California Drought, Midwest Chill Tied to Climate Change?

By Tom Yulsman | April 17, 2014 11:08 am
Climate Change

The Great Lakes on the night of April 16, 2014, as seen by the VIIRS instrument on the Suomi NPP satellite. Ice is still present on all the Great Lakes except Lake Ontario. (Source: CIMSS Satellite Blog)

Here we are in mid-April and the Midwest is experiencing yet another unusual wintry blast. No wonder there’s still quite a lot of ice in the Great Lakes, as you can see in the remarkable image above, captured under a full moon at night by the Suomi NPP satellite.

Click on it to enlarge it. The ice is particularly evident in Lake Superior at upper left.

Meanwhile, warm and dry conditions continue in California.

New NASA-funded research led by Simon Wang at Utah State University, suggests that this pattern — frigid cold in the North American mid-section and dry in California — is connected to global warming.  In this post, I’ll explain the connections identified in the research, which was published in Geophysical Research Letters. But before I get to the details, I do want to emphasize the caveats: This is just one study, and it’s in an area of cutting edge research. More about the caveats toward the end, but first…

The proximate cause of the cold/dry dichotomy is a “dipole” pattern of atmospheric pressure. It consists of low a pressure trough stretching from northern Canada down into the Midwest, which allows Arctic air to spill south; and a high pressure ridge centered in the Gulf of Alaska and stretching down the Pacific coast to California. This ridge tends to block weather systems from delivering desperately needed moisture to California.

You can see the pattern here:

climate change

A map showing how geopotential heights varied from the norm on April 14. (Source: NOAA/ESRL)

The colors in this map correspond to something known as “geopotential height anomalies.” I explained this phenomenon in some detail earlier this year in this post. Suffice it to say that warmer colors correspond to higher atmospheric pressure, warmer temperature, and dry conditions in California; cooler colors correspond to lower pressure and colder temperatures.

Note that blob of blue and purple over North America’s midsection, and the yellow and green blob to the west. This is the dipole pattern, and it has been remarkably persistent.

In their research, the Utah State scientists analyzed the historical data and found that this dipole pattern has actually been intensifying since the late 1970s. To figure out what’s going on, they used a new global climate model.

The scientists found that with natural variation alone, the dipole pattern should have actually been weakening since the late 1970s. But when emissions of greenhouse gases and their effect on the climate system were added into the computer simulations, the dipole did indeed seem to intensify. (Click here to see an infographic depicting these findings.)

There is also an intriguing link to El Niño, the much ballyhooed phenomenon tied to sea surface conditions in the equatorial Pacific ocean that causes climatic effects around the world.

The researchers found that the dipole pattern tends to turn up one year before an El Niño. Here’s how the scientists put it in their paper:

One striking result of the diagnosis is that the dipole corresponds strongly with circulation features of the year prior to an El Niño, and also appears to be triggered by a wind and SST pattern that has been identified as a potential long-lead precursor of El Niño.

By “SST” they mean sea surface temperatures. Based on observations of SSTs in the Pacific ocean, as well as wind patterns, the National Oceanic and Atmospheric Administration pegs the odds of an El Niño developing later this year at greater than 50 percent.

And here is another possible link to global warming: In the computer modeling, dry conditions over California were seen to be connected to the precursor conditions of an El Niño only when the climate system was “forced” by the addition of greenhouse gases.

The modeling also showed that continued climate change could make things worse: “It is important to note that the dipole is projected to intensify, which implies that the periodic and inevitable droughts California will experience will exhibit more severity,” the researchers wrote.

It’s important once again to keep the caveats in mind. This is just one study. Also, possible connections between the kinds of patterns observed this winter and global warming is an area of research at the cutting edge of climate science. That means we don’t have definitive answers yet. Further research will be needed to pin down what’s going on, and the degree to which — if any — global warming is involved.

For me, the research brings back the sage words of Wally Broecker, a renowned geoscientist at Columbia University’s Earth Institute: “The climate system is an angry beast, and we’re poking it with sticks.”

Have the Utah State researchers accurately identified a twitch in the climate dragon caused by our poking? Time will tell.


  • William Schnarel

    Odd – Every other study so far has found that the seeming extremes in weather in the reasonably recent past fall well within normal variances and are only extreme when viewed singularly. Not to mention that the weather therefore has been, bt definition, totally unaffected by global warming, either real (as a product of earths non-static environment) or imagined (as a product of man’s interference).

