Short-lived air pollutants (e.g., aerosols and ozone) affect climate differently than greenhouse gases. Using climate models, we found that during 1950–2014, these pollutants caused global cooling, stronger in the Arctic, increased vertical mixing in the Labrador Sea, and southward displacement of the tropical rain belt. These regional impacts oppose those of greenhouse gases. Hence, future reductions in pollution for better air quality must be accompanied by stricter greenhouse gas mitigation.