23 July 2012

Krugman vs. Research, Who You Gonna Believe?

In yesterday's NYT Paul Krugman writes:
[R]eally extreme high temperatures, the kind of thing that used to happen very rarely in the past, have now become fairly common. Think of it as rolling two sixes, which happens less than 3 percent of the time with fair dice, but more often when the dice are loaded. And this rising incidence of extreme events, reflecting the same variability of weather that can obscure the reality of climate change, means that the costs of climate change aren’t a distant prospect, decades in the future. On the contrary, they’re already here, even though so far global temperatures are only about 1 degree Fahrenheit above their historical norms, a small fraction of their eventual rise if we don’t act.

The great Midwestern drought is a case in point. This drought has already sent corn prices to their highest level ever. If it continues, it could cause a global food crisis, because the U.S. heartland is still the world’s breadbasket. And yes, the drought is linked to climate change: such events have happened before, but they’re much more likely now than they used to be.

Now, maybe this drought will break in time to avoid the worst. But there will be more events like this. Joseph Romm, the influential climate blogger, has coined the term “Dust-Bowlification” for the prospect of extended periods of extreme drought in formerly productive agricultural areas. He has been arguing for some time that this phenomenon, with its disastrous effects on food security, is likely to be the leading edge of damage from climate change, taking place over the next few decades; the drowning of Florida by rising sea levels and all that will come later.

And here it comes.
Krugman's claims raise an obvious question: Have US droughts actually become more common on climate time scales? Especially US Midwest droughts?

Instead of looking at the musings of a "climate blogger" (as entertaining as that may be) like Krugman does, let's instead look at scientific research that has examined trends in US droughts. A crazy idea, I know. Fortunately, scientists have examined empirical data on the frequency and severity of drought on climate time scales.

Here is Andreadis and Lettenmaier (2006) in GRL (PDF):
[D]roughts have, for the most part, become shorter, less frequent, less severe, and cover a smaller portion of the country over the last century.
A longer excerpt:
We used a constructed time series of soil moisture and runoff over the continental U.S. to examine trends in soil moisture and runoff, and drought characteristics related to these variables for the period 1925–2003. Over much of the country, there has been a wetting trend, reflected in a predominance of upward trends in both model-derived soil moisture and runoff. These trends are generally consistent with increases in precipitation during the latter half of the 20th century observed over most of the U.S. [Groisman et al., 2004], and are in general agreement with results from other studies [Dai et al., 2004; Milly et al., 2005]. Furthermore, trends in the simulated runoff are similar to those in observed records of streamflow at a set of index stations that have been minimally affected by anthropogenic activities. Trends in most drought characteristics are similar to those in soil moisture and runoff, that is, droughts have, for the most part, become shorter, less frequent, less severe, and cover a smaller portion of the country over the last century. The main exception is the Southwest and parts of the interior of the West ...
About that recent breathless NOAA press release and subsequent media frenzy ... Have a look at comments by John Neilsen-Gammon and also Cliff Mass, both of whom pushed the button.

PS. Here is the necessary disclaimer to ward off those, like Krugman, who use the notion of "deniers" to shout down inconvenient voices: Climate change is real, humans have a significant impact on the planet, and mitigation and adaptation policies both make sense, as I argue in The Climate Fix. None of that justifies treating climate science like astrology.


  1. Very telling that you never mention Dr. James Hanson in your post. Krugman is simply elaborating on what Dr. Hanson's recent paper. If you want to make an effective rebuttal address Hanson's paper, not Krugman's gloss. My first reaction to reading you was, why is he so obviously avoiding the meat of Krugman's article?

  2. -1-DGP

    Thanks for the comment. Hansen's latest paper (which I presume is the one you are referring to) says this:

    "The probability of occurrence of extreme anomalies as great as the Moscow heat wave in 2010 and the Texas/Oklahoma heat wave and drought of 2011 has increased by several times because of global warming (22), and the probability will increase even further if global warming continues to increase."

    What is ref #22?

    "Diaz, R. J., Rosenberg, R., 2008: Spreading dead zones and consequences for marine ecosystems. Science, 321, 926-928."

    So ... hardly an analysis of US drought of any sort, and I assume that the reference is a mistake rather than simply irrelevant to the claim.

    Please be more specific if you'd like a further response.


  3. DGP -- Never confuse a political extremist with a scientist. Especially a political extremist whose financial well-being is greatly enhanced by his activism.

    Upton Sinclair -- "It is difficult to get a man to understand something, when his salary depends upon his not understanding it!" [or his budget, his power, his royalties, his fame, and his receipt of large gifts]

  4. Krugman lost credibility by citing a climate blogger that is a partisan hack to most serious people. See Keith Kloor's and Richard Tol's recent tweets on this. The continued attempt by partisan hacks using a weather crisis to promote a climate crisis, has been shown to backfire over time. The fear of increased and deadlier hurricanes after Katrina is but one example of how silly such tactics are. You don't hear anyone suggesting that increased CO2 has led to the record lack of severe hurricanes making landfall in the US.

