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.
Would like to see more details of said “model” study. It keep referring to “in the short term”, etc. All the evidence points to the exact opposite effect happening “in the long term”, i.e. increasing amounts of CO2 lead to warmer climates, higher humidity, and heavier precipitations.
Also, I am suspicious about such an immediate effect, as it’s taken hundreds of years and a 40% growth in CO2 over that time for some effects to start to show themselves. By how much are they suggesting CO2 be cut? I really need to see the complete details of this study and so lI’m highly skeptical about the validity of this model study until I see other similar studies come along.
****
Article says:
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.
****
By that logic, the glacial periods @ur momisugly 180 ppm CO2 should have been wetter than the interglacials @ur momisugly 280 ppm (the Amazon rainforest was a mere shadow of its present extent during the glacial periods). And there must’ve been a vast, global desert in the past when CO2 was many times its current value.
Right……..
Pamela- great explanation. Very uncooperative planet we have .
I’ll be blunt -this explanation of the wet/dry is more like as some
cleric from the Medieval Church trying to explain how many
climate scientists can dance on the head of a pin…
R. Gates says:
March 26, 2011 at 9:08 am
Would like to see more details of said “model” study. It keep referring to “in the short term”, etc. All the evidence points to the exact opposite effect happening “in the long term”, i.e. increasing amounts of CO2 lead to warmer climates, higher humidity, and heavier precipitations.
Also, I am suspicious about such an immediate effect, as it’s taken hundreds of years and a 40% growth in CO2 over that time for some effects to start to show themselves. By how much are they suggesting CO2 be cut? I really need to see the complete details of this study and so lI’m highly skeptical about the validity of this model study until I see other similar studies come along.
This shouldn’t surprise you RG. If you dig deep enough you can find a “peer-reviewed” paper suggesting everything is caused by CO2, on either side of the equation. But you know this.
Also, you do realize your last sentence is logic by consensus. More model studies= validity.
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.
Mike, you need to get a grip on reality.
In the cold of a La Nina, the Pacific Northwest and Inland Northwest actually become wetter. Why? The Pacific generated weather systems pick up moisture from the swirling mass of warmed left over El Nino oceans, drop into the low pressure cool La Nina waters off our coastline, and dump as snow as it continues into land. All over. Everywhere. Snow on my front porch and blown through the screen of my back porch, blown under roof tiles, and into crevices. Snow under rocks and into the cracks of tree bark, and deep into last fall’s plowed furrows. More snow than I need or want. Been fishing in snow for crisake!
This bit of allegory was brought to you just in case someone attributes our wet Spring to global warming. Or is it our global warming due to a wet Spring. Or is it my dry mouth from last night’s attempt to rid our community of some of its wood fire producing CO2. Did our sudden decrease in CO2 cause yesterday’s sudden white sideways flight of global blizzard warming? Ohmygawd. It was me wut dun it.
Lord I apologize for saying bad things about global warming and for the starving pigmys in New Guinea. She said with a hat-tip to Larry the Cable Guy.
I went to the link provided by Mike for anna v at 5:22 am.
My interpretation of the article there is that . . . ‘if one looks for an increase in temperature in the middle troposphere every day, on some days you will find a higher temperature there than the day before. Then it disappears for a few weeks or months, then recurs at odd times. This seems enough to not falsify the hot spot theory.’
I think that’s about it. And it is not a lot.
The charts here are worth a look:
http://www.drroyspencer.com/
By my count the zero line has been crossed 14 times since 1979. If you use Dr. S’s graphic calculator, found here
http://discover.itsc.uah.edu/amsutemps/execute.csh?amsutemps
and click ch05 v2 and then 2010, 2011, and Average you can check the current month. (It is not been quality controlled yet; but will be in early April.)
These data validate Anna v’s statement at 3:47 am.
“This warm air higher in the atmosphere tends to prevent the rising air motions that create thunderstorms and rainfall.”
Since there has been a run up of CO2 for 150 years, there should be measured observations. Specific examples please.
They do realize, do they not, that this contradicts the Warmists dedicated mantra regarding severe weather. I. e. that a 2C increase in ground temperature will bring about a multi-fold increase in Thunderstorms as well as intensity iof lightening strikes.
I was wondering when some CAGW team was going to play the CO2 causes “quick changes” long before it affects temperature card. Now doesn’t that nicely explain why CO2 is to blame for so many of the world’s problems when there’s no empirical evidence of the warming part of global warming.
This study is nothing short of CAGW on artificial life support.
