Study: U.S. droughts can be explained by ocean forcing

Sea surface temperature can nudge the atmosphere into conditions, subsequently exacerbated or moderated by atmospheric variability, that can lead to drought.

In this paper, authors Richard Seager (Lamont-Doherty Earth Observatory, Columbia University) and Martin Hoerling (NOAA ESRL) examine the causes of North American drought, investigate the predictability of drought, and explore the contribution of climate disturbances to drought. 

Atmospheric models were forced using idealized and observed SST values to determine the contribution of tropical SST anomalies to precipitation and soil moisture as opposed to the contribution of atmospheric variability and other factors.

The authors find that up to 40 percent of the variability of annual mean precipitation in the North American south, southwest, and southern Great Plains can be explained by ocean forcing, and conclude that sea surface temperature can nudge the atmosphere into conditions, subsequently exacerbated or moderated by atmospheric variability, that can lead to drought.

The authors also find that the general warming trend over the United States, particularly in the southwest, may lead to a more rapid onset, and delayed resolution, of drought conditions in the future.

This paper is published in the June 2014 issue, and is part of a special collection on Global Drought Information System Worldwide.

Atmosphere and Ocean Origins of North American Droughts

RichardSeager Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York
MartinHoerling NOAA/Earth System Research Laboratory, Boulder, Colorado

Abstract

The atmospheric and oceanic causes of North American droughts are examined using observations and ensemble climate simulations. The models indicate that oceanic forcing of annual mean precipitation variability accounts for up to 40% of total variance in northeastern Mexico, the southern Great Plains, and the Gulf Coast states but less than 10% in central and eastern Canada. Observations and models indicate robust tropical Pacific and tropical North Atlantic forcing of annual mean precipitation and soil moisture with the most heavily influenced areas being in southwestern North America and the southern Great Plains. In these regions, individual wet and dry years, droughts, and decadal variations are well reproduced in atmosphere models forced by observed SSTs. Oceanic forcing was important in causing multiyear droughts in the 1950s and at the turn of the twenty-first century, although a similar ocean configuration in the 1970s was not associated with drought owing to an overwhelming influence of internal atmospheric variability. Up to half of the soil moisture deficits during severe droughts in the southeast United States in 2000, Texas in 2011, and the central Great Plains in 2012 were related to SST forcing, although SST forcing was an insignificant factor for northern Great Plains drought in 1988. During the early twenty-first century, natural decadal swings in tropical Pacific and North Atlantic SSTs have contributed to a dry regime for the United States. Long-term changes caused by increasing trace gas concentrations are now contributing to a modest signal of soil moisture depletion, mainly over the U.S. Southwest, thereby prolonging the duration and severity of naturally occurring droughts.

Source: http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-13-00329.1

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23 Responses to Study: U.S. droughts can be explained by ocean forcing

  1. Alan Robertson says:

    “Long-term changes caused by increasing trace gas concentrations are now contributing to a modest signal of soil moisture depletion, mainly over the U.S. Southwest, thereby prolonging the duration and severity of naturally occurring droughts.”
    __________________
    the money shot

  2. Pamela Gray says:

    Gotta have that bling in order to hear the climate gravy train go ch-ching!

  3. Doug Proctor says:

    The 40% attributable to ocean temps is only 40% of what was modeled. More contributors, different models, who knows. All for sure is that significant amounts come from ocean conditions.

    We love statistics more than we care they represent the truth. I wouldn’t be so critical if the authors admitted to uncertainty about how their work was reflective of actual processes OR made predictions based on certainty AND later reported the results.

    Academics have it both ways. Definite results and no post-mortem. Much like stockbrokers and politicians.

  4. Jon Alldritt says:

    That was my thought and when they gave no info on why sealed it.

  5. Pamela Gray says:

    Same guy who came to a different conclusion in 2011.

