Obama Science Advisor John Holdren Schools Political Scientist Roger Pielke On Climate And Drought


In an unprecedented move, the President’s Science Advisor, Dr. John P. Holdren, has published a devastating 6-page debunking of one of the country’s leading climate confusionists, Roger Pielke Jr.

I’ll excerpt Holdren’s comprehensive critique, “Drought and Global Climate Change,” below. Worsening drought may be the climate impact that affects the most people in the coming decades, as I discussed in my 2011 literature review in the journal Nature. It is valuable to see the the subject laid out so clearly by the nation’s top scientist.

Our understanding of drought and climate change is evolving pretty rapidly, so even the latest IPCC reports are already out of date. Having read much of the recent drought literature and interviewed many of the leading drought experts in the last few years, I can say that Holdren’s views are right in the mainstream of climatologists’ view of drought. I can think of no climate scientists who share Pielke’s startling assessment of Holdren’s views as “zombie science.”


In fact, some drought experts believe the situation is considerably worse than is widely understood. As one top researcher on the climate-drought link confirmed with me recently, “The U.S. may never again return to the relatively wet conditions experienced from 1977 to 1999.”

HOLDREN AND PIELKEJohn Holdren is one of the most distinguished scientists in America. He is a past president of the American Association for the Advancement of Science. Author of over 200 articles and papers, Holdren is a member of the National Academy of Sciences, the National Academy of Engineering, and a foreign member of the U.K.’s Royal Society.

I have known Holdren for more than two decades, and not only does he have more breadth of knowledge on all things climate than most, he is very judicious in his choice of words.

Roger Pielke Jr. is a political scientist who has publicly questioned the scientific integrity of more climate scientists than just about anyone else on the planet. He has smeared literally hundreds of scientists (as I document here).

That is no doubt a key reason Pielke was included on Foreign Policy‘s “Guide to Climate Skeptics.” No doubt that’s why the websites that most prominently feature or reprint Pielke’s attacks are climate denial sites like WattsUpWithThat and ClimateDepot. It is also why he is probably the single most disputed and debunked person in the science blogosphere, especially on the subject of extreme weather and climate change (see here and here). Typical are:

  • A Few Things Ill Considered: “His [Pielke’s] latest effort at sabotaging productive discourse on climate science and policy is a really low blow, putting to rest any lingering hopes one might have had that he still had some integrity stashed away in there somewhere.”
  • James Annan’s blog: “The consistently wrong chronicles…. Roger Pielke has been saying some truly bizarre and nonsensical things recently.”
  • Tim Lambert (Deltoid) has a whole category on Pielke: “Roger Pielke Jr has attempted to trash me using innuendo, fabrication and outright misrepresentation. I correct the record.”

Before his death, the widely revered climatologist Stephen Schneider described one of his run-ins with Pielke this way five years ago:

It is typical of a trickster and a careerist — which is how I personally see him — and so do most of my colleagues these days who I have discussed it with.

Now Pielke has embraced the widely discredited Bjorn Lomborg argument that climate action is bad for the poor, when the science makes clear that climate inaction would be devastating to the poor. Climate action is the only sustainable path out of poverty, as climate expert and development practitioner John Abraham explains in a UK Guardian piece that Pielke has yet to respond to.


It should be obvious that if you’ve garnered a 6-page debunking by the nation’s top scientist, then you’ve moved into the elite ranks of climate confusionists.

If you want the full story on how Pielke has attempted to scandalize his personal quibbles with Holdren (to use a phrase Dr. Stefan Rahmstorf first applied to Pielke), HotWhopper has a must read post. Here’s the short version.

Back in December, Pielke criticized Holdren for pulling his punches on climate science, tweeting, “Since becoming sci advisor Holdren has always stayed on safe (boring) ground in his public remarks.”

Then, in mid-February, when Holdren offered some straightforward well-grounded scientific statements about how climate change is worsening Western droughts, Pielke slammed him, tweeting “it is brazen for zombie science to show up in the White House!”

Talk about damned if you do and damned if you don’t!

As Holdren explains, in a February 25 hearing, “Senator Jeff Sessions (R-AL) suggested that I had misled the American people with comments I made to reporters on February 13.” In particular, Sessions quoted testimony Pielke had given in July:

It is misleading, and just plain incorrect, to claim that disasters associated with hurricanes, tornadoes, floods or droughts have increased on climate timescales either in the United States or globally.

