Global carbon emissions in overdrive

From 2000 to 2004, emissions grew at a rate of 3 percent a year – more than the highest rates used in recent key UN reports.

from the May 22, 2007 edition

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In trying to figure out how emissions-reductions burdens are apportioned, which number should dominate?

"There are very difficult discussions at the international level that must be dealt with," acknowledges Andrew Weaver, a climate scientist at the University of Victoria in British Columbia and chief editor of the Journal of Climate.

In broad terms, growing population and rising per capita economic growth have fueled the increase in emissions rates, Field explains. In addition, he says, two trends appear to be taking hold. Globally, the amount of energy used per unit of gross domestic product is leveling or increasing after years of decline. This could mean that gains in energy efficiency are slowing. It could also mean that the growth of heavy industry in developing countries is offsetting the shift to less energy-intensive activities in develped countries.

Second, the energy sources that countries are using are more carbon-intensive than in the past.

The Global Carbon Project study held two surprises for everyone involved, Field says. "The first was how big the change in emissions rates is between the 1990s and after 2000." The other: "The number on carbon intensity of the world economy is going up."

Meanwhile, scientists are noting that some of the natural "sinks" for the CO2 that humans are pumping into the atmosphere are becoming less efficient at absorbing emissions. Natural sinks – the oceans and plants on land – have been absorbing about half the emissions that humans produce. But the Southern Ocean, which serves as a moat around Antarctica, is losing its ability to take up additional CO2, reports an international team of researchers in the journal Science this week. The team attributes the change to patterns of higher winds, traceable to ozone depletion high above Antarctica, and to global warming.

"There's been a lot of discussion about whether the scenarios that climate modelers have used to characterize possible futures are biased toward the high end or the low end," Field adds. "I was surprised to see that the trajectory of emissions since 2000 now looks like it's running higher than the highest scenarios climate modelers are using."

If so, it wouldn't be the first time. Recently published research has shown that Arctic ice is disappearing faster than models have suggested.

Despite the relatively short period showing an increase in emissions growth rates, the Global Carbon Project's report "is very disturbing," Dr. Weaver says. "As a global society, we need to get down to a level of 90 percent reductions by 2050" to have a decent chance of warding off the strongest effects of global warming.

If this study is correct, "to get there we have to turn this corner much faster than it looks like we're doing," he says.

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