This press release below from Columbia University shown below suggests that irrigation cools the region undergoing irrigation. However, a study published three years ago of California’s central valley by Dr. John Christy suggests exactly the opposite. See this WUWT post from 2007, then read the Columbia story and decide for yourself.
From UAH: Irrigation most likely to blame for Central California warming
A two-year study of San Joaquin Valley nights found that summer nighttime low temperatures in six counties of California’s Central Valley climbed about 5.5 degrees Fahrenheit (approximately 3.0 C) between 1910 and 2003. The study’s results will be published in the “Journal of Climate.”
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From Columbia: Irrigation’s Cooling Effects May Mask Warming–For Now
If Water Runs Short, Some Regions May Suffer Significantly
Expanded irrigation has made it possible to feed the world’s growing billions—and it may also temporarily be counteracting the effects of climate change in some regions, say scientists in a new study. But some major groundwater aquifers, a source of irrigation water, are projected to dry up in coming decades from continuing overuse, and when they do, people may face the double whammy of food shortages and higher temperatures. A new study in the Journal of Geophysical Research pinpoints where the trouble spots may be.
“Irrigation can have a significant cooling effect on regional temperatures, where people live,” said the study’s lead author, Michael Puma, a hydrologist who works jointly with Columbia University’s Earth Institute and its affiliated NASA Goddard Institute for Space Studies. “An important question for the future is what happens to the climate if the water goes dry and the cooling disappears? How much warming is being hidden by irrigation?”
Scientists generally agree that in the last century, humans have warmed the planet about .7 degrees C (about 1.3 degrees F) by pumping vast amounts of carbon dioxide into the air. How much warmer earth will get depends not only on future carbon emissions but an array of other variables. For instance, earth’s oceans and vegetation have been absorbing a growing share of emissions, but recent studies suggest this uptake may be slowing. This could lead to more carbon dioxide in the air, and accelerated warming. On the other hand, humans are also cooling the planet to some degree, by releasing air-polluting particles that lower temperatures by reflecting the sun’s energy back into space. Pumping of vast amounts of heat-absorbing water onto crops is lowering temperatures in some regions as well, say the authors.
Scientists are just beginning to get a handle on irrigation’s impact. In a hundred years, the amount of irrigated farmland has grown four-fold, now covering an area four times the size of Texas. Puma and his coauthor, Benjamin Cook, a climatologist at Goddard and Columbia’s Lamont-Doherty Earth Observatory, are the first to look at the historic effects of mass watering on climate globally by analyzing temperature, precipitation and irrigation trends in a series of model simulations for the last century. They found that irrigation-linked cooling grew noticeably in the 1950s as irrigation rates exploded, and that more rain is now falling downstream of these heavily watered regions.
In warm, dry regions, irrigation increases the amount of water available for plants to release into the air through a process called evapotranspiration. When the soil is wet, part of the sun’s energy is diverted from warming the soil to vaporizing its moisture, creating a cooling effect. The same process explains why drying off in the sun after a swim at the beach can be so refreshing.
Globally, irrigation’s effect on climate is small—one-tenth of one degree C (about 0.2 degree F). But regionally, the cooling can match or exceed the impacts of greenhouse gases, say the scientists. For example, the study found some of the largest effects in India’s arid Indus River Basin, where irrigation may be cooling the climate up to 3 degrees C, (5.4 degrees F) and up to 1-2 degrees C in other heavily irrigated regions such as California’s Central Valley and parts of China. The study also found as much as .5 degree C cooling in heavily watered regions of Europe, Asia and North America during the summer.
The study suggests also that irrigation may be shaping the climate in other ways, by adding up to a millimeter per day of extra rain downwind of irrigated areas in Europe and parts of Asia. It also suggests that irrigation may be altering the pattern of the Asian monsoon, the rains that feed nearly half of the world’s population. These findings are more uncertain, the authors caution, and will require further research.
