It's also important to note ... that the IPCC models did not account for changes in human aerosol emissions, which have had a significant cooling effect at least over the past decade, or natural factors like solar activity, which has declined since 1990 as well.

But how would one know what kind of pattern the greenhouse-gas and aerosol emissions should produce?

Scientists believe that aerosols are diminishing over those two continents as a result of environmental controls, but aerosol emissions have been increasing in Asia as industry grows there, and that growth is expected to continue.

In a 1971 paper he calculated that human caused aerosol emissions might result in global cooling after 2000 but depending on circumstances these emissions might cause a warming effect, indicating that humans had been "an innocent bystander" in the recent cooling.

To slow the rate of anthropogenic-induced climate change in the 21st century and to minimize its eventual magnitude, societies will need to manage the climate forcing factors that are directly influenced by human activities, in particular greenhouse gas and aerosol emissions.

On the flip side, approximately two-thirds of that added energy was offset by the cooling effects of aerosol emissions.

The new study adds the effect of anthropogenic aerosol emissions to the framework of the previous studies.

Altogether, there seems to be a solid basis to conclude that anthropogenic aerosol emissions modulate certain types of weather events in areas where the atmospheric conditions are amenable.