maxwell | May 8, 2011 at 1:37 pm |
BLouis,
‘But while people cling to the unphysical “greenhouse”…
Can you explain in technical terms what exactly is ‘unphysical’ about the greenhouse theory? I’m writing a science sketch comedy act and I think this explanation would crack people up.
Sam,
‘Mainly due to presents of water (liquid and vapor) which absorbs most of the radiant energy from the sun.
That’s patently false. Just look at the absorption spectrum of liquid and vapor water on top of the solar spectrum. The solar spectrum (indicated by the colors on that picture) overlaps with the weakest portion of water’s absorption spectrum. Therefore, water absorbs almost no sunlight. There is some UV absorption, but so little sunlight is in that region that it doesn’t affect much in the atmosphere.
You actually might want to look at some data before saying something you don’t know and others know to be as false as claims come.
On top of that,
‘…ignoring the air is a good thermal insulator.’
shows you really have little to no idea how energy is transferred to the atmosphere or how climate models work. The only way to ‘insulate’ the surface of the earth is capture the emitted IR radiation that the earth gives off as a blackbody at non-zero temperature. Most of the molecules in the air of the atmosphere (O2 and N2) CANNOT absorb that energy due to very strict quantum mechanical rules on transitions between vibrational states. CO2 and water, on the other hand, CAN absorb IR radiation emitted by the earth because those rules on vibrational transitions are less severe for those molecules.
After IR absorption happens in CO2 and water molecules, collisions transfer that energy to O2 and N2 molecules which cannot easily get rid of it. Therefore, the translational energy of these molecules increases, causing an increase in the gas’s temperature, by the physical definition of temperature.
So the fact that air is a good insulator depends explicitly on the physical reality of the greenhouse effect. Therefore, if you’re using a greenhouse forcing in a climate model, you are implicitly accounting for the fact that air is not a good conductor of heat.
In bold is the part of his comment I found to be inaccurate and misleading.
After chilling a few days, I went back to make sure I didn't screw up.
I am sure that Maxwell is a very intelligent guy and much more up on molecular physics than I am. He though like many others I have seen participating in the debate, seem to miss the point of scale or significance.
The comment he rebutted mentioned the absorption of sunlight by air and water. I think I explained pretty well that as far as the oceans go, they do indeed absorb most of the sunlight and since the oceans cover about 70% of the Earth's surface, water absorbs most of the sunlight. In the air, water does not absorb most of the sunlight, it does absorb a significant amount. In the absorption spectrum that Maxwell referenced, water and water vapor appear to absorb a small percentage. The atmosphere reflects some sunlight, absorbs some and more that half of the sun's energy passes through to be absorbed or reflected by the surface. The significance of water vapor in the atmosphere to solar energy absorption depends on the total amount absorbed by the atmosphere as a whole.
In NASA's energy budget chart above, the atmosphere absorbs 16% of the incoming solar and clouds, water vapor, absorb 3%. Of the 19% of the solar incoming radiation absorbed, clouds only absorb nearly 16 percent. To me, 16% is significant, especially when the impact CO2 doubling is only about 1 percent. If you wish, 3% is 3 times greater that 1 percent. Anyway you wish to look at it, water vapor is more significant that CO2. So while Maxwell is undoubtedly a smart guy, his statement, "Therefore, water absorbs almost no sunlight," is pretty bogus.
Being a smart guy and a touch sensitive, Maxwell accused me of taking his statement out of context, accused me of being dense and basically thinks I am an idiot. I did not take his statement out of context! The rest is debatable.
When I mentioned that salt in seawater is similar to CO2 in the atmosphere. I got questioned by another denizen of the Curry blog. This denizen agrees that water absorbs sunlight, but that salt has little to do with it. I respectfully stand my ground and say phtttt. Once again, the matter of scale bites another smart guy in the ass.
While salt in seawater is not exactly the same as CO2 in air, it has a similar impact. Salt reduces the path length required for absorption as Maxwell so graciously explained in his comment on my blog. Without the salt, sunlight would penetrate deeper in the oceans making the warmer surface layer thicker or deeper if you prefer. With a deeper layer, it takes longer for the ocean to give up the heat it gains from the sun. I tried to explain in the blog post that other things, impurities, change the depth of absorption also. Those other impurities make a huge difference.
The silts contain nutrients that feed microorganisms. With the right balance of nutrients, salinity and sunlight the microorganisms thrive, the more complex organisms thrive on the small microorganisms and on up the food change. A large number of scientists have noticed that fish stocks vary closely with climate. Fish stocks may not drive climate, but the concentration of microorganisms may help drive climate. It is the chicken and the egg all over again.
As the concentration of microorganisms increase the more complex organisms that feed on those microorganisms increase to the point they overshoot the available food stocks. This depletes the abundance, changes the average penetration depth of sunlight, optimizes the conditions for a different type of microorganism, rebooting the cycle.
As conditions for the growth of different types of microorganisms optimize, the concentration depth of microorganisms changes, the average depth of sunlight penetration changes, the transfer of heat from the ocean changes. How much does this change climate? I got no clue, but if it changes the ocean heat uptake/loss by fraction of a percent, it changes climate significantly, it grows more significant as the change approaches one percent. One percent may not sound like much, but is significant when compared to a one percent increase in retention of the out going heat of the Earth, where the oceans produce about 70% of that outgoing heat.
I love simplicity, but somethings should not be overly simplified.
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