Myths and falsehoods from the assault on global warming science

MYTH: The scientific consensus on global warming has been undermined by recent events

MYTH: Erroneous Himalayan glacier statement in IPCC report undermines evidence of global warming

MYTH: IPCC report was wrong about the Amazon and drought

MYTH: New study debunks link between global warming and hurricane intensity

MYTH: CRU director Jones admitted that global warming stopped in past 15 years

MYTH: CRU scientists "destroyed" raw temperature data

MYTH: Scientists "fudged" data with a "trick" to "hide" temperature "decline"

MYTH: NASA admitted its data "are in even worse shape" than CRU data

MYTH: CRU scientists "suppressed" opposition

MYTH: The Earth has been cooling since 1998

MYTH: Snowstorms prove global warming does not exist

MYTH: The scientific consensus on global warming has been undermined by recent events

• Critics have seized on claims about the U.N.'s 2007 Intergovernmental Panel on Climate Change (IPCC) report and emails apparently stolen from the Climatic Research Unit from the University of East Anglia (CRU) as evidence that human-caused global warming is not happening. Conservatives in the media have repeatedly claimed that apparently stolen emails show that global warming is a "hoax," a "fraud," or "junk science," or that they put global warming science in question. For example, Rush Limbaugh, Sean Hannity, Sarah Palin, The Washington Times, Matt Drudge, Fox News' Bret Baier, the Fox Nation, and Fox & Friends hosts Steve Doocy, Gretchen Carlson, and Brian Kilmeade have all forwarded these claims.

• The Wall Street Journal, New York Post, The Washington Times, HotAir.com, Michelle Malkin, and BigGovernment.com, are all among those in the conservative media who claimed recent accusations against the IPCC are proof that global warming science is in question.

REALITY: "Climategate" attacks on scientists are "unfounded." FactCheck.org wrote:

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.

REALITY: Scientists have reaffirmed that warming is occurring and say the evidence is overwhelming. In response to the repeated attacks on global warming science, prominent scientists from around the world have come forward to reaffirm the wide consensus that man-made warming is occurring, and say the criticism has little bearing on the overwhelming amount of evidence. Among them are:

• 29 prominent scientists in the U.S.: "The body of evidence that human activity is the dominant cause of global warming is overwhelming." In a December 4, 2009, letter to Congress, 29 prominent scientists, including 11 members of the National Academy of Sciences, stated: "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."

• 1,700 scientists in the United Kingdom: Global warming "is due primarily to human activities." More than 1,700 scientists from the United Kingdom signed a statement responding "to the ongoing questioning of core climate science and methods." The statement said: "We, members of the UK science community, have the utmost confidence in the observational evidence for global warming and the scientific basis for concluding that it is due primarily to human activities."

• American Association for the Advancement of Science: "[S]cientific evidence" shows "that global climate change [is] caused by human activities." On December 4, 2009, the American Association for the Advancement of Science stated that it "has reaffirmed 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 statement also said that "the illegal release of private emails stolen from the University of East Anglia should not cause policy-makers and the public to become confused about the scientific basis of global climate change."

• Union of Concerned Scientists: "[T]he IPCC's conclusions remain indisputable," and "nothing" in "stolen emails has any impact on our overall understanding that human activities are driving" climate change. The Union of Concerned Scientists (UCS) stated that despite "minor errors" in the IPCC's 2007 report, "Overall, the IPCC's conclusions remain indisputable: Climate change is happening now and human activity is causing it. Nations around the world will have to adapt to at least some climate change, including sea level rise, changes in precipitation, disruptions to agriculture, and species extinctions." In response to the CRU emails, UCS said that 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."

• New York Times, Associated Press: Scientists say IPCC errors were "minor" and do not change consensus. The Times reported that the IPCC, "in reviewing complaints about possible errors in its report, has so far found that one was justified and another was 'baseless.' The general consensus among mainstream scientists is that the errors are in any case minor and do not undermine the report's conclusions." Similarly, the AP reported, "Scientists say the problems are minor and have nothing to do with the major conclusions about man-made global warming and how it will harm people and ecosystems."

