@NCAR claims: U.S. Southwest sliding into a drier climate, and it's all your fault

Weather patterns that bring moisture are becoming less frequent

From the NATIONAL CENTER FOR ATMOSPHERIC RESEARCH/UNIVERSITY CORPORATION FOR ATMOSPHERIC RESEARCH and the “there’s no natural variation component anymore” department comes this blame game claim that seems to ignore history, like the fact that tree rings show decade and century long droughts in the past:


BOULDER — The weather patterns that typically bring moisture to the southwestern United States are becoming more rare, an indication that the region is sliding into the drier climate state predicted by global models, according to a new study.

“A normal year in the Southwest is now drier than it once was,” said Andreas Prein, a postdoctoral researcher at the National Center for Atmospheric Research (NCAR) who led the study. “If you have a drought nowadays, it will be more severe because our base state is drier.”

Climate models generally agree that human-caused climate change will push the southwestern United States to become drier. And in recent years, the region has been stricken by drought. But linking model predictions to changes on the ground is challenging.

In the new study–published online today in the journal Geophysical Research Letters, a publication of the American Geophysical Union–NCAR researchers grapple with the root cause of current drying in the Southwest to better understand how it might be connected to a warming climate.

Weather systems that typically bring moisture to the southwestern United States are forming less often, resulting in a drier climate across the region. This map depicts the portion of overall changes in precipitation across the United States that can be attributed to these changes in weather system frequency. The gray dots represent areas where the results are statistically significant. Map courtesy of Andreas Prein, NCAR. CREDIT Map courtesy of Andreas Prein, NCAR.

Weather systems that typically bring moisture to the southwestern United States are forming less often, resulting in a drier climate across the region. This map depicts the portion of overall changes in precipitation across the United States that can be attributed to these changes in weather system frequency. The gray dots represent areas where the results are statistically significant. Map courtesy of Andreas Prein, NCAR.

–Subtle shift yields dramatic impact–

For the study, the researchers analyzed 35 years of data to identify common weather patterns–arrangements of high and low pressure systems that determine where it’s likely to be sunny and clear or cloudy and wet, among other things. They identified a dozen patterns that are typical for the weather activity in the contiguous United States and then looked to see whether those patterns were becoming more or less frequent.

“The weather types that are becoming more rare are the ones that bring a lot of rain to the southwestern United States,” Prein said. “Because only a few weather patterns bring precipitation to the Southwest, those changes have a dramatic impact.”

The Southwest is especially vulnerable to any additional drying. The region, already the most arid in the country, is home to a quickly growing population that is putting tremendous stress on its limited water resources.

“Prolonged drought has many adverse effects,” said Anjuli Bamzai, program director in the National Science Foundation’s Division of Atmospheric and Geospace Sciences, which funded the research, “so understanding regional precipitation trends is vital for the well-being of society. These researchers demonstrate that subtle shifts in large-scale weather patterns over the past three decades or so have been the dominant factor in precipitation trends in the southwestern United States.”

The study also found an opposite, though smaller, effect in the Northeast, where some of the weather patterns that typically bring moisture to the region are increasing.

“Understanding how changing weather pattern frequencies may impact total precipitation across the U.S. is particularly relevant to water resource managers as they contend with issues such as droughts and floods, and plan future infrastructure to store and disperse water,” said NCAR scientist Mari Tye, a co-author of the study.

–The climate connection–

The three patterns that tend to bring the most wet weather to the Southwest all involve low pressure centered in the North Pacific just off the coast of Washington, typically during the winter. Between 1979 and 2014, such low-pressure systems formed less and less often. The associated persistent high pressure in that area over recent years is a main driver of the devastating California drought.

This shift toward higher pressure in the North Pacific is consistent with climate model runs, which predict that a belt of higher average pressure that now sits closer to the equator will move north. This high-pressure belt is created as air that rises over the equator moves poleward and then descends back toward the surface. The sinking air causes generally drier conditions over the region and inhibits the development of rain-producing systems.

