except spring when virtually no change was detected. The largest temperature difference was observed in autumn and winter in the high latitudes, which is a region of negative surface heat balance.”

Gordon, 1981: “Lichenometric dating suggests that the maximum recent extent of cirque and small valley glaciers occurred before about A.D. 1850, although there is evidence for more extensive valley glacierization before about A.D. 1745. Between about 1850 and about 1968/69 progressive recession of the glaciers was interrupted by brief periods of reactivation during the 1880s, 1920s, and early 1940s. Since about 1968/69 the glacier fronts have advanced by up to 158 m following a marked climatic recession [cooling] during the 1960s and early 1970s. In general, fluctuations of the glaciers have been in sympathy with prevailing climatic trends and show a relatively rapid response following temperature changes and a lagged response of at least 9 yr following precipitation changes. Fluctuations of larger valley and icefield outlet glaciers are out of phase with the others which may reflect a greater time lag of 20 to 30 yr in their response to precipitation changes.”

Potter et al., 1981: “While the model computed a surface cooling of 0.6 K for the Northern Hemisphere, the global mean of ~0.2 K was substantially less than the 1 K [of anthropogenic global cooling] suggested by Sagan et al. We infer that man’s cumulative impact on planetary surface albedo over the past few thousand years has had a small and probably undetectable effect on global climate.”

Arrigo, 1982 : “The decade of 1971-80 was 1.5°F cooler than 1931-40. The latest 40-year period of general cooling in annual values is a result of down trends in winter, summer, and fall seasonal temperatures”

Idso, 1982: “A potential negative feedback relationship between atmospheric relative humidity and surface air temperature is described. Together with a recently proposed negative feedback mechanism involving atmospheric CO2, the phenomenon may be sufficient to prevent the global ice catastrophes which are a common prediction of many climate models following initial development of ice age conditions, and could well be of importance for the problem of the cool sun in Earth’s early history.”

Kelly et al., 1982: “It is now generally accepted that the mean surface air temperature over the landmasses of the Northern Hemisphere, averaged over the year, rose by ~0.7°C from 1880 to ~1940 and then fell by ~0.2°C by the 1960’s. … The warming [since the mid-1960s] has, however, only resulted in a return to temperature levels of the late 1950’s and early 1960’s, and must, at present, be considered short term (Wigley et al., 1981). It could represent a temporary halt in the long-term cooling trend; the beginning of a period of relatively stable, i.e., trend-free climate; or the beginning of a long-term warming trend.

“The 1880’s [in the Arctic] was the coolest decade during the study period, and was followed by a warming of 0.65°C to the 1900’s. Cooling then occurred; the average temperature during the 1910’s was ~0.45°C below the 1900’s. This cooling is less noticeable in the Northern Hemisphere average temperature d. Rapid warming affected the Arctic during the late 1910’s and 1920’s, with the average temperature peaking during the late 1930’s. A warming of ~1.60°C occurred between 1917 and 1921. While the average temperature of the Arctic was at a maximum in the 1930’s, the average temperature of the Northern Hemisphere was greatest in the decade of the 1940’s. After the 1930’s, temperatures fell: a drop of 0.85°C occurred up to the 1960’s.”

Verma et al., 1984: “Dewey and Heim (1981) have studied variations in N.H. seasonal snow cover based on satellite observations and have found that there was an overall increase in snow-cover area from 1966 to 1980. They also noted that there has been a trend toward earlier, more extensive snow cover in the fall and slower ablation in the spring. Their observations are supported by the results of a model study conducted by Choudhary and Kukla (1979) where-in they noted that the addition of more CO2 to the atmosphere could significantly reduce the shortwave energy absorbed at snow and ice surfaces and thus delay the recrystallisation of snow and dissipation of pack-ice, resulting in a cooling rather than a warming effect. They additionally noted that this process may contribute to an extension of snow and ice seasons marked by delayed snowmelt in spring, and early snow deposition in autumn.   Thus, during the last 3 decades, larger winter cooling anomalies, supported by observations and model studies, have greatly influenced the climate pattern – made it cooler and unstable.”

Karl et al., 1984: “An appreciable number of nonurban stations in the United States and Canada have been identified with statistically significant (at the 90% level) decreasing trends in the monthly mean diurnal temperature range between 1941–80.”

