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Health & Science

Climate-change science makes for hot politics

By Joel Achenbach and Juliet Eilperin,August 19, 2011

(Page 2 of 2)

That the planet has warmed is a fact hardly anyone disputes — it has been measured with instruments on land and sea and in space. That humans have contributed to the warming through industrial activities is a theory supported by multiple scientific organizations, including the National Academy of Sciences, the American Association for the Advancement of Science, the U.S. Global Change Research Program, the National Oceanic and Atmospheric Administration, and NASA.

“Ultimately, we go back to physics. If you burn fossil fuel, you make CO2,” said Richard B. Alley, a geophysicist at Penn State University and author of “Earth: The Operator’s Manual.” “You can do this with bookkeeping. How much did we burn? How much CO2 does that make? Where is it? There it is.”

One of the twists in the debate is that the data that show the planet warming over the past century — data that skeptics often deride as untrustworthy — also show that the rate of warming has slowed in the past decade or so. “The warming has slowed since 1998,” said Tom Peterson, chief scientist for NOAA’s National Climatic Data Center.

The most recent decade is still the warmest on record — warmer than the 1990s, which were warmer than the 1980s. And NOAA and NASA rate 2010 as tied with 2005 as the warmest year ever measured.

But the flattening of the trend has inspired skeptics to declare that global warming is over or that these are natural fluctuations not driven by human activity. Scientists say that’s hardly the case, noting that multiple factors are dampening the warming trend, including sunlight-blocking volcanic aerosols and soot emitted from China’s proliferating coal-fired power plants. And they stress that the effects of greenhouse gases build over time.

“The full impact of the greenhouse gases that we’ve already added to the system today won’t be felt for 20 or 30 years,” said Bill Chameides, dean of the Nicholas School of the Environment at Duke University and co-author of a recent National Academy of Sciences report, “America’s Climate Choices.”

When Chameides and his colleagues began their research in 2008, they assumed they’d have to rush to finish before the government took action on climate change. Instead, they watched the political landscape change as “Climategate” and other controversies incited public doubts about climate science. They delayed their report to take a fresh look at the research in its totality.

Their conclusion is stated in the report’s first sentence: “Climate change is occurring, is very likely caused by human activities, and poses significant risks for a broad range of human and natural systems.”

There are dissenting scientists, but they’re a small minority within the climate-science community. A 2010 study in the journal Proceedings of the National Academy of Sciences surveyed 1,372 climate scientists and found that 97 to 98 percent agreed that humans are contributing to global warming.

The general public is far more divided. A Pew Research Center poll published in October 2010 showed that over the previous four years, the number of respondents believing there is “solid evidence” that the Earth is warming dropped from 79 percent to 59 percent. There was a striking divide along partisan lines: Some 79 percent of Democrats believed in global warming, compared with 38 percent of Republicans.

A Washington Post-ABC News poll in November 2009 found conservative Republicans were least likely to believe global warming was occurring, with 45 percent saying it was happening. That represented a 20 percentage-point drop from the previous year.

Influential conservatives have pushed climate science to the fore of Republican politics. When Romney endorsed the consensus scientific view, talk-radio titan Rush Limbaugh immediately declared: “Bye-bye, nomination. Another one down.”

Climate change, said Marc Morano, publisher and editor of the skeptical Web site Climate Depot, is “a litmus test, pure and simple, for the presidential race.”

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