WASHINGTON — People who argue that global warming is bogus say that the controversy over leaked e-mails by climate scientists proves that they're right. Their argument boils down to a claim that the 2007 international review of climate science is a fraud.
Scientists involved in the dispute and others say that nothing in the e-mails undermines the work of thousands of scientists over the past 30 years who've concluded that the Earth is warming.
What the critics call "Climategate" continues to heat up the dispute in Congress and on the Internet, however.
Here's a look at the key issues:
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Q: What's at the heart of the controversy?
A: A key charge by people who disagree with the main body of scientific research on climate science is that the leak of climate researchers' e-mails and documents throws into question the finding of the Intergovernmental Panel on Climate Change in 2007.
Some of the scientists involved in the e-mails were among the thousands of scientists who've participated in four IPCC reviews.
The IPCC concluded in 2007 that warming was unequivocal. It said the evidence included increased temperatures of the air and ocean waters, the melting of snow and ice and rising sea level. The IPCC also said that there was a probability of greater than 90 percent that most of the rise in temperatures since the 1950s was due to the increase of greenhouse gases, mainly from burning coal, oil and natural gas.
Q: What happened, and who's involved?
A: Someone took e-mails from a server at the University of East Anglia's Climatic Research Unit in the United Kingdom. The e-mails are between the unit's scientists and other climate scientists. Many are routine, but some have raised questions about the behavior of some scientists.
The Climatic Research Unit is one of several research centers that collect air temperatures over land and sea around the globe. Scientists use the data to determine a global average. The main U.S. centers are NASA's Goddard Institute for Space Studies in New York and NOAA's National Climatic Data Center in Asheville, N.C. All have produced similar results about warming. The U.S. government sites are not part of the e-mail controversy.
Q: One of the e-mails talked about using a "trick" to "hide the decline." Is that fraud?
A: Scientists say they use the word "trick" to mean a clever and legitimate way to use data. In this case this use of data was discussed openly in scientific reports.
The e-mail was from Phil Jones, the director of the Climatic Research Unit at the University of East Anglia. Jones has stepped aside as director for the course of an investigation being conducted by Muir Russell, a former senior British civil servant.
In a 1999 e-mail, Jones 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) amd (sic) from 1961 for Keith's to hide the decline."
Jones says it referred to a 1999 diagram about climate change over 1,000 years.
Temperature records with thermometers begin in the mid-19th century. To get an understanding of earlier temperatures over hundreds of years, scientists use proxy data from things such as tree rings and ice cores.
The "trick" simply meant using two sets of data together to show temperature trends, said Michael Mann of Pennsylvania State University, the "Mike" in the e-mail. "It was all out in the open in our Nature article," he said.
So what was "the decline?"
It didn't mean declining temperatures.
Jones said his e-mail discussed the use of proxy data up until 1960 and actual temperature records after 1961. That refers to work by Keith Briffa and colleagues; Briffa is copied in on the e-mail.
Briffa's group used tree-ring density records that don't accurately reflect temperature changes after about 1960, when the ability of some kinds of tree rings to show temperature changes started to decline.
Mann's work showed that climate warming in the 20th century surpassed anything in the relatively stable millennium before. The National Academy of Sciences examined Mann's work and other reconstructions of temperature data, including Briffa's. It concluded that the warming trend in the 20th century that they found was plausible.
Q: What do scientific research organizations say about the controversy?
A: The IPCC's Working Group 1, which produced the part of the 2007 report that looks at the physical science of climate change, said in a statement last Friday that it "firmly stands behind the (report's) conclusions."
"The body of evidence is the result of the careful and painstaking work of hundreds of scientists worldwide. The internal consistency from multiple lines of evidence strongly supports the work of the scientific community, including those individuals singled out in these e-mail exchanges, many of whom have dedicated their time and effort to develop these findings in teams of Lead Authors within the production of the series of IPCC Assessment Reports during the past 20 years."
The American Geophysical Union, an international organization of scientists who study Earth and space, said the e-mails were being used to distort the scientific debate "about the urgent issue of climate change." It said it stood by its own 2007 statement that human activity was contributing to a warming of the climate.
Q: Does one of the e-mails show private doubts about warming?
A: The critics cite an e-mail on this issue from Kenneth Trenberth, a senior scientist and the head of the climate analysis section of the National Center for Atmospheric Research in Boulder, Colo.
"The fact is that we can't account for the lack of warming at the moment and it is a travesty that we can't. The CERES data published in the August BAMS 09 supplement on 2008 shows there should be even more warming: but the data are surely wrong. Our observing system is inadequate."
The comment referred to the inability of observations from satellites and on Earth to account for where all the energy has gone, Trenberth said. He wrote about this in a report this year that looked at how much heat went into the land, oceans and ice, along with changes in greenhouse gases and clouds.
"We can track this well for 1993 to 2003, but not for 2004 to 2008," he said. "It does NOT mean that global warming is not happening. On the contrary, it suggests that we simply can't fully explain why 2008 was as cool as it was, but with an implication that warming will come back, as it has."
A major La Nina, a Pacific Ocean circulation pattern of cool waters, was under way in 2008. Since June 2009, an El Nino, a pattern of warm waters, has begun. The highest sea surface temperatures on record were recorded this July, he said.
Q: Does one of the e-mails show that scientists tried to block publication of scientists with opposing views?
The e-mail that critics cite on this matter is one from Mann in 2003: "I think we have to stop considering Climate Research as a legitimate peer-reviewed journal. Perhaps we should encourage our colleagues in the climate research community to no longer submit to, or cite papers in, this journal."
According to Mann, the e-mail was in response to a paper by Willie Soon and Sallie Baliunas of the Harvard-Smithsonian Center for Astrophysics. They wrote an article that challenged the view that late 20th-century temperatures were unusually high. Climate Research published it.
The editor in chief, Hans von Storch, and other editors resigned in protest. Von Storch said the article didn't meet quality standards and the review process had been faulty.
The publisher, Otto Kinne, put out a statement after the controversy saying that the journal "should have been more careful and insisted on solid evidence and cautious formulations before publication."
The article nonetheless was evaluated and briefly commented on in the 2007 IPCC report.
"The entire report-writing process of the IPCC is subjected to extensive and repeated review by experts as well as governments," IPCC Chairman R.K. Pachauri said in a statement. He added that no individual or small group could exclude a peer-reviewed paper from assessment or stress a finding that isn't consistent with many other investigations.
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