Abstract
An emerging issue in air pollution today is how to improve local air quality and address global warming simultaneously. Particulate black carbon (BC), the main component of soot, is a pollutant that is well known to degrade air quality and impair human health. Because it absorbs solar radiation, soot also directly heats the atmosphere upon its exposure to sunlight. The absorption is enhanced when BC internally mixes with other airborne particle components as it ages. The enhancement is significant enough that BC from all sources may be the second leading cause of global warming after carbon dioxide and ahead of methane. Here, global simulations of the climate response of BC were run. It was found that, due to the short lifetime of BC (relative to the long lifetime of carbon dioxide), any emission reduction of BC may slow global warming faster and to a greater extent than any emission reduction of CO2 or CH4 for a specific period, where the period may be on the order of a decade. This result is relevant since the Kyoto Protocol global warming treaty of 1997 did not consider control of soot as a method of slowing warming. One commonly suggested control strategy for global warming has been to use more diesel vehicles, since they are perceived to release less CO2 than gasoline vehicles. However, in the absence of a particle trap, such vehicles appear to cause more warming over 100 years than their gasoline counterparts due to the soot emissions from them. With particle traps, such vehicles appear to have several side effects that affect air quality and climate. These will be discussed.