Why Leading Scientists Underestimated How Quickly We're Scorching the Atmosphere

In its most recent official report, the Intergovernmental Panel on Climate Change (IPCC) significantly underestimated the amount of greenhouse gas emissions that would occur during the last seven years, a miscalculation that has put the planet beyond the "range of possibilities" considered by some of the world's top climatologists. The overly optimistic predictions in the IPCC's Fourth Assessment, released in 2007, appear to have been driven, in part, by the political dynamics involved in the international effort. The underestimation means that government negotiators meeting in Copenhagen later this year to write a replacement to the Kyoto Protocol will have a tougher task than previously imagined.

"We're looking at future climate beyond anything we've considered," Chris Field, director of the global ecology department at the Carnegie Institution for Science, told the American Association for the Advancement of Science (AAAS) annual meeting in Chicago last month. "Actual emissions are at or above the total range of possibilities considered in the IPCC's Fourth Assessment."

The underestimation of greenhouse emissions occurred, Field said, because the IPCC failed to include in its scenarios the rapid increase in carbon dioxide from Asia's coal-reliant industrial expansion between 2000 and 2007.

"We were too optimistic," Field said. "There was no decrease in emissions from developed countries and the sharpest increases and overall intensity came from China and India that rely heavily on coal."

"It was assumed that coal would become less important," says Ken Caldeira, also of the Carnegie Institution. What happened, however, is that China and India developed rapidly while rising oil prices pushed wealthy nations to use more coal, which is more CO₂ intensive in its emissions. Scientists at NASA's Goddard Space Science Institute concur that the past five years' sharp increase in atmospheric CO₂ is attributable to the steep rise in global coal use, pushed upward by accelerated Asian economic and industrial development.

"IPCC scenarios assume an increase in energy efficiency during this period," Caldeira says. But that didn't happen. "Efficiency flattened out," he says.

Scientists involved in the IPCC process say that IPCC reports are designed to capture the long-term rather than short-term trends, and cannot incorporate data after a certain point, so the 2007 report relied on pre-2002 data. Nevertheless, widely available pre-2002 data would have suggested an upward trend in Asian emissions.

According to research by Kelly Sims Gallagher, director of the Energy Technology Innovation Project at Harvard University's Kennedy School of Government, China has been a net importer of oil since 1993. During the 1990s, writes Gallagher, Chinese car sales grew about 27 percent a year, doubling the number of cars on the road every 2.5 years. The US Energy Information Agency data shows coal consumption by China and India approximately tripling between 1980 and 2005.

Given the fact that the breakneck economic growth in India and China were well known phenomena, how could the Nobel prize-winning IPCC have omitted an increase in Asian carbon emissions from its scenarios? The short answer appears to be politics.

"Social and political dynamics are at work," in producing final IPCC reports, Fields said at the AAAS meeting.

Stanford University biology professor and climate scientist Stephen Schneider agrees. "The lead authors are constrained by government reviewers," Schneider says. "The political process cuts the edges and doesn't do a good job at the tails of the bell curve, which is where we are now.

"These reports are consensus documents and when it comes to politics, the interests of small island nations are different than those of the U.S., China, Russia, Saudi Arabia, and Kuwait."

There is a political and diplomatic incentive to low-ball emissions predictions becaue lower numbers make the task ahead appear less onerous.

"Overtly or covertly, if you have an optimistic baseline of what happens in the absence of policy, it makes what you need to do appear relatively modest," Caldeira says. "People who want to make the problem look more tractable have an incentive to make the baseline ore optimistic. If you have a more depressing picture, it's more difficult to make the transition."

For example, Caldeira says that if we're to stabilize atmospheric carbon at what's now considered tenable levels for the climate -- about 350 parts per million (we're now at about 385 ppm) -- the world's energy systems must be carbon neutral by mid-century. That's a daunting task that many governments appear hesitant to grapple with.

Not only has atmospheric carbon increased beyond the range of possibilities, but so too has effects of that increase on Earth's ecosystems. The retreat of Arctic Sea ice, the collapse of permafrost, ice sheet melt and that melting's contribution to sea level rise are occurring faster and with more intensity than expected. Atmospheric carbon dioxide, Field said, rose 3.5 percent annually between 2000 and 2007, compared with annual increases of 0.9 percent in the 1990s. Between 1993 and 2003, melting ice sheets accounted for 40 percent of sea level rise. That contribution is now estimated at 80 percent.

"The more we learn about the process [of climate change], the more severe the risk becomes," says Michael Oppenheimer, professor of geosciences and international affairs at Princeton University. Oppenheimer and Schneider are among the co-authors of a paper just published in the Proceedings of the National Academy of Sciences showing that the impacts of a 1-2°C rise in global mean temperature are much greater and pose greater environmental risks than previously anticipated.

Whether or not the Asian carbon surge continues, its impacts will be with us for decades -- even centuries -- because of the length of time carbon lingers in the atmosphere. "Nothing we could do now to stabilize carbon could be too fast or fast enough," says Tom Athanasiou, director of the organization Eco-Equity, an Earth Island Insitute-sponsored project. "The storyline was wrong."

The underestimation of recent greenhouse emissions threatens to complicate the work of government officials who will meet in Copenhagen in December to hammer out an international climate agreement to replace the Kyoto Protocol, which expires in 2012. With climate change occurring faster than scientists have the ability to predict -- and the impacts greater than anticipated -- an international deadlock is unacceptable, Anthanasiou says.

"Maybe the most important thing is to communicate the severity of the situation in a way that gets through people's defenses," he says.