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Cut methane and soot to curb warming: scientists

South China Morning Post – 14 Jan 2011

Pollution reduction measures would lead to US$6.5tr in annual gains from fewer deaths, less global warming and increased crop yields

An international team of scientists says it has figured out how to slow global warming in the short run and prevent millions of deaths from dirty air: Stop focusing so much on carbon dioxide.

They say the key is to reduce emissions of two powerful and fast-acting causes of global warming – methane and soot.

Carbon dioxide is the chief greenhouse gas and the one world leaders have spent the most time talking about controlling.

Scientists say carbon dioxide from fossil fuels like coal and oil is a bigger overall cause of global warming, but reducing methane and soot offers quicker fixes.

Soot is also a big health problem, so dramatically cutting it with existing technology would save between 700,000 and 4.7 million lives each year, according to the team’s research published online on Thursday in the journal Science.

Since soot causes rainfall patterns to shift, reducing it would cut down on droughts in southern Europe and parts of Africa and ease monsoon problems in Asia, the study says.

Two dozen scientists from around the world ran computer models of 400 different existing pollution control measures and came up with 14 methods that attack methane and soot.

The idea has been around for more than a decade and the same authors worked on a United Nations report last year, but this new study is far more comprehensive.

All 14 methods – capturing methane from landfills and coal mines, cleaning up cook stoves and diesel engines, and changing agriculture techniques for rice paddies and manure collection – were being used efficiently in many places, but not universally adopted, said the study’s lead author, Drew Shindell of Nasa.

If adopted more widely, the scientists calculate that would reduce projected global warming by 0.5 degrees Celsius by 2050.

Without the measures, the global average temperature is projected to rise nearly 1.2 degrees in the next four decades. But by controlling methane and soot, the increase is projected to be only 0.7 degrees.

It also would increase the annual yield of key crops worldwide by almost 150 million tonnes.

Methane comes from landfills, farms, drilling for natural gas, and coal mining.

Soot, called black carbon by scientists, is a by-product of burning and is a big problem with cooking stoves using wood, dung and coal in developing countries and in some diesel fuels worldwide.

Reducing methane and black carbon is not the very best way to attack climate change, air pollution, or hunger, but reducing those chemicals are among the better ways and work simultaneously on all three problems, according to Shindell.

And shifting the pollution focus does not mean ignoring carbon dioxide. Shindell said: “The science says you really have to start on carbon dioxide even now to get the benefit in the distant future.”

The new research won wide praise from other scientists, including a conservative researcher who held a top post in the George W. Bush administration. “So rather than focusing only on carbon dioxide emissions, where we have to make a trade-off with energy prices, this strategy focuses on ‘win-win-win’ pathways that have benefits to human health, agriculture and stabilising the Earth’s climate,” said University of Minnesota ecology professor Jonathan Foley, who was not part of the study. “That’s brilliant.”

John Graham, who oversaw regulations at the Office of Management and Budget in the Bush administration and is now dean of public and environmental affairs at Indiana University, said: “This is an important study that deserves serious consideration by policymakers as well as scientists.”

The study even does a cost-benefit analysis to see if these pollution control methods are too expensive to be anything but fantasy. They actually pay off with benefits that are as much as 10 times the value of the costs, according to Shindell. The paper calculates that as of 2030, the pollution reduction methods would bring about US$6.5 trillion in annual benefits from fewer people dying from air pollution, less global warming and increased crop production.

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