By Doug Struck
Washington Post Staff Writer
Sunday, November 18, 2007
The world will have to end its growth of carbon emissions within seven years and become mostly free of carbon-emitting technologies in about four decades to avoid killing as many as a quarter of the planet's species from global warming, according to top United Nations' scientists.
The stark choices laid out yesterday by the agency's Intergovernmental Panel on Climate Change (IPCC) describe the daunting task if the world is to avoid the consequences of a planet heated up by more than 3.6 degrees Fahrenheit (2 degrees Celsius) since 2000.
The panel, which distilled research from about 2,500 scientists, avoided conclusions about how much global warming is too much.
"The scientists now have done their work. I call on political leaders to do theirs," U.N. Secretary General Ban Ki-moon said upon formally receiving the report yesterday in Valencia, Spain.
But the tables laid out in the report describe mounting grim consequences for each degree of atmospheric heating of the planet and the difficult steps that must be taken to avoid even the worst of those consequences.
To avoid heating the globe by the minimum possible, an average of 3.6 degrees Fahrenheit, the world's spiraling growth in greenhouse gas emissions must end no later than 2015, the report said, and must start to drop quickly after that peak. By 2050, carbon dioxide and other atmospheric polluting gases must be reduced by 50 to 85 percent, according to the estimates.
That would require a drastic reworking of industrial processes, transportation, agricultural practices and even the buildings people live in, according to the report's calculations.
"We may have already overshot that target," said David Karoly, one member of the core team that wrote the report. Current emissions already are nearing the limit required in 2015 to limit the warming to 2 degrees Celsius, he said in an interview from Valencia.
Even at that threshold, the seas will continue to swell for centuries from thermal expansion and meltwater from ice caps and glaciers; the oceans will turn more acidic; most coral reefs will become lifeless expanses; floods and storms will increase; and millions of people will be short of the water they need, the report said.
"These are extremely serious findings," said IPCC Chairman Rajendra K. Pachauri.
But if the world misses that target and does not stabilize carbon dioxide emissions until 2030, for example, the planet's temperature will increase by as much as 6.3 degrees Fahrenheit above 2000 temperatures, the report said. That level of warming would result in widespread extinctions of species, a slowing of the global currents, decreased food production, loss of 30 percent of global wetlands, flooding for millions of people and higher deaths from heat waves.
Policymakers in Europe and other governments have generally regarded the 2-degree Celsius rise as the maximum the world should tolerate. The Bush administration has resisted making such a judgment, and John H. Marburger III, director of the White House Office of Science and Technology Policy, has said that goal "is not actually linked to regional events that affect people's lives."
The scientists who wrote the report officially declined to recommend such a threshold because it "involves value judgments."
"Unfortunately, that is a question people are ducking for too long," said Pachauri in an interview from Valencia after the end of the week-long deliberations by delegates of 130 countries. But, he acknowledged, global warming of 3 or 4 degrees Celsius would be "an insufferable burden that human society and other species would have to carry."
"We need to define thresholds beyond which we won't go. It really is a matter of life or death for some communities on Earth," Pachauri said in the interview. "The choice for us is to see where it is we want to draw the line."
In a final speech to the delegates, Ban described how impressed he was on recent trips to the Amazon jungle and Antarctica, both of which would be severely threatened if mankind does not curb global warming, he said.
"If the panel's most severe projection comes through, much of the Amazon rain forest will transform into savannah," he said. "These things are as frightening as science-fiction movies. But they are even more terrifying, because they are real."