• RealClimate.org: "[P]ublic perception of the IPCC, and of climate science in general, has been massively distorted by the recent media storm." The staff at RealClimate.org -- which is comprised of working climate scientists -- wrote in response to the media distortions of the IPCC report: "Overall then, the IPCC assessment reports reflect the state of scientific knowledge very well. There have been a few isolated errors, and these have been acknowledged and corrected. What is seriously amiss is something else: the public perception of the IPCC, and of climate science in general, has been massively distorted by the recent media storm. All of these various 'gates' -- Climategate, Amazongate, Seagate, Africagate, etc., do not represent scandals of the IPCC or of climate science. Rather, they are the embarrassing battle-cries of a media scandal, in which a few journalists have misled the public with grossly overblown or entirely fabricated pseudogates, and many others have naively and willingly followed along without seeing through the scam."

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MYTH: Erroneous Himalayan glacier statement in IPCC report undermines evidence of global warming

• After stating that "the great climate-change unraveling came none too soon," a New York Post editorial said that the IPCC's "key finding" "was revealed last month to be utterly bogus. ... The IPCC had claimed, with no evidence beyond a citation from a mass-market science magazine, that global warming would cause Himalayan glaciers to disappear by 2035."

• A Washington Times editorial seized on the Himalayan glacier data to claim that man-made climate change science is "dead" and "needs to be buried."

REALITY: Despite IPCC error on Himalayan glaciers, studies show that glaciers are melting all over the world. The IPCC recently acknowledged and apologized for erroneously citing claims that Himalayan glaciers would melt by 2035. However, the IPCC report highlights legitimate scientific studies showing that glaciers worldwide are melting.

Studies show the world's glaciers are melting rapidly. The World Glacier Monitoring Service (WGMS) issued a report in March 2008 showing that, according to a United Nations Environment Program press release, for 30 of the world's glaciers, "the average rate of melting and thinning more than doubled" in a year's time. WGMS later updated its data for 2007-08 and said that the "new data continues the global trend in strong ice loss over the past few decades." Moreover, scientists at the ETH Zurich university reportedly issued a study in 2009 showing that Swiss glaciers had retreated by 12 percent over the past decade.

Glacier experts link melting glaciers to global warming. Glacier expert Michael Zemp is quoted in a CNN.com article as saying, "Glaciers are the best proof that climate change is happening. This is happening on a global scale. They can translate very small changes in the climate into a visible signal." And a January 20 Guardian article reported that "Lonnie Thompson, a glaciologist at Ohio State University, said there is strong evidence from a variety of sources of significant melting of glaciers -- from the area around Kilimanjaro in Africa to the Alps, the Andes, and the icefields of Antarctica because of a warming climate. Ice is also disappearing at a faster rate in recent decades, he said."

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MYTH: IPCC report was wrong about the Amazon and drought

• The Wall Street Journal editorial board claimed that the IPCC's reports "are sloppy political documents intended to drive the climate lobby's regulatory agenda." To support this claim, the Journal cited "news that an IPCC claim that global warming could destroy 40% of the Amazon was based on a report by an environmental pressure group." The editorial further stated:

Take the rain forest claim. In its 2007 report, the IPCC wrote that "up to 40% of the Amazonian forests could react drastically to even a slight reduction in precipitation; this means that the tropical vegetation, hydrology and climate system in South America could change very rapidly to another steady state."

But as Jonathan Leake of London's Sunday Times reported last month, those claims were based on a report from the World Wildlife Fund, which in turn had fundamentally misrepresented a study in the journal Nature. The Nature study, Mr. Leake writes, "did not assess rainfall but in fact looked at the impact on the forest of human activity such as logging and burning."

REALITY: The IPCC's statement on the Amazon and drought are correct. Critics of the IPCC claim -- as the Journal did -- that the IPCC erred because it cited a World Wildlife Fund (WWF) report that said 40 percent of the Amazon rainforest is susceptible to drought; the critics say WWF came to that conclusion by misrepresenting a 1999 study in the journal Nature. But Daniel Nepstad, a co-author of the Nature study, has said that "the IPCC statement on the Amazon was correct," and more recent peer-reviewed research also supports the data.

Nature study author: "[T]he IPCC statement on the Amazon was correct." In response to the criticism of the IPCC, Nepstad -- who co-authored the Nature study the WWF report cited -- wrote:

The Intergovernmental Panel on Climate Change has been recently criticized in media coverage (e.g. Sunday Times) for presenting inaccurate information on the susceptibility of the forests of the Amazon Basin to rainfall reduction in its fourth assessment. The statement that has drawn the criticism reads as follows:

"Up to 40% of the Amazonian forests could react drastically to even a slight reduction in precipitation; this means that the tropical vegetation, hydrology and climate system in South America could change very rapidly to another steady state, not necessarily producing gradual changes between the current and the future situation (Rowell and Moore, 2000)." (IPCC 2007, Magrin et al. 2007)

