>> 'Water vapor accounts for almost all of the greenhouse effect'

yes it dwarfs CO2.

However as the CO2 is going up, water vapour is going down.  Fully formed cloud is becoming harder to find in the skys, and "ice clouds" are on the increase.

Thus the scientific analysis leads to a dilemma.

[In my view the level of CO2 is an indicator only, indicating the amount of oil released into our environment]

LOL, is it global warming (real warming) or is it  a tipping towards clear skys all year long and really is an underlying global cooling.

IMO, global cooling is actually happening and well, look out...  Agricultural land prices will tumble.. and...

And that decrease in cloud cover supports the theory of Svensmark that variations in cosmic ray activity (documented) can affect cloud cover (demonstrated in lab) and the cloud cover is what's accounting for changes in global warming ( papers published from 1995 onward).

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Hi Gar,

That's a good idea, it is such a short article I don't see how it could hurt.

"The problem with people who have no vices is that they tend to have some pretty annoying virtues." -- [paraphrased] Elizabeth Taylor

Thanks Cody.

And Greyflcn: thanks for the correction.

WhatI don't understand is the water vapor that should be the greatest greenhouse gas. I can imagine that in the models used to calculate global warming this is included, now I have been searching on why this is not mentioned that often. I found some arguments that the humidity increases by GHG which increase the global warming by water vapor which creates a cycle. Now what I don't understand is, if water vapor is the largest GHG does the climate change by water vapor not significantly increase the amount of water vapor in the spheres, more than the greenhouse gasses? So does the water vapor cycle, or the cycle of sun temperature-water vapor is not significantly larger than the water vapor-GHG cycle?

Hi svstudent,

The reason for the difference is in the atmospheric residence time of a water vapour pulse vs a CO2 pulse.  Because CO2 survives he seasonal cycles it has the chance to alter the climate, lasting many decades ensures it does.  Water vapour will just not stay artificially elevated long enough to do that.

"What if this weren't a hypothetical question?" -- unknown

Sometime many of you are forgetting to mention it is  important how water vapor is being used in the atmosphere. Even though our temperatures have went up since 1975, low level clouds have decreased while high level clouds have increased.

  So water vapor is magic, It comes and goes and does nothing in the atmosphere to warm or cool , because its "always" leaving.... no wait its there... no its gone...no its there... oh heck... I give up it seems to always be there at 95%. Without it the planet would be frozen. The 5 percent of other gases couldnt do a thing by themselves. Ahh but for Co2 we have ice core samples that show it does not force warmer temps and only follows, and we have moved into the next ice age no matter how high the Co2 amount gets.. So we know Co2 is not a cause of warming. And we know that realscience.com is the group of computer modeling peeps who made up the false claim that we are going into a warming in 50 years. They have their ego to protect at all costs, even when the science goes agaisnt them.  We havent had any earth warming since 1998. ( If you take the temps from 1998 until now the average is a cooling).
  We had a great warming from 1900 thru the 1930's when we didnt have the man made Co2 amounts to cause it..nor the cars to create it. Then we had a cooling from the 1940's up to the 1970's and that was during a time of more Auto's on the road. Again Co2 didnt make it hotter or do anything else to effect the natural changes.
 I see no effect change from any Co2 and nasa has reported that Co2 levels have gone backwards and not constantly increasing.
  Better get your sleds ready!

"Lets go surfin'

It's that simple.

Water vapor spends on average about 2 weeks in the troposphere. And any excess condenses, and rains out.

The only cause for variation in the water vapor content of the troposphere is if some other forcing causes a warming in the troposphere.

Which actually gives a great explanation how a targeted warming in the troposphere by CO2 accumulation can be multiplied into a rather large warming.

Can anyone comment on the magnitude of the cooling effect of water being evaporated at the surface of the earth (using surface heat) and then forming clouds at higher altitudes (emitting the heat high up in the troposphere)?  I would think that this cooling effect would increase as the temperature increases?  Certainly, water's heat of vaporization is very large and the amount of water being evaporated from the oceans is huge.  Couldn't this be a significant negative feedback that accelerates as the temperature rises?  WOuldn't it help to counter any heating caused by CO2 and other GHG  I haven't seen it in the GCMs, am I missing it??

   Any and all comments appreciated.

Thanks for this web site that I just recently got to know about. I have three questions:

Some one mentioned that water vapor traps unequally different wave lengths of radiation. Also, that trapping would easily get saturated in those wave lengths it traps. a) Is this important for forcing? b) Does it mean that forcing is rather independent of amount of water vapor in the atmosphere? c) How does CO2 behave w/ respect to the same phenomenon?

I encountered a claim that the trapping of radiation that CO2 does, takes place in the first 10 meters above ground. So, if you double CO2 concentration, the same trapping takes place in 5 meters. Therefore, there is no increase in RF with an increase of CO2 concentration. Is it so?

People seem to use computer models to compute RF's of different concentrations. Why not set up chambers and simply measure radiation penetration at different concentrations?

As a layman, two things baffle me here. Could someone explain them, fully, in layman's terms.

The first is, how on earth does the atmospheric residence time affect anything if 95% or whatever of the global warming gases in the atmosphere are water vapour?

If I take two bathtubs and fill one 95% full and leave the taps running so that the water going in is matched by the water going out of the overflow.

And fill the other 5% full and turn the taps off and leave the original water in there for years.

Why am I more likely to drown in the 5% full bath?!?!?!

And the other is statements such as:

"Water vapor is a feedback, not a forcing. That is, the amount of water vapor in the atmosphere roughly depends on how warm it is from other causes - such as other greenhouse gases. Thus the percent of global warming attributable to water vapor is irrelevant, because warming from water vapor responds to other causes, and lags them.

But, just a minute, don't even the man-made global warmers admit that, yes, while the graphs of temperature and CO2 levels look very similar, when you look at them in detail the CO2 changes lag the temperature changes.

So doesn't that mean the CO2 is a feedback not a forcing?

Actually, there's a third thing that baffles me: some man-made global warmers admit that, yes, the earth warms up first, by some unknown, mysterious, mystery, unknown means. That heats up the earth. Which releases CO2. Which heats up the earth. Which heats up the earth more. In a feedback loop. So humans, putting even more CO2 into the atmosphere, heat up the earth even more.

So it's all our fault.

But, wait a minute, if they don't know what unknown, mysterious, mystery, unknown means caused the initial warming, how do they know the same unknown, mysterious, mystery, unknown means doesn't continue and cause the ongoing warming?

Also, doesn't drops in CO2 levels lag drops in temperature.

So the end and reversal of global warmings are also brought about by some unknown, mysterious, mystery, unknown means.

So, if, basically, they don't know what unknown, mysterious, mystery, unknown means start global warming.

And they don't know what unknown, mysterious, mystery, unknown means end global warming.

How can they have a clue what unknown, mysterious, mystery, unknown means cause its increase in between the two?

Never mind that man is the cause of it!

The man-made UN global warming scientists say that they have taken lots of ice cores and measured the CO2 in them and, yup, there's a big leap in CO2 after the industrial revolution.

So it's all our fault.

But, wait a minute, didn't the scientist who ran the UN research on changes in atmospheric composition say that, oops, the man-made global-warming scientists don't make corrections for the CO2 loss from the ice cores with time and changes in their composition with increased pressure and that when you make the necessary allowances there is no appreciable change in CO2 levels from what would have been in the ice cores from pre-industrial times!

To say wator vaporization does not effect the climate is utter nonsense.  "A temporary effect?!!!"  When isn't wator vaporization occuring?  It is a constant, therefore, it has a constant effect on climate.

"Cross a liberal on duty and he becomes a man of hurtling irrationality." WFB, Jr.

Well said.  To say that the atmosphere "rains out" is completely absurd.  Water vaporization constantly replenishes and "wettens" the air.  It doesn't wait for two-week increments.

"Cross a liberal on duty and he becomes a man of hurtling irrationality." WFB, Jr.

Ok folks, what if man is an evolutionary adaptation to the ice ages.

FACT:  Ice ages are NOT normal in climate here - after all, they've only been around for 100,000,000 years - Earth's been here for 4.5B.  Thats only 2% of Earth's total history.  98% of the time - there was no ice.

FACT:  If man is an evolutionary advance, s/he sure is a strange one.  We 'evolved' bigger brains, but lost all the fur, nails and climbing ability which would protect us from natural predators.

FACT:  CO2 was higher than now at ALL times since before the ice ages.  From Day 1 of the planet right through 100,000,000 BC CO2 levels are orders of magnitude higher than they are now.  Earth was warmer - with no ice.

FACT:  Ice is a 'new' factor at sea level on Earth.  

FACT:  There is more CO2 dissolved in the oceans, in coal, in crude oil, oil shale and trapped in limestone and rock than is in the atmosphere today.  However, it ALL was in the atmosphere at one point.  Oil and coal are carbon fossils.  Dead  things essentially.

THEORY:  AS all that carbon was permanently removed from the atmosphere the planet cooled off.    We got ice, snow, and then ice ages.

THEORY:  What if man, with bare skin, no hair, no claws or sharp teeth, is the evolutionary adapation of life on this planet designed to free the trapped CO2 and warm the planet back up?  WE FIRST started buring coal and oil for warmth and light since we are cold without clothing and artifical heat.

WARNING:  Beware of unintended consequences, maybe we're burning all this fossil fuel for a reason - mother Earth , Gaia, wants us too . . . .

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From what I've read, water vapour is the most significant greenhouse gas in that it is responsible for 'trapping' most of the upwelling radiation. Other species (CO2 methane etc) account for a smaller portion of the greenhouse effect.

The difference between CO2 in the post-industrial age and water vapour is that CO2 is accumulating in the atmosphere due to our industry, whereas average (global) water vapour doesn't accumulate absent any other forcing. Rather water vapour concentration in the atmosphere is a function of temperature and pressure. If the temperature/pressure goes up, more water vapour.

Because the response time of water vapour is, relative to CO2, immediate, then water vapour is seen as a feedback to other climate parameters - temperature and pressure.

According to AGW theory, CO2 accumulation is continual and rising. If this incurs higher global temperatures, then more water vapour will accompany the rise, 'trapping' more upwelling infrared and exacerbating the heating effect.

To reply to a couple of posts upthread, WV does indeed 'rain out' of the atmosphere in relatively short order when encouraged by (downwards) changes in temperature/pressure, but this happens at a local level. No one is saying that WV 'rains out' across the whole globe at the same time. Rather, WV responds locally and concentrations go up and down at different points on the globe on very short time scales.

However, with rising global temperatures, the global average concentration of WV will go up, amplifying the rise.