With Secretary Clinton’s announcement  this week of a new coalition aimed at short-lived climate pollutants such as methane and soot, the U.S. is helping to focus international attention on a critical but frequently overlooked dimension of the climate challenge. To maximize its leadership on this front, the U.S. should also take stronger steps  to tackle these pollutants at home.
The new multilateral effort to address short-lived climate pollutants  (also called short-lived climate forcers) is an important recognition of both the scientific and political realities that surround climate change. A growing body of scientific evidence underscores the importance of near-term action to slow the rate of climate change, which is proceeding more rapidly than scientists predicted. Because methane, black carbon  and hydroflurorocarbons (HFCs) have relatively short atmospheric lifetimes, reductions in these compounds will have significant near-term benefits in reducing climate change. In contrast, carbon dioxide remains in the atmosphere for hundreds of years. Reductions in CO2 are critical to limit the amount of warming over the longer term, but have more limited impact in the near term.
To effectively manage the risks and reduce the costs of climate change, we need to address both -- reduce short-lived climate pollutants to slow the rate of change and reduce carbon dioxide to limit long-term warming. A recent UNEP study  showed that reductions in these short-lived pollutants using existing technologies can chop 0.4 degrees C from projected warming by 2050. With increasing risks of extreme weather, and the ensuing human and economic losses, these are investments well worth making.
But the case for reducing short-lived climate pollutants goes well beyond their climate benefits. Exposure to black carbon has widespread adverse health impacts and methane emissions contribute to ground-level ozone that harms agriculture and human health. These impacts are felt locally and regionally, so countries that undertake efforts to reduce these pollutants would reap near-term reductions in illness, premature deaths and crop losses. As efforts are made to expand participation in the initiative, these near-term and local benefits will be an important selling point.
Through a broad range of efforts – including voluntary programs to reduce methane emissions, regulation of diesel emissions, and the development of alternatives to HFCs -- the United States has made substantial progress in addressing these pollutants and can share these experiences with others. But to be effective, we must continue to lead by example. Significant opportunities exist here at home to take additional steps to reduce these short-lived pollutants. The U.S. can and should do more: to reduce black carbon emissions from the dirtiest diesel engines still on the road today; to limit methane emissions from natural gas production and distribution and agricultural systems; to expand capture and reuse of methane from coal mines, landfills, and wastewater treatment facilities; and to replace HFCs where alternatives with lower global warming potentials and higher energy efficiencies exist. A new C2ES policy fact sheet  takes a closer look at the options.
Expanding domestic actions to reduce these pollutants will be an important element of our ability to lead this important global intiative.
Steve Seidel is Senior Advisor at C2ES