A new policy paper in Science highlights that indirect greenhouse gases like carbon monoxide and volatile hydrocarbons contribute about 15% to global warming by extending methane's lifespan and boosting atmospheric carbon. Unlike CO2 or methane, these pollutants don't trap heat directly but amplify warming through chemical reactions. Scientists are calling for the UNFCCC to expand its monitoring and regulation beyond the original basket of gases. Lead author Ilissa Ocko notes these emissions rank as the third-largest warming contributor after CO2 and methane, yet remain excluded from international climate agreements. The paper urges policymakers to act now, especially as the U.S. has withdrawn from the Paris Agreement. Addressing these overlooked pollutants could offer a relatively low-cost way to cut near-term warming while broader decarbonization efforts continue.
