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Climate debate in the journals, on the Hill

On July 2, the World Meteorological Organization issued a statement saying that the number and intensity of weather extremes experienced around the world this year are evidence that global climate change is actually under way.

And while few people disagree that Earth’s surface has warmed over the past few decades, the arguments and accusations start flying when the discussion turns to whether or not the warming is an anomalous result of human activity or part of natural climate change.

The 2003 Iditarod Race ceremonially started in Anchorage as shown here, but the real start had to move farther north this past winter due to one of the warmest winters on record. Two recently published papers challenge the idea that the 20th century has seen unprecedented warmth. Photo by Jeff Schultz, Alaska Stock Images.

The most recent fray took place in the journals, with the publication of two articles in the January Climate Research and Energy & Environment by Willie Soon and Sallie Baliunas of the Harvard-Smithsonian Center for Astrophysics and colleagues, followed soon after by a scathing rebuttal in Eos. Soon and Baliunas’ two very similar papers challenge the view that natural factors cannot explain recent climate changes, and conclude that the 20th century is neither the warmest century over the last 1,000 years, nor is it the most extreme.

Studying more than 240 research papers published over the past four decades, they wanted to provide a detailed look at climate changes in different regions around the world to help give climate models greater accuracy. “We felt it was time to pull together a large sample of recent studies and look for patterns of variability and change,” Soon said in a press release.

In the July 8 issue of Eos, Michael Mann of the University of Virginia and 12 colleagues in the United States and the United Kingdom refuted Soon and Baliunas’ claims, saying that several reconstructions of large-scale temperature changes over the past millennium show unprecedented warmth in the late 20th century.

“Such anomalous warmth cannot be fully explained by natural factors, but instead, require a significant anthropogenic forcing of climate that emerged during the 19th and 20th centuries,” Mann and co-authors wrote. “There is a compelling basis for concern over future climate change.”

Agreeing with Mann, Climate Research Editor-in-Chief Hans von Storch resigned from the publication in late July, saying that the Soon and Baliunas paper was flawed and should not have been published. Two other editors also resigned over the paper’s publication.

Nonetheless, over the past seven months, decision makers, including the Bush administration and some members of Congress, have used the Soon and Baliunas papers to bolster their arguments on climate change. On July 29, testifying in front of the Senate Committee on Environment and Public Works, Soon said: “There is no convincing evidence from each of the individual climate proxies to suggest that higher temperatures occurred in the 20th century than in the Medieval Warm Period.” During that period, between about A.D. 800 and 1300, industry could not have been a factor.

On the other side of the debate was Mann, arguing that evidence from paleoclimate sources (including tree rings, ice cores, ocean sediments and corals) overwhelmingly supports the unprecedented warmth theory. “This is almost certainly a result of the dramatic increase in greenhouse gas concentrations due to human activity,” he testified.

Hydroclimatologist David Legates of the University of Delaware apologized to the committee for the presence of such heated scientific discussion in a Senate hearing room. “But hopefully a healthy scientific debate will not be compromised, and we can push on towards a better understanding of climate change,” he said.

On July 24, the Bush administration issued a strategic plan for its Climate Change Science Program. The plan pledges resources to assess natural climate variability and reduce uncertainty about the causes and effects of climate change. One specific goal is to seek further knowledge about climate and the role of anthropogenic greenhouse gases.

The plan has come under harsh criticism from some political leaders. “Too little, too late,” said Sen. Joseph Lieberman (D-Conn.) following the plan’s release. “Instead of wasting more time by reopening this debate, the president should be taking action to stop global warming.”

Lieberman has sponsored the Climate Stewardship Act of 2003, co-sponsored by Sen. John McCain (R-Ariz.), to provide funding for a research program on abrupt climate change and to accelerate the reduction of greenhouse gas emissions through a cap and trade program. The act was originally offered as an amendment to a major energy bill, but Lieberman and McCain decided to bring the act to a separate vote on the Senate floor at a “later date,” likely in September.

Sen. Olympia Snowe (R-Maine), a co-sponsor of the McCain/Lieberman bill, said in a statement that she is pleased that debate on this crucial issue will occur when the Senate returns in September. “I have said from the beginning, climate change must be part of the energy debate and we must enact a cap and trade system to limit greenhouse gas emissions.”

Megan Sever

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