Reduced rainfall in the northern tropics linked to industrial emissions

Some people have suggested injecting such emissions into the atmosphere to counteract global warming caused by increased CO2 from human activities.

http://www.eurekalert.org/pub_releases/2015-02/du-rri020915.php

Public Release: 9-Feb-2015
Durham University

Scientists have produced a rainfall record strongly suggesting that man-made industrial emissions have contributed to less rainfall in the northern tropics.

The research team, led by experts at Durham University, UK, reconstructed rainfall patterns stretching back more than 450 years by analysing the chemical composition of a stalagmite recovered from a cave in Belize, Central America.

They identified a substantial drying trend from 1850 onwards, coinciding with a steady rise in sulphate aerosols in the atmosphere as a result of burning fossil fuels to drive the industrial boom in Europe and North America.

Importantly they also identified nine short-lived drier spells in the northern tropics since 1550 following very large volcanic eruptions in the Northern Hemisphere that produced similar emissions as those produced by burning fossil fuels.

This provided very strong evidence that any injection of sulphate aerosols into the upper atmosphere could lead to shifts in rainfall patterns, the researchers said.

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The findings confirm previously published observations using 20th Century historical data and computer modelling, the researchers said.

Lead author Dr Harriet Ridley, from the Department of Earth Sciences at Durham University, said: "The research presents strong evidence that industrial sulphate emissions have shifted this important rainfall belt, particularly over the last 100 years.

"Although warming due to man-made carbon dioxide emissions has been of global importance, the shifting of rain belts due to aerosol emissions is locally critical, as many regions of the world depend on this seasonal rainfall for agriculture.

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