Drought has “for the most part, become shorter, less, frequent, and cover a smaller portion of the U.S. over the last century”. Globally, “there has been little change in drought over the past 60 years.”

The first quote in the second paragraph is from the U.S. Climate Change Science Program’s 2008 report, “Weather and Climate Extremes in a Changing Climate,” and the second is from a 2012 paper by Sheffield et al. in the journal Nature.


As an important aside, Sheffield’s paper has been disputed. I recently interviewed Aiguo Dai, and he thinks the Sheffield analysis is flawed. Dai stands by his conclusion in a 2012 paper in Nature Climate Change that “Historical records of precipitation, streamflow, and drought indices all show increased aridity since 1950 over many land areas.”

When Holdren rebutted Pielke’s charges in Senate testimony, Pielke demanded “If you do indeed believe that my views are ‘outside the scientific mainstream’ could you substantiate that claim”?

Holdren’s full devastating reply is “Drought and Global Climate Change: An Analysis of Statements by Roger Pielke Jr.”

Besides reviewing the drought literature, Holdren makes a crucial point that “any reference to the CCSP 2008 report in this context should include not just the sentence highlighted in Dr. Pielke’s testimony but also the sentence that follows immediately in the relevant passage from that document and which relates specifically to the American West.” Here are the two key sentences from the report in their entirety):

Similarly, long-term trends (1925–2003) of hydrologic droughts based on model derived soil moisture and runoff show that droughts have, for the most part, become shorter, less frequent, and cover a smaller portion of the U.S. over the last century (Andreadis and Lettenmaier, 2006). The main exception is the Southwest and parts of the interior of the West, where increased temperature has led to rising drought trends (Groisman et al., 2004; Andreadis and Lettenmaier, 2006).

Amazingly, Pielke’s testimony did include the second sentence about rising drought trend in the SW and West — which would seem to render most of his attack (and Sen. Sessions’ attack) on Holdren moot — but Pielke buried it in a footnote. Again, Hotwhopper explains just how head-exploding this all is.

Holdren makes a key point that I have made repeatedly — severe drought is much more than just a reduction in precipitation. He explains: “In my recent comments about observed and projected increases in drought in the American West, I mentioned four relatively well understood mechanisms by which climate change can play a role in drought. (I have always been careful to note that, scientifically, we cannot say that climate change caused a particular drought, but only that it is expected to increase the frequency, intensity, and duration of drought in some regions ― and that such changes are being observed.)”

These four mechanisms are:

  1. In a warming world, a larger fraction of total precipitation falls in downpours, which means a larger fraction is lost to storm runoff (as opposed to being absorbed in soil).
  2. In mountain regions that are warming, as most are, a larger fraction of precipitation falls as rain rather than as snow, which means lower stream flows in spring and summer.
  3. What snowpack there is melts earlier in a warming world, further reducing flows later in the year.
  4. Where temperatures are higher, losses of water from soil and reservoirs due to evaporation are likewise higher than they would otherwise be.

Holdren reviews the scientific literature on those statements in his reply, noting “the second, third, and fourth mechanisms reflect elementary physics and are hardly subject to dispute (but see also additional references provided at the end of this comment).” Holdren states:

As I have also noted in recent public comments, additional mechanisms have been identified by which changes in atmospheric circulation patterns that may be a result of global warming could be affecting droughts in the American West. There are some measurements and some analyses suggesting that these mechanisms are operating, but the evidence is less than conclusive, and some respectable analysts attribute the indicated circulation changes to natural variability. The uncertainty about these mechanisms should not be allowed to become a distraction obscuring the more robust understandings about climate change and regional drought summarized above.

Holdren is being characteristically conservative in his language here. As I’ve written, climate scientists specifically predicted a decade ago that Arctic ice loss would bring on worse droughts in the West — and California is now in the death-grip of a brutal, record-breaking drought, driven by the very change in the jet stream that scientists had anticipated.

But Holdren’s main point is the important one — quite separate from any changes in precipitation that climate change may cause, there is little dispute that human-caused climate change is worsening droughts in the West and Southwest. I recommend his entire paper to readers interested in this important subject.