This is important because scientists are concerned that unchecked global warming could cause already dry areas to get drier. (Global warming may also cause wet areas to get wetter.) Cao and Caldeira’s findings indicate that reducing atmospheric carbon dioxide could prevent droughts caused by climate change.
Via press release in Eurekalert, from Stanford, and the Carnegie Institution:
Cutting carbon dioxide helps prevent drying
Washington, D.C.—Recent climate modeling has shown that reducing the concentration of carbon dioxide in the atmosphere would give the Earth a wetter climate in the short term. New research from Carnegie Global Ecology scientists Long Cao and Ken Caldeira offers a novel explanation for why climates are wetter when atmospheric carbon dioxide (CO2) concentrations are decreasing. Their findings, published online today by Geophysical Research Letters, show that cutting carbon dioxide concentrations could help prevent droughts caused by global warming.
Cao and Caldeira’s new work shows that this precipitation increase is due to the heat-trapping property of the greenhouse gas carbon dioxide in the atmosphere. Carbon dioxide traps heat in the middle of the atmosphere. This warm air higher in the atmosphere tends to prevent the rising air motions that create thunderstorms and rainfall.
As a result, an increase in the atmospheric concentration of carbon dioxide tends to suppress precipitation. Similarly, a decrease in the atmospheric concentration of carbon dioxide tends to increase precipitation.
The results of this study show that cutting the concentration of precipitation-suppressing carbon dioxide in the atmosphere would increase global precipitation. This is important because scientists are concerned that unchecked global warming could cause already dry areas to get drier. (Global warming may also cause wet areas to get wetter.) Cao and Caldeira’s findings indicate that reducing atmospheric carbon dioxide could prevent droughts caused by climate change.
“This study shows that the climate is going to be drier on the way up and wetter on the way down,” Caldeira said, adding:”Proposals to cool the earth using geo-engineering tools to reflect sunlight back to space would not cause a similar pulse of wetness.”
The team’s work shows that carbon dioxide rapidly affects the structure of the atmosphere, causing quick changes precipitation, as well as many other aspects of Earth’s climate, well before the greenhouse gas noticeably affects temperature. These results have important implications for understanding the effects of climate change caused by carbon dioxide, as well as the potential effects of reducing atmospheric carbon dioxide concentrations.
“The direct effects of carbon dioxide on precipitation take place quickly,” said Cao. “If we could cut carbon dioxide concentrations now, we would see precipitation increase within the year, but it would take many decades for climate to cool.”
Recently, it was found that a reduction in atmospheric CO2 concentration leads to a temporary increase in global precipitation. We use the Hadley Center coupled atmosphere-ocean model, HadCM3L, to demonstrate that this precipitation increase is a consequence of precipitation sensitivity to changes in atmospheric CO2 concentrations through fast tropospheric adjustment processes. Slow ocean cooling explains the longer-term decrease in precipitation. Increased CO2 tends to suppress evaporation/precipitation whereas increased temperatures tend to increase evaporation/precipitation. When the enhanced CO2 forcing is removed, global precipitation increases temporarily, but this increase is not observed when a similar negative radiative forcing is applied as a reduction of solar intensity. Therefore, transient precipitation increase following a reduction in CO2-radiative forcing is a consequence of the specific character of CO2 forcing and is not a general feature associated with decreases in radiative forcing.
If someone will send me a copy of the paper (willis [at) surfacetemps.org) I’ll be happy to take a look.
The beauty of the paper seems to be that it describes a situation (a quick reduction in atmospheric CO2 concentration) that, as far as I know, hasn’t been observed in nature …
So usually I’d ask “Where’s the comparison of the model with the observations?” But it appears they’ve sidestepped that very neatly.
But heck, I could be wrong, it’s just a press release and an abstract. The paper may say something different.
w.
One little factoid is that the turnover of water vapour in the atmosphere is each 9 days.
40 times more precipitation falls each year than there is water vapour in the atmosphere at a specific time.
This turnover rate means that it should just get wetter period. On average, there should be 2% to 7% more precipitation per year.
There is no rationale for it to get dryer anywhere. The last time it was a little warmer at the Holocene Optimum 8,000 years ago, the Sahara greened up due to the extra rainfall. There were even large lake bodies and Hippos. The deserts of Central Asia were forested and the Australian desert had much more rainfall. When it cooled down about 5,000 years ago, the Sahara dried up and populations were forced south and/or east into the Nile River valley for example.
The last time it was 3C warmer, 10 million years ago, the entire planet was one big forest. Grassland or savanna only occurs where it is dryer and/or cooler and there was hardly any grassland conditions on the planet at all.
Drought schmout! In areas known for low water equivalent snow pack in the past El Nino years, we are now in up to our hoo hahs and tittoos in high water equivalent snow pack.
Looks like yet another set of scientists drunk on grant money.
Must we arm chair coaches always be the stern teacher? Apparently. Let me see the hindcast. There are plenty of great floods in the past century with precip records. Cough it up. And no splicing.
It’s the CO2 placebo effect. It does what you think it does.
this is just nonsense
just more “models”
no actual tests and measurements
http://www.letterdash.com/HenryP/more-carbon-dioxide-is-ok-ok
Is there any other branch of ‘science’ that develops so much theory, yet tests so little of it?
The tropospheric hot spots are there. Problem is, they come and go with short-term weather systems and longer term weather pattern variations, but this ground to tropopause layer is not showing an overall long-term relatively faster climate warming trend at its upper reaches compared to its lower reaches. No one has found a permanent and growing hot spot.
Could it be because the heat is escaping through vertical splitting events at the tropopause caused by jet stream perturbations?
“In the higher regions of the tropopause, temperature is about -60 °C. At this heights, relatively small bands with very high wind speeds (up to 500 km/h), the jet streams, occur. In this regions very important processes take place that cause vertical splitting, decomposition and new formation of the tropopause.”
http://www.kowoma.de/en/gps/additional/atmosphere.htm
“The results of this study show that” THIS MODEL INDICATES THAT “cutting the concentration of precipitation-suppressing carbon dioxide in the atmosphere would increase global precipitation” IN THE MODELLED VERSION OF THE PLANET.
There, that’s corrected it.
Richard
Recent climate modeling has shown that reducing the concentration of carbon dioxide in the atmosphere would give the Earth a wetter climate in the short term. . . . Their findings, published online today by Geophysical Research Letters, show that cutting carbon dioxide concentrations could help prevent droughts caused by global warming.
Huh. The results of modeling are not “findings”—they are not evidence. They don’t “show” anything. Now, if they were backed by observations, that would be a different matter. But so far, they haven’t proven that their models accurately depict the real world. I don’t take climate models at face value, too many instances of cosmetic—and wholesale—surgery for that.
Mike says:
March 26, 2011 at 5:22 am
Just for anna v:
The best ‘advanced’ answer ss comes up with is: “the discrepancy is most likely due to data errors”
So when their hypothesis is tested with real-world data and it disproves their hypothesis, it MUST be ‘data errors’, because of course, their models CAN’T be wrong!
Real scientists accept the measured data and adjust their hypothesis. AGW ‘believers’ come up with fantastic tales explaining away contradictory data(or just keep ‘adjusting’ it, again & again).
Points out the difference between skeptics & AGW believers – some believe real measured experimental data and others believe Sim-Climate computer games.
to paraphrase a line from the Dirty Dozen …
Thats a pretty theory you’ve got there, but can it fight ?
Mike says:
March 26, 2011 at 5:18 am
I have no idea if the results are correct, but what they are doing is not inherently illogical as some people here seem to think.
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Ian Holton says:
March 26, 2011 at 1:32 am
This shows that global precipitation is increasing with increasing with increasing CO2 http://www.bom.gov.au/cgi-bin/climate/change/global/timeseries.cgi?graph=global_r®ion=global&season=0112&ave_yr=0,
then they say that …
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Mike, it is illogical to base assumptions made by a model which isn’t grounded in reality. Ian has graciously offered direct refutation to these inane prognostications.
Anthony, I’m getting the feeling that many of your readers still aren’t convinced about the wetdry dynamic. And while the authors of this ……….. study entirely missed the mark, they themselves inadvertently described it perfectly.
“Cao and Caldeira’s new work shows that this precipitation increase is due to the heat-trapping property of the greenhouse gas carbon dioxide ……………..
an increase in the atmospheric concentration of carbon dioxide tends to suppress precipitation.”
And that ladies and gentlemen is wetdry! What’s not to understand? This is exactly as Dr. Syme intuitively knew. Apparently, the dept. of lexicography has some spies and others are beating him to publication.
For those that still don’t understand or can’t get their head around this, this post may help, http://wattsupwiththat.com/2011/03/25/now-its-climate-change-to-be-killing-the-joshua-trees/#comment-629090
CO2 will cause it to be hot, cold, wet, dry, more violent, responds quickly but takes a long time and so on. It reminds me of the movie where the guy asks the prostitute what’s your name. She says what ever you want it to be, as they, slightly intoxicated, walk into a dark blind alley.
