Experts at the Massachusetts Institute of Technology using a sophisticated computer model examined what they think is the most likely outcome of UN climate treaty negotiations and found that the talks are likely to come up short.
Facing a deadline to reach a new treaty by the end of next year in Paris, the world's nations seem unwilling to make the kind of pledges that would rein in global warming to safe levels by century's end, the researchers concluded.
"Our analysis concludes that these international efforts will indeed bend at the curve of global emissions" of carbon dioxide and other planet-warming greenhouse gases, they said. "However, our results also show that these efforts will not put the globe on a path consistent with commonly stated long-term climate goals."
The MIT team reviewed the pollution-reduction commitments that climate delegates from around the world seem likely to bring to the negotiating table. They then cranked those measures through models and found that the atmosphere's blanket of CO2 would continue to rise much higher than 450 parts per million, the level that might keep the planet from warming beyond 2 degrees Celsius.
Indeed, the team predicted that emissions would grow so fast by the year 2050, that greenhouse gas concentrations would exceed 530 or 580 parts per million by the end of the century. (This summer, concentrations measured at the Mauna Loa Observatory, the world's longest-running CO2 monitoring station, peaked at above 400 ppm for an entire month. And there is no long-term slackening in sight.)
The pessimistic forecast may put new pressure on world leaders to increase their ambition as they gather in September in New York at a meeting called by UN Secretary General Ban Ki-moon—the goal of which is to give an urgently needed boost to the climate talks.
The UN meeting coincides with the annual Climate Week activities in New York, and with a large protest march being organized by advocates to demand stricter measures to tackle man-made climate change.
The MIT report, "Expectations for a New Climate Agreement," was written by Henry Jacoby and Henry Chen of MIT's program on the science and policy of global change.
Their analysis is based on the assumption that the agreement reached in Paris next year will likely involve voluntary pledges, not a legally binding formula.
"We have consulted widely with persons engaged in preparing for these negotiations, and with others familiar with the workings of the international climate regime, to formulate judgments regarding the efforts nations will be willing to pledge by 2015," the researchers wrote. But they confessed that "our evaluation of the contributions likely to be put forward by individual nations is based on clues we find in national communications, discussions with observers of conditions in various countries and—by necessity—a good deal of guesswork."
They said they hope their conclusions, however approximate or pessimistic, "will contribute to a more effective global outcome by stimulating timely and open discussion of potential national actions and their consequences."
Despite all the uncertainties about what form an agreement would take and what actions different nations would promise, they said it was important to understand that "global emissions as far out as 2045 or 2050 will be heavily influenced by achievements in the negotiations over the next 18 months."
One reason for their pessimism, they wrote, is that it appears unlikely that the world's richer countries will live up to their commitments to give $100 billion in aid to poorer nations to help them achieve more ambitious carbon targets.
For the past several years now the UN talks have been proceeding under the assumption that nations want to find a way to keep global warming within 2 degrees Celsius. But to have a reasonable chance of doing that, the world's scientists have concluded that countries can release no more than roughly 1,000 gigatons of carbon dioxide into the atmosphere in total, a global pollution budget that is already more than half spent. At the current rate the world will exhaust its budget within 20 or 30 years.
MIT's conclusions suggest that the budget is, indeed, likely to be busted, with 3 degrees Celsius of warming the likely result. If the talks collapse entirely, it could be even worse than that.
Read the study: