From the Carnegie Institution – maybe we should build more cooling towers.
Washington, DC. — Scientists have long debated about the impact on global climate of water evaporated from vegetation. New research from Carnegie’s Global Ecology department concludes that evaporated water helps cool the earth as a whole, not just the local area of evaporation, demonstrating that evaporation of water from trees and lakes could have a cooling effect on the entire atmosphere. These findings, published September 14 in Environmental Research Letters, have major implications for land-use decision making.
Evaporative cooling is the process by which a local area is cooled by the energy used in the evaporation process, energy that would have otherwise heated the area’s surface. It is well known that the paving over of urban areas and the clearing of forests can contribute to local warming by decreasing local evaporative cooling, but it was not understood whether this decreased evaporation would also contribute to global warming.
The Earth has been getting warmer over at least the past several decades, primarily as a result of the emissions of carbon dioxide from the burning of coal, oil, and gas, as well as the clearing of forests. But because water vapor plays so many roles in the climate system, the global climate effects of changes in evaporation were not well understood.
The researchers even thought it was possible that evaporation could have a warming effect on global climate, because water vapor acts as a greenhouse gas in the atmosphere. Also, the energy taken up in evaporating water is released back into the environment when the water vapor condenses and returns to earth, mostly as rain. Globally, this cycle of evaporation and condensation moves energy around, but cannot create or destroy energy. So, evaporation cannot directly affect the global balance of energy on our planet.
The team led by George Ban-Weiss, formerly of Carnegie and currently at Lawrence Berkeley National Laboratory, included Carnegie’s Long Cao, Julia Pongratz and Ken Caldeira, as well as Govindasamy Bala of the Indian Institute of Science in Bangalore. Using a climate model, they found that increased evaporation actually had an overall cooling effect on the global climate.
Increased evaporation tends to cause clouds to form low in the atmosphere, which act to reflect the sun’s warming rays back out into space. This has a cooling influence.
“This shows us that the evaporation of water from trees and lakes in urban parks, like New York’s Central Park, not only help keep our cities cool, but also helps keep the whole planet cool,” Caldeira said. “Our research also shows that we need to improve our understanding of how our daily activities can drive changes in both local and global climate. That steam coming out of your tea-kettle may be helping to cool the Earth, but that cooling influence will be overwhelmed if that water was boiled by burning gas or coal.”
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I hope I got this right: increased evaporation has a cooling effect, but evaporation cannot affect the global energy balance? IAW, there must be warming somewhere to offset this cooling, right?
Hm.
One thing’s for sure: this is again our fault, for chopping down trees. I bet the CO2 police will now enforce a massive tree planting policy, aimed at us.
“Using a climate model”…………………..
?????
sigh……
John Christy put out a paper on this effect years ago.
http://ams.confex.com/ams/84Annual/techprogram/paper_68739.htm
Due to irrigation of the central valley in California, daytime temperatures went down and
nighttime temperatures went up. By introducing water and irrigation to a desert region, the net effect overall was a slight warming. I suspect that much of the measured slight warming worldwide is due to this irrigation effect.
Will there also be increased organics released into the air from all this water evaporating from trees? These will tend to increase nucleation sites for water droplets and increase cloud cover.
I am amazed that this paper was accepted by the reviewers. Does no one search the internet or look at Russian literature. Look at this web site http://www.bioticregulation.ru/pubs/pubs2.php
Wait. Are you saying sophisticated IPCC climate models don’t take this into account? Really?
They obviously needed a few hundred thousand in grants to conclude on something that bleeding obvious, previously known, and well established.
There is not one shred of evidence given to support that statement, is there? Yet this will be added to a catalog listing it as a scientific paper supporting the “consensus.”
“evaporation of water from trees and lakes could have a cooling effect on the entire atmosphere.”
And evaporation of Ocean water ?
It is very presumtious to state the world has been getting warmer over several decades,
I have lived through several decades and can see no difference since my boyhood.
Iwould like the truth and some proof of this statement please!!
I am having a hard time reconciling these two statements:
New research from Carnegie’s Global Ecology department concludes that evaporated water helps cool the earth as a whole, not just the local area of evaporation, demonstrating that evaporation of water from trees and lakes could have a cooling effect on the entire atmosphere.
and
Globally, this cycle of evaporation and condensation moves energy around, but cannot create or destroy energy. So, evaporation cannot directly affect the global balance of energy on our planet.
These statement appear to contradict each other. If the first is true, the AOGCMs need to account of evapotranspiration. If the second is true, they do not. Which is it?
As the Daily Bayonet says- “Wait, What?”
It appears that this climate model study has stomped on CACC.
The authors state- “The researchers even thought it was possible that evaporation could have a warming effect on global climate, because water vapor acts as a greenhouse gas in the atmosphere.”
“was” possible?!?
The settled science says that surface warming from any forcing causes increased humidity due to evaporation of water. The increased water vapor concentrations then cause a greater greenhouse effect, further warming the surface. This positive feedback is claimed to double or triple the temperature increase from CO2 alone.
