Climategate: Scientists Fabricated Climate Data (2009)
Introduction
In November 2009, a server at the University of East Anglia's (UEA) Climatic Research Unit (CRU) was hacked and approximately 1,000 emails and 3,000 other documents were leaked online. The timing — just weeks before the Copenhagen climate summit — was widely noted. Critics, primarily in conservative media and climate-sceptic blogosphere, argued that selected phrases from the emails proved that climate scientists had fabricated, manipulated, or suppressed data to create a false impression of global warming. The episode was quickly labelled "Climategate" by analogy with Watergate.
The core claim — that scientists falsified data — has been examined by five independent inquiries across two continents and found to be false. This page explains what the emails actually said, what the investigations found, and why the conspiracy framing fails.
The Leaked Emails: What Were the Phrases?
Two phrases attracted most attention:
"Mike's Nature Trick"
An email from CRU director Phil Jones referred to using "Mike's Nature trick" to "hide the decline." Critics presented this as an admission of deliberate deception. In context:
- "Mike's Nature trick" referred to a method published by Michael Mann in Nature in 1998: combining tree-ring proxy records with the modern instrumental temperature record (a standard, openly published technique for visualising multi-century temperature reconstructions).
- The word "trick" in scientific correspondence commonly means a clever analytic technique, not a deception.
- The technique was published and peer-reviewed, not concealed.
"Hide the Decline"
This phrase referred to a specific known problem in dendrochronology: tree-ring data from certain high-latitude and high-altitude sites shows an anomalous decline after approximately 1960, diverging from the instrumental temperature record. This "divergence problem" was openly discussed in published literature — it was not a secret. Jones's email discussed how to present the data clearly without the divergence artefact obscuring the modern temperature signal. The "decline" being hidden was a known proxy anomaly, not a decline in global temperatures.
The Five Independent Investigations
Following the leak, five independent panels investigated the allegations of scientific misconduct:
1. UK House of Commons Science and Technology Committee (March 2010)
The committee examined the emails and the conduct of CRU scientists. It found no evidence that Jones had manipulated data or acted improperly, though it criticised the university's response to Freedom of Information requests. It concluded that Jones's scientific reputation remained intact.
2. Independent Climate Change Email Review — Muir Russell (July 2010)
Sir Muir Russell, a former vice-chancellor, led a panel that reviewed the emails and interviewed scientists at length. The review found: "We saw no evidence of any deliberate scientific malpractice in any of the work of the Climatic Research Unit." It found that the rigour and honesty of the CRU scientists were not in doubt. It criticised the scientists for insufficient openness about sharing data and code, but explicitly distinguished this from scientific fraud.
3. Science Assessment Panel — Oxburgh Report (April 2010)
Lord Oxburgh chaired a review of the scientific work itself, examining eleven papers. The panel found no evidence of scientific misconduct or data manipulation. It concluded that the science was "conducted with integrity."
4. Penn State University investigation (July 2010)
Penn State University investigated Michael Mann (whose "trick" was cited in the emails). The inquiry found no credible evidence that Mann had engaged in, or participated in, falsification of research data, destruction of emails, misuse of confidential information, or deviation from accepted practices. Mann was cleared on all four charges.
5. NOAA Inspector General (February 2011)
The US National Oceanic and Atmospheric Administration conducted its own independent review of the temperature data itself. It found no evidence of impropriety or that NOAA's temperature records had been manipulated.
All five panels reached the same conclusion: no data fabrication, no scientific misconduct.
Why the Underlying Science Has Not Changed
The climate-sceptic framing assumed that the CRU temperature record was uniquely central to global warming evidence, and that discrediting it would unravel the science. This assumption was wrong for several reasons:
- Multiple independent datasets. NOAA, NASA GISS, the Japan Meteorological Agency (JMA), Berkeley Earth (an independent project funded partly by sceptic-affiliated sources), and others have all produced temperature reconstructions. They converge closely despite being derived from independent station networks and different methodologies.
- Berkeley Earth. Richard Muller, a physicist who had been publicly sceptical of the temperature record before 2012, led an independent reanalysis funded in part by the Koch-affiliated foundations. Berkeley Earth confirmed the warming trend. Muller subsequently stated publicly that he had been wrong to be sceptical.
- Post-Climategate observations. Every year since 2009 has confirmed continued warming: 2023 and 2024 were the two hottest years in the global instrumental record. 17+ years of post-Climategate observations have validated the projections.
What the Emails Did Reveal (The Legitimate Concerns)
The investigations were not exonerations without reservation:
- Insufficient data sharing. Multiple panels criticised CRU for resisting Freedom of Information requests and not proactively sharing raw data and code. This is a legitimate scientific-transparency criticism.
- Tone in peer review discussions. Some emails showed scientists discussing ways to prevent specific papers they considered poor quality from appearing in journal literature, raising questions about appropriate peer-review conduct.
- The divergence problem in public communication. Some panels noted that clearer public communication of the tree-ring divergence problem would have pre-empted some of the misrepresentation.
These criticisms are valid. They do not support the fabrication claim.