No hotspot. Surface doesn’t cool as quickly. By “surface” we’re largely talking about the ocean (71%) and rocks, soil, trees, ice, lakes, rivers, and other dense things (29%). This doesn’t create a hotspot at altitude. It creates a less cool surface with a normal adiabatic lapse rate. Presumably the slightly warmer water evaporates slightly faster which water vapor then does rise until it condenses forming clouds and rain. We should see increased rainfall not decreased. Accelerated evaporation, cloud formation, and rainfall serve to remove heat from the surface and help it along on its way to outer space by lifting it a few thousand feet higher through the densest part of the atmosphere and during the day the increased cloud cover reflects sunlight which reduces surface heating. In effect there is a negative feedback from water vapor that puts a ceiling on maximum surface temperature which is why there has never been a runaway greenhouse in the earth’s history even when CO2 concentration were as much as 20 times greater than today.
CO2 is a greenhouse gas alrighty and when there’s 8x times the amount we have today the earth gets lush and green from pole to pole just like the inside of a busy greenhouse not like the ice age conditions of today when a good fraction of the surface is well below freezing stopping the primary producers in the food chain (green plants) from producing.
AGW boffins write on the blackboard 100 times:
Ice is bad. Actively growing plants are good.
John F. Hultquist says:
March 26, 2011 at 9:49 am
“I went to the link provided by Mike for anna v at 5:22 am.
My interpretation of the article there is that . . . ‘if one looks for an increase in temperature in the middle troposphere every day, on some days you will find a higher temperature there than the day before. Then it disappears for a few weeks or months, then recurs at odd times. This seems enough to not falsify the hot spot theory.’”
I guess you and anna v are not serious. If the relevant hypotheses are about the hotspot then they have been falsified many times over. By contrast, if the hypotheses are about the phenomena described then they are not about the hotspot.
This paper is strong evidence to end the practice of anonymous peer (pal) review. When the stench is this bad, the peer reviewers cannot come away smelling like roses.
http://wattsupwiththat.com/2011/02/17/peer-review-pal-review-and-broccoli/
Actually, given that the nucleation sites for condensation in cloud formation are limited, more water vapor in the air means that it will have to mix more and farther with air before it can condense out. This means that wetness will more likely spread than simply wet places get wetter. Probably both, to be realistic.
As an AGWer, I had similar concerns to R. Gates, and I found the paper at Cao’s site. What they are looking at is the transient response to steps in CO2. This is my interpretation. If CO2 changes quickly, the atmosphere responds first, followed by the slower and more permanent surface response (mostly the ocean temperature). When CO2 reduces, the atmosphere has to cool to meet the new radiative balance, while the ocean stays warm due to its inertia. This is what results in more convection and precipitation, at least until the ocean catches up. The opposite happens when CO2 steps up quickly, and the atmosphere warms faster than the surface leading to drier conditions in this transient state, which actually lasts decades.
Witchdoctor science. Desperate waving of rattles and references to computer model ju-ju. The devil mask isn’t working anymore. CAGW is dying.
Regarding the “tropospheric hot spot”, I’d invite folks to take a look at my paper on “Tropical Tropospheric Amplification“. If there’s enough interest I’ll open a new thread.
w.
Look! Up a the sky! It’s SUPER MAN! No, – – it’s MAJIC GAS! It wets! It dries! It makes climatologist and computer modelers rich!
/sarc
It use to be that if someone of lesser emotional stability or immaturity would get totally wrapped-up in a “show” you would gently remind them, “It’s ONLY TV” or “It’s ONLY a movie.” Isn’t it a shame on all science that we now have to remind some folks that, “It’s ONLY a model.”
Of course, everyone knows the ENSO controls global water vapour levels (and no climate model can properly simulate this).
ENSO versus total column water vapour up to Feb, 2011.
http://img822.imageshack.us/img822/8886/ensovstcwv1948feb11.png
If you want to see a mid-month update on whether water vapour levels have continued to decline in March as would be expected with its relationship with the ENSO, one can have a look at the update provided by Dr. Roy Spencer.
http://www.drroyspencer.com/wp-content/uploads/AMSRE_integ_vapor_2002_thru_March_17_2011.gif
Bill Illis says:
March 26, 2011 at 6:29 am
“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.”