The Rowell and Moore review report [the WWF report] that is cited as the basis of this IPCC statement cites an article that we published in the journal Nature in 1999 as the source for the following statement:

"Up to 40% of the Brazilian forest is extremely sensitive to small reductions in the amount of rainfall. In the 1998 dry season, some 270,000 sq. km of forest became vulnerable to fire, due to completely depleted plant-available water stored in the upper five metres of soil. A further 360,000 sq. km of forest had only 250 mm of plant-available soil water left.[Nepstad et al. 1999]" (Rowell and Moore 2000)

The IPCC statement on the Amazon is correct, but the citations listed in the Rowell and Moore report were incomplete. (The authors of this report interviewed several researchers, including the author of this note, and had originally cited the IPAM website where the statement was made that 30 to 40% of the forests of the Amazon were susceptible to small changes in rainfall).

[...]

After the Rowell and Moore report was released in 2000, and prior to the publication of the IPCC AR4, new evidence of the full extent of severe drought in the Amazon was available. In 2004, we estimated that half of the forest area of the Amazon Basin had either fallen below, or was very close to, the critical level of soil moisture below which trees begin to die in 1998. This estimate incorporated new rainfall data and results from an experimental reduction of rainfall in an Amazon forest that we had conducted with funding from the US National Science Foundation (Nepstad et al. 2004). Field evidence of the soil moisture critical threshold is presented in Nepstad et al. 2007.

In sum, the IPCC statement on the Amazon was correct. The report that is cited in support of the IPCC statement (Rowell and Moore 2000) omitted some citations in support of the 40% value statement.

RealClimate: Amazon "issue" is "completely without merit." In a February 14 post on "IPCC errors: facts and spin," Real Climate noted that claims that the IPCC statement on Amazon forest dieback are false are "completely without merit." RealClimate noted that Nepstad has said that the IPCC was correct and stated the "only issue is that the IPCC cited the WWF report rather than the underlying peer-reviewed papers by Nepstad et al. These studies actually provide the basis for the IPCC's estimate on Amazonian sensitivity to drought."

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MYTH: New study debunks link between global warming and hurricane intensity

• HotAir.com's Ed Morrissey claimed that a new study in Nature Geoscience "concludes that hurricane strength has little to do with global warming" and "nothing to do with AGW or carbon emissions," and that it's "yet another reason to dismiss the highly-politicized" and not "reliable" IPCC report.

REALITY: The Nature Geoscience and IPCC findings on future impact of global warming on hurricane intensity are consistent. The Nature Geoscience study did not say -- as Morrissey claimed -- that "hurricane strength has little to do with global warming." Rather, it said that "greenhouse warming" will increase hurricane "intensity" while decreasing hurricane "frequency." This finding is consistent with the IPCC report, which found that "it is likely that future tropical cyclones ... will become more intense," but there is "less confidence in projections of a global decrease in numbers of tropical cyclones." While the two reports differed on whether human-caused warming has already changed hurricane activity, the author of the Nature Geoscience study said the IPCC provided "an accurate summary of science that existed at that point."

Study in Nature Geoscience says models project increases in hurricane intensity due to greenhouse warming. The study (subscription required) Morrissey cited, which was authored by 10 climate experts, states that "greenhouse warming" will cause an increase in tropical cyclone (hurricane) intensity but a decrease in tropical cyclone frequency:

[F]uture projections based on theory and high-resolution dynamical models consistently indicate that greenhouse warming will cause the globally averaged intensity of tropical cyclones to shift towards stronger storms, with intensity increases of 2-11% by 2100. Existing modelling studies also consistently project decreases in the globally averaged frequency of tropical cyclones, by 6-34%. Balanced against this, higher resolution modelling studies typically project substantial increases in the frequency of the most intense cyclones, and increases of the order of 20% in the precipitation rate within 100|[nbsp]|km of the storm centre.

IPCC report also said "it is likely that future tropical cyclones ... will become more intense." From the IPCC's 2007 Synthesis Report:

Based on a range of models, it is likely that future tropical cyclones (typhoons and hurricanes) will become more intense, with larger peak wind speeds and more heavy precipitation associated with ongoing increases of tropical sea-surface temperatures. There is less confidence in projections of a global decrease in numbers of tropical cyclones. The apparent increase in the proportion of very intense storms since 1970 in some regions is much larger than simulated by current models for that period.