Why It Was Effective Disinformation
Climategate was a case study in effective selective quotation. The phrases were short, memorable, and superficially damaging when stripped of context. The rebuttals required understanding dendrochronology, proxy reconstruction methodology, and the history of atmospheric physics — technical knowledge the general public could not be expected to possess. The timing (weeks before Copenhagen) maximised political impact. The narrative was picked up internationally and continues to circulate despite the investigation outcomes.
Verdict
Debunked. Five independent panels cleared the scientists of data fabrication and misconduct. The specific phrases cited by critics had mundane professional meanings. Independent temperature datasets from NOAA, NASA GISS, Berkeley Earth, JMA, and others validate the underlying science. Post-2009 observations have confirmed continued warming. The most the investigations found was insufficient data-sharing transparency — a real criticism that falls far short of fabrication.
Evidence Filters10
Muir Russell Review clears scientists of misconduct
DebunkingStrongThe Independent Climate Change Email Review chaired by Sir Muir Russell (July 2010) examined the emails and interviewed scientists. It found no evidence of deliberate scientific malpractice and concluded the rigour and honesty of the CRU scientists was not in doubt.
Oxburgh Report: no evidence of scientific misconduct
DebunkingStrongLord Oxburgh's Science Assessment Panel (April 2010) reviewed eleven CRU scientific papers and found no evidence of scientific misconduct or data manipulation, concluding that the science was conducted with integrity.
Penn State investigation clears Michael Mann on all four charges
DebunkingStrongPenn State University's inquiry into Michael Mann (July 2010) found no credible evidence that he had falsified research data, destroyed emails, misused confidential information, or deviated from accepted practices. Mann was cleared on all counts.
House of Commons Science and Technology Committee: no manipulation
DebunkingStrongThe UK parliamentary committee (March 2010) found no evidence that Jones had manipulated data or acted improperly, though it criticised the university for resisting Freedom of Information requests. Jones's scientific reputation was found to be intact.
NOAA Inspector General review confirms no impropriety
DebunkingStrongThe US NOAA Inspector General (February 2011) independently reviewed the temperature data and found no evidence of impropriety or manipulation of NOAA temperature records.
Berkeley Earth independent reanalysis confirms warming trend
DebunkingStrongBerkeley Earth, an independent project whose principal investigator Richard Muller had previously been publicly sceptical of the temperature record, produced its own reconstruction from scratch using different station networks. Berkeley Earth confirmed the warming trend. Muller stated publicly that he had been wrong to be sceptical.
"Hide the decline" referred to a published proxy divergence problem, not temperature
DebunkingStrongThe tree-ring divergence problem (certain proxies diverge from the instrumental record after 1960) was openly published in peer-reviewed literature before the emails were written. "Hiding the decline" referred to not grafting the anomalous proxy data onto a temperature chart — not suppressing evidence of cooling temperatures.
Emails were selectively quoted from professional correspondence
DebunkingThe quoted phrases appeared damaging when stripped of their professional context. "Trick" in scientific correspondence routinely means a clever analytic technique. The emails, read in full, show scientists discussing methodological choices openly, not concealing fraud.
CRU criticised for insufficient data sharing — a legitimate concern
SupportingWeakMultiple investigations criticised the CRU for resisting Freedom of Information requests and failing to proactively share data and code. This is a valid scientific-transparency criticism that the conspiracy framing exploited but that falls far short of fabrication.
Rebuttal
Insufficient data-sharing is a legitimate criticism of open-science norms. However, it does not constitute data fabrication. The temperature data CRU held has been independently reproduced by multiple groups — if the data had been fraudulent, the independent reproductions would not agree.
Post-2009 temperature records continue to confirm warming
DebunkingStrongEvery year from 2010 through 2024 has added to the observational record. 2023 and 2024 were the two hottest years in the global instrumental record. These observations are independent of any CRU data and would be inexplicable if the warming trend had been fabricated.
Evidence Cited by Believers1
CRU criticised for insufficient data sharing — a legitimate concern
SupportingWeakMultiple investigations criticised the CRU for resisting Freedom of Information requests and failing to proactively share data and code. This is a valid scientific-transparency criticism that the conspiracy framing exploited but that falls far short of fabrication.
Rebuttal
Insufficient data-sharing is a legitimate criticism of open-science norms. However, it does not constitute data fabrication. The temperature data CRU held has been independently reproduced by multiple groups — if the data had been fraudulent, the independent reproductions would not agree.
Counter-Evidence9
Muir Russell Review clears scientists of misconduct
DebunkingStrongThe Independent Climate Change Email Review chaired by Sir Muir Russell (July 2010) examined the emails and interviewed scientists. It found no evidence of deliberate scientific malpractice and concluded the rigour and honesty of the CRU scientists was not in doubt.
Oxburgh Report: no evidence of scientific misconduct
DebunkingStrongLord Oxburgh's Science Assessment Panel (April 2010) reviewed eleven CRU scientific papers and found no evidence of scientific misconduct or data manipulation, concluding that the science was conducted with integrity.
