Climategate Email Scandal

Overview

On the morning of November 17, 2009 — two weeks before the United Nations Climate Change Conference in Copenhagen, where world leaders were supposed to negotiate a binding agreement to reduce greenhouse gas emissions — a zip file appeared on a server in Tomsk, Russia. It contained 1,073 emails and 72 documents stolen from the Climatic Research Unit (CRU) at the University of East Anglia in Norwich, England. Within days, the file had been downloaded and dissected by climate change skeptics around the world, and a handful of phrases plucked from the emails — most notoriously “hide the decline” and “Mike’s Nature trick” — were being brandished as proof that climate science was a fraud.

The timing was exquisite, and almost certainly deliberate. The Copenhagen conference represented the best opportunity in years for meaningful international climate action. The leaked emails, re-christened “Climategate” by bloggers who recognized the branding power of the suffix, arrived at exactly the right moment to sow maximum doubt. Within weeks, what had been a hack of a university email server had become an international political event, cited by senators, amplified by cable news, and used to justify inaction on climate policy that would persist for over a decade.

Here is what actually happened: scientists at a climate research institute sometimes wrote snarky emails. They discussed how to present data clearly. They expressed frustration with colleagues they considered incompetent and with critics they considered bad-faith actors. They occasionally discussed how to resist Freedom of Information requests they believed were designed to waste their time rather than advance legitimate inquiry. In short, they behaved like professionals in any field where the stakes are high, the critics are relentless, and the email chains are long.

Here is what did not happen: they did not fake their data, fabricate their conclusions, or conspire to deceive the world. Eight independent investigations, conducted by bodies ranging from the UK Parliament to the U.S. National Science Foundation, reviewed the emails and the underlying science. Every single one reached the same conclusion: the science was sound, and the accusations of fraud were unfounded.

Origins & History

The Climatic Research Unit at the University of East Anglia was, at the time of the hack, one of the world’s leading climate research institutions. It maintained one of the three major global temperature records (alongside NASA’s Goddard Institute and NOAA’s National Climatic Data Center), and its director, Phil Jones, was a central figure in the field of paleoclimatology — the study of past climates.

Jones and his colleagues had been the subject of intense attention from climate skeptics for years before the hack. Steve McIntyre, a retired Canadian mining executive who ran the blog Climate Audit, had been filing Freedom of Information requests for CRU’s raw temperature data and methodological code since at least 2005. McIntyre’s stated goal was to verify CRU’s temperature reconstructions independently; CRU’s response was that much of their raw data was subject to confidentiality agreements with national meteorological services and could not be shared freely. This dispute — legitimate concerns about scientific transparency on one side, legitimate concerns about data ownership on the other — created a poisonous atmosphere well before the emails were leaked.

The emails were extracted from CRU’s backup server sometime in late 2009. The identity of the hacker (or hackers) has never been definitively established. The UK’s Norfolk Constabulary investigated for three years before dropping the case in 2012, citing the expiration of the statute of limitations. Some investigators suspected Russian state actors, given the initial upload to a Tomsk server and Russia’s economic interest in undermining climate legislation (as a major fossil fuel producer), but no conclusive attribution was made.

The initial dump included 1,073 emails spanning 13 years, from 1996 to 2009. A second, larger batch — dubbed “Climategate 2.0” — was released in November 2011, containing an additional 5,000 emails. Skeptics mined both batches for damaging quotes, which were presented without context on blogs, in opinion columns, and on television.

The Key Emails

Several emails became focal points of the controversy:

“Hide the decline.” On November 16, 1999, Phil Jones wrote an email describing a chart he was preparing for the cover of a World Meteorological Organization report. He wrote: “I’ve just completed Mike’s Nature trick of adding in the real temps to each series for the last 20 years (ie from 1981 onwards) and from 1961 for Keith’s to hide the decline.” To skeptics, this was a smoking gun: a scientist admitting to hiding evidence that temperatures were declining.

In context, “the decline” referred not to a decline in global temperatures but to a well-documented technical problem in dendroclimatology: after approximately 1960, certain tree-ring proxy data stopped correlating with actual measured temperatures. This “divergence problem” was well-known and extensively discussed in the scientific literature (including in the IPCC reports themselves). “Mike’s Nature trick” referred to a technique published by Michael Mann in Nature in 1998, in which direct thermometer measurements were used for the period where reliable instrument records existed, rather than relying on proxy data that was known to be unreliable for that period. “Trick” in this context meant “technique” — a common usage in scientific and mathematical discourse.