Author's study said IPCC made conclusions based on science at the time. The study's co-author, Tom Knutson, is quoted in an AP article as saying the IPCC based its conclusion that warming "had already altered storm activity" on the science that was available at the time:

In 2007, the authoritative Intergovernmental Panel on Climate Change said it was "more likely than not" that man-made greenhouse gases had already altered storm activity, but the authors of the new paper said more recent evidence muddies the issue.

"The evidence is not strong enough that we could make some kind of statement" along those lines, Knutson said. It doesn't mean the IPCC report was wrong; it was just based on science done by 2006 and recent research has changed a bit, said Knutson and the other researchers.

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MYTH: CRU director Jones admitted that global warming stopped in past 15 years

• Gateway Pundit blogger Jim Hoft claimed in a headline on February 14, "It Was All a Lie: Climategate Scientist Admits There Is No Global Warming."

• In his Washington Post column, George Will wrote: "Global warming skeptics, too, have erred. They have said there has been no statistically significant warming for 10 years. Phil Jones, former director of Britain's Climatic Research Unit, source of the leaked documents, admits it has been 15 years."

REALITY: Jones said: "I'm 100% confident that the climate has warmed." The conservative media seized on a BBC interview in which Jones said that temperature data do not show "statistically significant" warming since 1995 in order to suggest he "admitted" warming stopped or is not occurring. In fact, Jones stated in the interview he's "100% confident that the climate has warmed," but that 15 years is generally too short a time period to achieve statistically significant results. Jones added that statistical significance is "much more likely for longer periods." From Jones' BBC interview:

B - Do you agree that from 1995 to the present there has been no statistically-significant global warming

Yes, but only just. I also calculated the trend for the period 1995 to 2009. This trend (0.12C per decade) is positive, but not significant at the 95% significance level. The positive trend is quite close to the significance level. Achieving statistical significance in scientific terms is much more likely for longer periods, and much less likely for shorter periods.

C - Do you agree that from January 2002 to the present there has been statistically significant global cooling?

No. This period is even shorter than 1995-2009. The trend this time is negative (-0.12C per decade), but this trend is not statistically significant.

[...]

E - How confident are you that warming has taken place and that humans are mainly responsible?

I'm 100% confident that the climate has warmed. As to the second question, I would go along with IPCC Chapter 9 - there's evidence that most of the warming since the 1950s is due to human activity.

RealClimate.org: Media are distorting Jones' comments about warming over the past 15 years. In a February 15 post, RealClimate responded to a Daily Mail article that had distorted Jones' comments by claiming Jones "admits ... [t]here has been no global warming since 1995.″ The RealClimate scientists wrote:

What Jones actually said is that, while the globe has nominally warmed since 1995, it is difficult to establish the statistical significance of that warming given the short nature of the time interval (1995-present) involved. The warming trend consequently doesn't quite achieve statistical significance. But it is extremely difficult to establish a statistically significant trend over a time interval as short as 15 years -- a point we have made countless times at RealClimate.

RealClimate also noted that Jones had "confirmed to us that our interpretations of his comments in the BBC interview are indeed the correct ones, and that he agrees with the statements in our piece above."

Long-term data show clear warming trend with 2000-2009 as warmest decade on record. The IPCC stated in 2007 that multiple lines of observational evidence establish that "warming of the climate system is unequivocal." NASA's Goddard Institute for Space Studies (GISS), the National Climatic Data Center (NCDC) of the National Oceanic and Atmospheric Administration, the U.K. Met Office, and the World Meteorological Organisation (WMO) have all stated that 2000-2009 was the warmest decade on record for the globe.

From the Met Office:

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MYTH: CRU scientists "destroyed" raw temperature data

• On Fox News' Special Report, senior political analyst Brit Hume said: "Now it has come out that the original raw data used to create these models has been destroyed or otherwise disposed of. The response of the alarmists to these revelations has been that the emails were taken out of context and that the destruction of all that raw data was done for space reasons. There's a one-word answer to all of that: Please."

• On Fox Business' Cavuto, The Washington Examiner's Michael Barone said they "destroyed all the original data. Only data that they have now is data that they have manipulated and adjusted, perhaps to fit their hypotheses. And, as a result, we're not being asked to [lower greenhouse gas emissions] on the basis of science." Later, Barone said, "They have non-retrievable data. They say they can't get their original data. They have non-replicable data."

REALITY: Raw temperature data still exists at original meteorological stations. Contrary to the claim that the CRU scientists "destroyed" raw temperature data to cover up cooling and that the results, therefore, can not be replicated, scientists say the original data are still at the meteorological stations where they obtained them. Moreover, other climate organizations have replicated CRU's results using similar data sets to demonstrate a similar long-term warming trend.

