Azara Blog: Rice harvest harmed by "brown clouds"

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Date published: 2006/12/05

The BBC says:

Pollution-laden clouds may be partly to blame for India's dwindling rice harvests, according to research.

A US team found brown clouds, which cloak much of South Asia, have a negative impact on rice output by reducing sunlight and rainfall.

They discovered elevated levels of greenhouse gases also reduced yields.
Since the 1980s, India has faced ever-declining growth rates in harvests of its staple food, raising concerns that shortages could occur.

To investigate the cause, researchers looked at the impact of the "brown clouds" or "Asian haze" which cover the region.

South Asia has one of the most widespread atmospheric brown clouds on the planet.

These layers of air pollution, which contain soot and other fine particles, are primarily created from burning fossil fuels and other organic matter.

The clouds interfere with the local climate by blocking the Sun's radiation from reaching the ground, leading to cooler and dimmer conditions. Recent research has revealed the polluted haze can also reduce rainfall.

Using climate models and historical data on Indian rice harvests, the team built up a picture of the brown clouds' effect on rice growth over the years.

"We found if there had been no atmospheric brown clouds between 1985 and 1998, the annual rice harvest yield would have been 11% higher than it was," said Maximilian Auffhammer of the University of California at Berkeley.

The team concluded the clouds had a negative effect on rice yields.

He said while the cooler night-time temperatures caused by the clouds were beneficial for the rice, the negative impact of the decreasing rainfall outweighed these benefits.

All fairly obvious but worth the quantification.

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