|The current eruption of Pavlov Volcano|
Photo by astronauts on the International Space Station
In fact, Sid Perkins in a ScienceNOW article on September 19, 2011 pondered reviewed a paper published in PNAS that asked what would happen if an eruption like the Laki eruption of 1783 happened today. Four such eruptions have occurred in Iceland over the past 1,150 years, so this is not an academic exercise. Laki produced 122 million metric tons of sulfur dioxide gas, about what humans produce in a year now. One-fifth of the Icelandic population died, tens of thousands died in Europe, and it is likely that the famines that resulted from the weather and short-term climate changes caused by the eruption contributed to political unrest. In particular, there has been speculation that it contributed to the French Revolution. Anja Schmidt at the University of Leeds in the U.K. and colleagues ran climate simulations of a hypothetical eruption under current conditions.** In the first three months after such an eruption began, aerosols and dangerous particle concentrations would be concentrated over Iceland and northwestern Europe, but also elevated in southern Europe, as much as 60% above normal levels. In the ensuing year, the air pollution would kill an estimated 142,000 people (over the normal death rate). Such an eruption might shut down European air traffic for six months or more, and have a huge impact on European crop yields. These, in turn, could not be replaced because of the shutdown of air and possibly shipping traffic.
** Schmidt, A., et al., "Excess mortality in Europe following a future Laki-style Icelandic eruption," Proceedings of the National Academy of Sciences, published online before print September 19, 2011, doi:10.1073/pnas.1108569108 PNAS September 19, 2011.