First, diesel fuel has a considerably higher carbon content than gasoline, so burning a gallon of diesel emits 22.2 pounds of CO2 vs. 19.4 for gasoline
A diesel car with the same mpg as a gasoline car would have considerably higher carbon dioxide emissions per mile.
we have known for a number of years that black carbon (BC) or small soot particles are a major greenhouse gas — and that diesel engines are a major source of BC. A March 2008 review article published in Nature Geoscience, “Global and regional climate changes due to black carbon,” found that BC may be as much as 55% as potent in total greenhouse warming as CO2.
the addition of control devices to diesel vehicles to reduce their soot and nitrogen oxide emissions, required to meet California and EPA Tier 2 Permanent Bin emission standards and to address the climate problem of soot, reduces the gas mileage of the diesel vehicles.
the addition of a particle trap to diesel increases the NO2:NO ratio in diesel exhaust increases, exacerbating photochemical smog. Finally, even with a particle trap, diesel vehicles still emit more particles than do gasoline vehicles.
when diesel vehicles have 30% better mileage than gasoline vehicles, diesel vehicles emitting particles continuously at a particulate matter emission standard of 40 mg/mi or 80 mg/mi may warm climate more than gasoline vehicles for more than 100 yr for a CO2 lifetime of 30 years. However, diesel emitting at 10 mg/mi (Tier 2, bins 2-6 emission standard) may
warm climate relative to gasoline for about 10 yr at 30% higher mileage.
Black carbon in soot is the dominant absorber of visible solar radiation in the atmosphere. Anthropogenic sources of black carbon, although distributed globally, are most concentrated in the tropics where solar irradiance is highest. Black carbon is often transported over long distances, mixing with other aerosols along the way. The aerosol mix can form transcontinental plumes of atmospheric brown clouds, with vertical extents of 3 to 5 km. Because of the combination of high absorption, a regional distribution roughly aligned with solar irradiance, and the capacity to form widespread atmospheric brown clouds in a mixture with other aerosols, emissions of black carbon are the second strongest contribution to current global warming, after carbon dioxide emissions. In the Himalayan region, solar heating from black carbon at high elevations may be just as important as carbon dioxide in the melting of snowpacks and glaciers. The interception of solar radiation by atmospheric brown clouds leads to dimming at the Earth’s surface with important implications for the hydrological cycle, and the deposition of black carbon darkens snow and ice surfaces, which can contribute to melting, in particular of Arctic sea ice.
– from gristmill
please dont buy car. use public trasport.