Facebook Twitter Tumblr Close Skip to main content
A Project of The Annenberg Public Policy Center


Hacked e-mails show climate scientists in a bad light but don't change scientific consensus on global warming.


In late November 2009, more than 1,000 e-mails between scientists at the Climate Research Unit of the U.K.’s University of East Anglia were stolen and made public by an as-yet-unnamed hacker. Climate skeptics are claiming that they show scientific misconduct that amounts to the complete fabrication of man-made global warming. We find that to be unfounded:

  • The messages, which span 13 years, show a few scientists in a bad light, being rude or dismissive. An investigation is underway, but there’s still plenty of evidence that the earth is getting warmer and that humans are largely responsible.
  • Some critics say the e-mails negate the conclusions of a 2007 report by the Intergovernmental Panel on Climate Change, but the IPCC report relied on data from a large number of sources, of which CRU was only one.
  • E-mails being cited as “smoking guns” have been misrepresented. For instance, one e-mail that refers to “hiding the decline” isn’t talking about a decline in actual temperatures as measured at weather stations. These have continued to rise, and 2009 may turn out to be the fifth warmest year ever recorded. The “decline” actually refers to a problem with recent data from tree rings.


Skeptics claim this trove of e-mails shows the scientists at the U.K. research center were engaging in evidence-tampering, and they are portraying the affair as a major scandal: “Climategate.” Saudi Arabian climate negotiator Mohammad Al-Sabban went so far as to tell the BBC: “It appears from the details of the scandal that there is no relationship whatsoever between human activities and climate change.” He said that he expected news of the e-mails to disrupt the U.N. climate summit in Copenhagen this month. An article from the conservative-leaning Canada Free Press claims that the stolen files are proof of a “deliberate fraud” and “the greatest deception in history.”

Missing the Mark

We find such claims to be far wide of the mark. The e-mails (which have been made available by an unidentified individual here) do show a few scientists talking frankly among themselves — sometimes being rude, dismissive, insular, or even behaving like jerks. Whether they show anything beyond that is still in doubt. An investigation is being conducted by East Anglia University, and the head of CRU, Phil Jones, has “stepped aside” until it is completed. However, many of the e-mails that are being held up as “smoking guns” have been misrepresented by global-warming skeptics eager to find evidence of a conspiracy. And even if they showed what the critics claim, there remains ample evidence that the earth is getting warmer.

Even as the affair was unfolding, the World Meteorological Organization announced on Dec. 8 that the 2000-2009 decade would likely be the warmest on record, and that 2009 might be the fifth warmest year ever recorded. (The hottest year on record was 1998.) This conclusion is based not only on the CRU data that critics are now questioning, but also incorporates data from the U.S. National Aeronautics and Space Administration (NASA) and the National Oceanic and Atmospheric Administration (NOAA). All three organizations synthesized data from many sources.

Some critics claim that the e-mails invalidate the conclusions of the Intergovernmental Panel on Climate Change, the world scientific body that reaffirmed in a 2007 report that the earth is warming, sea levels are rising and that human activity is “very likely” the cause of “most of the observed increase in global average temperatures since the mid-20th century.” But the IPCC’s 2007 report, its most recent synthesis of scientific findings from around the globe, incorporates data from three working groups, each of which made use of data from a huge number of sources — of which CRU was only one. The synthesis report notes key disagreements and uncertainties but makes the “robust” conclusion that “warming of the climate system is unequivocal.” (A robust finding is defined as “one that holds under a variety of approaches, methods, models and assumptions, and is expected to be relatively unaffected by uncertainties.”)

The IPCC has released a statement playing down the notion that CRU scientists skewed the world body’s report or kept it from considering the views of skeptical scientists:

Intergovernmental Panel on Climate Change: The entire report writing process of the IPCC is subjected to extensive and repeated review by experts as well as governments. Consequently, there is at every stage full opportunity for experts in the field to draw attention to any piece of literature and its basic findings that would ensure inclusion of a wide range of views. There is, therefore, no possibility of exclusion of any contrarian views, if they have been published in established journals or other publications which are peer reviewed.

