IPCC report is out

Global warming called 'unequivocal' - Print Version - International Herald Tribune

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





In a bleak and powerful assessment of the future of the planet, the leading international network of climate change scientists concluded for the first time Friday that global warming is "unequivocal" and that human activity is "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 is 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 their 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 fuel.

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 Dr. Susan Solomon, a chairwoman of the panel that produced the report. She noted that in calling the link between people and climate change "very likely" the scientists had increased certainty on a connection from their previous estimate of 66 percent to 90 percent. "Warming of the climate system is now unequivocal, unequivocal," she said.

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 — had been already widely accepted in many quarters.

"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 powerful science now in hand.

"Policy makers paid us to do good science, and now we have very high 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 Penn State University. "So now act, the ball's back in your court."

Climate change will cause far-flung ramifications for 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 teams of officials from more than 100 countries after three days and nights of wrangling over wording.

Even Solomon, known as a staid and conservative scientist, chose to highlight dramatic examples. If greenhouse gases, which trap heat, cause temperatures to rise 1.9 to 4.6 degrees Celsius (3.4 to 8.3 Fahrenheit) as the report predicts it might, that could lead to a sea level rise of 7 meters, or 23 feet, if the temperature rise were sustained over thousands of years, she said.

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

The report lays out four different scenarios of global warming, depending on how humanity responds. All predict a continued rise in temperature and sea level for the next century. Temperatures will rise between 1.8 and 6.4 degrees Celsius (3.2 to 11.5 Fahrenheit) depending on the scenario. Sea levels will go up 18 to 55 centimeters, or 7 to 21 inches.

"It is very likely that hot extremes, heat waves and heavy precipitation events will continue to become more frequent," said the report.

Officials here made clear that the effects would be felt in the very near future — indeed, they are being felt now.

"If you are a South Asian child born in 2007 you may well in your lifetime be facing inundation of your lands and being turned into an environment refugee," Steiner said.

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 for increases in the greenhouse gases.

But Dr. Rajendra Pachauri, a 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 move 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 panel operates under the aegis of the United Nations and was chartered in 1988 — a year of record heat, burning forests and the first big headlines about global warming — to provide regular reviews of climate science to governments to inform policy choices.

Government officials are involved in shaping the summary of each report, but the scientist-authors, who are unpaid, have the final say over the thousands of pages in four underlying technical reports that will be released later this year.

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.

One big question mark involves how much arctic ice will melt and how fast, which would have a major impact on sea levels.

The report essentially caps a half-century-long scientific 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 system in potentially momentous ways.

Two subsequent reports by the panel to be released this spring are to focus on how the world should respond to climate change.

One will deal with mitigation — efforts by countries to reduce the production of heat trapping gases. 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 adaptation, or how countries might respond to climate change that scientists are now sure will inevitably occur.

Should rivers be artificially widened to accommodate increased rainfall that is likely to occur in much of Europe, for example? Should dikes be reinforced to prevent flooding in low-lying cities, or is sea level rise likely to be so great that such land should be abandoned and its residents moved inland?

In two weeks, the European Union will convene a meeting in Berlin on how to adapt to changing in water conditions, like heavier rains and flooding.

Andrew C. Revkin reported from New York.