Cleaner air is revealing previously masked warming

Sulphate aerosols from fossil-fuel combustion reflect sunlight and alter clouds, partly offsetting greenhouse warming, but their short atmospheric lifetime means that cooling disappears quickly when pollution falls.[1] Declining aerosol pollution may now add roughly 0.05°C to 0.1°C of warming per decade, while greenhouse gases add about 0.2°C per decade and remain the dominant driver.[1] Why it matters: Cuts to harmful sulphur pollution benefit health and ecosystems but expose warming that aerosols had temporarily masked, complicating assessments of how quickly the planet is heating.[1] Key insights: Sulphur emissions have fallen sharply in Europe, North America and China, while shipping rules have also reduced the pollution.[1] | One study estimates that declining sulphur pollution has added around half a degree to summer warming in western-central Europe since 1980.[1] | Earth’s energy imbalance—the surplus energy warming the planet—has roughly tripled over the past two decades, although the result depends on the comparison years.[1] | Natural variability such as El Niño can raise temperatures temporarily, so successive record-hot years alone do not prove that the underlying warming rate has accelerated.[1] Cheatsheet facts: What changed: Reduced sulphate pollution is rapidly removing part of the cooling effect that had masked greenhouse warming.[1] | Why now: Recent temperature records, falling aerosol emissions and a growing Earth energy imbalance have intensified scrutiny of whether warming is accelerating.[1] | Watch next: Watch updated measurements of Earth’s energy imbalance and estimates separating aerosol-related warming from the larger greenhouse-gas contribution.[1]