Efforts to limit climate change generally focus on reducing carbon dioxide emissions caused by burning fossil fuels. However, another byproduct of fossil fuel combustion is black carbon, a major component of soot. Sources include diesel truck and car engines as well as wood fires, kilns, and stoves. Particles of black carbon in the atmosphere absorb sunlight and can have significant effects on the temperature, as do ozone, methane and other chemicals. A report jointly authored by the United Nations Environment Program and World Meteorological Organization, “Integrated Assessment of Black Carbon and Tropospheric Ozone”, analyzed the impact of black carbon and other substances on the atmosphere and modeled predictions for the difference that emissions reduction would have on climate and population health.