The facts support this assertion. In one 2004 e-mail that’s come under much scrutiny, Jones wrote of two controversial papers that “Kevin and I will keep them out [of the IPCC report] somehow — even if we have to redefine what the peer-review literature is!” But both papers under discussion, Kalnay and Cai (2003) and McKitrick and Michaels (2004), were cited in one of the three working group reports from which the 2007 IPCC report is synthesized.

Mixed Messages

The 1,000-plus e-mails sometimes illustrate the hairier side of scientific research. Criticisms of climate change are sometimes dismissed as “fraud” or “pure crap,” as in this 2005 e-mail from CRU Director Phil Jones. Other messages, like a 2007 e-mail from Michael Mann of Penn State University, show indignation at being the target of skeptics’ ire. Some of the e-mails are in bad form; for instance, climate scientist Benjamin Santer of Lawrence Livermore National Laboratory makes a crack about “beat[ing] the crap out of” opponent Pat Michaels.

Claims that the e-mails are evidence of fraud or deceit, however, misrepresent what they actually say. A prime example is a 1999 e-mail from Jones, who wrote: “I’ve just completed Mike’s Nature trick of adding in the real temps to each series for the last 20 years (i.e., from 1981 onwards) and from 1961 for Keith’s to hide the decline.” Skeptics claim the words “trick” and “decline” show Jones is using sneaky manipulations to mask a decline in global temperatures. But that’s not the case. Actual temperatures, as measured by scientific instruments such as thermometers, were rising at the time of the writing of this decade-old e-mail, and (as we’ve noted) have continued to rise since then. Jones was referring to the decline in temperatures implied by measurements of the width and density of tree rings. In recent decades, these measures indicate a dip, while more accurate instrument-measured temperatures continue to rise.

Scientists at CRU use tree-ring data and other “proxy” measurements to estimate temperatures from times before instrumental temperature data began to be collected. However, since about 1960, tree-ring data have diverged from actual measured temperatures. Far from covering it up, CRU scientists and others have published reports of this divergence many times. The “trick” that Jones was writing about in his 1999 e-mail was simply adding the actual, measured instrumental data into a graph of historic temperatures. Jones says it’s a “trick” in the colloquial sense of an adroit feat — “a clever thing to do,” as he put it — not a deception. What’s hidden is the fact that tree-ring data in recent decades doesn’t track with thermometer measurements. East Anglia Research Professor Andrew Watson explained in an article in The Times of London:

Watson: Jones is talking about a line on a graph for the cover of a World Meteorological Organisation report, published in 2000, which shows the results of different attempts to reconstruct temperature over the past 1,000 years. The line represents one particular attempt, using tree-ring data for temperature. The method agrees with actual measurements before about 1960, but diverges from them after that — for reasons only partly understood, discussed in the literature.

Other quotes that skeptics say are evidence of “data manipulation” actually refer to how numbers are presented, not to falsifying those numbers. For instance, in one e-mail climate scientist Tom Crowley writes: “I have been fiddling with the best way to illustrate the stable nature of the medieval warm period.” Crowley is referring to the best way to translate the data into a graphic format. We’re the first to admit that charts and graphs can give a false or misleading impression of what data actually show. In the past, for instance, we’ve criticized a pie chart used by some liberals to make military spending look like a much larger slice of the federal budget than it really is. In fact, it’s been a major contention of climate change skeptics that a so-called “hockey stick” chart, so named because it shows a steep climb in temperatures in the last few decades, exaggerates the true extent of warming. That claim is contradicted by climate scientists, including the creator of one of the most contended “hockey stick” charts, and we make no judgment about that dispute here. We simply note that “fiddling” with the way data are displayed — even in a way that some may see as misleading — is not the same thing as falsifying the numbers.

