Atmospheric absorption spectra?

[Jeff M]

Absorption spectra are the charachteristic "lines" which are absorbed (or emitted, if gas is heated) by a gas. Each type of molecule (like CO2 or H2O) absorbs specific portions of the infrared spectrum. This chart shows how much of each portion of the infrared spectrum is absorbed, and by which gas in the atmosphere
http://www.globalwarmingart.com/wiki/Image:Atmospheric_Transmission_png
Notice that :
- the bands affected by CO2 are already ~100% absorbed
- The band where the outgoing infrared is allowed, is weakly affected by water vapor
- The smaller chart at the side shows 40 watts directly radiated back to space, 195 watts of thermal radiation - this would be due to conduction and convection transferring heat to upper atmosphere.

Now , nobody seriously suggests that increasing CO2 will directly increase the greenhouse effect. The hypothesis is that increased CO2 will cause increased water vapor and that will increase the effect. But :
- Gases rise as they warm (convection). Water vapor is 18/28ths (by mole wt.) of the other gases, so it rises well - until it reaches an altitude cool enough to condense it (which releases heat)
-Water vapor content varies (humidity). areas with low hunidity are that way for reasons. The bitter cold of the upper atmosphere or the arctic. The heat of the deserts ( causes increased convection of H2O)
- Although water vapor only reaches to 25000 feet (the highest clouds) , 2/3rd of the atmosphere is below 25000 feet - barometric pressure decreases rapidly. So is 2/3rds of whatever greenhouse effect
is due to other gases.
- increased water vapor means an increase in the evaporation/ convection/ condensation cycle - a very effective negative feedback. If it's cold out, the wator vapor ends up being snow over wider areas- ( has anyone noticed? )increased albedo is another negative feedback. And increased albedo from more cloud cover.

Nobody seriously questions that CO2 is a greenhouse gas, or that there's a greenhouse effect. Nor that global warming has been occuring since the little ice age ended ~1860. Statements that "scientists don't question greenhouse effect or global warming" are misleading.

The questions :
- Is all that beyond the understanding of voters?
- shouldn't the media and schools be talking about the facts of the matter, rather than scary speculations about inundated cities & such?
- Since the energy policies needed to fight AGW would make 4$ gasoline look like a warning shot, shouldn't there be serious debate, including educating the public?
- If 4$ gas was a warning shot, wouldn't cap & trade be like having the green gang ( or gang green, if you prefer) shoot us in the foot, after the warning shot?
- Since gas prices began receding immediately after pres. Bush forced discussion of the idea of talking about increased oil drilling in the USA, shouldn't we send him a thank you note, every time we buy gas for 1.50?

 

[Ben O]

It does seem that the scientific basis for AGW has been blown out of proportion. We know that the "enhanced greenhouse effect" is very minor for the reasons you outlined and theories about other warming mechanisms like radiative transfer and some complicated dynamic occuring in the upper layer of the atmosphere are speculative and incomplete.

I've seen the research from Heinz Hug which shows that the atmosphere is virtually completely opaque to the absobtion bands of CO2 implying that additional CO2 will have a negligible effect on climate, while other skeptics suggest that CO2 doubling may be enough to cause a measurable effect.

With so many careers being built on climate change, it's hard to separate fact from fiction these days.

 

[Benjamin]

(a) You'd still get an increase in greenhouse warming even if the atmosphere were saturated, because it's the absorption in the thin upper atmosphere (which is unsaturated) that counts (b) It's not even true that the atmosphere is actually saturated with respect to absorption by CO2, (c) Water vapor doesn't overwhelm the effects of CO2 because there's little water vapor in the high, cold regions from which infrared escapes, and at the low pressures there water vapor absorption is like a leaky sieve, which would let a lot more radiation through were it not for CO2, and (d) These issues were satisfactorily addressed by physicists 50 years ago, and the necessary physics is included in all climate models.