Scientists: The data were not destroyed. Both Jones and Gavin Schmidt, a climate modeler at NASA, have stated that the raw data are still at the original weather stations. Jones is quoted in a Greenwire article as saying, "We haven't destroyed anything. The data is still there -- you can still get these stations from the [NOAA] National Climatic Data Center." Also, in response to a comment on RealClimate asking whether it is true that the CRU lost the data, Schmidt replied, "No. The original data is curated at the met services where it originated."

Scientists note that datasets from other research centers show the same long-term climate trends. Greenwire also reported that Tom Karl, director of NOAA's Climatic Data Center, "noted that the conclusions of the IPCC reports are based on several data sets in addition to the CRU, including data from NOAA, NASA and the United Kingdom Met Office. Each of those data sets basically show identical multi-decadal trends." The article further noted that Ben Santer, a climate scientist at Lawrence Livermore National Laboratory, "said CRU's major findings were replicated by other groups, including the NOAA climatic data center, the NASA Goddard Institute for Space Studies, and also in Russia."

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MYTH: Scientists "fudged" data with a "trick" to "hide" temperature "decline"

• On his Fox News show, Glenn Beck said, "How about Phil Jones, head of the Climatic Research Unit at the University of East Anglia? 'I have just completed Mike's Nature trick of adding in the real temps to each series for the last 20 years to hide the decline.' Yes, he is talking about a trick that another scientist previously used in a peer-reviewed journal to apparently hide the decline in temperatures. Incredible."

• The hosts at Fox & Friends have also repeatedly claimed the emails "prove" scientists were "doctoring" data or "fudging the numbers."

REALITY: "Hide the decline" refers to unreliable tree-ring data, not actual temperature readings. The Morning Call of Allentown, Pennsylvania, reported that Penn State scientist Michael Mann -- whose "trick" was referenced in Jones' email -- "said his trick, or 'trick of the trade,' for the Nature chart was to combine data from tree-ring measurements, which record world temperatures from 1,000 years ago until 1960, with actual temperature readings for 1961 through 1998" because "scientists have discovered that, for temperatures since 1960, tree rings have not been a reliable indicator." Jones has also stated that it is "well known" that tree ring data "does not show a realistic trend of temperature after 1960," and the CRU has said that "[t]he 'decline' in this set of tree-ring data should not be taken to mean that there is any problem with the instrumental temperature data."

Temperature records show there was no "decline" in actual temperatures to hide. In a December 8 London Times column, Andrew Watson, research professor at the University of East Anglia explained, "The tree-ring measure declines, but the actual temperatures after 1960 go up." Jones has similarly explained that "it was absolutely necessary to remove the incorrect impression given by the tree rings that temperatures between about 1960 and 1999 (when the email was written) were not rising, as our instrumental data clearly showed they were." Indeed, measurements from each of the major climate centers show the clear warming trend.

Scientists have stated that the word "trick" is being misinterpreted. Scientists say the word "trick" is a commonly used expression and does not indicate deception. Bob Ward, director of policy and communications at the Grantham Research Institute on Climate Change and the Environment at the London School of Economics, is quoted in a Guardian article as saying of Jones' email: "Scientists say 'trick' not just to mean deception. They mean it as a clever way of doing something -- a short cut can be a trick." RealClimate also explained that "[s]cientists often use the term 'trick' to refer to ... 'a good way to deal with a problem', rather than something that is 'secret', and so there is nothing problematic in this at all." Further, Penn State concluded in an investigation of charges against Mann that they "were not falsifying data; they were trying to construct an understandable graph for those who were not experts in the field. The so-called 'trick' was nothing more than a statistical method used to bring two or more different kinds of data sets together in a legitimate fashion by a technique that has been reviewed by a broad array of peers in the field."

AP: U.K. investigation shows "no evidence" that CRU scientists "had tampered with data." The Associated Press reported on March 31 that "[t]he House of Commons' Science and Technology Committee said Wednesday that they'd seen no evidence to support charges that the University of East Anglia's Climatic Research Unit or its director, Phil Jones, had tampered with data or perverted the peer review process to exaggerate the threat of global warming -- two of the most serious criticisms levied against the climatologist and his colleagues." The House of Commons issued the report on March 31.