Penn State investigation clears Michael Mann on all four charges
DebunkingStrongPenn State University's inquiry into Michael Mann (July 2010) found no credible evidence that he had falsified research data, destroyed emails, misused confidential information, or deviated from accepted practices. Mann was cleared on all counts.
House of Commons Science and Technology Committee: no manipulation
DebunkingStrongThe UK parliamentary committee (March 2010) found no evidence that Jones had manipulated data or acted improperly, though it criticised the university for resisting Freedom of Information requests. Jones's scientific reputation was found to be intact.
NOAA Inspector General review confirms no impropriety
DebunkingStrongThe US NOAA Inspector General (February 2011) independently reviewed the temperature data and found no evidence of impropriety or manipulation of NOAA temperature records.
Berkeley Earth independent reanalysis confirms warming trend
DebunkingStrongBerkeley Earth, an independent project whose principal investigator Richard Muller had previously been publicly sceptical of the temperature record, produced its own reconstruction from scratch using different station networks. Berkeley Earth confirmed the warming trend. Muller stated publicly that he had been wrong to be sceptical.
"Hide the decline" referred to a published proxy divergence problem, not temperature
DebunkingStrongThe tree-ring divergence problem (certain proxies diverge from the instrumental record after 1960) was openly published in peer-reviewed literature before the emails were written. "Hiding the decline" referred to not grafting the anomalous proxy data onto a temperature chart — not suppressing evidence of cooling temperatures.
Emails were selectively quoted from professional correspondence
DebunkingThe quoted phrases appeared damaging when stripped of their professional context. "Trick" in scientific correspondence routinely means a clever analytic technique. The emails, read in full, show scientists discussing methodological choices openly, not concealing fraud.
Post-2009 temperature records continue to confirm warming
DebunkingStrongEvery year from 2010 through 2024 has added to the observational record. 2023 and 2024 were the two hottest years in the global instrumental record. These observations are independent of any CRU data and would be inexplicable if the warming trend had been fabricated.
Timeline
CRU server hacked; emails leaked online
A server at the University of East Anglia's Climatic Research Unit is hacked and approximately 1,000 emails and 3,000 documents are posted to a Russian server. Climate-sceptic bloggers and media rapidly disseminate selected phrases, calling the episode "Climategate."
UK House of Commons Science and Technology Committee report
The parliamentary committee finds no evidence that Jones manipulated data or acted improperly. It criticises UEA for resisting Freedom of Information requests but concludes Jones's scientific reputation is intact.
Source →Muir Russell and Oxburgh reports both clear scientists
Two reports are published within weeks of each other: the Muir Russell Review finds no evidence of deliberate scientific malpractice; the Oxburgh Science Assessment Panel finds no evidence of data manipulation and concludes the science was conducted with integrity.
Source →NOAA Inspector General review finds no impropriety
The US NOAA Inspector General independently reviews the temperature data and finds no evidence of impropriety or manipulation of NOAA temperature records — the fifth independent investigation to clear the scientists.
Berkeley Earth confirms warming trend; Muller recants scepticism
Verdict
Five independent investigations (UK House of Commons, Muir Russell, Oxburgh, Penn State, NOAA Inspector General) all cleared the CRU scientists of data fabrication and misconduct. The phrases "hide the decline" and "Mike's Nature trick" had mundane professional meanings. Multiple independent global temperature datasets (NOAA, NASA GISS, Berkeley Earth, JMA) produce consistent results, and 17+ years of post-2009 observations confirm continued warming. Criticisms of insufficient data-sharing transparency were valid but do not support the fabrication claim.
Frequently Asked Questions
What did "hide the decline" actually mean?
It referred to the tree-ring divergence problem: certain tree-ring proxy records show an anomalous decline after approximately 1960 relative to the instrumental temperature record. This divergence problem was openly discussed in published peer-reviewed literature before the emails were written — it was not a secret. The phrase referred to not grafting the anomalous proxy data onto a temperature visualisation, not to suppressing evidence of a decline in global temperatures.
What was "Mike's Nature trick"?
It referred to Michael Mann's analytic technique, published openly in *Nature* in 1999, of combining tree-ring proxy records with the modern instrumental temperature record to produce a multi-century temperature reconstruction. In scientific correspondence "trick" means a clever analytic technique, not a deception. The technique was published and peer-reviewed, not concealed.
How many investigations were there and what did they conclude?
Five independent investigations: the UK House of Commons Science and Technology Committee (March 2010), the Muir Russell Review (July 2010), the Oxburgh Science Assessment Panel (April 2010), Penn State University (July 2010), and the NOAA Inspector General (February 2011). All five cleared the scientists of data fabrication and scientific misconduct. Some criticised the university for insufficient data-sharing transparency.
Is the global temperature record reliable independent of CRU data?
Sources
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Further Reading
- paperThe Independent Climate Change Email Review (Muir Russell Report) — Sir Muir Russell et al. (2010)
- paperBerkeley Earth Surface Temperature project — Richard Muller et al. (2012)
- bookThe Hockey Stick and the Climate Wars: Dispatches from the Front Lines — Michael E. Mann (2012)
- articleRealClimate: The CRU hack — context and commentary — RealClimate editors (2009)