    • Common Sense


  • William Schnarel

    The drought in California has been caused by liberal politicians and left-wing eco-wackos who won’t allow the existing rainwater to be captured for use, not nature

    • Common Sense

      California has a long history of droughts. This one is actually very typical. This climate change nonsense has to stop.

      • RickRollington

        You’re an idiot.

    • Clint Sheehan

      No sir they don’t have a short yellow bus for adults.

    • Tom Yulsman

      William: Thank you for commenting here, and I hope you will do so again. But I have to ask that you reserve the ad hominem attacks for another blog. I don’t allow them here. You have every right to disagree with people on the issues. And we can debate them here civilly. But I won’t tolerate language like “eco-wackos.”

    • Tom Yulsman

      William: As I’ve said elsewhere, no ad hominem attacks are allowed here. So feel free to debate, but comments like yours about “wackos” are just not acceptable.

    • Getplanted

      Mr. Schnarel,

      We “left-wing eco-wackos” have been working for water conservation for decades. You right wing industry anti-environmentalists have been hacking away at our quality of life for centuries.

  • Uncle Al

    All observation is Climate Change promising human extinction that can only be ended in 100 years by the Carbon Tax on Everything now.

    Revelation 22:7: Gauged, renormalized, perturbation theoried, dualed, promoted into higher dimensions, exhaustively peer reviewed and published. Wrong, Aristotle versus Galileo.

  • disqus_atlq8Zmtsd

    I hate these predictive computer model studies. Confirmation bias is just too unavoidable in them. The selection of the computer model is inevitably going to be made based on the “value” of its predictions. This means that ethos of the person selecting will play heavily in determining what kind of model is selected.

    Not a criticism of you, Tom. As always you were very careful to report on the research while passing out grains of salt.

  • Common Sense

    At least the title of this article included a question mark. That’s a start.

  • Vincent Wolf

    Why not blame it on Obama as everything else is?

  • DaveAlaska

    Time to de-fund NASA. They are spending all my stolen tax money attempting to justify more government in my life, but they cannot even get a human into orbit anymore..

  • Tracy Best

    You folks just refuse to listen to scientific evidence! Climate change is real and statisically valid.Unplug your ears, listen to the world around you, and quit worshiping the almighty dollar. That’s what it all comes down to is the money to be made in the hydrocarbon-based fuel, the products that use them and how it will effect your pocketbook.. Clearly you folks don’t care about the environment nor any living species on Earth (including humans). Yes, I am a liberal AND a PhD Chemist AND I care about the environment. Quit whining and educate yourselves!

    • DaveAlaska

      Hopefully, we will mitigate or avoid the next ice age — unless you hate Canada of course: that place is all ice, miles deep ice, except during brief interglacials like the current one.

    • Common Sense

      I have educated myself. What I have discovered is that the effect of CO2 on the climate is logarithmic.

  • Grant Klokeid

    The answer to your question is NO.

  • RickRollington

    Discover shouldn’t allow comments on climate change articles. Too many right-wing morons out there spewing Koch brothers talking points.

    • Common Sense

      What they shouldn’t allow….is name calling.

      • Tom Yulsman

        I strongly agree. And when it comes to ad hominem attacks, I have a two strikes and you’re out policy. So Rick, in the future, please keep it to the issues.

        • Common Sense


  • Carlos D. Aguirre

    Clearly, climate change showing its effects so visibly. Actions must be take to combat it before it is too late.



ImaGeo is a visual blog focusing on the intersection of imagery, imagination and Earth. It focuses on spectacular visuals related to the science of our planet, with an emphasis (although not an exclusive one) on the unfolding Anthropocene Epoch.

About Tom Yulsman

Tom Yulsman is Director of the Center for Environmental Journalism and a Professor of Journalism at the University of Colorado, Boulder. He also continues to work as a science and environmental journalist with more than 30 years of experience producing content for major publications. His work has appeared in the New York Times, Washington Post, Audubon, Climate Central, Columbia Journalism Review, Discover, Nieman Reports, and many other publications. He has held a variety of editorial positions over the years, including a stint as editor-in-chief of Earth magazine. Yulsman has written one book: Origins: the Quest for Our Cosmic Roots, published by the Institute of Physics in 2003.


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