    Then there is the bigger picture with studies indicating 200+ year droughts in the Southwestern USA within the last 2000 years. It seems odd to me that anybody with paleoclimate knowledge would suggest that today's drought and heat are the worst ever. I agree with Roger. Krugman's choice of citing a political hack to support his article instaed of seeking unbiased sources is a major faux pas.

  5. Krugman is in favor of just about anything and everything that entails or justifies more state control. The fact that it is hot in July is but one example.

  6. Droughts would matter less if vegetation had closer to 1000 ppm of CO2 to grow with. More CO2 = less water all plant life needs to thrive.

    This is a Monsanto unapproved message

  7. Krugman - that great science denier.

  8. In the July 19 issue of Nature p 273 there is an editorial by Max Moritz. His title at UC Berkeley sounds a lot like yours. He's suggesting Wildfires in the western US may attributable to AGW.

  9. Joe Romm works for an organization, the Center for American Progress, that refuses to reveal who funds it:

    Krugman doesn't mention that in his paragraph about funding of "climate change deniers."

  10. I came across a comment elsewhere showing that the HadCRUT3V full year global temperature anomaly for 1990 was +.248 dgreesC and YTD 2012 is +.249 degreesC. How is it that people at the NYT seem oblivious to what is going on globaly as far as temperatures and pretending this is about global warming when there is no global anomaly in temperature to support the claim? Is the new motto "All the news that's print to fit"? I think that Krugman's brain is such that he thinks he see the climate of Venus in his backyard when he looks out his window. lol

  11. In my opinion, global warming is now part of a larger American financial war against Europe. That is what Krugman and others are being paid to support by.

    Since 'someone' hacked the UEA computer in a crime so complex, dastardly and evil that the greatest minds in Britain have admitted defeat, only EU countries will commit to cutting emissions.


    A global climate deal that we were told was essential for the survival of the human race is now seen as no longer possible. Where are the crazy people who told us we are all going to die ? Have they told their children they are going to die ?

    American rating agencies colluded in the creation of an artificial housing boom and sale of toxic assets to European banks. They are now in the process of dismantling European civilisation and replacing it with American Social Darwinism (austerity)in an analogous operation to the sacking of Rome by the Vandals and Visigoths.

    My school and university class mate Dougie Ferrans ran the $150 billion HBOS investment fund that crashed and stalled the UK financial system. He emailed me "the people who stole the money are a lot smarter than me".

  12. Let's be serious, here. They ran a password guess script on an academic computer server. Given the usual level of password security on such servers, calling this " a crime so complex, dastardly and evil that the greatest minds in Britain have admitted defeat" is pretty darn insulting to Britain.

    Question; are the evil geniuses behind the US housing bubble the same ones who created the Irish and Spanish bubbles, or are those different geniuses?

    Frankly, the EU seems completely capable of destroying its own financial system, without any help from the US at all.

  13. Thanks Right Wing Professor

    I was being extremely ironic when I referred to the climategate hack being complex. A crime which had global publicity and multi trillion dollar implications was left in the hands of the local police.

    Norfolk police's Julian Gregory explains why investigation into the University of East Anglia's hacked emails was so complex.


    My response to Julian Gregory would be the same as I made to a local officer lying through his teeth at a public meeting a few months ago. "No one is that stupid. Not even you".

    Hackers are caught. Gary McKinnon (Scotland)invaded NASA looking for UFO evidence and Julian Assange caused $100,000 of damage to Nortel Corp. He was looking at 10 years in jail, but the judge was a really, really, really, really nice man and let him off scot free. That was lucky.


    The housing bubble was global because it was fuelled by the runaway worldwide sale of mortgage backed securities to financial institutions. Rating agencies were passing junk as AAA. Spanish and Irish banks not only had to deal with worthless American garbage, but also the simultaneous bursting of their own enormous property bubbles caused by the collapse of Lehmans and the credit crunch.

    The EU is an extremely right wing, neoliberal project with some social padding. The padding is being removed.

  14. I do not think that I have ever heard anything so blatantly untrue and totally dishonest as "EU is an extremely right wing, neoliberal project". A "right wing" or "neo-liberal", it can only be one or the other, not both at the same. Not unless one suffers from cognitive dissonance which left wing loonies appear to have no problem with whatsoever.

  15. DGP: Very telling that you never mention Dr. James Hanson in your post. Krugman is simply elaborating on what Dr. Hanson's recent paper

    It's also very telling that Krugman failed to attribute the "loaded dice" analogy to Hansen. Shades of plagiarism/but it doesn't matter/a climate scientist did it.

  16. Dr. Pielke, this comes across as a cheap shot towards Krugman, Romm, et al. I realize you have been engaged in a spat with Romm, but really - this kind of post is beneath you.

  17. Carrick,

    Krugman does attribute the loaded dice analogy to James Hansen, both in his op-ed and his blog pieces.

  18. Sometimes I wonder if there's an NYT "guidebook" on discussing anything related to climate science. And in this guidebook, there's a "rule" which states (something along the lines of) "If a climate scientist says so, it must clearly be true; so no need to fact-check; but if a skeptic says so, verify, minimize, divert - and preferably ignore/bury".

    For a(nother) recent example of this "rule" in operation, pls see: