While long-lived greenhouse gases—particularly carbon dioxide (CO2)—continue to occupy center stage in international climate negotiations, another group of pollutants has been gaining attention among scientists and policy-makers: the so-called “short-lived climate forcers,” including black carbon and ozone. These pollutants have been regulated in the United States for decades due to their impacts on air quality, but their impacts on climate have only recently become a hot topic. Why so much interest? The answer relates to the specific characteristics of these pollutants and their behavior in the atmosphere.
How Air Pollution Affects Climate: Short-Lived Climate Forcers Unlike CO2 and other long-lived climate gases, which remain in the earth’s atmosphere and continue to affect climate for hundreds or even thousands of years after they are emitted, short-lived climate forcers remain in the atmosphere for much shorter periods—sometimes as little as a few days. As a result, emissions controls affecting short-lived forcers have the potential to provide climate benefits sooner. The potential for reductions in these pollutants to produce near-term climate benefits has excited widespread interest; especially as international action on the long-lived greenhouse gases (GHGs) has proven elusive.
This article explores some of the key characteristics of short-lived climate forcers, including their relatively short life spans and their regional nature. It describes some of the challenges inherent in managing them as both climate pollutants and air pollutants, including the need to be more careful in designing mitigation strategies. Finally, it describes the latest approaches for estimating the value to society of reductions in climate pollutants, based on avoided climate damages.