Air pollution is linked to more than 4 million deaths around the globe every year, according to the World Health Organization. Atmospheric pollutants like aerosols and ozone affect not only human health but also the global climate—though they stay in the atmosphere for significantly shorter time periods than carbon dioxide. Their short atmospheric life span makes aerosols, ozone, and methane—so-called short-lived climate forcers (SLCFs)—prime targets for rapid mitigation. But until now, there was little consensus on what impact SLCF mitigation might have on either the environment or human health.