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But recent climate studies suggest that report significantly underestimates the potential severity of global warming over the next 100 years, a senior member of the panel warned.
"We are basically looking now at a future climate that is beyond anything that we've considered seriously in climate policy," said Chris Field, who was a coordinating lead author of the report.
"Without effective action, climate change is going to be larger and more difficult to deal with than we thought."
Fresh data has shown that greenhouse gas emissions have grown by an average of 3.5 percent a year from 2000 to 2007, Field told reporters at a meeting of the American Association for the Advancement of Science.
That's "far more rapid than we expected" and more than three times the 0.9 growth rate in the 1990's, he said.
While increased economic activity could have contributed to the growth in emissions, Field said it appears as though the bulk of the growth is "because developing countries like China and India saw a huge upsurge in electric power generation, almost all of it based on coal."
Further complicating the problem is that higher temperatures could thaw the Arctic tundra and ignite tropical forests, potentially releasing billions of tons of carbon dioxide that has been stored for thousands of years.
That could raise temperatures even more and create "a vicious cycle that could spiral out of control by the end of the century."
"We don't want to cross a critical threshold where this massive release of carbon starts to run on autopilot," said Field, a professor of biology and of environmental Earth system science at Stanford University.
The amount of carbon that could be released is staggering.
Since the beginning of the Industrial Revolution an estimated 350 billion tonnes of carbon dioxide (CO2) have been released through the burning of fossil fuels.
The new estimate of the amount of carbon stored in the Arctic's permafrost soils is around 1,000 billion tonnes. And the Arctic is warming faster than any other part of the globe.
Several recent climate models have estimated that the loss of tropical rainforests to wildfires, deforestation and other causes could increase the concentration of carbon dioxide in the atmosphere from 10 to 100 parts per million by the end of the century.
The current level is about 380 parts per million.
"Tropical forests are essentially inflammable," Field said. "You couldn't get a fire to burn there if you tried. But if they dry out just a little bit, the result can be very large and destructive wildfires."
Recent studies have also shown that global warming is reducing the ocean's ability to absorb carbon by altering wind patterns in the Southern Ocean. Faster winds blow surface out of the way, causing water with higher concentrations of carbon dioxide to rise to the surface.
Sea levels are also rising faster than previously estimated as ocean temperatures warm and melting ice in mountain glaciers and at the poles flows into the ocean, warned Anny Cazenave, of France's Centre National d'Etudes Spatiales.
Fresh analysis using satellite imaging has shown that in the past 16 years, average sea levels have risen at a rate that is twice as fast as the last century: more than three millimeters a year.
Some regions have seen levels rise as much as one centimeter a year, Cazenave told reporters.
The expanding use of biofuels could also contribute to global warming because farmers are cutting down and burning down tropical forests to plant crops, said Holly Gibbs of Stanford University.
"If we run our cars on biofuels produced in the tropics, chances will be good that we are effectively burning rainforests in our gas tanks," she warned.
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Image of icebergs in Vincennes Bay in the Australian Antarctic Territory, from AFP.
"We are basically looking now at a future climate that is beyond anything that we've considered seriously in climate policy," said Chris Field, who was a coordinating lead author of the report.
"Without effective action, climate change is going to be larger and more difficult to deal with than we thought."
Fresh data has shown that greenhouse gas emissions have grown by an average of 3.5 percent a year from 2000 to 2007, Field told reporters at a meeting of the American Association for the Advancement of Science.
That's "far more rapid than we expected" and more than three times the 0.9 growth rate in the 1990's, he said.
While increased economic activity could have contributed to the growth in emissions, Field said it appears as though the bulk of the growth is "because developing countries like China and India saw a huge upsurge in electric power generation, almost all of it based on coal."
Further complicating the problem is that higher temperatures could thaw the Arctic tundra and ignite tropical forests, potentially releasing billions of tons of carbon dioxide that has been stored for thousands of years.
That could raise temperatures even more and create "a vicious cycle that could spiral out of control by the end of the century."
"We don't want to cross a critical threshold where this massive release of carbon starts to run on autopilot," said Field, a professor of biology and of environmental Earth system science at Stanford University.
The amount of carbon that could be released is staggering.
Since the beginning of the Industrial Revolution an estimated 350 billion tonnes of carbon dioxide (CO2) have been released through the burning of fossil fuels.
The new estimate of the amount of carbon stored in the Arctic's permafrost soils is around 1,000 billion tonnes. And the Arctic is warming faster than any other part of the globe.
Several recent climate models have estimated that the loss of tropical rainforests to wildfires, deforestation and other causes could increase the concentration of carbon dioxide in the atmosphere from 10 to 100 parts per million by the end of the century.
The current level is about 380 parts per million.
"Tropical forests are essentially inflammable," Field said. "You couldn't get a fire to burn there if you tried. But if they dry out just a little bit, the result can be very large and destructive wildfires."
Recent studies have also shown that global warming is reducing the ocean's ability to absorb carbon by altering wind patterns in the Southern Ocean. Faster winds blow surface out of the way, causing water with higher concentrations of carbon dioxide to rise to the surface.
Sea levels are also rising faster than previously estimated as ocean temperatures warm and melting ice in mountain glaciers and at the poles flows into the ocean, warned Anny Cazenave, of France's Centre National d'Etudes Spatiales.
Fresh analysis using satellite imaging has shown that in the past 16 years, average sea levels have risen at a rate that is twice as fast as the last century: more than three millimeters a year.
Some regions have seen levels rise as much as one centimeter a year, Cazenave told reporters.
The expanding use of biofuels could also contribute to global warming because farmers are cutting down and burning down tropical forests to plant crops, said Holly Gibbs of Stanford University.
"If we run our cars on biofuels produced in the tropics, chances will be good that we are effectively burning rainforests in our gas tanks," she warned.
---------------------------------------
Image of icebergs in Vincennes Bay in the Australian Antarctic Territory, from AFP.