“Most previous modeling studies were idealized experiments used to explore potential impacts, but this is a much more realistic simulation of the actual impacts,” said David Lobell, a Stanford University scientist who studies climate impacts on agriculture and was not involved in the study. “Their results show some interesting differences by time period and region that will lead to more research and contribute to more accurate simulations of future climate, particularly in agricultural areas.”
Irrigation has increased because it boosts crop yields, supporting many millions of small farmers, said Upmanu Lall, head of the Columbia Water Center at the Earth Institute. But concern is growing that groundwater supplies in India and China may not keep up. “Near term and future climate predictions are essential for anticipating climate shocks and improving food security,” he said. “The study points to the importance of including irrigation in regional and global climate models so that we can anticipate precipitation and temperature impacts, and better manage our land, water and food in stressed environments.”
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NOTE: The scientific paper was not provided with the press release.
Bernie says:
September 8, 2010 at 6:03 pm
As a glider pilot we always avoided irrigation areas because there were less thermals there in the daytime becuase of the cooling effect. But I would expect temperatures to be higher than surrounding areas during the night due to the extra humidity.
And darker plowed fields generate more heat than do fileds covered with stalks.
There is a simple way to test their “simulations.” Study areas that were traditionally arid and that are now becoming wetter due to land use changes (new irrigation projects). Southeastern New Mexico, with lots of huge pecan orchards in middle of the desert, would be a good starting point, assuming that there is any decent long-term historical data on humidity and air temp.
Based on what science? Flatulence from spherical cows?
GIGO: Garbage In; Grants Out
Models removed so far from the reality experienced by sentient people outside of an airconditioned cocoon, it’s not even a good joke.
Hmmmmm let’s see.
Dr. Spencer or NASA GIS. . . who to trust ?
Well that’s a no brainer. Roy is objective, NASA GIS is one of the leading AGW fear mongering, hysteria pandering, grant seeking, eco-grifting rent seeking organizations that exists.
I’ll trust Dr. Spencer.
REPLY: That’s great, but the story mentions Dr. Christy. – Anthony
Bernie @ur momisugly 6:03 PM
Welcome. Excellent observation. When your life is on the line, you do tend to notice things like updrafts and downdrafts.
I am not sure of the protocol but I have been commenting since the start of this site. Can we come to some arrangement?
“When the soil is wet, part of the sun’s energy is diverted from warming the soil to vaporizing its moisture,…”
Sophistry knows no bounds.
“But some major groundwater aquifers, a source of irrigation water, are projected to dry up in coming decades from continuing overuse, and when they do, people may face the double whammy of food shortages and higher temperatures.”
“Irrigation can have a significant cooling effect on regional temperatures, where people live,” said the study’s lead author, Michael Puma, a hydrologist who works jointly with Columbia University’s Earth Institute and its affiliated NASA Goddard Institute for Space Studies. “An important question for the future is what happens to the climate if the water goes dry and the cooling disappears? How much warming is being hidden by irrigation?”
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Anybody notice the tone of this press release? Usual alarmist crap.
Generally, real famine and pestilence occurs during cold times, not warm.
They are not only barking up the wrong tree, they are in the wrong forest.
Chris
So… a tiny percentage of the global land mass is irrigated and they are suggesting that this negates 15% of the effects of GHG’s planet wide, all sources, and including any warming that was built up over the decades before irrigation became prevalent? While I doubt the numbers, I find the assumption that human activity will potentially result in some catastrophic change in the environment that will spell disaster that we cannot survive the more interesting topic.
This assumption that we humans are destined to be the victims of mother nature’s whims are simply not borne out by the evidence. The fact is that humans dominate this planet precisely because we are capable of exterting a measure of control over our environment, and a greater level of control than the alarmists want to admit. Consider the case above. The fear expressed is that the acquifers supplying the irrigation systems may dry up, exposing us to both a sudden jump in global temperatures and a sudden drop in food supply. Scary, scary, scary.
