Tuesday, May 23, 2017

Will More CO2 Cause More Warming?

It was recently argued that Venus, which has a 95% CO2 atmosphere, is consequently suffering from runaway greenhouse gas warming.  If Venus is so hot because of its CO2, then when we add CO2, we, too will get hot. Just like Venus.

Hold on, Hoss, it's not as simple as that.  Yes, Venus has a lot of CO2.  It's also closer tot he sun and receives almost twice as much solar radiation.  It also has a much higher atmospheric pressure, nearly 90 times as high as the earth's.  Looking at Venus and trying to extrapolate Climate behavior on Earth on that basis is just plain silly.

They would have you believe that the Venusian model is just a scaled up version of our CO2 "problem."  As if the mechanism is identical between our 0.04% and the 95% of Venus.  It's not.

CO2 has an absorption peak at 15µm. This gets nothing from sunlight, because it's well out of the solar spectrum, but it's almost smack in the middle of the planetary thermal radiation band. Picks up about 8% of the energy across that band, and then re-radiates it as broad-spectrum IR. This is heat given off by the planet after being warmed by the sun.

Now the CO2 picks up a little of that IR energy all across the band. Mostly it's insignificant, because compared to the 15µm peak, it's effectively nothing. But it's NOT zero.

According to Dr. Heinz Hug, the CO2 in our atmosphere absorbs all the energy there is in this band in about 10m. Double the amount of CO2, and all you do is make it so the energy is absorbed in 5m instead. At the low levels of CO2 in our atmosphere, even at the geologically historical high of 2,000ppm, the 15µm absorption will still dominate. The shoulders of the absorption band will have a small effect, moving it from 8% to, say 10% of the planetary IR, but that still leaves 90% of the heat getting through to space.

But we only have 400ppm CO2, not Venus' 965,000ppm. The 90 atmospheres of pressure has a huge effect, because it amplifies the amount of CO2 in a given volume by 90x, making it so there's 147,737 times as much CO2 in a given volume of air on Venus as there is on Earth. Instead of it taking 10 meters to absorb all the energy in the absorptive bandpass, it now takes about 7 µm.

At that density of CO2, the out of band absorption beyond the 15µm absorptive bandpass quits being effectively zero. Yes, compared to the 15µm band, it's pathetic, but there's enough CO2 there to suck it all up, all across the band. There's no measurement of the actual absorptive coefficient of the out of band area, but it's not zero (basic microwave physics, and yes, I AM an expert in that area), and there's enough CO2 in Venus' atmosphere to saturate the planetary IR radiation band even in the out of band areas.

Basically Venus' atmosphere is opaque at the planetary IR emission frequencies. There's enough CO2 to dominate across the band, not just the sensitive 15µm area. One way to think of it is signal to noise in your FM radio, where CO2 is the noise you're trying to see a signal through. If you have a decent receiver, you can pick out a clean signal, no matter if the noise floor is 400 or 2000. That signal stands strong above it. make the noise floor 150,000 and you're not going to get a thing. It's actually the mirror of that, but the metaphor holds.

This is supported by direct measurements, because in spite of receiving nearly twice the solar radiation as Earth, Venus's black body radiation is 27.4°C cooler than Earth.

The effect of increasing CO2 in an already saturated system is zero, until you saturate the system so much that the out of band absorptive capacity starts getting felt.  Levels of CO2 that high would kill all animal life on earth (thought the plants would be real happy).

But wait, we see in the paleo atmospheric levels taken from ice cores that rising global temperatures accompany rising CO2 levels.  Common mistake in data analysis: correlation does not imply causation.  If CO2 drove the global climate, then it should be a leading indicator.  The ice core record lacks the resolution to tell if CO2 Rises before or after temperature rises.   But if it were the primary driver of temperature, we would expect CO2 and cooling temperatures to track as well. We do not see this.  What we see is a very close correlation between rising temperatures and CO2 levels, and then CO2 lags temperature in the cooling cycle, sometimes by a considerable amount.

This is exactly what we would expect is we consider the CO2 dissolved in the ocean. Gas solubility in a liquid is very temperature sensitive.  The higher the temperature, the less gas can be dissolved int he liquid. There is 10 times as much CO2 in the ocean as in the atmosphere. We would expect that if the ocean were to warm up, some CO2 would be released out of solution, causing an atmospheric rise. But as the ocean cools down, if the atmopshere and the ocean are near equilibrium it takes much longer for the CO2 to enter solution than it does to be forced out of it by temperature.  The historical levels reflect this.

Global warming doomsayers make the case that the ocean losing CO2 will make the ocean more alkaline, and we're instead seeing acidification. Rising temperatures will cause a change in pH, regardless of any CO2 loss or gain.
This fact is clearly evident when we measure the pH of water at 0°C we find it to be 7.47, but the same water at 100°C will have a pH of 6.14. There a definite corelation of pH and temperature. But CO2 levels in the ocean trail the temperature by a good bit as the ocean cools. If the ocean pH is dropping while the ocean temperature rises, this can partly be attributed to the effect of temperature, but not all.  The sudden additional of human produced CO2 does place the ocean CO2 levels out of equilibrium.  Even though the temperatures are going up by whatever mechanism, there's still more atmospheric CO2 than can be accounted for in the ocean.  

Once again, correlation does not imply causation.  Are CO2 levels rising?  Yes.  Is this reflected by a rising pH in the oceans?  Yes, and this is something that should be addressed.  Is the increase in CO2 causing a greenhouse warming of the planet.  Absolutely not.  Every watt of IR energy that's being picked up and re-radiated by atmospheric CO2 was being re-radiated at lower levels of CO2. It just doesn't get as far through the atmosphere as it used to. That's just physics. Another mechanism for the observed warming should be considered, such as variability of cloud cover, atmospheric water vapor ( a much more effective and more abundant greenhouse gas than CO2) or perturbations in solar output. 

There's also the question of the data reliability.  We're basing these measurements off of data taken for decades and even centuries.  The methods of measurement and collection have changed dramatically.  Has a measurement bias crept in?  Are the temperature tracking stations today experiencing the same local conditions as they or their forebears did 100 years ago? Formerly rural stations are now finding themselves in urban growth areas, which are known heat sinks.  Can we even trust the data, when an audit of US weather stations show that 69% of them are inaccurate by more than 2°C and do not conform to NOAA siting guidelines.

Anthropogenic global warming proponents need to address the physics of atmospheric IR absorption, and accurately show how more CO2 will affect a saturated system. They need to answer the questions of reliability of US weather stations, and by inference that of the rest of the world (assuming a first world country like the US can afford to do weather measurement as well or better than anyone else). They need to address the details of water Vapor effects on climate as thoroughly as they're trying to do to make Carbon the culprit.

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