Many of the world’s deserts, including the Sahara, are found in such regions of sinking air, which typically lie around 30 degrees latitude on either side of the equator. Climate models project that these zones will move further poleward. The result is a generally drier Southwest.

While climate change is a plausible explanation for the change in frequency, the authors caution that the study does not prove a connection. To examine this potential connection further, they are studying climate model data for evidence of similar changes in future weather pattern frequencies.

“As temperatures increase, the ground becomes drier and the transition into drought happens more rapidly,” said NCAR scientist Greg Holland, a co-author of the study. “In the Southwest the decreased frequency of rainfall events has further extended the period and intensity of these droughts.”


The study was funded in part by the National Science Foundation, NCAR’s sponsor, and the Research Partnership to Secure Energy for America.

125 thoughts on “@NCAR claims: U.S. Southwest sliding into a drier climate, and it's all your fault

  1. They analyzed THIRTY-FIVE (35) years of data – wow. That should have given them a pretty good picture of past conditions. If I’m not mistaken, pioneers coming across the great plains in the mid-19th century to California referred to it as the Great Western Desert. Is their anything these people do besides make predictions with (simplistic) computer models. How about using a bit of common sense! How about doing a study that, for once, predicts the postive aspects of a warmer climate – after all most plants and animal species (including humans) prefer warmth to cold. How about referring to history, particularily the middle ages, where people benefitted from a warmer climate.

    • (simplistic) computer models
      Simplistic, yes. Simple, no — they can be and should be. And for all their complexity, they also exclude primary relevant factors.
      There appears to be little accounting of PDO flux, and the study does not address the negative-PDO induced droughts of the 1950s.

    • It’s tantamount to measuring rainfall for 5 minutes outside your house, and concluding a flood will occur due to the obvious trend.

      • They measured a 6.5% change over 35 years? So…if a place gets 20 inches of rain a year, a 6% change is….1.2 inches difference. Over the course of 35 years is 0.0342 inches per year.
        How exactly does one “measure” either one over an area the size of two entire states??? These people are insane.

      • Not to mention the Pacific climate shift of the late ’70s since when our constant flow of tropical cyclones came to an abrupt end in SE Queensland.
        35 years of climate Nat Var.

    • There are plenty of records from the local towns in the area and the US weather review has detailed entries from around 1855 and sometimes earlier. 35 years is not long enough to base a study such as this on, any more than anyone can claim that we have a permanently altered warmer/cooler climate based on a few decades of information
      We need to look at evidence as far back as it goes, which in this case includes tree rings as they are a reasonable measure of drought/flood.

      • When was the last time you saw any one of the 57 known GCMs or global climate model graphs for your state or borough or shire that showed what the historical drought conditions for you locality have been.
        I mean a global climate model is not a model of the weather in the American South West.
        It’s not even a model of the Northern, or Southern or Western or Eastern hemispheres.
        And just for good measure, NONE of the 57 global climate models is even a correct model of the global climate.
        Fortunately, nobody has yet used the GCMs to paint us a picture of the climate of the solar system, and its drought history.

      • Well the dust bowl was a region of unusually low humidity back then, and in any case, that is not the American South West any how.

  2. Sometimes, in mischief mode, I may steer a conversation around to The Lake District, here in Cumbria.
    It rains a lot there, west-facing mountains etc etc and the rain keeps getting worse. We keep being told this and its no surprise when you keep moving the recording stations further uphill.
    My question is though – Did all the rain make the lakes or, are the lakes creating the rain?
    And it makes sense does it not – big bodies of water evaporate, make clouds and hence rain.
    For The Lake District its pretty much a pedantic mischief but..
    what about when we apply it to somewhere like the Aral Sea…….

    • The Aral Sea problem appears to be a result of overtapping the Oxus.
      Unaccounted-for rain gauge moves create an inhomogeneity in the raw data, and that would need to be factored in.