    “The six severe multiyear droughts that have struck western North America in the instrumental record have all been attributed (by the use of climate models) to variations in SSTs in the tropics, particularly persistent La Niña–like SSTs in the tropical Pacific Ocean (15–19). The projected future climate of intensified aridity in the Southwest is caused by different processes [though in the future I will change my mind], because the models vary in their tropical SST response to anthropogenic forcing. Instead, it is caused by rising humidity that causes increased moisture divergence and changes in atmospheric circulation cells that include a poleward expansion of the sub- tropical dry zones. The drying of subtropical land areas that, according to the models, is imminent or already under way is unlike any climate state we have seen in the instrumental record.”

    http://www.tiggernut.com/ClimateChange/Seager_Model_Projections.pdf

    My takeaway? Seager has learned how to continue to suck the climate gravy train teat while keeping one hand firmly over his ass.

  6. JJ says:

    Pamela Gray says:

    Same guy who came to a different conclusion in 2011.

    Did he?

    Re-read the abstract for the current article. Pay very careful attention to what it says. In particular, pay careful attention to what is not said.

    There is something very dishonest going on here, but it is not what you think it is. It’s worse.

  7. Jack Hydrazine says:

    And what drives ocean temperatures?

  8. Bob Tisdale says:

    And because the CMIP5 climate models used for attribution and projection studies cannot simulate annual, decadal or multidecadal variations in sea surface temperatures, they have no value a producing predictions of future droughts.

  9. Otter (ClimateOtter on Twitter) says:

    Didn’t a pro-AGW scientist just recently say that sea-surface temperature data was ‘lousy’? That seems to bode ill for any attempts to link drought to ‘man-made’ anything, which I am sure they would attempt to claim with this finding.

  10. izen says:

    @- Bob Tisdale
    “And because the CMIP5 climate models used for attribution and projection studies cannot simulate annual, decadal or multidecadal variations in sea surface temperatures, they have no value a producing predictions of future droughts.”

    Absolutely correct. CMIP5 models are incapable of accurate predictions at the local or short timescale level. So predicting the location or date of a drought is beyond their capabilities.

    However climate modelling is the best {only?} Way we have of projecting the probabilities of drought given the changing climate.
    The dice are loaded, drought is much more likely with recent changes in SST.

  11. izen says:

    @- Otter (ClimateOtter on Twitter)
    “Didn’t a pro-AGW scientist just recently say that sea-surface temperature data was ‘lousy’? ”

    No, the quote is -
    Stephen Briggs from the European Space Agency’s Directorate of Earth Observation says that surface air temperature data is the worst indicator of global climate that can be used, describing it as “lousy”.

    And pointing out that as most {~90%} of the energy goes into the oceans so SSTs and sea level rise are much better metrics of warming than a noisy and minor component of the system, the surface air temps.
    Even if that is where we live.

  12. Latitude says:

    wonder what it would take to get them to stop using that word…….forcing

  13. Bill_W says:

    JJ said: “Re-read the abstract for the current article. Pay very careful attention to what it says. In particular, pay careful attention to what is not said.

    There is something very dishonest going on here, but it is not what you think it is. It’s worse.”

    I can’t see the correct article or abstract. Can you elaborate JJ?

  14. JJ says:

    Bill_W says:

    I can’t see the correct article or abstract. Can you elaborate JJ?

    The abstract is posted above, at the end of the press release that Anthony has reposted here. The article is paywalled. This means that it is highly unlikely that the press or the public is going to see what is in the article. So for all intents and purposes, the abstract becomes the article for 99.9% of the public who are exposed to the press release.

    What message do you take away from the press release and the abstract?

  15. Pamela Gray says:

    In looking for a preprint pdf, (which I FOUND: http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&cad=rja&uact=8&ved=0CEMQFjAD&url=http%3A%2F%2Fwww.ldeo.columbia.edu%2Fres%2Fdiv%2Focp%2Fglodech%2FPDFS%2FSeager_Hoerling.pdf&ei=QF2kU_LlAsWvyATG44L4Cw&usg=AFQjCNE0pJY_flbsUNQZSJS5mKJvYh9RTg&sig2=PNZbVqymrjbv2_DDaatH9Q
    …I ran across a number of interesting facts about the co-author. It seems that Martin Hoerling is someone who has more often than not, been on the natural climate variability side of AGW proponents (and I know how tortured that sounds). He has riled the feathers of folks like Climate Progress because of his NOAA “non-peer reviewed” reports on the…wait for it…weather being just…wait for it…weather.

