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Black carbon climate science and emission control strategies: A policy-relevant summary

This paper provides policy-relevant guidance on black carbon, a solid particle emitted during incomplete combustion. When emitted into the atmosphere and deposited on ice or snow, black carbon causes global temperature change, melting of snow and ice, and changes in precipitation patterns. Additionally, public health protection is a strong argument for actions that control black carbon. Exposure to particulate matter is responsible for hundreds of thousands of deaths globally each year.

Fossil fuel combustion in transport, solid biofuel combustion in residential heating and cooking, and open biomass burning from forest fires and controlled agricultural fires are the sources of about 85 percent of global black carbon emissions. According to the IPCC, black carbon is the third largest contributor to the positive radiative forcing that causes climate change.

Controls on black carbon can produce rapid regional and global climate benefits. A climate change mitigation strategy that incorporates short-lived forcing agents like black carbon can more rapidly reduce the positive radiative forcing that causes climate change, especially when rapid action is needed to avert tipping points for large-scale impacts like the loss of arctic summer sea ice, the Himalayan-Tibetan glaciers, and the Greenland ice sheet.

Black carbon reductions supplement but do not replace actions to control carbon dioxide and other greenhouse gases. Controls on black carbon will reduce both positive and negative radiative forcing, so decisions to act on a climate basis alone should focus on the net effect. The highest priority targets strictly from a climate mitigation perspective are sources that cause net positive radiative forcing such as combustion of fossil fuels low in sulfur and deposition of black carbon on ice and snow surfaces.