Cleaner air strengthens the Pacific trade winds without a detectable change in El Nino
Air quality policy will cut aerosol and ozone precursor emissions, and studies disagree on how the tropical Pacific circulation and the El Nino Southern Oscillation (ENSO) will respond. Here we show, in 12 Earth system models with and without air quality controls, that the cuts strengthen the Pacific trade winds and offset half to two thirds of the weakening projected without them. The response is absent with prescribed sea surface temperatures and detectable only after 2040. It is consistent with the Indian Ocean warming relative to the Pacific, which also ranks the responses to cuts made region by region. ENSO amplitude changes by less than a tenth of its value, the smallest change this ensemble could detect. The change implied by the mean state shift is a sixth of that, and an ENSO model trained without the reduced emission runs predicts none. El Nino's regional impacts still change, because the background climate does.