Saturday, February 03, 2007

Global warming called 'unequivocal'

Global warming called 'unequivocal'
By Elisabeth Rosenthal and Andrew C. Revkin
Copyright by The International Herald Tribune
February 2, 2007

PARIS: In a bleak and powerful assesment of the future of the planet, the leading international network of climate change scientists concluded for the first time Friday that global warming was "unequivocal" and that human activity was "very likely" to blame. The warming will continue for hundreds of years, they predicted.

The scientists, members of the Intergovernment Panel on Climate Change, said that new science had also allowed them to conclude that the warming caused by human activity was probably influencing other aspects of climate change, including a rise in the number of heat waves, extreme storms and droughts, as well as ocean warming and wind patterns.

A vast improvement in the science of climatology, including "large amounts of new and more comprehensive data," has allowed the group to become far more confident and specific in its predictions since its last assessment, in 2001, the authors said. The conclusions were presented at a press conference in Paris, along with a summary of the group's much anticipated fourth report.

Until Friday, there was still the scientific possibility that the global climate change in the last 50 years could be explained by natural variation rather than man-made influences, particularly the burning of fossil fuels.

The scientists, representing 13 countries and whose work was vetted by representatives from hundreds of nations, left little doubt of where they stood.

"There is no question that this is driven by human activity," said Susan Solomon, one of the panel's leaders. She noted that in calling the link "very likely" scientists had increased certainty on a connection from their previous estimate of 66 percent to 90 percent. "Warming of the climate system in now unequivocal, unequivocal."

Achim Steiner, executive director of the United Nations Environment Program, said the report represented a tipping point in the accumulating data on climate change, even though the basic message of the document — that human activity is creating dangerous warming — was widely accepted.

"Feb. 2, 2007, will perhaps be remembered as the day" when global thinking about climate change moved from debate to action, he said. "The focus will shift from whether climate change is due to human activity, to what on earth are we going to do about it."

Indeed, many of the report's authors called on governments to heed the evidence. "Policy makers paid us to do good science, and now we have high, very scientific confidence in this work — this is real, this is real, this is real," said Richard Alley, one of the lead authors and a professor at Pennsylvania State University. "So now act, the ball's back in your court."

[The Bush administration played down the U.S. contribution to climate change on Friday and called for a "global discussion" of the problem, Reuters reported from Washington.

["We are a small contributor when you look at the rest of the world," the energy secretary, Sam Bodman, said of greenhouse gas emissions. "It's really got to be a global discussion."]

Climate change will cause far-flung ramifications for both humans and nature, according to the 21-page summary of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, which was approved early Friday by officials from more than 100 countries after three days and nights of wrangling over wording.

The ripple effect of warming has devastating implications for humans that will continue for centuries even if carbon emissions could be stabilized at 2000 levels, because the gases persist for years. In fact, the impact that carbon emissions have on climate has increased 20 percent in the last 15 years, Solomon said.

In the report, the authors lay out six possibilities resulting from global warming, depending in part on how man responds. All predict a continuing rise in temperatures and sea level for the next century. Temperatures will rise from 1.8 to 6.4 degrees Celsius (3.2 to 11.5 Fahrenheit) by 2099.

While the report projected a modest rise in sea levels by 2100 — from 18 to 55 centimeters — it concluded that seas would continue to rise and coastlines to retreat for at least a thousand years.

Even the midrange projections for warming would likely seriously disrupt ecosystems, water supplies and agricultural production.

"The new report powerfully underscores the need for a massive effort to slow the pace of global climatic disruption before intolerable consequences become inevitable," said John Holder, president of the American Association for the Advancement of Science and a climate expert at Harvard University.

"Since 2001, there has been a torrent of new scientific evidence on the magnitude, human origins and the growing impacts of the climatic changes that are under way," he said. "In overwhelming proportions, this evidence has been in the direction of showing faster change, more danger."

The report warns that heat waves, droughts and intense storms will continue to become more frequent.

Generally, the scientists said, more precipitation will fall at higher latitudes, which are likely also to see lengthened growing seasons, while semi-arid, subtropical regions already chronically beset by drought could see a further 20 percent drop in rainfall under a midrange scenario.

But Rajendra Pachauri, chairman of the panel, said the report was heartening in the sense that it gave politicians very specific information on which to act. "The science has moved several steps beyond what was possible before," he said. "You see the extent to which human activity is influencing greenhouse gases. You are able to see the costs of inaction."

The scientific panel operates under the aegis of the United Nations and was chartered in 1988 — itself a year of record heat and forest fires — to provide regular reviews of climate science. Its scientist-members are unpaid.

Big questions remain about the speed and extent of some impending changes, both because of uncertainty about future population and pollution trends and the complex interrelationships of the emissions, clouds, dusty kinds of pollution, the oceans and Earth's veneer of life. Scientists remain unsure about how much Arctic ice will melt and how fast, which will have a major impact on sea levels.

The report caps a half-century effort to discern whether humans, through the buildup of carbon dioxide and other gases released mainly by burning fuels and forests, could influence the Earth's climate.

Two subsequent reports by the panel will be released this spring, focusing on how the world should respond to the new evidence.

One report will deal with mitigation, efforts by countries to reduce the production of heat trapping gasses. These include international efforts like the Kyoto Protocol, as well as programs that encourage individuals to use solar heating in their homes and to take public transportation rather than driving.

The second will focus on how countries might respond to the climate change that scientists are now sure will occur. Should rivers be widened to accommodate increased rainfall that is likely to occur in much of Europe? Is sea level rise likely to be so great that low- lying cities should be abandoned?

In two weeks, the European Union will convene a meeting in Berlin on how to adapt to changing conditions, like heavier rains and flooding. Politicians "need to include new scientific climate change projections into their plans," said André Jol, climate change specialist at the European Environment Agency in Copenhagen. "But this is all very new and there will be a lot of ideas."

Andrew C. Revkin reported from New York.


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