“Redefine peer review.” In a 2003 email, Jones wrote that he and a colleague would “redefine what the peer-review literature is” rather than include certain papers they considered methodologically flawed in the IPCC report. This email was cited as evidence of gatekeeping and suppression of dissent. Subsequent investigations found that while the language was intemperate, the papers in question were in fact included in the IPCC assessment, and the IPCC process included mechanisms for considering all relevant literature regardless of individual scientists’ opinions.

Resisting FOI requests. Several emails discussed strategies for avoiding Freedom of Information requests, including one in which Jones wrote that he would rather delete data than hand it over. These emails reflected genuine frustration with what Jones and his colleagues perceived as a coordinated campaign of FOI requests designed to overwhelm and distract rather than to advance scientific understanding. The subsequent Muir Russell investigation found that CRU had not complied well with the spirit of FOI legislation — a legitimate criticism — but that this did not invalidate their scientific findings.

Key Claims

Climate skeptics and conspiracy theorists made several allegations based on the emails:

• Climate scientists deliberately manipulated data to exaggerate warming trends and “hide” evidence of cooling. The “hide the decline” email was the primary exhibit.

• The peer review process was corrupted by a clique of scientists who colluded to suppress dissenting research and prevent publication of papers that challenged their conclusions.

• Global temperature records were fabricated or cherry-picked. CRU’s refusal to share all raw data was interpreted as evidence that the data would not support their published conclusions.

• The IPCC process was compromised because key IPCC authors were the same scientists whose emails revealed bias and gatekeeping.

• The timing of the leak exposed a conspiracy. The release just before Copenhagen was interpreted not as strategic sabotage by hackers, but as the actions of a courageous whistleblower exposing fraud before world leaders could act on false science.

• The entire edifice of climate science was built on fraudulent data. Climategate was presented as the unraveling of a decades-long scientific conspiracy to deceive the public for political and financial reasons.

Evidence & Investigations

The most important fact about Climategate is that it was the most thoroughly investigated alleged scientific fraud in modern history — and every investigation reached the same conclusion.

UK House of Commons Science and Technology Committee (March 2010): Found that Phil Jones’s scientific reputation was intact, that the “hide the decline” phrase had been misinterpreted, and that CRU’s data was consistent with other independent temperature records.

Oxburgh Panel (April 2010): An independent panel led by Lord Oxburgh reviewed CRU’s key publications and found “no evidence of any deliberate scientific malpractice.”

Independent Climate Change Email Review — Muir Russell Inquiry (July 2010): The most comprehensive investigation, chaired by Sir Muir Russell, concluded that the “rigour and honesty” of the CRU scientists was “not in doubt.” It criticized CRU for inadequate data sharing and poor handling of FOI requests, but found no evidence that data had been manipulated to support predetermined conclusions.

Penn State University Investigation (February and June 2010): Investigated Michael Mann specifically and cleared him of all allegations of research misconduct.

U.S. Environmental Protection Agency (September 2010): The EPA Inspector General reviewed the emails and found they did not undermine the scientific basis for the EPA’s endangerment finding on greenhouse gases.

National Science Foundation Inspector General (August 2011): Cleared Michael Mann of all allegations, finding “no evidence of research misconduct.”

Additional reviews by the UK Information Commissioner’s Office, NOAA, and other bodies reached similar conclusions.

Meanwhile, the underlying science was independently verified. The Berkeley Earth Surface Temperature project — initially funded by the Charles Koch Foundation, a major funder of climate skeptic organizations — set out to rebuild the global temperature record from scratch using raw data and independent methods. Its results, published in 2012, confirmed the CRU and NASA temperature records almost exactly. Even funding from climate skeptics produced results that validated the science the skeptics were challenging.

Cultural Impact

Climategate’s impact on climate policy was devastating, and it is difficult to overstate how disproportionate this impact was relative to the actual substance of the emails.

