Tackling methane and soot could reduce global warming

Posted: 15 February 2002

Reducing methane emissions and soot could yield a major near-term success story in the battle against global warming, providing time to work on technologies to reduce future carbon dioxide emissions, according to a new report from the Goddard Institute for Space Studies, a division of the US National Aeronautics and Space Administration (NASA).

The rate of growth of greenhouse gas emissions has dropped since its peak in 1980, with the CFC phase-out being the most important factor, according to the study.

"The decrease is due in large part to cooperative international actions of the Montreal Protocol for the phase-out of ozone depleting gases," said Dr James Hansen, director of the Goddard Institute for Space Studies in New York. "But it is also due in part to slower growth of methane and carbon dioxide, for reasons that aren't well understood and need more study." Methane is second only to CO2 in contributing to global warming. It is a naturally occurring gas, a product of a variety of biological processes. But in terms of climate change, it is the unnatural concentration of the gas from human induced factors that has researchers concerned. Sources of methane include garbage disposal, rice cultivation, industrial production, and cattle herds.

The rate of methane growth has slowed during the past decade, and it may be possible to halt its growth entirely and eventually reduce atmospheric amounts, the report suggests.

Smoke and soot contribute to global warming. Credit: James HansenAnother warming agent deserving special attention, according to the authors, is soot, a product of incomplete combustion. Diesel powered trucks and buses are primary sources of airborne soot in the United States. Even larger amounts of soot occur in developing countries. Reducing emissions would have important health benefits.

Currently, technologies are within reach to reduce methane and soot in ways that are cheaper and faster than reducing carbon dioxide, the scientists say.

If fossil fuel use continues at today's rates for the next 50 years, and if growth of methane and air pollution is halted, the warming in 50 years will be about 1.3 degrees Fahrenheit (0.7 Celsius), the Goddard study shows.

That amount of warming is significant, according to Hansen, but it is less than half the warming in the "business as usual scenarios that yield the spectre of imminent disaster."

Read an online summary of the paper.