Reducing Methane And Soot Could Help Curb Global Warming

Reducing methane and soot (black carbon) emissions along with carbon dioxide could more effectively rein in projected global warming than a CO₂-only reduction strategy, according to a climate modeling study (Science, DOI: 10.1126/science.1210026). A team led by Drew T. Shindell at NASA’s Goddard Institute for Space Studies at Columbia University screened hundreds of pollution-control measures and identified 14 cost-effective strategies that could collectively reduce the impact of CH₄ and soot emissions by 90% by 2030. Methane interacts with nitrogen oxides to make tropospheric ozone, and soot settles on ice and snow—both species trap heat and are air pollutants. The researchers found that implementing the 14 strategies, which include aeration of flooded rice paddies and using diesel particulate filters in vehicles, could reduce warming by 0.5 °C by 2050. This reduction would keep mean global warming to less than 2 °C until 2070, relative to the preindustrial mean temperature. Climate scientists believe 2 °C warming is the approximate threshold at which disruptive climate changes will begin. As an added benefit, soot reduction would prevent several million annual premature deaths from air pollution, and ozone reduction would increase crop yields by tens of millions of metric tons per year, Shindell and coworkers estimate.