Stopping the runaway train of world carbon emissions is getting harder by the day, a new global analysis suggests. The culprit is a voracious global appetite for carbon-heavy fossil fuels. In 2003 and 2004, the amount of carbon released for every joule of energy used increased, reversing a long-standing trend, the study reports. That means greenhouse gas levels are rising even faster than previously feared, the authors say, although others aren't so sure.
As countries develop, they typically generate less carbon dioxide for every unit of energy used. That's because they typically move away from coal toward more carbon-efficient fuels such as natural gas, and economies evolve away from heavy manufacturing toward less energy-intensive service industries. But that trend of less carbon dioxide per unit of energy seems to be reversing globally.
Christopher Field of the Carnegie Institution in Palo Alto, California, and co-authors analyzed the relations between energy use, carbon emissions, and economics using public data through 2004. The bottom line: From 2000 to 2004, emissions levels have increased 3% per year--three times the rate of increase from 1990 to 1999.
China is a big driver, the authors argue. That nation's robust economic growth has more than doubled its emission levels since 1990, and carbon-intensity began to increase in 2003 and 2004. China's reliance on coal is largely to blame, according to the scientists, who published their results yesterday in the Proceedings of the National Academy of Sciences.
Other experts warn that economic data coming out of China may not be reliable. And "basing a change in trend on just 2 years' data really is a bit of a stretch," says Tom Wigley of the National Center for Atmospheric Research in Boulder, Colorado, although he adds that it's good to alert people to the possibility.