Klige, 1985: “The author attempts to quantify the amount of water released (by various means) by the world’s glaciers, and to determine the variations in these figures provoked by the warming trend which was observed for the first half of this century, and the cooling trend observed in the 1960s and 1970s. Unfortunately Antarctica has generally had to be excluded from these calculations since data on a number of components of the water balance of the Antarctic Ice Sheet are simply not available. Perhaps most significant are the author’s predictions that the anticipated future rise in air temperatures will provoke increased precipitation and hence increased accumulation on the major ice sheets. Even despite increased melting in coastal areas of Greenland and Antarctica the net effect will be a positive mass balance and ultimately a lowering of sea level”

Skeeter, 1985 : “However, even though the amount of carbon dioxide in the atmosphere has continued to rise, cooling temperatures have been reported since about 1940. The first study to report this reversal in temperature trends was done by Mitchell in 1961. Mitchell updated Willett’s work through the 1950s and found that temperatures had fallen 0.2°C by the late 1950s from a peak in the early 1940s.  In 1970, Mitchell stated that by the late 1960s global temperatures had fallen 0.3°C from the peak in the 1940s, approximately one-half of the prior rise.  Similarly, Budyko reported that temperatures in the Northern Hemisphere fell 0.3-0.4°C between 1940 and 1976.  Summaries by Schneider and Dickenson, Kalnicky, Robuck, Roberts, and Agee all report Northern Hemisphere temperatures declines by at least 0.5°C since the 1940s.  In summary, Gribbin states “In worldwide terms, we are in a situation where the earth is cooling more quickly than it warmed up earlier this century.  From the above it is clear that the general consensus in the recent literature is that there has been a cooling in the Northern Hemisphere since the early 1940s.”

Hoffert and Flannery, 1985: “As described more fully in the accompanying state-o f-the-art report on the Detecting the Climatic Effects of Increasing Carbon Dioxide (see Chapter 4 by Wigley et al. 1985), there is no clear indication of a monotonic warming over this period [1880-1980], as would be anticipated from the observed buildup of CO2 in the atmosphere.”

Stewart and Glantz, 1985: “ One could effectively argue that in the early 1970s the prevailing view was that the earth was moving toward a new ice age. Many articles appeared in the scientific literature as well as in the popular press speculating about the impact on agriculture of a 1-2°C cooling. By the late 1970s that prevailing view had seemingly shifted 180 degrees to the belief that the earth’s atmosphere was being warmed as a result of an increasing CO2 loading of the atmosphere.”

Bryant, 1987: “Conclusions: The scenario of a CO2-warming globe contains many uncertainties. The warming of the atmosphere is not an established fact, and even if it was there may be no need to invoke increased atmospheric CO2 or other ‘greenhouse’ gases as the cause when such warmings have been a part of our temperature time series historically. If temperatures are increasing, sea-levels may not be rising globally because of melting near-polar ice or thermal expansion of oceans. Evidence now coming to light indicates that it is extremely difficult, if not impossible, to delineate an eustatic signature above tectonically or climatically induced ones. In this regard, sea-level rise may not be a hazard of the future except in local areas where isostatic factors are causing the land to sink (areas of subsidence) or the ocean to rise (for instance, areas affected by more frequent El Nino-Southern Oscillation events). … A common factor underpinning our uncertainties about a CO2-warming atmospheric scenario is that the Earth is not covered adequately with enough data points to evaluate the scenario conclusively. Even where geophysical time series are available, they are clouded by the inherent fluctuations of their variances.”

Ramanathan et al., 1989: “Water vapour and cloud are the dominant regulators of the radiative heating of the planet. ..The greenhouse effect of clouds may be larger than that resulting from a hundredfold increase in the CO2 concentration of the atmosphere. … The size of the observed net cloud forcing is about four times as large as the expected value of radiative forcing from a doubling of CO2. The shortwave and longwave components of cloud forcing are about ten times as large as those for a CO2 doubling.

Lindzen, 1989: “Judging from much of what one sees in the media, there is little doubt about the coming global warming. The question is simply whether it will be unprecendentedly bad (1.5° warming) or worse (5°C warming). To quote from Stephen Schneider at a recent conference hosted by Robert Redford at Sundance, Utah, ‘there will be no winners.’ The Democratic National Committee has made dealing with the warming an issue on a par with dealing with the drug problem. Still, if one visits the Center for Meteorology and Physical Meteorology at M.I.T. (where I happen to teach) one encounters a general attitude of skepticism. There is a common feeling at M.I.T. and elsewhere, that this question has become enmeshed in hysteria. Such environmental scares are not unheard of. In recent years we have confronted the destruction of the ozone layer by supersonic transports, the coming ice age (popular in the early 70s, and the subject of Stephen Schneider’s book, The Genesis Strategy), and nuclear winter. All these scares have withered for good reason. It is only fair to add that none of these earlier scares has been put forth with the vehemence associated with ‘global warming.’ In this paper, I propose to go over the scientific bases for our present concerns. I hope to show that both the data and our scientific understanding do not support the present level of concern.”

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