Those 76 Billion Tons of Greenhouse Emissions Cuts Obama Just Announced ...

Eli is a contributing correspondent for Science magazine.

...they're from restrictions to refrigerants, not carbon dioxide, which may be why they didn't get much media attention. But those tons, measured in equivalent mass of carbon dioxide, represents a big climate bullet that the world will probably dodge.

Yesterday, the U.S. State Department and the Environmental Protection Agency proposed strengthening a global treaty called the Montreal Protocol, which regulates refrigerants and other chemicals that destroy the ozone layer. Mexico and Canada also back the proposal, putting more diplomatic muscle behind an effort to clamp down on chemicals called hydrofluorocarbons (HFCs), mostly used in air conditioners or refrigerators. They also happen to be greenhouse gases 2400 times as potent as carbon dioxide.

In a paper in the Proceedings of the National Academy of Sciences in June scientists estimated that if growth in HFC production is unchecked, the gases could contribute to greenhouse warming at the equivalent of roughly 9 billions of CO2 a year by 2050—more CO2 than the United States currently emits from power plants, cars, and farms combined. So climate scientists are thrilled that Obama is leading efforts to limit their use. "This is a very substantial proposal," says physicist David Fahey of the National Oceanic and Atmospheric Administration.

HFC's became popular after the members of the Protocol limited production of chlorofluorocarbons and gydrochlorofluorocarbons in the 1980s and 1990s; both chemicals destroy stratospheric ozone. (HFC's, designed to be the replacement, don't destroy ozone.) But diplomats didn't expect the growth in demand for the chemicals to be as fast as it has, mostly because of rapid industrial development in China and India.

The proposed rules, which will be considered by the 195 member states at the November meeting of the parties, would cut production of the chemicals by 85% by 2033 and 2043 for developed and developing countries respectively. Because cost of substitute chemicals are considered affordable, the limits have a good shot of getting passed, says Durwood Zaelke of the nonprofit Institute for Governance and Sustainable Development, based in Washington, D.C.

Last month, Obama said that he would push to regulate HFC's but gave no details; today the State Department estimated that the move would prevent the estimated production and emissions of the equivalent of between 76 billion and 83 billion tons of CO2.

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