  3. If the precipitation data presents cyclic variation similar to hurricanes and typhoons [they are in opposite phase] — 60 year cycle –, 1980 to 2010 shall not indicative of the dry or wet conditions unless we specify which part of the cycle, this period is referring. We generally call it a truncated data that mislead the drought or flood condition.
    Also, meteorological drought is different from hydrological drought; hydrological drought is different from agriculture drought; agriculture drought is different from meteoological drought. Meteorological drught relates to in-situ precipitation and hydrological drought relates to catchment area preciitation; agriculture drought relates to precipitation, crop & soil.
    Dr. S. Jeevananda Reddy

  4. One of the ways of defining drought comes from the groundwater level. If more people are taking more water out of the ground at a rate faster than it is being replaced, then it would seem fair to say that the resulting drought is man-made. What car you drive, or what light bulbs you use is of course irrelevant.

    • There are, as I recall, three different types of drought. Agricultural (soil moisture), meteorological (rain fall), and hydrological (levels in streams and lakes). It’s more complicated than many people make it out to be.

    • Well hardly. The lack of sufficient water might be a result of overuse by humans, but a drought is a problem of inadequate resupply of water from natural sources (the sky); not a problem of excessive use.
      Drought is a natural phenomenon. Misuse of limited water may be a man made problem.

  5. LOL.
    You mean the sort of drought that caused the “decline” that had to be hidden?
    It just gets better and better folks.

  6. Gotta love climate science. What ever it’s doing right now, warming or cooling, is what it will keep doing unabated, until we are all dead.

    • Greenpeace are taking photos of the worst affected bushfire ravaged areas of Tasmania and claiming it as proof of man made global warming .
      I have just one question , has this area never ever been burnt before now ? Or is that just the unbeliever in me .

      • Well, if you don’t allow people to clear a fire break and/or remove the fuel loading around properties then when a bush fire starts the affects are worse. What about the Victorian fires – started by lightning

      • Interesting. Usually they take a photograph of the environment and proclaim that this is the way it has always looked and should always look. Forevah!!!!!

  7. It was understandable that many of us thought at the start, that GHG global warming would express as a slow, rather uniform blanket like effect that did not single out small regions for special treatment.
    The paper under discussion has taken the non uniform evolved GHG hypothesis to heights that are , well, not credible. I would recommend shelving it for another 25 years so the vagaries of Nature can be expressed and perhaps allow humility in apology.

  8. I guess my high school history lessons were wrong then. The Anasazi native Americans didn’t abandon their pueblos because of drought after all. The NCAR has proven to me droughts are only because of AGW.

    • Sigh … It was all because the Anasazi drove too many SUVs. The Wise ones tried to warn them. But they did not listen.
      It does not, BTW, take a climate scientist to project that there are probably more water users in the Western US (exclusive of a narrow coastal strip from Monterrey North) than natural precipitation can support. Probably ought to do something in the way of improved water management. But that’s SUCH a drag …
      I know. Let’s blame climate change. That’ll fix everything.

      • gary turner: Absolutely. Four wheel drive is magic and 4WD design and repair is taught in the fourth year at Hogwarts. Those things can go anywhere in time and space. MarkW must not watch TV commercials (lucky him).

  9. It was well known 20 years ago that the last three decades of the 20th century were unusually wet in Colorado as the population boomed. There were concerns that the state may not have enough water for the future. It’s old news.

  10. “In the Southwest the decreased frequency of rainfall events has further extended the period and intensity of these droughts.”
    Who would have thought that it’s the lack of rain. I’m glad there was a study to tell us this.

  11. Didn’t all this change this year? With the arrival of “The Christ Child”, El Nino, didn’t the south west get a good dousing of rain?

    • Yes, it did.
      But please don’t confuse “climate scientists” with facts, ie actual observations of the real world.

    • So far it’s been a pretty “average” rainfall year, which is great in the midst of a drought, but won’t bring the drought to an end. The Southwest still needs above average precipitation in the next couple months to put a dent in the drought.

