Short-Lived Climate Pollutants

EM—April 2019: This month's issue explores the emissions of two short-lived climate pollutants—methane and black carbon—in the transport sector and discuss ways to reduce them.

by Bryan Comer, Ph.D.

In the fight against climate change, most of the focus has been placed on reducing carbon dioxide (CO2), a “long-lived” climate pollutant that contributes to warming centuries into the future. Other climate pollutants are “short-lived,” remaining in the atmosphere for a few years in the case of methane or only a few days in the case of black carbon. However, in this relatively short time, these pollutants have a much stronger warming effect—in the case of black carbon, a global warming potential that is 3,200-times stronger than CO2. In this issue of EM, we explore emissions of two short-lived climate pollutants—methane and black carbon—in the transport sector and discuss ways to reduce them.

First, Jori Sihvonen discusses the air quality and climate tradeoffs of using natural gas as a transportation fuel. The author notes that while natural gas can reduce air pollution, its climate performance is undermined by even small amounts of largely unregulated fugitive methane emissions throughout the natural gas supply chain.

Second, Bill Hemmings outlines aviation's non-CO2 climate impacts. He explains that in addition to CO2, airplanes emit nitrogen oxides, water vapor, and soot that create contrails and ozone that only last from minutes to days, but nevertheless worsen global warming. Therefore, the author suggests that the now is the time to reduce aviation's short-lived climate forcers.

In the third article, Ray Minjares and Francisco Posada report on the transition to soot-free buses in megacities such as London and Santiago. They explain that these large cities are moving to cleaner bus fleets to tackle the twin problems of air pollution and climate change.

Next, in my article, I explain the long road toward regulating black carbon emissions from the international maritime shipping sector. I suggest that even though the pace of progress has been slow, the International Maritime Organization is poised to take action to meaningfully reduce black carbon emissions from ships, but the time for delay is over.

Lastly, Thomas Brewer tells us how distributed ledger technologies (DLTs), including “blockchain,” could improve enforcement and verification of environmental regulations. He also describes the potential challenges and climate tradeoffs of DLTs, including the electricity needed to power them, while explaining that DLTs will continue to find new applications as the digital revolution marches on.

We invite EM readers to reflect upon the relative attention paid to CO2, greenhouse gases, and short-lived climate pollutants and to consider how this balance could or ought to be adjusted. Enjoy!