Bill, there still are in Lake Chad, a large lake in the Sahel. This lake got ‘left behind’ in the desertification of the Sahara and is thus a beautiful ‘fossil’ of the Holocene Warm (and wet) Period over the Sahara.
http://bing.search.sympatico.ca/?q=Lake%20Chad%20animals&mkt=en-ca&setLang=en-CA
“….There are many floating islands (in Lake Chad) home to a wide variety of wildlife, including hippopotamus, and large communities of migrating birds (and indigenous) and over 40 species of fish (one the lungfish – known to paleontologists before re discovered in modern times)…..(precis and comment’s author in brackets)… ”
Much has been written about the huge decrease in size (dropped to 1/20th its surface area since 1960s, naturally blamed on CO2 but massive growth in irrigation use is the most likely culprit plus fluctuating climatic factors.
http://climatesanity.wordpress.com/2007/11/18/the-shrinking-of-lake-chad-cannot-be-blamed-on-anthropogenic-co2/
Chad has been one of Al Gore’s and (I believe Climate Progress’s) poster lakes, but with the return of heavier rains since 2007, we have this kind of “wetdry” thinking:
“The arid lands have refused to suck up rainfall and flooding is occurring. There are hopes that the drought will end by early 2011”:
http://www.ehow.com/list_7457255_nigeria_s-deserts.html
Jim D;
Congrats as an AGW’er for actually reading a paper! 90% when an AGW’er quotes a paper I ask if they read it, they say no, I offer to show it to them, mumble, mumble, they’re not technical enough to read it mumble mumble….but quoted it anyway even though they don’t understand it. By actually reading it do you know what you are? An AGW’er in “transition” mode! But on to the paper:
“As an AGWer, I had similar concerns to R. Gates, and I found the paper at Cao’s site. What they are looking at is the transient response to steps in CO2.”>>>
Giant hole number one. CO2 doesn’t increase in steps it increases by 1 part per million every few months. More accurately it might go up 3, down 2, up three, down 2, etc. for a net of +2 over an entire year. So they modeled something that doesn’t ever happen.
” This is my interpretation. If CO2 changes quickly, the atmosphere responds first, followed by the slower and more permanent surface response (mostly the ocean temperature).”>>>
Giant hole number two. CO2 doesn’t change in steps as per above, and it doesn’t change quickly either. From 1920 until now it went from 280 to 389! They modeled jumps of much larger changes than can actually occur!
“When CO2 reduces, the atmosphere has to cool to meet the new radiative balance, while the ocean stays warm due to its inertia. This is what results in more convection and precipitation, at least until the ocean catches up.”>>>
Giant hole number three. If the theory is that GHG’s retain heat from the increased absorption of LW from the earth’s surface being absorbed and partly re-radiated downward, then the statement above relies on the thermal heat capacity of CO2 at 389 parts per MILLION being high enough to affect the over all temp of the atmosphere. That being ludicrous, decreases in CO2 by the AGW’s own defnitions require that the land surface cool FIRST, the oceans second>>>
“The opposite happens when CO2 steps up quickly, and the atmosphere warms faster than the surface leading to drier conditions in this transient state, which actually lasts decades.”>>>
This statement is comprised of “Giant hole numbers 1 & 2” and the paper quoted “quick” changes in precipitation to changes in atmospheric temps almost unnoticeable. But ignoring that, let’s go with Giant hole number four. The daily heating cooling cycle at surface is (for sake of argument) 15 degrees C and is the primary driver of convection. Let’s suppose The surface temp varies daily from +10 to +25. It warms an almost unnoticeable (their contention, not mine) 0.01 degrees. Now the surface is fluctuating from 10.01 to 25.01 and somewhere in the mid tropopshere it has gone from -19 to -19.01! Yup, there’s a warm air layer that most surely lay a licken on the 1,500 TIMES larger DAILY temperature change that is the PRIMARY driver of convection and tell it to stop. ROFLMAO.
I have asked this question on several sites and it is never even acknowledged: what is the optimal ‘global’ temp and why.
Jim D says:
March 26, 2011 at 11:02 am
During the period of stable temperatures recently where CO2 continues increasing, the only atmosphere responce has been the opposite expected for CO2 retaining it. This is the supposed argument of it causing increasing +AO and +NAO with cooling stratopshere above the Arctic when the opposite has happened since early 2000’s. This is evidence against CO2, where atmospheric natural cycles clearly dominate. This supports why the surface has been stable because the atmosphere has also not responded to it either. This evidence shows that CO2 does not change the atmosphere quickly and must therefore have low sensitivity towards climate. With it having low sensitivity, over periods longer than a decade (as now) should show some responce, yet we still have stable global temperatures. It is clear to most honest scientists that there is nothing to be alarmed about CO2’s affect on climate.
Just more members of “The Team” making unproven projections with computer models.
Climate Science Modelers have No connection to reality. Just more GI GO. Time for them to get real jobs doing real things. Maybe flippin burgers or diggin ditches, you know, something useful that they are competent at. pg
Matt G, it is often said that the warming has stopped when in fact 2010 was one of the warmest years on record, and the early 2000’s were anomalously high, so what we have now is back on the expected curve after an upward detour.
davidmhoffer says:
March 26, 2011 at 12:47 pm
Good work, sir, Thanks. Also, good mentoring.