The fact is that even if the acquifer does dry up, it is highly unlikely to do so instantly. It would happen over a period of years at a minimum, but more likely decades. Consider the options we as humans have. Yes, desalinating sea water and pumping it overland to replace the water from the acquifers would be energy intensive and expensive, but the point is we could do it, and the cooling effect of irrigation claimed in the study above would far more than off set the emissions from fossil fuel used to accomplish the task. Nuclear would be even better. Alternatively, Canada is home to 10% of the world’s fresh water while occupying a fraction of the global land area. While diverting rivers in Canada to supply fresh water for irrigation in the US would galvanize protests from the environmentalists, the point is that while it is not currently politicaly correct, accomplishing this feat is well within our technological capabilities and when the choice becomes divert or starve, the environmental objections tend to get drowned out. Either solution is fine with me, as a red neck Canuck I am happy to sell the US the oil or uranium to power desalination, or the fresh water instead.
This notion that mankind is destined to be the helpless victim of his own effects on the environment is true only if one assumes that environmental change by default causes our collective IQ to drop to the level of an ape. Hooo hooo hah hoo, not gonna happen.
To timetochoseagain (7:03):
Christy actually says that the daytime temps cooled, even as the nighttime temps warmed:
“While nighttime temperatures have risen, there has been no change in summer nighttime temperatures in the adjacent Sierra Nevada mountains. Summer daytime temperatures in the six county area have actually cooled slightly since 1910. Those discrepancies, says Christy, might best be explained by looking at the effects of widespread irrigation.”
That is from the 2007 presser you can access from the link above. So both studies agree on more daytime cooling the last century. No disagreement.
davidmhoffer says:
September 8, 2010 at 8:06 pm
Wonderfully articulated! I can’t even add to your statement other than to reiterate man’s ability to move water. Many may find this inconceivable, but I’m pretty sure it can still happen.
I knew they’d make a play for water, in fact, if one looks back, I’m sure I stated as much here. But it still amazes me how people believe we can’t, couldn’t, or wouldn’t be able to handle some H2O displacement. Heat = more evaporation, which = more rain, which would, or should allay the fears of the alarmists, yet, inexplicably, they are still afraid of water going away. Ladies!!! Water doesn’t go anywhere!!! It’s ok, take your panties out of the wad and relax. We can move it from A to B and even create electricity while we do it!! It’s ok. Just calm down.
The phenomenon is, in my opinion, more important than some seem to think. It goes right to the heart of the entire GHG theories, and I am a bit surprised that more work hasn’t been done on testing the models on the Regional scale that is way easier to study and get good data from than the globe is.
rbateman says on September 8, 2010 at 6:09 pm:
I see a budget buzzsaw coming, and it’s going to be looking for the thousands of $600 uncertainty screwdrivers that the budget is being charged with.
Sometime ago I ordered a #2 Pozi-Drive screw driver from HP. I got really annoyed when I learned that it cost $40. The high price was because it was made in Germany by Walthers.
Terry says:
September 8, 2010 at 8:29 pm
The phenomenon is, in my opinion, more important than some seem to think. It goes right to the heart of the entire GHG theories, and I am a bit surprised that more work hasn’t been done on testing the models on the Regional scale that is way easier to study and get good data from than the globe is.
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That’s because it blows their world up. More heat = more evaporation, which = more rain. If it gets colder, then less H2O is available for the cycle. They can’t really discuss it beyond the sophistry demonstrated in the story above, else, too many thoughts would be expounded upon it. Water isn’t a problem.
I think there is a correlation between the increase in anthropological CO2 and the average drop in IQ. Can I get a grant to study this?
This is quite interesting from several points of view. One is more back up to the contention that local climate can be effected by human activities, all be it in this case quite small. I think Roy Spencer has written about this as has Roger Pielke Sr. Another is the point that some aquifers are being over drawn and this is not a good long term idea. Without the full study to read all we really know is what the press release gives and my experience has been press releases are almost always misleading. My experience in Alberta suggests the general conclusions given at least make sense. Another issue not mentioned is the rather wasteful methods of delivering water to many crops in many areas. I have noticed some improvements by some farmers here in Alberta over the last 5 or 6 years, however.