Much has also been made of the scientists’ discussion of Freedom of Information Act requests for their raw data. In fact, the vast majority of CRU’s data is already freely available. According to the University of East Anglia, a small amount of the data is restricted by non-publication agreements. Discussion of British FOIA requests in the stolen e-mails show scientists bristling at demands that they supply records of their own correspondence, computer code and data to people whose motives they question. In one e-mail about a request for data and correspondence, Santer writes critically of Steven McIntyre, a Canadian science blogger who runs the Climateaudit.org Web site:

Ben Santer e-mail, Nov. 12, 2009: My personal opinion is that both FOI requests [for data related to a 2008 paper and for correspondence dating back to 2006] are intrusive and unreasonable. Steven McIntyre provides absolutely no scientific justification or explanation for such requests. … McIntyre has no interest in improving our scientific understanding of the nature and causes of climate change. He has no interest in rational scientific discourse. He deals in the currency of threats and intimidation. We should be able to conduct our scientific research without constant fear of an “audit” by Steven McIntyre; without having to weigh every word we write in every email we send to our scientific colleagues.

It’s clear from the e-mails that there are people with whom the scientists would rather not share. What’s less clear is whether any deliberate obstruction actually occurred — that’s one of the subjects of the East Anglia investigation. Some e-mails refer to long discussions with lawyers and university officials about what the scientists may, or must, make available and to whom. In others, scientists let their critics know directly that data are freely accessible, or mention that they’ve already sent the information along, though they may not fulfill their opponents’ every informational wish.

Climate change skeptics also say that the e-mails prove they’ve been excluded from peer review. In one e-mail, for example, climate scientist Tom Wigley of the University Corporation for Academic Research writes: “If you think that [Yale professor James] Saiers is in the greenhouse skeptics camp, then, if we can find documentary evidence of this, we could go through official AGU channels to get him ousted.” Saiers later departed from the journal in question (Geophysical Research Letters, or GRL). However, Saiers says he isn’t a warming skeptic and that Wigley had nothing to do with his departure. When another professor (and blogger) asked Saiers about the Wigley e-mail, Saiers responded: “I stepped down as GRL editor at the end of my three-year term. … My departure had nothing to do with attempts by Wigley or anyone else to have me sacked.”

Investigators are still sifting through 13 years’ worth of CRU e-mails looking for evidence of impropriety. But what’s been revealed so far hasn’t shaken the broad scientific consensus about global warming. In an open letter to Congress posted on Climate Science Watch and other sites, 25 leading climate scientists (including eight members of the National Academy of Science) wrote:

Letter to Congress from U.S. scientists, Dec. 4: The body of evidence that human activity is the dominant cause of global warming is overwhelming. The content of the stolen emails has no impact whatsoever on our overall understanding that human activity is driving dangerous levels of global warming. … Even without including analyses from the UK research center from which the emails were stolen, the body of evidence underlying our understanding of human-caused global warming remains robust.

Confusing the Public

News coverage of the e-mails and the various claims about what they supposedly show may have contributed to public confusion on the subject. A Dec. 3 Rasmussen survey found that only 25 percent of adults surveyed said that “most scientists agree on global warming” while 52 percent said that “there is significant disagreement within the scientific community” and 23 percent said they were not sure. The truth is that over the 13 years covered by the CRU e-mails, scientific consensus has only become stronger as the evidence for global warming from various sources has  mounted. Reports from the National Academies and the U.S. Global Change Research Program that analyze large amounts of data from various sources also agree, as does the IPCC, that climate change is not in doubt. In advance of the 2009 U.N. climate change summit, the national academies of 13 nations issued a joint statement of their recommendations for combating climate change, in which they discussed the “human forcing” of global warming and said that the need for action was “indisputable.”

