Screwups in Climate Science

Recent events have given climate science a black eye, but nowhere near the knockout punch depicted in the media.

E-mails documenting overly partisan behavior on the part of a group of climate scientists should not and cannot be dismissed out of hand. To be sure, those involved have had to contend with unrelenting attacks by climate skeptics, but that's no excuse. It's time for a little self-reflection on the part of the climate science community and a renewed affirmation of our commitment to the scientific method.

Similarly, the revelations of errors and poor scholarship in the latest assessment of the Intergovernmental Panel on Climate Change (IPCC) are serious, although not surprising given its sheer volume (four separate reports totaling almost 3,000 pages) and the number of scientists who helped prepare it. Perhaps more damaging was the initial response by IPCC chairman Rajendra Pachauri who, rather than calmly considering them, called the reported errors "voodoo science." The IPCC should assess its own mission, organization, and procedures before undertaking its next scientific assessment.

These mistakes are unfortunate and disappointing, but their depiction in much of the blogosphere and media has grossly overblown their significance. Here are two examples where media outlets have fallen well below their own standards for accurate, objective reporting.

On Tricks and Hiding in Hacked Messages

Much has been written about the e-mail hacked from Phil Jones, director of the University of East Anglia's Climate Research Unit, that mentions using a statistical "trick" to "hide the decline."

The use of the word trick has been interpreted as evidence of nefarious data-manipulating. Unlikely. Trick is a term of art commonly used in statistics and science as shorthand for a clever, elegant method. For example, on February 14, 2010, a New York Times piece on advances in biotechnology reported that a "firm ... similarly tricked out yeast to produce an antimalarial drug." No suspicions of underhandedness there.

The words "hide the decline" have been widely suggested to mean that scientists colluded to obscure falling temperatures, specifically those purportedly from the first decade of the 2000s. This is simply wrong.

  1. The e-mail in question, written in November 1999, came hot on the heels of arguably the warmest year on record (1998). So what decline would they be hiding?

  • A careful examination of the messages' content, including "Mike's trick," reveals that Jones was referring to a poorly understood decline in the density of tree wood, starting in the 1960s, that causes the temperatures inferred from tree rings in the 20th century's later years to diverge from the instrumental record. To be sure, this divergence is not a welcome development for scientists like those at the University of East Anglia who have been using tree rings to infer temperatures over the past millennium. Perhaps in hiding the divergence they were trying to make the results look cleaner. But they could not have been trying to cover up any data. The divergence was already well known among climate scientists and discussed in detail in the scientific literature (e.g., here and here).
  • Finally, for the record, there has been no long-term decline in global temperatures. Temperatures in the first decade of the 2000s were higher on average than those of the '90s.
  • So why so many misinterpretations of Jones' and his colleagues' intention? Perhaps the reason is that so many press items placed the word "temperature" directly after the phrase "hide the decline."

    • Here's an example from the New York Times: "Jones ... said he had used a 'trick' ... to 'hide the decline' in temperatures."
    • And another from the Washington Post: "he had used 'a trick' to 'hide the decline' in a chart showing global temperatures."
    • This from a Wall Street Journal opinion piece: "In [the e-mails] scientists appear to ... give tips on how to 'hide the decline' of temperature in certain inconvenient data."
    • And this from a Washington Times editorial: "Mr. Jones talked to Mr. Mann about the 'trick of adding in the real temps to each series ... to hide the decline [in temperature].'"

    Were these pieces intended to mislead the public? I have no idea. Did they end up misleading? I believe so. (To their credit, some media reports got this right. See here.)

    Himalayan Meltdown

    The IPCC incorrectly stated the near-term fate of Himalayan glaciers with this: "Glaciers in the Himalaya are receding faster than in any other part of the world ... and, if the present rate continues, the likelihood of them disappearing by the year 2035 and perhaps sooner is very high if the Earth keeps warming at the current rate. Its total area will likely shrink from the present 500,000 to 100,000 km2 by the year 2035 (WWF, 2005)." We now know that this was inaccurate [pdf] and that the IPCC review process [pdf] failed to catch the error.

    The media have accurately reported such details, but what's been left out -- the whole story -- has led to misconceptions by lots of people I've spoken to.

    The statement that Himalaya's glaciers will vanish in a few decades was clearly not the IPCC's consensus finding. By my own count, the assessment discusses their fate in three other places, all in a much more nuanced, more accurate, and less alarmist context.

    Here's an example from the IPCC summary for policy makers which prefaces the report containing the error: "Glacier melt in the Himalayas is projected to increase flooding, and rock avalanches from destabilised slopes, and to affect water resources within the next two to three decades. This will be followed by decreased river flows as the glaciers recede."

    The Bottom Line

    Did the IPCC make a mistake? Yes? Are such mistakes of concern? Absolutely (especially in light of revelations of other errors). But does this undermine the entire assessment's credibility? I think not. Are the mistakes a sign of a concerted effort to mislead the public? Hardly.

    The worst thing we scientists can do at this point is contend that these missteps are inconsequential. But it's egregious for the media, through inaccurate inference, exaggeration, and a failure to give all the facts, to over-blow their significance. Doing so will undermine and erode public confidence in the state of our understanding of global warming. In fact the scientific evidence that the globe is warming and that this warming is connected to human activities remains strong.

    Originally posted at