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MYTH: NASA admitted its data "are in even worse shape" than CRU data

• A March 30 FoxNews.com article advanced global warming skeptic Chris Horner's claim that climate scientists' emails show that the CRU temperature data are inaccurate, and that NASA's, "by its own admission," "are in even worse shape."

• The Fox Nation linked to the FoxNews.com article with the headline, "NASA Rocked by 'Climategate II' "

REALITY: NASA did not say its data are "in worse shape" than CRU's. Apart from the fact that there is no evidence that CRU scientists tampered with temperature data, NASA did not say its data are "in worse shape" than CRU's. The accusation is based on distortions of an email exchange in which a reporter asked NASA whether it is "correct to say that NASA's data is more accurate than" other groups' data. Neither of the two NASA scientists who replied suggested that NASA's data are wrong or unreliable.

NASA scientist said that NASA data are "accurate" but intended for a different purpose than other data sets. In the email exchange, a USA Today reporter asked NASA whether "it [is] correct to say that NASA's data is more accurate than NCDC's since it has more sources? In the media, it would be ideal to refer to one source rather than two." NASA scientist Reto Ruedy replied that for the reporter's purposes, using NCDC data for U.S. means and CRU's data for global means is more accurate. From Ruedy's email:

No, your statement is NOT correct; to get the US means, NCDC's procedure of only using the best stations is more accurate. If that were our goal, we would proceed in the same way. Actually, whenever we report on US means in our publications, we recompute all US means using only USHCN data.

My recommendation to you is to continue using NCDC's data for the US means and Phil Jones' data for the global means. Our method is geared to getting the global mean and large regional means correctly enough to assess our model results.

We are basically a modeling group and were forced into rudimentary analysis of global observed data in the 70's and early 80's since nobody else was doing that job at the time. Now we happily combine NCDC's and Hadley Center's data to get what we need to evaluate our model results. For that purpose, what we do is more than accurate enough. But we have no intention to compete with either of the other two organizations in what they do best.

NASA's Hansen stated that NASA's "method of analysis has features that are different than the analyses of the other groups." In a subsequent email, NASA's James Hansen told the reporter that NASA's "method of analysis has features that are different than the analyses of the other groups." From the email:

Well, I guess that I would say it a bit differently.

Our method of analysis has features that are different than the analyses of the other groups. In some cases the differences have a substantial impact.

For example, we extrapolate station measurements as much as 1200 km. This allows us to include results for the full Arctic. In 2005 this turned out to be important, as the Arctic had a large positive temperature anomaly. We thus found 2005 to be the warmest year in the record, while the British did not and initially NOAA also did not. Independent satellite IR measurements showed that our extrapolations of anomalies into the Arctic were conservative. I am very confident that our result was the correct one in that instance.

Also, as we show in our 2001 paper, our urban warming correction in the U.S. differs from the NOAA correction (we have a larger adjustment, which decreases recent temperatures relative to last century). I would not claim that one is superior to the other, but the different results provide one conservative measure of uncertainty. In general it has proven very useful to have more than one group do the analysis.

Also it should be noted that the different groups have cooperated in a very friendly way to try to understand different conclusions when they arise. You will see that we had co-authors from the other groups on our 2001 paper. And in general it is a bad idea to anoint any group as being THE authority. Science doesn't usually work best that way.

NASA, CRU, and NCDC data all show similar long-term warming trends. While, as Hansen noted, there are some differences in how NASA, CRU, and NCDC analyze the data, all three show a similar long-term warming trend. Hansen included the following chart in a NASA document released in March:

On its website, the Met Office explains:

One important thing to note is that the difference between the GISS [NASA] and HadCRUT3 [CRU] analyses are smaller than the calculated uncertainties on the HadCRUT3 data set -- the data sets are not inconsistent. The largest component of the uncertainty arises from the fact that temperatures over large areas of the Earth's surface remain unobserved. There are very few observations in the Arctic and Antarctic. GISS attempts to estimate temperatures in these areas, HadCRUT3 does not. This is the major source of difference between the analyses, which can be seen if, instead of a global average, one takes the average temperature anomaly between 60S and 60N. Over this slightly smaller area, the GISS and HadCRUT3 analyses give very similar results.

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MYTH: CRU scientists "suppressed" opposition

• On Fox News Sunday, host Chris Wallace claimed that the leaked emails "seemed to indicate that some of the climate change advocates were suppressing opposition."

• In a Wall Street Journal op-ed, Cato Institute fellow and author Patrick Michaels claimed that the emails reveal "a silencing of climate scientists" and "dramatically weakened the case for emissions reductions."

