By Janet Raloff
There’s not much time to reach binding international agreements for limiting greenhouse gas emissions if climate negotiators are going to meet the goal of keeping global average temperatures from climbing no more than 2 degrees Celsius above those typical of pre-industrial times. Continuing with a business-as-usual approach to energy use into the foreseeable future could foster a 4 degree C warming, perhaps as early as the 2060s, a package of new papers concludes.
Such a dramatic temperature increase would be expected to trigger extensive, recurring droughts in some parts of the world, flood coastlines as sea levels rise and drastically alter the types of crops that can survive where lands remain arable, notes Mark New of the University of Oxford in England. New contributed to several of the 11 papers in the Philosophical Transactions of the Royal Society A. The journal issue, officially dated January 13, 2011, has been posted early online to coincide with the November 29 start in Cancun, Mexico of the United Nations Framework Convention on Climate Change.
Climate negotiators tend to focus on political goals, like setting timetables of 2020 or 2050 for when binding emissions limits should go into effect, notes Oxford’s Niel Bowerman. “But Mother Nature doesn’t care about what we emit in any particular year,” the atmospheric physicist says. “What matters is cumulative carbon emissions.”
His Oxford colleagues have calculated that to keep maximum global temperature increases below 2 degrees Celsius, humanity can spew greenhouse gases equivalent to no more than 1 trillion metric tons of carbon (or 3.67 million metric tons of carbon dioxide) by 2200. Already, he adds, regarding this carbon limit: “We’re just over halfway there.”