fossil-fuels

If you’ve ever pumped gas in the United States, you’ve seen the sticker: “This product may contain up to 10 percent ethanol by volume,” declares one at a Massachusetts Shell station. Since 2005, Washington has mandated that an increasing amount of ethanol be mixed into gasoline every year, encouraging refiners and retailers with cash incentives.

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.