These days you'd be hard-pressed to find a single article that discusses global warming without making at least implicit mention of carbon dioxide. Given its role as the most significant global warming pollutant, this shouldn't exactly come as much of a surprise; what is unusual, however, is that relatively little has been said about some of the other GHG offenders.
While we do get the occasional methane story--especially in the context of methane-to-energy technologies--we haven't heard much about black carbon, which is contained in soot emitted from vehicles. At a recent House hearing, five top scientists stated that black carbon could account for close to 16% of the planet's gross warming and that it may be second only to carbon dioxide in its potency as a GHG--ahead of methane.The black carbon absorbs incoming sunlight, converting it into infrared radiation and emitting it to the atmosphere--a process we outlined in an earlier post describing the impact of "dirty snow" on global warming. Because of its short atmospheric lifetime, the scientists suggested that reducing soot could provide a quick, effective way to slow global warming in the short-term.
Mark Jacobson, a professor of civil and environmental engineering at Stanford University, explained that diesel-engine vehicles account for a disproportionate amount of soot emissions. An early priority, he said, should be improving the efficiency and cleanliness of engines by switching to alternative fuels, adding particle traps and adopting new vehicles technologies.
"In sum, there is not an advantage and a potential disadvantage of diesel versus gasoline in terms of climate and air pollution impact. However, neither type of vehicle is satisfactory or useful for solving climate and health problems as the emissions from both are very high. Even modest improvements in mileage standards for all vehicles are beneficial, but will only delay the eventual increase in emissions due to a larger population.
A more certain method of reducing global arming caused by both fossil-fuel soot and carbon dioxide is to convert vehicles from fossil fuels to electric, plug-in hybrid or hydrogen fuel cell vehicles, where the electricity or hydrogen is produced by a renewable energy sources [sic], such as wind, solar geothermal, hydroelectric, wave, or tidal power."