  12. Based on a 35 year study. 35years!! 35 years is just weather, not climate. Any projection based on less then 180 years is worthless as a predictor of future trends…pg

    • 180 years takes us right back to the Little Ice Age, which is also a worthless starting point for projections, so it looks like you forgot your “sarc tag”.

  13. Climatologists will have to re-invent past studies that did, and then did not find an increase or decrease in oceanic-atmospheric trends that were exclusive to the last half of the 20th century attributed to anthropogenic CO2 increase. I well remember the plethora of studies that heralded the rising Arctic Oscillation as a canary in the coalmine harbinger of anthropogenic catastrophe. I still have to laugh out loud when that oscillation fell into negative territory. You would think the phrase “anthropogenic drivers” is the most often used phrase. It isn’t. The phrase heard most often near the water cooler down the hallway of climatologists’ offices? “Never mind.”

  14. We move into a desert, make it green by taping the water table and the Colorado River, exhaust those resources, then blame anthropogenic CO2 emissions when it reverts to its natural state. Science at its very best!

  15. From the head post:

    […] blame game claim […]

    Say that really fast 5 times. Almost as good as “The Leith Police dismisseth us.”

  16. Since mid-2007, I have been measuring and reporting daily rainfall at my house on the west side of Tucson, Arizona. Here are the results:
    Here is the total rainfall recorded in inches since 2008:
    2008: 12.09
    2009: 10.00
    2010: 11.56
    2011: 10.83
    2012: 10.85
    2013: 7.95
    2014: 11.36
    2015: 14.32
    Where is the drought?

    • ..Hey, not fair, you took actual measurements !! Don’t you know that only computer models can tell us what is happening in the world ! Didn’t you watch ” Matrix ” ??….

    • In SoCal, where population went up 87% since 1970 while total state water storage increased 26%. Essay False Alarms. Cause greens don’t like dams and reservoirs as much as they don’t like fossil fuels. Hard to see anything useful that they do like. Zero GHG nuclear electricity? Nope. GMO crops that improve yields and cut down on toxic pesticides? Nope. Preserving jungle habitat for orangutangs and carbon sequestration? Nope, burn it all down for palm oil plantations for green biofuel. Grid solar and wind aren’t useful because of intermitency. And so on.

    • I’ll bet a lot of that is Summer thunderstorms. Because of the prevailing Westerly winds, those rarely make it West of the Sierra Nevada. Unfortunately almost all the people in California live West of the Sierra crest and depend on Winter rain/snow (plus all the rivers elsewhere they can hijack) for water.

  17. “They identified a dozen patterns that are typical for the weather activity in the contiguous United States and then looked to see whether those patterns were becoming more or less frequent. (over35 years of data)”
    You have got to be kidding me! Looking for frequency changes of large scale weather patterns over 35 years? How does this stuff get published? 60 years would be too short for what they are trying to do! At least this paper can be used in an intro stats class or research methodology class to demonstrate the perils of low sample size!
    What an embarrassment for the authors, the reviewers, NCAR and the journal.
    Basic science fail.

  18. Climate models generally agree that human-caused climate change will push the southwestern United States to become drier. And in recent years, the region has been stricken by drought.
    As sentient climate models do not exist, what is probably meant is that the assumptions in the climate models are programmed to show the assumed effect of CO2 will change the path of the modeled weather systems. The modelers and climate ‘scientists’ have decided that this extra 1% of atmospheric CO2 comes from anthropogenic sources.- as they can’t (don’t want to) think of anything else.

  19. “… they are studying climate model data for evidence of similar changes in future weather pattern frequencies.”
    Good trick! Could they apply that technique to lottery numbers, do you think?

    • .. As a youngster ( 18, many moons ago ) I actually wrote a program ( in Basic ) that did just that…Took only 20 command lines and 48 hours of inputting data from all sources, then running the program for 48 hours and I got …. not even one match of the previous combinations !! Aaahhh, to be young and stupid again…those were the days !

