It is notoriously claimed that every cloud has a silver lining, and those worried about climate change may be assured that this is true of ash clouds as well. It seems that although volcanos put out a great deal of CO2 themselves, it is estimated that the flight cancellations across Europe have resulted in a reduction in CO2 per day emmissions in excess of the (very roughly) estimated CO2 emmissions by day by the volcano itself.
Of course, this ignores the primary effect of ash-heavy volcanic erruptions, which is to reflect/block more sunlight in the atmosphere, thus producing a cooling trend which can last several years. When Krakatoa blew itself up in 1883, the following years was called "the year without a summer", with global average temperatures falling by 2.2 °F and the average temperatures not returning to trend until 1888. (In an interesting side note, the climate effects of Krakatoa also represented the last time that Western Europe suffered significant food shortages as a result of climate-induced crop failure. By the turn of the century, the global grain market was so well established that only war and economic disruption could cause food shortages in the developed world.)
So people stuck in airports across Europe can, at least, reflect that The Day After Tomorrow will now instead be The Day After the Day After Tomorrow (Or Perhaps The Next Day). And perhaps there's a way forward here in the contentious global warming debate. Surely we can all agree that volcanos are pretty cool. I think it's high time that we establish a UN panel to site new volcanos around the world. Each industrial nation will be required to host its fair share of volcano offsets. Sunsets will be more beautiful, the weather will be cooler, and life will generally be more exciting. I, for one, welcome our new volcanic overlords.