Curbing Methane and Soot Not as Helpful as Previously Thought, Study Suggests

Reducing the amount of short-lived, climate-warming emissions such as soot and methane may be as effective in limiting global warming as previously thought, a new analysis led by the Department of Energy's Pacific Northwest National Laboratory (PNNL) suggests.

Soot, also known as black carbon, is largely given off by vehicles and wood stoves while methane, a component of natural gas, is released from a wide range of sources, including coal mines, oil wells, cattle, rice paddies and landfills. Both are referred to as "short-term climate forcers" due to their relatively short lives in the atmosphere -- soot lasts a matter of weeks and methane roughly a decade, compared to carbon dioxide's lifespace of 1,000 or more years.

Published in the Proceedings of the National Academy of Sciences, the study argues that even if the world were to severely cut emissions of these pollutants through the implementation of all feasible and available technology, doing so would result in an average temperature reduction of just 0.16 degrees Celsius by 2050, compared to the previously ascribed 0.5-degree reduction.

The reason for this discrepancy, according to the study's authors, has to do with the quality of the computer climate model used in the past versus the one used in the latest study.

In this case, the team employed the PNNL-designed Global Change Assessment Model (GCAM), which takes into account, according to the study's press release, "ongoing future changes in technology, society and the economy, including energy and land use," incorporating greenhouse gases and pollutants resulting from such activities.

In the past, however, the researchers argue that scientists relied on information generated from far less dynamic and integrated models.

Based on their results, the study's authors warn that further action should focus less on these short-term emissions and instead emphasize a comprehensive climate policy targeting big players like carbon dioxide.

"Focusing on soot and methane may be worth targeting for health reasons, as previous studies have identified substantial health benefits from reducing those emissions," the study's lead author and climate researcher Steve Smith said. "To stabilize the global climate, however, the focus needs to be on carbon dioxide and other greenhouse gases."

Such a policy -- that is, one that focuses on reducing all greenhouse gases substantially -- could lower global average temperatures by 0.27 degrees in 2050 with far greater reductions through 2100.