    • ……… Tom in Florida
      February 11, 2016 at 4:32 am
      As the late Sam Kinison said: “It’s a desert, a f*****g desert…”

  20. NCAR: they are government employed pseudo-scientists being paid to imagine things and manufacture causes to support their political appointee overseers wishes.
    The push to rationalize a drive for CO2 emissions taxes is about the to get very desparate.
    Climate Change alarmism has been and always will be about the Left’s drive for more and newer sources of tax revenue and top down control.

  21. Thirty five years of data?? Thirty five years?? I submitted almost two hundred more years of data here (230 years to be exact as of 2012, going back to 1769):
    Neil Jordan
    February 18, 2012 at 1:00 pm
    Dr. Christy: Thank you for your effort in bringing old records to light. There is another set of California records going back to 1769 that you might consider, related to the “Lynch Index” that was in the California Weather Sumary CD. Jim Goodridge sent me a California Weather CD in 2002 that contained the file “Lynch Index.xls” that tabulates Southern California rainfall from 1769-1770 to 1999-2000. The CA Weather CD updated to 2009 does not appear to have that file. The state climatologist at http://www.water.ca.gov/floodmgmt/hafoo/csc/ might provide some information.
    The Lynch Index was based on the August 1931 report, “Rainfall and Stream Run-Off in Southern California Since 1769” by H. B. Lynch, for the Metropolitan Water District of Southern California. The report is available on-line at http://cepsym.info/history/RainfallStreamRunoffSoCA_since1769.pdf
    The Lynch Index spreadsheet correlates the index from the 1931 report with the rainfall record for Los Angeles. The index stops at 1930, and DWR did an extension to 2000. I did a linear regression analysis on the data, and also an extension (ref Bedient & Huber) of the data to present. Slopes of the regression lines are close to zero.
    Moderators: The following text is verbatim from the spreadsheet. Truncate if it does not fit within your format and perhaps I can provide the information another way.
    Thank you.
    Note 11 Feb 2016: The full 230 years of Southern California rainfall are tabulated at the WUWT link above. I truncated this post to save space.

  22. Don’t they call the primary geological feature of the southwest United States the Mojave Desert? On the boarder of California and Nevada “Death Valley” one of the hottest places on Earth? In recent geological history, say the last 60,000 years, there has been nothing but drought in these parts!

    • ..and the Sonoran Desert and the Chihuahuan Desert. Hot. Dry. Where cows eat cactus to stay alive during droughts. Ranchers burn the thorns off. Acres and and acres with something resembling a poor man’s flame thrower. On foot. We’re talking AGW’d-no rain-worth-mentioning-this-year-serious-ozoneless hot here.

  23. Just in case, I think that electricity should be turned off to the South West, Washington DC and wherever NCAR, NASA and live. Sometimes I wish I could do that. I wonder if we would hear any screaming.

  24. …linking model predictions to changes on the ground is challenging.

    Isn’t it though? It would be sooo much easier if we didn’t have those damn dirty d**iers always looking over our shoulder, questioning everything we do. Why do they have to make life so difficult for us?
    Damn dirty d**iers!

    • yep, it takes on awful lot of work to correct those pesky data to finally agree with the models. Very time consuming.

  25. The water alarmists in SW US are continually keeping the public’s attention on Lake Mead water levels. But don’t look at Lake Powell-Glen Canyon levels-inflows/outflows and the upper Colorado River reservoir stats and snow pack. Don’t go there.
    They had to keep the public placated to maintain political support for the new $817million 3rd intake tunnel. That tunnel was uncapped in September, flooding the completed tunnel. Now another $650 million pumping station is to be completed by 2020 to bring the new tunnel water to the system.
    The point is the pols need water alarmism and an always ever imminent crisis to keep the public support to build these massive new projects, like a water tunnel and pump station that may never be needed. These $billion dollar projects are partially paid for with large bond sales that add significant new charges to users water bills. The unions and their Democrat lap dogs love these jobs programs.
    The bottom line is big bathtub ring photos of Lake Mead make for great alarmist hype. And it is The upstream Lake Powell-Parker Dam outflows that controls that picture. Eyes should stay focused on the government’s control and releases on the Upper Colorado once the 2016 snow pack melt season starts. Currently the western Rockies are at or above their 1984-2010 averages. So there will be lots of inflow to Lake Powell, currently 105 ft below its full level.