The Copenhagen conference — COP15, held in December 2009 — ended in failure. While the causes of Copenhagen’s collapse were complex and primarily political (including disagreements between developed and developing nations over emissions targets and financial commitments), the Climategate controversy provided cover for politicians who wanted to avoid binding commitments. U.S. Senator James Inhofe, the most prominent climate skeptic in Congress, traveled to Copenhagen to declare that “the science behind global warming has been thoroughly debunked” by the leaked emails. The political narrative — that climate science was discredited — persisted long after the investigations cleared the scientists.

Public trust in climate science measurably declined in the wake of Climategate. Polling by Gallup showed that the percentage of Americans who believed global warming was exaggerated rose from 35% in 2008 to 48% in 2010. A 2010 study in Nature Climate Change found that media coverage of the stolen emails temporarily reversed a decade-long trend of increasing public concern about climate change.

The scandal also had a chilling effect on climate scientists themselves. Jones suffered severe depression and considered suicide during the height of the controversy. Other climate researchers reported increased harassment, death threats, and reluctance to engage in public communication. The lesson of Climategate — that even private emails between colleagues could be weaponized — made scientists more cautious and more guarded, which arguably reduced public engagement at a time when it was most needed.

Climategate also established a template for science denialism that would recur during the COVID-19 pandemic. The playbook — selectively quote scientists’ private communications, strip quotes of context, amplify through partisan media, and declare the entire field discredited — was deployed with striking similarity against Anthony Fauci and public health officials beginning in 2020.

Timeline

• 1990 — The IPCC publishes its First Assessment Report, establishing the scientific basis for concern about human-caused climate change.
• 1998 — Michael Mann publishes the “hockey stick” graph in Nature, showing a sharp rise in global temperatures in the 20th century.
• 2003 — Steve McIntyre begins filing FOI requests for CRU raw data.
• 2005 — McIntyre and Ross McKitrick publish a critique of Mann’s hockey stick methodology. The dispute intensifies.
• November 17, 2009 — A zip file containing 1,073 emails and 72 documents stolen from CRU appears on a Russian server.
• November 20, 2009 — Climate skeptic blogs begin publishing selected email excerpts. The term “Climategate” is coined.
• November-December 2009 — The story dominates media coverage in the weeks leading up to the Copenhagen climate conference.
• December 2009 — The Copenhagen climate conference (COP15) ends without a binding agreement.
• February 2010 — Penn State clears Michael Mann in its first investigation.
• March 2010 — The UK House of Commons Science and Technology Committee clears Phil Jones.
• April 2010 — The Oxburgh Panel finds no evidence of scientific malpractice.
• July 2010 — The Muir Russell inquiry publishes its report, clearing CRU scientists but criticizing data-sharing practices.
• November 2011 — A second batch of 5,000 emails is leaked (“Climategate 2.0”).
• July 2012 — Norfolk Constabulary closes its investigation into the hack without identifying the perpetrators.
• October 2012 — The Berkeley Earth project, partially funded by Koch Foundation, independently confirms CRU temperature records.

Sources & Further Reading

• Muir Russell, Sir. “The Independent Climate Change E-mails Review.” July 2010.
• House of Commons Science and Technology Committee. “The disclosure of climate data from the Climatic Research Unit at the University of East Anglia.” March 2010.
• Oxburgh, Lord. “Report of the International Panel set up by the University of East Anglia to examine the research of the Climatic Research Unit.” April 2010.
• Pearce, Fred. The Climate Files: The Battle for the Truth About Global Warming. Guardian Books, 2010.
• Mann, Michael E. The Hockey Stick and the Climate Wars. Columbia University Press, 2012.
• Leiserowitz, Anthony, et al. “Climategate, Public Opinion, and the Loss of Trust.” American Behavioral Scientist, 2013.
• Rohde, Robert, et al. “Berkeley Earth Temperature Averaging Process.” Geoinformatics & Geostatistics, 2013.
• Montford, Andrew. The Hockey Stick Illusion. Stacey International, 2010. (A sympathetic account of the skeptic perspective.)

Related Theories

• Climate Change Hoax — The broader conspiracy theory that climate change is fabricated
• IPCC Corruption — Claims that the IPCC process is politically corrupted
• Climate Scientists Bribed — The theory that researchers are financially motivated to exaggerate warming
• COVID-19 Plandemic — Used a similar playbook of selectively quoting scientists to undermine institutional trust