Recent research suggests that if we can clean up diesel engines and inefficient cook stoves in India and China for example, that could delay the effects of greenhouse-gas buildup even if pollution from coal-fired power plants persists. The study concludes that if every country were to do what California has done in the last couple of decades to clean up diesel emissions, it would slow down global warming by 15 percent.
Aerosol pollutants such as sulfur dioxide, soot, and ozone are all bad for human health, but they have different effects on the climate. Some of the aerosols are warming the planet, and some are cooling the planet. For example, sulfates that form from coal-plant exhaust reflect sunlight back into space, acting to shade the planet and cool it off. Black-carbon particles from diesel exhaust, on the other hand, absorb sunlight and heat up, warming the atmosphere. Add them together, and on balance they could be cooling the planet! That is, they mask some of the temperature increase that would have occurred as a result of carbon dioxide emissions. But this effect would be more significant if the particulates that help heat up the atmosphere were removed.
What would happen if we immediately got rid of only the black-carbon aerosols? Doing that might lead to a cooling of the planet by half a degree to a degree Celsius. However the impact on temperature is hard to pin down. For one thing, pollution affects clouds and rainfall, which have complicated effects on climate. So it is not easy to assess.