Volcanic eruptions affect Asian rainfall [in SE Asia]

2010-11-04
ANI (India)

A new research has revealed that volcanic eruptions 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 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 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. Volcanoes can be important players in climate over time," said Kevin Anchukaitis, study's lead author.

Large explosive eruptions send up sulfur compounds that turn into tiny sulfate particles high into the atmosphere, where they deflect solar radiation. Resulting cooling on earth's surface can last for months or years.

The tree rings showed that huge swaths of southern China, Mongolia and surrounding areas consistently dried up in the year or two following big events, while mainland southeast Asia got increased rain.

However, the researchers also maintained there are many possible factors involved, and it would speculative at this point to say exactly why it works this way.

"The data only recently became available to test the models. Now, it's obvious there's a lot of work to be done to understand how all these different forces interact," said Rosanne D'Arrigo, one of the study's co-authors.

Ultimately, said Anchukaitis, such studies should help scientists refine models of how natural and manmade forces might act together to in the future to shift weather patterns-a vital question for all areas of the world.

The study appeared in the online version of the journal Geophysical Research Letters.