WASHINGTON—Instead of slowing down, worldwide carbon-dioxide levels have taken a sudden and alarming jump since the year 2000, an international team of scientists reported Monday.
CO2 emissions from fossil fuels—mostly coal, oil and gas—are increasing at three times the rate experienced in the 1990s, they said.
The rapid acceleration could make the battle against global warming even more difficult than it already appears.
Instead of rising by 1.1 percent a year, as in the previous decade, emissions grew by an average of 3.1 percent a year from 2000 to 2004, the latest year for which global figures are available, the scientists reported in this week's issue of the Proceedings of the National Academy of Sciences.
"Despite the scientific consensus that carbon emissions are affecting the world's climate, we are not seeing evidence of progress in managing those emissions," said Chris Field, director of the Carnegie Institution's Department of Global Ecology in Stanford, Calif., a co-author of the report.
"In many parts of the world, we are going backward," Field said. "The trends relating energy to economy growth are definitely headed in the wrong direction."
The spurt in the CO2 emission rate is especially worrisome because it marks a reversal of a long-term trend toward greater energy efficiency and away from carbon-based fuels, the report's authors said.
Molecules of heat-trapping carbon dioxide—the leading "greenhouse" gas—make up about 380 parts per million of the particles in the atmosphere. If emissions continue to increase at the rate of 3.1 percent a year, CO2 concentration would rise to 560 parts per million in 2050 and soar to 1,390 parts per million in 2100, according to Michael Raupach, an atmospheric scientist at the Center for Marine and Atmospheric Research in Canberra, Australia.
"A CO2 future like this would spell major climate-change disaster in the latter part of the 21st century," Raupach said in an e-mail message.
"This study is a signal that global action is urgently needed to reverse the adverse trends, or the challenges of responding to climate change will be more difficult," Carnegie Institution President Richard Meserve said.
The CO2 acceleration is happening fastest in China and other developing areas. It's increasing more slowly in the advanced economies of the United States, Europe and Japan, the report said.
"The emissions growth rate in the U.S. has remained nearly steady for the last 20 years, at a little under 1 percent a year," Raupach said. "The growth rate in Europe has averaged less than half that in the U.S. over those 20 years, but it has increased a little in the last five years."
Last week the National Academy of Sciences joined 12 similar bodies from around the world—including Europe, China and Russia—in urging cooperation in reducing carbon usage.
To meet the threat, the Proceedings of the National Academy of Sciences report recommends greater efficiency in transportation and power production and more use of low-carbon or no-carbon energy sources, such as solar, wind and nuclear power.