Aerosol Particles Dry Out South Asian Monsoons

[one...two...tree 2,762]

WASHINGTON (Reuters) - Summer monsoons that provide up to 80 percent of the water South Asia needs have gotten drier in the past half century, possibly due to aerosol particles spewed by burning fossil fuels, climate scientists said on Thursday.

Monsoon rains are driven by looping air circulation patterns over India, and the aerosols appear to have interfered with these patterns, researchers reported in the journal Science.

Between 1950 and 1999, the drying was most pronounced in central-northern India, with a 10 percent drop in average June-September rainfall, the researchers said. The rest of India experienced a decrease of about 5 percent over the same period, they added.

This does not seem to be a direct consequence of greenhouse gas emissions, even though the burning of fossil fuels and biomass that produces the aerosol particles also emits climate-warming carbon dioxide, the researchers said.

Particle pollution can increase the risk of heart disease, lung cancer and asthma attacks and interfere with the growth and function of the lungs, according to the American Lung Association, which has fought to curb these emissions in the United States.

Over South Asia, aerosol particles have actually slowed down climate warming by reacting with sunlight and reflecting some of it back into space, said study co-author Yi Ming of the U.S. National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey.

That same cooling effect tends to slow down the north-south air circulation that delivers the monsoon rains, Ming said in a telephone interview.

The Northern Hemisphere, including India, tends to emit more aerosol particles because it is more heavily developed than the Southern Hemisphere, Ming said. This could offer hope that the aerosol drying of the monsoon could be reversed.

This is because developed countries such as the United States and much of Europe have taken steps to cut down on particle pollution, which means less gets into the air.

Ming and his colleagues project that if India and other Asian countries continue to develop their economies, they too will cut back on particle emissions.

"The aerosol levels will be cut a lot out of concern for human health, like what happened in the U.S. and Europe," Ming said. "Once countries are rich enough, they want to clean their air."

This could begin to reverse the monsoon's drying trend in 20 to 30 years, he said. However, it would do nothing to reduce the emissions of carbon dioxide associated with more developed economies, and dealing with that, Ming said, "will be a very difficult policy challenge."

http://www.scientificamerican.com/article.cfm?id=aerosol-particles-dry-out-monsoons

[lostinblue 1,989]

˜Heavy Himalayan snowfall cause of drought in India

Ashis Ray, TNN Apr 23, 2010, 02.26am IST

LONDON: Reading University, one of UK's leading research centres, claims to have solved a riddle that has perplexed scientists since the 19th century. An intensive study carried out by it has reached the conclusion that heavy snowfall over the Himalayas in winter and spring can be the direct cause of drought in India, especially in the early part of the summer monsoon.

Given that last winter was quite severe and mammoth quantities of snow may have fallen on the Himalayan range, all concerned in the Indian agrarian sector need to be vigilant about a delayed monsoon and plan accordingly. This is what the report appears to suggest.

Andy Turner, lead author of the research at Walker Institute of the university, said: ''Our work shows how, in the absence of a strong influence from the tropical Pacific, snow conditions over the Himalayas and the Tibetan Plateau could be used to help forecast seasonal monsoon rainfall for India, particularly over northern India during the onset month of June.''

These findings are highly significant because Indian agriculture is heavily dependent on early rainfall; a lack of this in the crucial growing season tends to have a devastating impact on crops, as was experienced last year. The work is a part of Reading's Climate Programme of the National Centre for Atmospheric Science ( NCAS).

Scientists have known since the 1880s that increased snow over the Himalayas can be linked with weaker summer monsoon rains in India. However, according to Reading, the mechanisms explaining this correlation have never been properly understood. The latest research shows that greater snowfall reflects more sunlight and produces a cooling over the Himalayas. This in turn means a weakening of the monsoon winds that bring rain to India.

The relationship is said to be strongest in the absence of warm (El Nino) or cold (La Nina) environments in the tropical Pacific, since these are normally the dominant control factors over the Indian rains. A spokesperson for Reading university said its research is based on extensive experiments with the British Met Office/Hadley Centre climate model.

http://articles.timesofindia.indiatimes.com/2010-04-23/india/28141792_1_summer-monsoon-snowfall-himalayas

[Saddle Bronc 124]

Half correct about fossil-fuels--of which the bulk that actually affect the monsoons are overconsumed "renewables" (straw, wood, ...), as has long been pointed out (..."deforestation in the Northern Plains and Shivaliks has led to desiccation of the climate in many areas"--lifted this from a 1975 article).

[one...two...tree 2,762]

Half correct about fossil-fuels--of which the bulk that actually affect the monsoons are overconsumed "renewables" (straw, wood, ...), as has long been pointed out (..."deforestation in the Northern Plains and Shivaliks has led to desiccation of the climate in many areas"--lifted this from a 1975 article).

No one talking about climate and energy refers to straw, wood or whatever else you were referring to as "renewables." Following that logic, crude oil would also be a renewable.

[mawilson 2,133]

Following that logic, crude oil would also be a renewable.

It is. Just takes millions of years to "renew".