This work is behind a pay wall
The abstract does not mention comparison with data. Is anybody subscribed and can they tell us if the comparison exists in the paper?
Otherwise, it is GIGO video games.
Between a paper with data and a paper with model outputs, data trumps.
Fascinating discussion. I am wondering, just how far from home does that solar energy go? I am thinking the solar energy invested in evaporation (in this case, of irrigation water) is matched by the energy released during condensation; energy released to the atmosphere, raising the temperature of the air. Cooling here, warming there.
Lots of glider pilots on this forum, I have noticed. Any glider pilot anticipates “overdevelopment” (convective cloud generating rain showers) first and worst (because it puts us on the ground tout suite) over areas that experienced showers last night, or in this case and as was mentioned in a previous post areas that experienced irrigation recently. The point is, in a glider pilot’s world, the evaporation frequently leads to condensation within a few miles laterally and within a mile or even less vertically. So has there been any change in energy within the volume encompassed by a typical convective cell?
Flaws in my logic?
Bruce
Just another “hidden warming” story to provide an excuse for the recent cooling and find more “control handles” besides CO2.
“Stressed environments, regional and global climate models, climate shocks”, I’ve heard enough. Thank you.
NOTE: The scientific paper was not provided with the press release.
How surprising? (O_o)
Irrigation has increased because it boosts crop yields, supporting many millions of small farmers, said Upmanu Lall, head of the Columbia Water Center at the Earth Institute. But concern is growing that groundwater supplies in India and China may not keep up.
Oh yes, and there it is, doom and gloom awaits us all, save the Earth, stop irrigation. Think of the poor small farmers in India and China, Donate generously and quickly.
davidmhoffer says:
September 8, 2010 at 8:06 pm
“Alternatively, Canada is home to 10% of the world’s fresh water while occupying a fraction of the global land area. While diverting rivers in Canada to supply fresh water for irrigation in the US . . .”
The preliminary plans for a scheme such as this were detailed some 30+ years ago by a large engineering firm (from L.A., I think). I do not find a link to that work but there is no shortage of such:
http://www.polarisinstitute.org/turning_on_canadas_tap
The humidity is raised due to irrigating. This increases the heat capacity of the atmosphere. This means more heat energy is required to raise the atmosphere’s temperature and more heat energy needs to be lost to lower the atmosphere’s temperature. This makes the high temperatures lower and the low temperatures higher, as was shown by the first study.
The rest is BS.
The highest temperatures are recorded where there is the least amount of green house gases (where the humidity is the lowest).
John said:
“Irrigation cancels out about 15% of warming from all other causes, and this is the first we have heard of it?
This really needs a fact check — I’m not saying it is wrong, but I’m saying we need to know if it is right.”
Amen.
Here are some side affects of diverting flood waters into river channels.
Ground water is found further below the surface than it used to be. Those massive floods kept land in a perpetual swamp. That also meant that shallow hand-dug wells had swampy flavored water in them. When the flood waters were prevented, ground water levels sunk and so did the wells, resulting in better tasting water (and quite a few dry wells that had to be deepened or drilled).
After irrigation ditches and gates replaced untimely flooding (same amount of water overall being spread out, but diverted to where it was needed and controlled better), the folks that get their knickers in a twist over fish getting caught in irrigation ditches decided to fish screen them. Suddenly, much of the spawning ground was cut off and restricted to the fast moving rivers. No flooded valley and no irrigation ditches for spawning. Fish numbers plummeted.
So now lots of money is being spent changing the river channels to incorporate a more meandering route, simulating the flooding affects of debris. Why didn’t they just remove the fish screens?
Well that’s it then. Let”s start irrigating barren areas of the world with sea water – and lower the T even more. 🙂
Problem solved.
Pamela Gray
true enough. And do not forget the peat bogs all around the world that were purposely dried up. Russia won’t soon. But will nothing about it.