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.
“These findings are more uncertain”- ” This is a more realistic simulation” they say.
I say BS. They just want more money to carry on more simulations. The people in the U.S. , I hope are sick of this crap and will hopefully wake up soon.
Key points: “Globally, irrigation’s effect on climate is small—one-tenth of one degree C (about 0.2 degree F).” Presumably not cumulative. So why is it important?
Oh, here’s the reason: “will lead to more research” and “… will require further research.”
Hop on the gravy train.
GHG’s, according to all I am aware of, holds heat.
that is supposedly why night time temps are up.
I wonder if people in the Sahara or Gobi would be interested in knowing that at night the water vapor would make things cooler.
Here in the Gulf Coast, I think people will be surprised to find that humid air is cooler than dry air.
How are these articles different in conclusions?
Christy’s said that nightime temps were increasing, but he didn’t say that total average temps were increasing. His study simply said that with substantial water available during the day, the water absorbed heat, and then released it at night, raising nighttime temps.
Is this necessarily different from the conclusions of the new study?
The new study says that water absorbs heat during the day, and then that some of the water (the part that doesn’t remain on the ground to release heat at night) evaporates, so that that part of heat created by the sun doesn’t remain on the ground but instead is transferred to water which leaves the area to perhaps rain downwind. Hence cooling during the day and likely daily average cooling.
If you follow the link above back to the 2007 post on Christy’s study, you will see that Anthony did some analysis on Chico’s daily temps, and found — consistent with Christy — that nighttime temps were increasing for the last century. He also found — consistent with the new study — that daytime and daily average temps were decreasing with time, presumably as increased acreage became irrigated between 1900 and 2000.
Please correct me if I’m wrong, but where is the contradiction between these two studies?
Did this study just say that irrigation is responsible for cancelling 1/7 of global warming worldwide?
These two passages seem to say so:
1. “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. ”
2. “Globally, irrigation’s effect on climate is small—one-tenth of one degree C (about 0.2 degree F).”
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.
It is soooo typical for warmists to take the simplistic approach which assumes, more or less, that global warming is happening and that any instance of it not being apparent must be a short-term masking of global warming. After all they KNOW it is happening, duh, so any time it is not, must be a temporary setback.
Irrigation also has an effect on the weather.
A friend of mine grew up in Montana in an area of dry land farming.
As she grew older, more and more land was irrigated, and summertime afternoon thunderstorms began to be commonplace.
As more land was irrigated, those thunderstorms became a daily occurrence.
Certainly, somebody has done a study about this effect, which should be an expected resullt of the introduction of more water vapor into a previously-arid hot climate.
We use irrigation in south Florida to warm and prevent frost and freeze damage.
Once again, the authors have no idea what valleys were like prior to controlled river levels and irrigation. Wallowa valley was considered too wet for crops when first settled by whites. The Nez Pierce Indians knew this too. Once river flooding was controlled and irrigation ditches built, LESS water was spread throughout the valley than before. MORE water stayed in the rivers. The soil dried enough on the valley floor to grow grass and alfalfa with a wheat field here and there (most of the dry crops were raised on hillsides and on top of the surrounding higher plains).
Before the dams were built along the Snake and Columbia, the same thing occurred. The land was SWAMPY! Once river levels were controlled, more water stayed in the river with some of it pumped out when the farmers needed it as opposed to washing over the land during floods, whether you needed it or not.
Stupid is as stupid does.
What does David Christy say in response to these claims?
Would irrigation act similiar (but not the same) to the ocean?. Cooling effect in summer, warming effect in winter – in other words a moderating influence. I understand the ocean is a body of water as compared to a spray/thin layer of water. It would also depend on the temperature of the ground water and the comparable air temperature.
As usual, uhhh, NO.
Here is a little sample of the GHCN of the Northern SJV:
Temp… http://www.appinsys.com/GlobalWarming/climgraph.aspx?pltparms=GHCNT100XJanDecI188020090900310AR42572481001x42572483001x42572483003x
Prec… http://www.appinsys.com/GlobalWarming/climgraph.aspx?pltparms=GHCNP100AJanDecI188020090900310AR42572481001x42572483000x42572483001x
1950 and beyond does NOT support any of their assessments or conclusions. Measurement, as typical, is the only issue. I might be convinced of a “land use issue” for the southern San Joaquin Valley (No good GHCN stations), but not irrigation. Sacramento seems to have more “adjustments” in the “non-adjustment” data (Running cooler than the Davis Farm in the past 20 years).
Nonsense as usual.
