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MYTH #97: Scientists tried to "hide the decline"

DENIERS SAY:

Secret emails from East Anglia prove that temperatures are going down, and scientists want to hide the decline from us.

SCIENCE SAYS:

"Hide the decline" doesn't mean what you think it means. 

There is overwhelming scientific evidence of man-made global warming.

In late 2009, private emails were stolen from climate scientists at the University of East Anglia. Climate deniers pored over hundreds of pages of emails and seized on a few remarks they took out of context in a fruitless attempt to prove that climate change isn't real. One of these was scientist Phil Jones' use of the phrase "hide the decline." In context, the statement relates to Jones’ research on changes in global temperature. Although data from weather stations show that temperatures have risen since the second half of the 20th century, tree ring data in the northern latitudes show a decline. For this reason, it is widely acknowledged by scientists that tree-ring data are not reliable after 1960, and therefore should not be used for temperature reconstructions after that date. Jones no doubt chose his words poorly in referring to this fact. But several independent and thorough reviews of the stolen emails found Jones and other scientists did not have any scientific or ethical lapses.

Additional info from the Union of Concerned Scientists


The manufactured controversy over emails stolen from the University of East Anglia's Climatic Research Unit has generated a lot more heat than light. The email content being quoted does not indicate that climate data and research have been compromised. Most importantly, nothing in the content of these stolen emails has any impact on our overall understanding that human activities are driving dangerous levels of global warming. Media reports and contrarian claims that they do are inaccurate.

Investigations Clear Scientists of Wrongdoing


At least six official investigations have cleared scientists of accusations of wrongdoing.

  • A three-part Penn State University investigation cleared scientist Michael Mann (PDF) of wrongdoing.
  • Two reviews commissioned by the University of East Anglia "supported the honesty and integrity of scientists in the Climatic Research Unit."
  • A UK Parliament report concluded that the emails have no bearing on our understanding of climate science and that claims against UEA scientists are misleading.
  • The National Oceanic and Atmospheric Administration Inspector General's office concluded there was no evidence of wrongdoing on behalf of their employees.
  • The National Science Foundation Inspector General's (PDF) office concluded, "Lacking any direct evidence of research misconduct ... we are closing this investigation with no further action."

Other agencies and media outlets have investigated the substance of the emails.

  • The Environmental Protection Agency, in response to petitions against action to curb heat-trapping emissions, dismissed attacks on the science rooted in the stolen emails.
  • Factcheck.org debunked claims that the emails put the conclusions of climate science into question.
  • Politifact.com rated claims that the emails falsify climate science as "false."
  • An Associated Press review of the emails found that they "don't undercut the vast body of evidence showing the world is warming because of manmade greenhouse gas emissions."

While the emails have raised some concerns, the email content being quoted does not indicate that climate data and research have been compromised. Most importantly, nothing in the content of these stolen emails has any impact on our overall understanding that human activities are driving dangerous levels of global warming. Media reports and contrarian claims that they do are inaccurate.

For example, in an email exchange from 1999, University of East Anglia Climatic Research Unit Director Phil Jones wasn't "hiding" anything about past climate data that wasn't already being openly discussed in scientific papers. He was using a "trick"— a technique —published in the peer-reviewed scientific literature.

The "trick" is actually a technique (in other words, a "trick of the trade") used in a peer-reviewed, academic science journal article published in 1998. "Hiding the decline," another phrase that has received much attention, refers to another technique used in another academic science journal article. In any case, no one was tricking anyone or hiding anything. Rather, this email exchange shows scientists communicating about different ways to look at the same data that were being discussed at the time in the peer-reviewed literature. Later the same data were discussed at length in a 2007 Intergovernmental Panel on Climate Change (IPCC) report.

In some parts of the world, tree rings are a good substitute for a temperature record. Trees form a ring of new growth every growing season. Generally, warmer temperatures produce thicker tree rings, while colder temperatures produce thinner ones. Other factors, such as precipitation, soil properties, and the tree's age also can affect tree ring growth.

The "trick," which was used in a paper published in 1998 in the science journal Nature, is to combine the older tree ring data with thermometer data. Combining the two data sets can be difficult, and scientists are always interested in new ways to make temperature records more accurate.

Tree rings are a largely consistent source of data for the past 2,000 years. But since the 1960s, scientists have noticed there are a handful of tree species in certain areas that appear to indicate temperatures that are warmer or colder than we actually know they are from direct thermometer measurement at weather stations.

"Hiding the decline" in this email refers to omitting data from some Siberian trees after 1960. This omission was openly discussed in the latest climate science update in 2007 from the IPCC, so it is not "hidden" at all.

Why Siberian trees? In the Yamal region of Siberia, there is a small set of trees with rings that are thinner than expected after 1960 when compared with actual thermometer measurements there. Scientists are still trying to figure out why these trees are outliers. Some analyses have left out the data from these trees after 1960 and have used thermometer temperatures instead.

Techniques like this help scientists reconstruct past climate temperature records based on the best available data.

Adapted from © Union of Concerned Scientists
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