Global emissions of carbon dioxide are growing at a faster clip than the highest rates used in recent key UN reports.
CO2 emissions from cars, factories, and power plants grew at an annual rate of 1.1 percent during the 1990s, according to the Global Carbon Project, which is a data clearinghouse set up in 2001 as a cooperative effort among UN-related groups and other scientific organizations. But from 2000 to 2004, CO2 emissions rates almost tripled to 3 percent a year – higher than any rate used in emissions scenarios for the reports by the Intergovernmental Panel on Climate Change (IPCC).
If the higher rate represents more than a blip, stabilizing emissions by 2100 will be more difficult than the latest UN reports indicate, some analysts say. And to avoid the most serious effects of global warming, significant cuts in CO2 emissions must begin sooner than the IPCC reports suggest. At the moment, no region of the world is "decarbonizing its energy supply," the analysis says.
The Global Carbon Project's calculations should be viewed with caution, says Michael Oppenheimer, a climate-policy specialist at Princeton University in New Jersey. Economies have been recovering from a recession at the turn of the millennium. And a spike in natural-gas prices – of uncertain duration – has given coal a second wind in developed countries. These short-term factors have probably contributed to the growth in emissions rates, he says.
Yet longer-term forces may be at play to sustain the high emissions rates. For instance, "There is concern among many experts that factors such as China's continued, very rapid coal-based growth may not be a blip that would turn around," he says.
The analysis is the Global Carbon Project's first cut at an annual effort to report on trends in CO2 emissions and the factors contributing to them, says Christopher Field, a scientist with the Carnegie Institution of Washington.
"We're trying to figure out a small set of numbers that give people a clear picture" of what's happening, says Dr. Field, a member of the Global Carbon Project's science steering committee and a co-author of the analysis, which appears in Monday's edition of the Proceedings of the National Academy of Sciences.
The analysis comes at a time when negotiators for the G-8 group of leading industrial countries have been trying to work out the wording of a section on climate change, proposed for the final declaration at the group's meeting in Germany next month. Last week, US negotiators red-penciled key portions, severely weakening the statement.
The analysis also comes as countries prepare for a new round of UN-sponsored climate talks, scheduled for December in Bali. Negotiators are trying to establish a track for talks that would provide a seamless transition between the 1997 Kyoto Protocol's first reporting period, which runs from 2008 to 2012, and a new international regime to combat global warming that would follow – one in which developing countries would start taking an active role.
So far, developing countries account for only about 23 percent of emissions accumulated since the start of the Industrial Revolution. But they also account for 73 percent of the global emissions growth in 2004. This has been largely driven by China's explosive growth.
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.