Abstract:
Global warming from anthropogenic greenhouse gas emissions presents by far the clearest signal of human influence on climate. But on top of greenhouse warming and its many impacts, anthropogenic and natural short-lived climate forcers (SLCFs) drive their own important and complex climate-change signals. SLCFs include atmospheric aerosol particulates (sulphate haze, dust, sea-salt) and reactive chemical species (methane, ozone, nitrogen oxides, etc.) that have lifetimes and mixing length scales orders of magnitude shorter than carbon-dioxide and other greenhouse gases. Their chemical reactivity, their interactions with solar-terrestrial EM radiation, their role in precipitation and cloud dynamics, and their spatial and temporal heterogeneity present a grand theoretical and modelling challenge. But research on SLCFs has advanced rapidly, which has allowed for key insights to emerge. I’ll survey work showing how the recent cleanup in aerosol pollution from East Asia has caused some global warming; what we can learn from a clean comparison between simple and complex numerical aerosol schemes; and the unexpected and disturbing short- and long-term climate impacts of fires ignited by a hypothetical nuclear war scenario.