Scientific Consensus on Global Warming Solidifies

Oct 12, 09:40 PM

Current Headlines: CHICAGO _ The scientific consensus on global warming looked much different when Al Gore left elective office in 2001 than it does today.

Most of the remaining doubts that some scientists harbored about the impact of human activity on global temperatures have disappeared in the last decade. Gore's recital of climate facts in his movie "An Inconvenient Truth" contains some flaws, but most experts agree that he is correct on the biggest point: the earth is on a path toward a perilously warm climate, and the release of greenhouse gases is playing the key role.

The research behind that conclusion has been coming for decades, but some of the most dramatic findings emerged only in the last few years.

Perhaps most striking is a thawing in the last few months around the North Pole, where the amount of sea ice reached at all-time low in September, with 27 percent less ice than the previous record set in 2005. Satellite images of the Arctic show what some researchers say could be the start of a feedback loop that causes the Arctic ice to shrink permanently.

"We may be near some sort of tipping point where the loss of (polar) ice in summer is more extreme, and the recovery in winter is less complete," said John Walsh, a professor in the department of atmospheric sciences at the University of Illinois in Champaign and a lead author for the IPCC, the international science group that shared Friday's award of the Nobel Peace Prize with Gore.

Walsh said consequences of the ongoing Arctic changes could include disruption of normal ocean currents and an increase in sea levels if more melted ice flows into the ocean from Greenland.

Many scientists give Gore high marks for alerting the public to the reality of global warming, but the praise is not universal. A British judge this week cited nine "scientific errors" in "An Inconvenient Truth," though the judge also said the movie is "broadly accurate" and can be shown in British schools so long as teachers provide additional scientific context.

Kerry Emanuel, an atmospheric scientist at the Massachusetts Institute of Technology, said he has mixed feelings about Gore's approach. Emanuel said that while Gore has helped persuade the public to take climate change seriously, his movie contains "some exaggerations that make climate scientists wince," including an implied link between Hurricane Katrina and global warming. While research suggests that warmer water may increase hurricane intensity, most experts believe it's impossible to trace any single hurricane to global warming.

"By making scientifically unsupportable statements, (Gore) gives his critics a wide opening to cast doubt on his conclusions and on his motives," Emanuel wrote in an e-mail response to questions. "Gore should have ganged up long ago with someone from the other side of the aisle to persuade the U.S. to take the problem seriously."

Despite such shortcomings, most experts said Gore's overall point faithfully reflects what climate researchers have found.

The increasingly clear message of research on climate change began to emerge in the 1970s. The conclusions solidified as scientists gathered more data on prehistoric levels of carbon dioxide and other "greenhouse gases" that help warm the earth. That research shows that pollution from sources such as power plants and automobiles is causing a spike in greenhouse gases, unprecedented in the 500,000-year record preserved within the ice of Antarctica.

In his movie, Gore ascends in a forklift to dramatize how much greenhouse gases have increased in recent decades, and how computer models predict the rise could affect global temperatures. Some experts said that illustration is the core of his message.

"There's a lot of science in there that people have a hard time refuting," said Jerry Melillo, director of the ecosystems center at the Marine Biological Laboratory in Massachusetts who helped author past IPCC reports.

Gore had long immersed himself in research on climate change, said Rosina Bierbaum, who served as associate director for environment in the Clinton administration's office of science and technology.

"(Gore) spent a great deal of time honing and trying to understand the science, far more than you'd expect from a policymaker," Bierbaum said.

___

(c) 2007, Chicago Tribune.

Visit the Chicago Tribune on the Internet at http://www.chicagotribune.com/

Distributed by McClatchy-Tribune Information Services.

_____

PHOTOS (from MCT Photo Service, 202-383-6099):

GRAPHICS (from MCT Graphics, 202-383-6064):

For reprints, email tmsreprints@permissionsgroup.com, call 800-374-7985 or 847-635-6550, send a fax to 847-635-6968, or write to The Permissions Group Inc., 1247 Milwaukee Ave., Suite 303, Glenview, IL 60025, USA. 1049949