  26. Yesterday A.M. , the Weather Network advised 4 cm( less than 2 inches ) of snow for London, Ontario, Canada for the next two days…..As of right now, Thursday 12:49 , we are at eight inches and still coming down heavy !! AND the web site is STILL calling for less then 1 cm for the next 8 hours ??…NUTS !

    • London Short Term Forecast
      Thu Afternoon
      A few flurries
      A few flurries
      Feels like: -18
      POP: 60%
      Snow: ~1 cm
      Wind: 30 km/h W
      Wind gust: 54 km/h
      Humidity: 61%
      Hourly Forecast
      Thu Evening
      Partly cloudy
      Partly cloudy
      Feels like: -21
      POP: 20%
      Snow: –
      Wind: 20 km/h SW
      Wind gust: 36 km/h
      Humidity: 66%
      Hourly Forecast
      Thu Overnight
      Partly cloudy
      Partly cloudy
      Feels like: -21
      POP: 20%
      Snow: –
      Wind: 15 km/h W
      Wind gust: –
      Humidity: 61%
      Hourly Forecast
      Fri Morning
      A few flurries
      A few flurries
      Feels like: -20
      POP: 40%
      Snow: <1 cm
      Wind: 20 km/h SW
      Wind gust: 41 km/h
      Humidity: 72%
      Hourly Forecast

  27. One problem with the AGW linkage NCAR attempts with their 35 years of weather system data is that for over half that period, there as been essentially no lower troposphere warming.
    Another problem is that GCMs do not downscale regionally. So climate models can say nothing about lower forming off the Pacific Northwest, nor drying conditions in the US SW.

  28. ..Just imagine the benefits Canada and ALL North America would experience IF Glo.Bull warming was really happening…Canada is the 2nd largest country in the world and 90% of it is frozen ! D’oh !

  29. Well, there is a water problem in the US southwest. But it seems to be mostly related to increasing human population outstripping the supply from aquifers and relatively small supply from rivers. Any contribution from warmer temperatures is minor by comparison.

      • …Don’t you know..only sand created by Unicorn shit is allowed to create deserts…How Unicorn shit is created is a study that needs to be funded !!……do I need need to add a sarc here ? LOL

      • And according to model “data” there will be more and more of the wrong kind of sand in 10,000 years time. We must act NOW !!

    • there was a guy on the wireless saying that that jet stream was speeding up because of CO2 emissions causing the climate change and that would make air travel more expensive. he somehow proved that the losses to a plane acting against a force were not balanced by the gains of the same force acting on the plane in the opposite direction.
      I don’t understand it.
      I have him here Dr Paul Williams

      • @zemlik – He is right, or rather he would be right if pilots flew in the jet stream both ways. As I understand it, you ride the jet stream when it’s going your way (i.e. east) and you fly outside the jet stream when you’re going west. That way, he’d be wrong, faster jet stream would mean fuel and time savings.
        Of course, there’s no actual evidence that jet streams are speeding up. Just another piece of fabricated propaganda fantasy, to show how incredibly versatile CO2 is – it can do anything you want it to, you just have to write a model. If your model shows a benefit from increased CO2, you’ve obviously made a mistake because CO2 is inherently EVIL and cannot by definition be beneficial.

  30. The coldest air of the winter and perhaps during all of last winter will plunge across the New York City area during Valentine’s Day weekend.
    The polar vortex is a storm that is typically centered near the North Pole and tends to keep the coldest air trapped in northern Canada. Occasionally, this storm weakens or shifts enough to allow frigid air to plummet southward into the United States.
    The combination of wind and cold will make for dangerous conditions for the homeless and those not properly dressed this weekend.

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