REALITY: Charges of suppression unsupported by evidence. Critics have frequently pointed to a March 11, 2003, email in which Mann suggested a boycott of the journal Climate Research over the publication of a 2003 study by Willie Soon and Sallie Baliunas, and a July 8, 2004, email, in which Jones criticized two papers and said he couldn't "see either of these papers being in the next IPCC report. Kevin and I will keep them out somehow -- even if we have to redefine what the peer-review literature is!" But the Climate Research publisher later conceded the Soon-Baliunas paper should not have been published as it was written, and the papers Jones criticized were included in the IPCC report despite his objections.

Climate Research editors and publisher conceded Soon-Baliunas paper was flawed. The New York Times reported that the Soon-Baliunas paper "has been heavily criticized by many scientists, including several of the journal editors. The editors said last week that whether or not the conclusions were correct, the analysis was deeply flawed." The Times further noted that the "publisher of the journal, Dr. Otto Kinne, and an editor who recently became editor in chief, Dr. Hans von Storch, both said that in retrospect the paper should not have been published as written." The Wall Street Journal reported on July 31, 2003, (accessed via Factiva) that three editors, including von Storch, "resigned in protest over the journal's handling of the review process that approved the study."

CRU scientists did not keep the papers to which they objected out of IPCC. As the Yale Forum on Climate Change & the Media explained, Jones had criticized "two papers, one by [Eugenia] Kalnay and [Ming] Cai (2003) in Nature and one by [Ross] McKitrick and [Patrick] Michaels (2004) in Climate Research, both dealing with effects of land-use change on temperature measurements. Despite Jones' dislike of the papers and his threat to keep them out of the IPCC Fourth Assessment Report, both papers were subsequently included in the Assessment, suggesting that no small group of scientists could be final arbiters of what is included in the IPCC reports."

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MYTH: The Earth has been cooling since 1998

• An Investor's Business Daily editorial claimed, "As it turns out, the earth hasn't been warming at all, at least not in the last decade, and reputable scientists have said it may continue to cool for decades to come."

• Washington Post columnist George Will has repeatedly claimed that the Earth has been cooling or has not warmed since 1998.

• Numerous Fox News and other media personalities have made similar claims.

REALITY: 2000-2009 decade was warmer than the 90s, which were warmer than the 80s. Global warming skeptics have seized on the fact that 1998 was the hottest year on record, according to Met Office data, (NASA and NOAA say 2005 was the warmest on record) in order to claim that the Earth has cooled. But scientists reject the idea for several reasons: 1) scientists have identified a long term warming trend that spans several decades; 2) scientists say a decade is too short a time span to make meaningful conclusions about long-term global warming; and 3) the 2000-2009 decade is the hottest on record.

AP: "Statisticians Reject Global Cooling" and have identified a "distinct decades-long upward trend." In an experiment, the Associated Press "gave temperature data to four independent statisticians and asked them to look for trends, without telling them what the numbers represented." Their conclusion was that the "experts found no true temperature declines over time." From the AP's October 26, 2009, article:

Global warming skeptics base their claims on an unusually hot year in 1998. Since then, they say, temperatures have dropped -- thus, a cooling trend. But it's not that simple.

Since 1998, temperatures have dipped, soared, fallen again and are now rising once more. Records kept by the British meteorological office and satellite data used by climate skeptics still show 1998 as the hottest year. However, data from the National Oceanic and Atmospheric Administration and NASA show 2005 has topped 1998. Published peer-reviewed scientific research generally cites temperatures measured by ground sensors, which are from NOAA, NASA and the British, more than the satellite data.

The recent Internet chatter about cooling led NOAA's climate data center to re-examine its temperature data. It found no cooling trend.

"The last 10 years are the warmest 10-year period of the modern record," said NOAA climate monitoring chief Deke Arndt. "Even if you analyze the trend during that 10 years, the trend is actually positive, which means warming."

The AP sent expert statisticians NOAA's year-to-year ground temperature changes over 130 years and the 30 years of satellite-measured temperatures preferred by skeptics and gathered by scientists at the University of Alabama in Huntsville.

Statisticians who analyzed the data found a distinct decades-long upward trend in the numbers, but could not find a significant drop in the past 10 years in either data set. The ups and downs during the last decade repeat random variability in data as far back as 1880.

Saying there's a downward trend since 1998 is not scientifically legitimate, said David Peterson, a retired Duke University statistics professor and one of those analyzing the numbers.

