The aerosol emissions from wildfire have traditionally been presumed to exert a minor influence on climate, a view that is exemplified by the prescription of wildfire emissions as being external to the climate system in nearly all current hindcasts and projections. This work explores this presumption using CESM2 and other climate models in a range of contexts and demonstrates the opportunties that exist in treating wildfire as a coupled component of the climate system.

In examining recent fires, this work identifies a significant and unexpected climate response to the 2019-20 Australian bushfires, whose emissions brightened clouds across the Southern Hemisphere and heightened the chances of an ensuing multi-year La Niña event similar to that observed. Relevant mechanisms and long-term responses are assessed. This work also identifies an important influence of biomass emissions on CMIP6 hindcasts and projections, demonstratating spurious late-historical era warming across multiple models as a result of discontinuities in imposed emissions. Strong associated responses throughout the climate system are identified. Lastly, this work explores the role of fire as an interactive component of ENSO and demonstrates improvements in the representation of its asymmetry, diversity, and power spectrum when biomass emissions are considered.

Together these findings highlight the potential benefits of treating wildfire as a coupled climate process, both for seasonal predictions and long-term projections. Challenges faced in doing so and related emerging opportunities are discussed.