volcanoes and "global cooling/warming"

Interesting stuff from Joe D'Aleo at Intellicast.com (hat tip: Randy Baker)!

...high latitude volcanoes produce this summer cooling over the United States by favoring higher latitude blocking.

June was cool across the north.

It spread south in July.

On a larger scale and longer term, more major eruptions tend to lead to global cooling while extended periods of low activity warming. This is because volcanic aerosols reflect solar radiation back to space, reducing the amounts of solar energy reaching the surface. An anomalously clean atmosphere allows more solar heating.