Lava from Java pushing rainfall farther

Huge volcanic eruptions are having an effect on short-term rainfall patterns, potentially disrupting over half of the world’s crops’ growing season.

The information has come to light after research in Asia followed the distribution of weather patterns during monsoon seasons, between June and September, following volcanic eruptions.

Previous research had shown significant cooling effects in global and regional climate records after eruptions over the past 20,000 years, but data from the University of Columbia’s research shows short-term variations over shorter periods.

The lower temperatures reduce the levels of evaporation after the eruption, which in turn means there is less water vapour in the atmosphere. Less water vapour in a region means less precipitation, and subsequently a change to the weather conditions from the expected seasonal variations.

Climatic effects of volcanoes have been well noted in the long-term record, but this is the first time that observable weather research has used tree rings (dendrochronology) to monitor rainfall variations in this region.

El Nino Southern Oscillations are known to be drivers of climatic conditions around the world, specifically altering the southern hemisphere. Interpretations of these latest data has led the researchers to understand the significance of volcanic eruptions in counteracting the effects of El Nino during monsoon season.

However, this has not meant there is less rain, but the regions in which it falls is dramatically altered; southern China and Mongolia experience substantially drier periods following eruptions, while mainland southeast Asia, for example Thailand, Vietnam, Laos and Cambodia, endure far more intense periods of rainfall.

The Philippines is in the midst of one of the largest volcanic eruptions of the past 20 years, as the Merapi eruption has already substantially disrupted air travel and prevented aid reaching the region following a tsunami only a few weeks ago. However, the researchers point out that it is unlikely to have a dramatic effect on either short or long term climate trends.

While the size of the volcano’s eruption is not comparable to Mount Pinatubo, there are similarities with the tectonic activity of the devastating 1991 disaster, which killed around 800 people through the eruption and subsequent landslides.

If you liked this article, you may be interested in this report from Discovery News on the same topic.