By Joseph D’Aleo, CCM

Climatologists may disagree on how much the recent global warming is natural or manmade but there is general agreement that volcanism constitutes a wildcard in climate, producing significant global scale cooling for at least a few years following a major eruption. However, there are some interesting seasonal and regional variations of the effects. Robock (2003) and others have shown that though major volcanic eruptions seem to have their greatest cooling effect in the summer months, the location of the volcano determines whether the winters are colder or warmer over large parts of North America and Eurasia.

In the blog story from the All About Climate link on Volcanism_and_Climate, we also show how unusually low volcanic aerosol activity after a long period without a major volcano as we are experiencing currently, produces a global warming with greatest warming in polar regions just as high aerosol content seems to lead to cooling maximized in the polar regions.

Image shows annual mean temperature anomalies in degrees celsius for all years with abnormally (>1/2 STD) high and low aerosol content. For larger images and more details see the full story here