“But because water vapor plays so many roles in the climate system, the global climate effects of changes in evaporation were not well understood.”
This is a direct challenge to the water vapor positive feedback being settled science. This is heresy, a direct challenge nailed to the front door of the CACC cathedral.
But now we have this paper’s stunning claim.
“Using a climate model, they found that increased evaporation actually had an overall cooling effect on the global climate.”
This is another Trenberth travesty. Say goodbye to the water vapor based positive feedback multiplying factor for CO2 warming. The AR5 lead authors will have to find a way to exclude this paper from the next report, even if they have to redefine what peer reviewed literature is…
Just one more reason treehuggers will use to stop timber sales. Before loggers came along, our forests burned naturally, cleaning up the floor and continually replacing fully mature adult trees with meadows and thinned younger trees. We replaced that with something similar: timber sale harvest/slash burning. For some reason, tree huggers want to replace all of that with some kind of no touch no burn forest system that will only lead to one thing: catastrophic burns from fuel heavy forests. And this is good how?
“The Earth has been getting warmer over at least the past several decades, primarily as a result of the EMISSIONS OF CARBON DIOXIDE from the burning of coal, oil, and gas” (caps added)
Immediate deduction of 30 IQ points and a major downgrade of the value of the presentation and content.
Is this now simply another attack on human activities and an argument for de-industrializing and planting more trees?
Forget mowing the lawn ever again—I have a great excuse! There oughta be a law.
Wait a minute…I thought evaporation resulted in cloud formation, which reflected heat back to Earth and warmed the planet. At least, that’s what the IPCC has been saying for the past couple decades. I mean, it’s in their models, it can’t be wrong.
Re: the Amazon
The rainforest is resilient and grows back very quickly. Recent estimates have it growing back much faster than it is being cleared. As farmland the soil is poor and only produces a few crops and then the people move on. The forest takes the land back. There is more rainforest now than there was 40 years ago. City expansion is really not a big factor.
The Greenies always talk about the damage without ever talking about the healing. Bleached coral reefs recolor back to health rather quickly. Greenies NEVER go back later to check on bleached corals as they really do not want to know that they have recovered quite nicely, thank you. They want the crisis to be human and resolution not be natural.
So the lake in Central Park helps cool and the Atlantic ocean is not mentioned. Of course the Atlantic is but one of the oceans and maybe they might evaporate a little as well.
Isn’t this a rather involved way of saying that water vapor acts as a negative feedback on temperature?
When does the editor resign?
The big engine is in the sky, its big and hot, sometimes very hot sometimes not so hot, but how can we tax it folks?
“Water evaporated from trees cools global climate”
[church lady]Well, isn’t that inconveeenient?[/church lady]
So when I sweat and it evaporates taking heat from me into the surrounding air, that heat radiates back and makes me hotter?
Shouldn’t apologies and resignations be forthcoming? Clouds sure seem to be doing a lot of things while not playing a significant role in our climate.
roger samson says:
September 16, 2011 at 4:34 am
…In fact folks, anthropogenic warming may slowly be occurring due to deforestation.
++++++++
Good to hear from you, Roger. For folks who don’t know, Roger is probably the single greatest motivator for switchgrass as a native, local biofuel. Practically created the concept. I have several products to test courtesy of him.
Yeah, but Roger, what do you have as info on the (natural) reforrestation of the NE USA as people left the farms? Is total forest cover in, say, the USA increasing? Virginia, NY (etc) are getting massive regrowth. Then, is there an increase in Arctic vegetation with increasing temps? I read once it’s about 6 C in the past 150 years. That should bring a very large increase in mass, a draw-down of CO2 and an increase in transpiration.
I am not arguing against your point, I want to look at the global forest cover. One of Harold Annegarn’s remote sensing students is trying to use satellite radar to estimate the total biomass using average tree height. Resolution is tricky but it is already working for very tall and short trees.
We see reports now and then about total tree cover but they are always alarmist and never talk about areas with increasing vegetation, as if that is ‘off message’. That means it is not a ‘report’ but a ‘message’. What can you report? Is there any correlation (even anti-) with tree cover or total biomass and temps?
I would not be at all surprised to find a long-lasting influence. It is abnormal for watered soil to have nothing growing on it.
The cooling effect of trees is that the energy coming from our star does not heat the surface of the earth but the leaves of the tree.
These leaves evaporate water to cool themself.
Both the ground under the trees and the leaves don’t accumulate heat so the moment the sun is gone there is no heat radiation. Our buildings and roads do accumulate heat. That’s why a big city is a bad place to sleep when it’s warm and moisty.
The Carnegie Institution says:
“The Earth has been getting warmer over at least the past several decades, primarily as a result of the emissions of carbon dioxide from the burning of coal, oil, and gas, as well as the clearing of forests.”
The Earth has not been warmer this last decade and the emission of carbon dioxide has continued. The premise and the conclusion, primarily as a result, is illogical and unfounded.