After spending many years working in underground mines I can make this safe empirical conclusion:
Moisture in the air makes you hotter.
Although I’m not aware that it has any effect at all on temperature. Both these studies sound like a crock to me.
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.
Overall there would be cooling due to the evaporation but also heating due the albedo change of the land.
It´s vegetation, it´s plant life. Plants and trees have a real interchange between ground and the atmosphere, much more than computer models and modellers in air-conditioned rooms with artificial light could ever imagine.
To understand this just think in post normal science and “modern” specialization: How in the world a “climate scientist” or an “ecologist”watching 8 hours a day at a computer screen can know about nature. It´s impossible.
Where there have been built or made irrigations of many types, the most inmediate consequence it has been an increase in humidity and even in deserts it has began raining.
These phenomena have been known by millenia until “illustration”tag it as “ignorance”, “superstition”, etc.
We, “modern and presumptuosly evolved men”, have trashed real science to replace it by child games and wishes, we have trashed, also, sanity, health from our lives.
Back in the “underdeveloped” neolithic times, cromlechs, trilithons, had a precise purpose on managing the “field” that, unless we trash our self indulgement and consideration about what the other people may think or say about “us”; we, the nice and intelligent guys who know everything, as mommy and daddy taught us to believe.
As Herman Hesse´s character Magister Ludi in “The Glass bed game” called this era: “The pamphlet Era”.
Same old meme in the journal of irreproducable results?So its worse than we knew?
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.
The paragraph beginning with “unless we…” should end by saying: “we won´t understand anything”
Pamela Gray- exactly, well put. Grande Ronde Valley has a similar history. My family did dry land wheat and cattle in both Washington and NE Oregon, and the benefits of irrigation and power are tremendous. Now we have “Hay Duke” Kitzhaber D-Retread
runnning for Oregon Governor, who wants to kill that flood control on the Snake, by blowing up the Snake River Dams.
The Grande Ronde and Wallowa Valleys will be covered with wind machines,
no people, or animals, imho, but that is what the appear to want…
Uber says:
September 8, 2010 at 6:03 pm
Actually, pard, what they are doing is keeping us in the dark and feeding us ….
And that’s what I think of thier main haulage.
[funny, but a little over the top ~ ctm]
Central California has had a huge increase in smog in the last 40 years. I mean huge. Bakersfield used to be visible 40 miles away. Now you can’t make detail but a couple miles away. The smog is mostly is and around the fields. And it is due to the inversion and a perverse mix of vapors I have been told by residents of Central California. Manure, nitrous oxide, a bit of water vapor, ammonia, diesel fumes,etc. If someone said that it was a localized heat sump, i would not be surprised.
I suspect that in areas where industrial and transport exhaust is less, where ranches were rarer, and the agriculture was mere vegetation irrigation might have a cooling effect.
This study confirms the findings of previous research on the cooling effect of irrigation on daytime temps. Over large areas the addition of so much water vapor does have regional effects on temp, convection and precip. Christy’s study seemed to focus more on nighttime temps.
This is a good example of a mesoscale anthropogenic impact which has little or no direct connection to CO2. Global average temperature is a hollow metric. People live in regional climates where variations are much larger than the global average.
What I find amazing is they are talking about aquifers drying up and the most they can find to worry about is if it will cause warming.
intrepid_wanders-Christy et al did not use GHCN for the SJV, in point of fact Christy painstakingly gathered data from the area that wasn’t available from GHCN or USHCN. The number of stations used is vastly more. So before you criticize, you ought to know exactly what was done. Please see for yourself:
http://journals.ametsoc.org/doi/pdf/10.1175/JCLI3627.1
John-The contradiction is that what Christy generally found was that where there was warming in the minimum, the maximum temperatures did NOT cancel the warming, as they remained fairly steady. They found that both maximum and minimum temps were pretty stable in the mountains, but the valley saw net warming. This study says that the cooling of maximum temps would be greater than the minimum temps, I think. Precisely the opposite seems to happen. Now WHY is that? The reason is because climate models do not handle the boundary layer dynamics behind this discrepancy very well. There are a number of things that I could say about this, but I just recommend this:
Walters, J. T., R. T. McNider, X. Shi, W. B. Norris, and J. R. Christy (2007), Positive surface temperature feedback in the stable nocturnal boundary layer, Geophys. Res. Lett., 34, L12709, doi:10.1029/2007GL029505.
don’t forget this from just a while ago:
http://wattsupwiththat.com/2010/08/09/corn-as-a-local-climate-forcing/