2000-2009 was warmest decade on record. GISS, NCDC, the U.K. Met Office, and WMO have all stated that 2000-2009 was the warmest decade on record for the globe. Charts from GISS and the U.K. Met Office displaying global average temperatures clearly show that temperatures trended upward in recent decades.

From the Met Office:

From GISS:

PolitiFact: Experts say "it's misleading to look at only the last 10 years." After Republican strategist Mary Matalin claimed "for the last decade the climate has been cooling," PolitiFact.com wrote that several experts told them "it's shortsighted to say changes within a decade mean that climate change is going away." From PolitiFact:

If 1998 is the starting point, a year many climate skeptics tend to cite, everything looks cooler in comparison, said Raymond Bradley, a climate scientist at the University of Massachusetts. He also pointed out that, when evaluating the impact of climate change on temperature, it's misleading to look at only the last 10 years.

A decade is such a small period of time that "it's like saying, 'It was cold here last week. What happened to climate change?'" Bradley said.

It's a point we heard repeatedly from the climate experts we interviewed. They all agreed that, while climate temperatures may dip from year to year, it's shortsighted to say changes within a decade mean that climate change is going away.

WMO uses 30-year temperature averages "to eliminate year-to-year variations." Regarding long-term climate averages, WMO "requires the calculation of averages for consecutive periods of 30 years, with the latest covering the 1961-1990 period. However, many WMO members, including the UK, update their averages at the completion of each decade. Thirty years was chosen as a period long enough to eliminate year-to-year variations."

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MYTH: Snowstorms prove global warming does not exist

• Many conservative media figures and outlets have cited large snowstorms and cold weather as evidence that global warming is not happening or to attack Al Gore for his advocacy on global warming. These include Fox News' Sean Hannity, Gretchen Carlson, Steve Doocy, Stuart Varney, Eric Bolling, Glenn Beck, Trace Gallagher, Bill Hemmer, Laura Ingraham, and the Fox Nation. Matt Drudge, Rush Limbaugh, The Washington Times, the New York Post, and many others have also made the same argument.

REALITY: Snowstorms do not disprove global warming. The overwhelming consensus on warming comes from scientists' measurement and reconstruction of temperatures over many years (i.e. long-term trends), and not from individual, random weather (snowstorms, heat waves, etc). Moreover, scientists say snow and cold weather will not go away as a result of global warming and predict that it may actually increase snowfall in some areas.

NASA: Weather and climate are different, and greenhouse gases are warming the Earth. According to NASA: "The difference between weather and climate is a measure of time. Weather is what conditions of the atmosphere are over a short period of time, and climate is how the atmosphere 'behaves' over relatively long periods of time." NASA further explained that "weather consists of the short-term (minutes to months) changes in the atmosphere," including snow and heat waves. On the other hand, climate is "the description of the long-term pattern of weather in a particular area," or "the average weather for a particular region and time period, usually taken over 30-years." NASA has also said of the recent winter weather:

To many people's confusion, these weather events happened against a backdrop of increasing man-made greenhouse gas levels in the atmosphere that are gradually warming the planet. But scientists stress this weather does not mean that those gases are no longer exerting a warming influence. Nor does it go against the grain of basic global warming theory. Cold snaps and bouts of natural cooling that could last years are expected naturally even as the climate continues on a long-term warming trend, forced by man-made emissions.

Scientists say cold weather will not go away because of global warming, and warming may increase snowfall. As explained in a January 6 AP article, "experts say the cold snap doesn't disprove global warming at all -- it's just a blip in the long-term heating trend." The article quoted Gerald Meehl, a senior scientist at the National Center for Atmospheric Research in Boulder, Colorado, as saying snow is "part of natural variability" and that with global warming, "we'll still have record cold temperatures. We'll just have fewer of them." Moreover, Kevin Trenberth, a climate scientist at the National Center for Atmospheric Research, was quoted in an NPR article explaining that a predicted "consequence" of warming is an increase of snowfall in some areas. From the article:

Most don't see a contradiction between a warming world and lots of snow. That includes Kevin Trenberth, a prominent climate scientist at the National Center for Atmospheric Research in Colorado.

"The fact that the oceans are warmer now than they were, say, 30 years ago means there's about on average 4 percent more water vapor lurking around over the oceans than there was, say, in the 1970s," he says.

Warmer water means more water vapor rises up into the air, and what goes up must come down.

"So one of the consequences of a warming ocean near a coastline like the East Coast and Washington, D.C., for instance, is that you can get dumped on with more snow partly as a consequence of global warming," he says.

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