    Martin also prefers to use statistical analysis of past weather to understand current weather and has not shown up on many, if at all any, AGW scare articles. I see two questions:

    1. Why the use of models now?
    2. Why bed down with Seager, a known catastrophist (see the link below) who would sell his children for another chance to use an IPCC model to further his career in obtaining teat time from the climate gravy train?

    http://ocp.ldeo.columbia.edu/cgi-bin/ocp_pub/all?year=3&author=Seager&lname=Seager&fname= Richard

  16. Pamela Gray says:

    LOL! Where that last word (Richard) came from I don’t know! Guess I was cutting and pasting too fast. And I copied right off the search engine bar! My name is not Richard.

  17. mpainter says:

    I got as far as the first sentence of the second paragraph above. That told me all I needed to know to evaluate this (would-be) scienific study.

  18. JJ says:

    Pamela Gray says:

    LOL! Where that last word (Richard) came from I don’t know!

    It appears to have been part of the link that you pasted, being the first name of author Seager.

  19. Pamela Gray says:

    I find it deliciously ironic that articles like the one above can be scrutinized pretty much only here on this blog. Why only here? Because Anth*** includes a very handy US Climate Reference Page section that we can use to compare the conclusions with reality. Let’s hope Martin quickly reverses this short foray into the AGW climate gravy train scam and gets back to doing what is necessary in terms of providing excellent analysis of historical statistical data. Martin, back away from the climate model game controller, do not make eye contact with the others in the room, and keep your back to the door as you quickly but calmly exit.

  20. Pamela Gray says:

    Speculation abounds wrt my questions posed earlier. Do you suppose this little play date with Seager was “encouraged” by higher ups to shore up sagging budgets in the NOAA program, or at least to give the impression that Martin is a “team player” given the negative image he has with AGW political/media/internet hacks?

    In 2013 Martin gave a ppt presentation via phone (click on his name when you get to the link below for his presentation – very interesting) that clearly indicated GHG emission changes were not significantly involved in causing droughts. I would presume he meant based on the standard severity metrics would include how long they last.

    So it stands to reason to ask why the tagged on final sentence in the featured abstract above and in the article it stems from that has him saying otherwise?

    http://www.westernstateswater.org/improving-drought-prediction-at-seasonal-to-inter-annual-timescales-workshop-presentations/

  21. Pamela Gray says:

    Read the paper. Apparently no research was done. It was a review of already completed (by someone else? Or maybe Seager?) model runs compared (which they did as little of that as possible) to observations. The tome begins and ends with catastrophic [imaginary] trends in extreme events, including everything but the toilet bowl. And ends with the ever-present payment to the teat of climate gravy train grants.

    What is weird is that the body and summary of the work simply and elegantly refutes their introduction and their teat payment final statement. So is it possible that Seager wrote the beginning and ending teat payment and Martin wrote the rest, using Seager’s model research done previously by Seager and others? I can’t see a signal for Seager’s style of writing in the body or summary but it shines its brightest in the intro and payment section.

    The whole thing would flow better if the beginning and ending actually matched what was discovered on review of these model runs. The fact they don’t match means to me it is a flagrant blatant attempt at 1) teating, and 2) cloaking Martin in team player status. How that cloak must itch.

  22. Pamela Gray says:

    Which brings me to the newly defined climate science research article outline and why I find it weird that the above paper actually uses real data along with model data and says that both are rather unpredictable. It appears that the new outline was followed for the most part with the exception of including observations. I believe that is what Martin brought to the table. Otherwise Seager’s footprint is on this work, if not on Martin’s pen.

    Scary Climate Introduction
    Methods (using pretend data you can’t have)
    Results (using pretend data you can’t have)
    Discussion (using pretend data you can’t have)
    Conclusion (using pretend data you can’t have)
    Scary Climate Payment

  23. Frank says:

    I would like this!!!…

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