Large, explosive volcanoes such as Indonesia's Merapi (erupting here in 2006) have the potential to change weather patterns if their eruptions are big enough.
Now, scientists have shown that eruptions also affect rainfall over the Asian monsoon region, where seasonal storms water crops for nearly half of earth's population.
Tree-ring researchers at Columbia University's Lamont-Doherty Earth Observatory showed that big eruptions tend to dry up much of central Asia, but bring more rain to southeast Asian countries including Vietnam, Laos, Cambodia, Thailand and Myanmar-the opposite of what many climate models predict. Their paper appears in an advance online version of the journal Geophysical Research Letters.
The growth rings of some tree species can be correlated with rainfall, and the observatory's Tree Ring Lab used rings from some 300 sites across Asia to measure the effects of 54 eruptions going back about 800 years.
The data came from Lamont's new 1,000-year tree-ring atlas of Asian weather, which has already produced evidence of long, devastating droughts; the researchers also have done a prior study of volcanic cooling in the tropics.
"We might think of the study of the solid earth and the atmosphere as two different things, but really everything in the system is interconnected," said Kevin Anchukaitis, the study's lead author. "Volcanoes can be important players in climate over time."