http://www.nytimes.com/2016/10/18/opinion/another-big-step-on-climate.html 2016-10-18 04:46:01 Another Big Step on Climate A new global agreement will phase out a powerful planet-warming chemical used in air-conditioners and refrigerators. === The answer to The accord reached in Kigali, Rwanda, follows the ratification by enough countries of last year’s Paris agreement broadly reducing greenhouse gases to allow it to take effect, as well as a narrower agreement to limit emissions from aircraft. It completes a trifecta of diplomatic accords aimed at keeping the rise in global temperatures below 3.6 degrees Fahrenheit (two degrees Celsius) over the average preindustrial temperatures — a point beyond which the manifest consequences of climate change, including rising sea levels and droughts, are likely to become exponentially worse. Saturday’s agreement takes aim at widely used chemical refrigerants called hydrofluorocarbons, or HFCs. Although they now make up only a small part of the greenhouse gases in the atmosphere, HFCs are extremely powerful heat-trappers and, if left unchecked, would make it hard not to exceed the 3.6 degree threshold. One factor driving the negotiations was the rapid growth of air-conditioning in nations like China and India. HFCs were once seen as a technological godsend. They were developed in response to the 1987 Montreal Protocol, a global agreement requiring nations and manufacturers to find a substitute for chlorofluorocarbons, or CFCs, then the dominant refrigerant, which was destroying the planet’s ozone layer. The chemical industry replaced that chemical with HFCs, which don’t harm the ozone layer but, as it turned out, added greatly to global warming. The new agreement took seven years and required many determined advocates — major Western governments, the small island nation of Micronesia, poor African nations that fear drought and even starvation and persistent environmental groups. It was hardly a slam dunk. Despite obvious threats to their populations from rising sea levels and droughts, some developing countries like India pushed back hard, in part because their people were on the verge of being able to afford air-conditioners powered by HFCs. The outcome was compromise — resulting, in part, from the last-minute efforts of Secretary of State Countries have an enormous amount of work to do on all climate-changing pollutants, chiefly carbon dioxide. But the HFC agreement makes the job a little bit easier.