Re: Hmmm
Volcanoes are a tricky one because depdning on the type of eruption, they can either relase a lot of gases that are direct or indirect greenhouse gases, or they can inject a lot of dust into the upper atmosphere, which can have a cooling effect e.g. the postulated cause of the little ice age, or they can eject a large amount of tephra, which would reduce the albedo of ice from nearly 1 to nearly zero (depending on the type of magma involved, for example the volcanoes in Iceland eject oceanic basalt, which is nearly black, whilst volcanoes on continental crust eject comparatively lighter material). All in all, I'd be inclined to say the incerased volcanism would have seen a short-lived cooling effect, balanced out by the short-lived warming effect of the vapourised ice, and an additional warming effect due to both the ejecta directly onto the ice*, and the dust and ash that would spread further and settle onto the ice decreasing the albedo.
*Surprisingly, volcanoes are surpisingly bad at completely melting ice. The volcanoes in Iceland that are covered by glaciers year-round tend to melt only the ice directly above the erupting vent, and often not all the way to the surface. The effects this actually produces are flash flooding when the water breaks through the ice (often tens of meters high) and the collapse of the roof of the void created when this happens. The bulk of the glaciers still persist, however. When we're talking about kilometres of thickness of ice, as in "snowball Earth", many volcanoes may never have managed to erupt all the way through the ice sheet at all.
Biting the hand that feeds IT
