Neely said previous observations suggest that increases in stratospheric aerosols since 2000 have counter balanced as much as 25 per cent of the warming scientists blame on human greenhouse gas emissions. "This new study indicates it is emissions from small to moderate volcanoes that have been slowing the warming of the planet," said Neely in the study published in journal Geophysical Research Letters. The new project was undertaken in part to resolve conflicting results of two recent studies on the origins of the sulfur dioxide in the stratosphere, including a 2009 study led by the late David Hoffman of NOAA indicating aerosol increases in the stratosphere may have come from rising emissions of sulfur dioxide from India and China.
Comment: The standard line on these ice falls is that they are always from "leaky planes", but there is a more troubling explanation.
Giant Ice Meteors Fall From Clear Skies