Short-lived Climate Forcers (SLCF): Near-term climate protection and clean air benefits
Human well-being is threatened through both climate change and degraded air quality. Air pollution and climate change are intimately interrelated with respect to sources, atmospheric processes and human and environmental impacts. Current science emphasizes the urgent need to address air pollution and climate change through an integrated approach, achieving co-benefits.
Short-lived climate forcers (SLCFs)—black carbon, methane and tropospheric (ground-level) ozone— are harmful air pollutants that also contribute significantly to climate change. They have a short lifetime in the atmosphere (days to about a decade) relative to carbon dioxide (CO2), hence are often referred to as short-lived climate forcers. Recent scientific evidence demonstrates that control of black carbon particles and methane (tropospheric ozone precursor) through rapid implementation of proven emission reduction measures would have immediate and multiple benefits for human well-being.
Black carbon, a component of particulate matter, is produced by both natural processes and human activity from a wide range of sources, including diesel engines, cookstoves and brick kilns. It is a major cause of premature deaths, resulting from outdoor and indoor pollution. Black carbon contributes to global warming by absorbing sunlight and, when deposited, melting of snow and ice.
Tropospheric or ground-level ozone (smog) is not directly emitted; it is a secondary pollutant that is formed by atmospheric photochemical processes and must be controlled by reducing its precursor pollutants, primarily nitrogen oxides, carbon monoxide and volatile organic compounds, as well as methane. Tropospheric ozone damages human health when inhaled and also reduces crop yields.
Methane, a precursor of tropospheric ozone, is included as one of the six greenhouse gases controlled under the Kyoto Protocol. Major methane emissions include ruminant livestock, rice cultivation, microbial waste processing (landfills, manure, and waste water), coal mining, and oil and natural gas systems.
Both near-term and long-term strategies are essential to protect climate. Reductions in near-term warming can be achieved by control of the short-lived climate forcers whereas carbon dioxide emission reductions, beginning now, are required to limit long-term climate change.