Last year’s extreme drought, wildfires and the devastation of Hurricane Sandy have driven home the high economic costs associated with extreme weather. The increasing frequency and intensity of such events make it clear that climate change presents a real and present danger. It no longer can be dismissed as a problem only of concern to our children or grandchildren.
This increased urgency has also caused an important shift in our understanding of what actions are required to slow the rate of climate change. Recent studies  have focused on the need for a two-pronged approach. Reducing emissions of carbon dioxide, some portion of which stays in the atmosphere for centuries, is critical to long-term efforts. But curbing greenhouse gases with shorter atmospheric lifetimes will have significant near-term climate and public health benefits.
A new C2ES policy brief  outlines a range of administrative actions the federal government can take under existing authorities to reduce these shorter-term pollutants: black carbon, methane and hydrofluorocarbons (HFCs).
Unlike carbon dioxide, these pollutants contribute to climate change over much shorter periods -- from weeks to a few decades. Roughly 30 to 40 percent of warming experienced to date may be attributed to short-lived climate pollutants. One analysis  suggests that a set of global actions to limit methane and black carbon could reduce projected increases in temperature by 0.5 degrees Celsius in 2050, while also avoiding 2.4 million premature deaths from exposure to air pollution.
Most importantly, by substantially cutting emissions of these substances now, their atmospheric levels quickly drop, reducing their contribution to climate change.
Take HFCs as an example. Widely used in refrigeration and car air conditioning, these chemicals were developed to replace ozone-depleting substances (chlorofluorocarbons - CFCs) a few decades ago. But they are becoming an increasingly significant contributor to climate change and are expected to double to 4 percent of the nation's greenhouse gas emissions by the end of the decade.
HFC-134a is one of the most widely used HFCs. Despite its relatively short atmospheric lifetime (about 14 years), it is a very powerful greenhouse gas. There are more climate-friendly alternatives to HFC-134a. The Environmental Protection Agency can move forward with its plan to remove HFC-134a from its list of acceptable chemicals for use in car air conditioners on a timetable consistent with the introduction of more environmentally acceptable alternatives.
Other potential steps the U.S. government can take to reduce short-lived climate pollutants include:
-- Through an executive order, the U.S. government can lead by example by mandating that federal agencies purchase products made without HFCs, retrofit or replace their dirtiest diesel engines to reduce black carbon emissions, and require actions to reduce methane emissions from oil and gas wells and coal mines on federal lands;
- EPA can strengthen rules or programs, where cost-effective options exist, to limit methane emissions from oil and gas operations, landfills, coal mines, and animal feeding operations; and
- We can build on ongoing EPA programs to accelerate the retrofitting or replacement of existing diesel-powered trucks emitting black carbon.
The U.S. showed international leadership a year ago by launching, with five other countries and the United Nations Environment Programme, a new international coalition  dedicated to addressing short-lived climate pollutants. Now it's time for the U.S. to develop its own comprehensive domestic program to limit these dangerous emissions.
Ultimately, we need to address the carbon dioxide emissions we are pumping into the atmosphere that will still be there for a century and longer. But while we make more substantial progress on that challenge, we can take significant steps now that will have a big impact on our planet's warming in the immediate future.