Big volcanic eruptions can cool the tropics

Washington, Jan 6 (ANI): Climate researchers have shown that big volcanic eruptions over the past 450 years have temporarily cooled weather in the tropics.

The researchers included Rosanne D'Arrigo, a scientist at the Tree Ring Lab at Columbia University's Lamont-Doherty Earth Observatory, Rob Wilson of Lamont and the University of St. Andrews, Scotland; and Alexander Tudhope of the University of Edinburgh, Scotland.

Scientists already agree that large eruptions have lowered temperatures at higher latitudes in recent centuries, because volcanic particles reflect sunlight back into space.

For instance, 1816, the year following the massive Tambora eruption in Indonesia, became known as "The Year Without a Summer," after low temperatures caused crop failures in northern Europe and eastern North America.

More extensive evidence comes in part from tree rings, which tend to grow thinner in years when temperatures go down.

This is one of the first such studies to show how the tropics have responded, according to lead author Rosanne D'Arrigo.

"This is significant because it gives us more information about how tropical climate responds to forces that alter the effects solar radiation," said D'Arrigo.

Along with tree rings, the researchers analyzed ice cores from alpine glaciers, and corals, taken from a wide area of the tropics.

When things cool, not only do trees tend to grow less, but isotopes of oxygen in corals and glacial ice may shift.

All showed that low-latitude temperatures declined for several years after major tropical eruptions.

The samples, spanning 1546 to 1998, were taken from Nepal down through Indonesia and across the Indian and Pacific oceans; the ice cores came from the Peruvian Andes.

The researchers used materials they collected themselves, as well as samples from the archives of other scientists.

The data show that the most sustained cooling followed two events: an 1809 eruption that probably took place in the tropics, but whose exact location remains unknown; and the 1815 Tambora eruption, one of the most powerful recorded in human history.

Following Tambora, between 1815 and 1818, tropical temperatures dropped as much as 0.84 degrees C (1.5 degrees F) below the mean.

A slightly bigger one-year drop came in 1731, with a drop of 0.90 degrees Celsius.

The researchers said that this may be connected to eruptions at the Canary Islands' Lanzarote volcano, and Ecuador's Sangay around this time.(ANI)