January 8, 2013, by Tim Radford
FOR IMMEDIATE RELEASE The biggest obstacle to limiting the warming of the Earth’s atmosphere by greenhouse gases, scientists say, is the failure of politicians to act. LONDON, 8 January – Researchers who tested 500 possible scenarios for climate change have just confirmed that prompt political action is more likely to limit global warming to a 2°C rise than a delayed response. This less-than-surprising conclusion – it echoes both peasant proverb and ancient fable – demolishes the argument that it would be better to wait until the science of climate is better understood. Climate scientists have warned that under a “business as usual” scenario, the planet could warm by 6°C in this century: hotter than at any time in the last 65 million years. Governments almost everywhere agreed in 2009 to control greenhouse gas emissions and to try to restrict warming to 2°C. Now a team of scientists based at the International Institute of Applied Systems Analysis in Austria report in Nature that they considered the uncertainties over policy, including the detailed impact of carbon dioxide and other gases on the climate system, the effect of any steps to reduce the emissions, the future global demand for energy, any imposed global carbon price and the timing of any actions to limit emissions. They found that the time to act is now. If nations brought forward global action on emissions from 2020 to 2015, the chance of success would rise from 56 to 60%. The price of achieving 60% probability in 2015 would be US$60 a tonne of carbon dioxide equivalent. The price of achieving the same probability by starting in 2020 would be $150 a tonne.
More support for bold policies
“With a twenty-year delay you can throw as much money as you have at the problem and the best outcome you can get is a fifty-fifty chance of keeping temperature rise below two degrees,” says Keywan Reihi, one of the authors. The study supports an earlier analysis by the scientists of the Global Carbon Project, who reported in Nature Climate Change in November that “aggressive” action would be required to contain average warming within 2°C. The need to limit fossil fuel use remains at the heart of the climate change issue. There are huge uncertainties about future demand, population growth, agricultural needs, technological advances and all the possible climate feedbacks associated with a steady temperature rise. But political timing remains the decisive factor. “Ultimately, the geophysical laws of the Earth system and its uncertainties dictate what global temperature rise to expect,” says Joeri Rogelj, lead author of the IIASA paper. “If we delay for twenty years, the likelihood of limiting temperature rise to two degrees becomes so small that the geophysical uncertainties don’t play a role any more.” He told the Climate News Network: “In the end even a 50-50 chance of staying below 2°C will become unattainable, no matter how much money you throw at the problem… we shall never achieve the same probability as with immediate action. Some chances are lost forever.” – Climate News Network
Tim Radford, a founding editor of Climate News Network, worked for The Guardian for 32 years, for most of that time as science editor. He has been covering climate change since 1988.