David Stockwell proved that CSIRO’s drought model predictions were backwards. See: Show us your tests: Australian drought models i.e., Australian rainfall was actually increasing, contrary to CSIRO’s predictions of decreasing rainfall.
This is another excellent opportunity for a brilliant statistician to test the validity/incoherence of climate change (aka catastrophic anthropogenic global warming).
Unfair Andrew! You deliberately picked a CAGW hypothesis backed only by flimsy modeling, easily falsifiable by just looking out the window. Try picking on one of the more robust CAGW findings. Wait a minute. There aren’t any. Never mind.
All arguments are about higher temperatures globally, not actually higher CO2. So the questions should be:
In historic times such as the MWP, the Roman WP, the Minoan WP, were dry areas drier and wet areas wetter? At the same time, were moderate areas “more” moderate for life in general? Considering both from the historical records, was there more negative (for man, animal and plant life) areas or positive areas?
All this work by so many people using models when the historical data shows how it was one way and the other!
Oh, right. Never has it been warmer than today. Not in 600,000 years. (Didn’t we get rid of that lie, though?)
Seriously: what “is” going to happen has already happened within recorded times. We do not need to postulate, model and conjecturize. The Chinese, Japanese and Arabs have very long records of what was going on before the Westerners learned to write, let along write computer code. Is this an ego problem – if we didn’t explain it, it means nothing?
Here’s a quote I found on a site about a different topic yesterday that sums this up nicely:
So they are saying that if we decrease precipitation suppressing CO2 dry areas will experience increased drywet and wet areas will likewise experience increased wetdry.
I may have this backwards but that really doesn’t matter since these models definitively without a doubt show that . . . . well, I’m not actually sure what they show, but I am sure these unscientist are trying to call attention to the Climate/Weather Emergency that may or may not happen.
Where are all the AGW believers on this thread?
Its too silly to touch.. isn’t it!?!
Its “intellectuals” like these guys that would put “OMG” and “LOL” in the dictionary.
Apparently the sceptical world has been looking for the wrong item. No hot spot exists because its been masked. One must look for a coldhot spot as in dryerwetter moisture caused by dehydrated water found in oceanic waves of various sizes. Don’t be misled by hotcold spots as they are fairly common and literally found in most atmospheric places along with wetterdryer air conditions.
/sarc as opposed to /nosarc and /unintentionalsarc just to be clear about it.
Thats some catch that Catch-22!
Explanation: Used when talking about the necessity of making a choice that is going to have a negative outcome no matter which decision is taken.
“There was only one catch and that was Catch-22, which specified that a concern for one’s own safety in the face of dangers that were real and immediate was the process of a rational mind. Orr was crazy and could be grounded. All he had to do was ask; and as soon as he did, he would no longer be crazy and would have to fly more missions. Orr would be crazy to fly more missions and sane if he didn’t, but if he was sane, he had to fly them. If he flew them, he was crazy and didn’t have to; but if he didn’t want to, he was sane and had to. Yossarian was moved very deeply by the absolute simplicity of this clause of Catch-22 and let out a respectful whistle.
“That’s some catch, that Catch-22,” he observed.
“It’s the best there is,” Doc Daneeka agreed.”
http://en.wikiquote.org/wiki/Catch-22
Studies during gelogical periods show drier weather overall where periods of much colder ice ages occur. This is reflected in proxies around the world and in contradiction with this model study. These colder periods had levels of atmospheric CO2 much lower and much higher than nowadays. The latter only occuring going back, when the continental plates were in a much different position to now. These findings also supported wetter poles and tropics when warmer, but drier mid-lattitudes. When cooler had drier poles and tropics, but with wetter mid-lattitudes. The reason for many contridictions in these studies is because not using established facts and making it up as go along.
Ian Holton says:
March 26, 2011 at 1:32 am
“…Excuse me, my mind has become befuddled with confusing contradictions and opposite statements!……what does it cause and what does not it cause?!…….Me thinks they(AGW scientists) have lost the plot!!!”
Like all good communists, they are romantics at heart. As their credibility has tanked, they have switched from prose to poetry.
Mike says:
March 26, 2011 at 5:18 am
“I have no idea if the results are correct, but what they are doing is not inherently illogical as some people here seem to think.”
Inherently illogical? That is a strong standard. How about just illogical? That would be contradictory on its face, right? Well, it asserts that increasing CO2 concentrations cause more precipitation and suppress precipitation. That is “prima facie” contradictory. Check out:
James Sexton says:
March 26, 2011 at 7:30 am
Bob Barker says:
March 26, 2011 at 5:04 am
“I think a moratorium on funding studies using climate models would be in order.”
Except for the purposes of “opera buffa.”