No Clear Sign That Less Soot, Methane Reduces Global Warming
August 14, 2013

No Clear Sign That Less Soot, Methane Reduces Global Warming

redOrbit Staff & Wire Reports - Your Universe Online

Reducing emissions of only soot and methane won't do as much to reduce global warming as some previous research has suggested, according to a new study published Monday in the Proceedings of the National Academy of Sciences (PNAS).

"Cutting back only on soot and methane emissions will help the climate, but not as much as previously thought," said study author Steve Smith, a climate researcher at the Department of Energy's Pacific Northwest National Laboratory (PNL).

The researchers advise focusing instead on reducing levels of greenhouse gas emissions.

"If we want to stabilize the climate system, we need to focus on greenhouse gases such as carbon dioxide, nitrous oxide and methane,” Smith said. "Concentrating on soot and methane alone is not likely to offer much of a shortcut."

Soot, also known as black carbon, is made of fine, carbon-based particles that are given off by car and truck tailpipes and wood stoves. Methane, the main component of natural gas, is released from leaking pipelines, coal mines, oil wells, cattle, rice paddies and landfills.

Both soot and methane remain in the atmosphere for relatively short periods of time – a few weeks for soot and up to a decade for methane. But carbon dioxide remains in the atmosphere for 1,000 years or more, Smith and colleagues said in their report.

Previous research has suggested that reducing soot and methane emissions could curtail human-caused global temperature increases by an average of about 0.9 degrees Fahrenheit by 2050. But the current study, which used computer models, concluded that cutting soot and methane emissions would reduce temperature increases by about 0.28 degrees Fahrenheit by 2050 – far less than predicted in previous studies.

By comparison, reducing emissions of carbon dioxide and other greenhouse gases would cut temperature increases by 0.49 degrees Fahrenheit by 2050, the researchers said.

"Focusing on soot and methane may be worth targeting for health reasons, as previous studies have identified substantial health benefits from reducing those emissions," Smith noted.

"To stabilize the global climate, however, the focus needs to be on carbon dioxide and other greenhouse gases," he concluded.