Leading scientists are unequivocally reaffirming the consensus on global warming in the wake of “Climategate.” White House science adviser John Holdren said at a congressional hearing on climate change: “However this particular controversy comes out, the result will not call into question the bulk of our understanding of how the climate works or how humans are affecting it.” The American Association for the Advancement of Science released a statement “reaffirm[ing] the position of its Board of Directors and the leaders of 18 respected organizations, who concluded based on multiple lines of scientific evidence that global climate change caused by human activities is now underway, and it is a growing threat to society.” The American Meteorological Society and the Union of Concerned Scientists have also reiterated their positions on climate change, which they say are unaffected by the leaked e-mails.

by Jess Henig

Correction, Dec. 22: We originally wrote: “There are two investigations underway, by the U.K.’s Met Office and East Anglia University.” But the Met Office is not conducting an investigation. The Times of London had reported that the Met Office would reexamine its data, but that article was incorrect. A spokesperson for the office told us that there were no plans to do so. The Met Office does plan to release the station temperature records publicly, but not to reevaluate them. The university investigation is continuing.


Walsh, Bryan. “Has ‘Climategate’ Been Overblown?” TIME. 7 Dec 2009.

Black, Richard. “Climate e-mail hack ‘will impact on Copenhagen summit.’” BBC News. 3 Dec 2009.

Ball, Tim. “The Death Blow to Climate Science.” Canada Free Press. 21 Nov 2009.

Webster, Ben. “Met Office to re-examine 160 years of climate data.” The Times of London. 5 Dec 2009.

BBC News. “Chair for climate e-mail review.” 3 Dec 2009.

Satter, Raphael G. “Climate-unit chief steps aside amid probe.” Associated Press. 2 Dec 2009.

Sandell, Clayton. “Climate: 2009 Caps Hottest Decade on Record.” ABC News. 8 Dec 2009.

World Meteorological Association. “2000-2009, The Warmest Decade.” Press release. 8 Dec 2009.

Intergovernmental Panel on Climate Change. “Statement on News Reports Regarding Hacking of the East Anglia University Email Communications.” 4 Dec 2009.

Pachauri, R.K. and Reisinger, A., eds. “Climate Change 2007: Synthesis Report.” Intergovernmental Panel on Climate Change, 2007.

Solomon, S. et al. “Climate Change 2007: The Physical Science Basis.” Intergovernmental Panel on Climate Change, 2007.

Briffa, K.R. et al. “Trees tell of past climates: but are they speaking less clearly today?” Philosophical Transactions of the Royal Society of London B 1998.

D’Arrigo, Rosanne et al. “On the ‘Divergence Problem’ in Northern Forests: A review of the tree-ring evidence and possible causes.” Global and Planetary Change 2007.

Watson, Andrew. “Climate change e-mails have been quoted totally out of context.” The Times of London. 8 Dec 2009.

McIntyre, Stephen and Ross McKitrick. “Corrections to the Mann et. al. (1998) proxy data base and northern hemispheric average temperature series.” Energy and Environment. 2003.

Rutherford, S. et al. “Proxy-based Northern Hemisphere Surface Temperature Reconstructions: Sensitivity to Method, Predictor Network, Target Season, and Target Domain.” Journal of Climate. 2004.

East Anglia University. “CRU Update 2.” Press release. 24 Nov 2009. Archer, David et al. “Open Letter to Congress from U.S. Scientists on Climate Change and Recently Stolen Emails.” 4 Dec 2009.

Rasmussen Reports. “Americans Skeptical of Science Behind Global Warming.” 3 Dec 2009.

National Research Council. “Surface Temperature Reconstructions for the Last 2,000 Years.” National Academies Press, 2006.

U.S. Global Change Research Program. “Global Climate Change Impacts in the United States.” Cambridge University Press, 2009.

G8+5 Academies. “G8+5 Academies’ joint statement: Climate change and the transformation of energy technologies for a low carbon future.” May 2009.

Harris, Richard. “Stolen Climate E-Mails Cause A Ruckus In Congress.” NPR. 2 Dec. 2009.

American Association for the Advancement of Science. “AAAS Reaffirms Statements on Climate Change and Integrity.” 4 Dec 2009.

Seitter, Keith. “Impact of CRU Hacking on the AMS Statement on Climate Change.” American Meteorological Society. 25 Nov 2009.

Frumhoff, Peter. “Contrarians Using Hacked E-mails to Attack Climate Science.” Union of Concerned Scientists. 23 Nov 2009.