Increasing boreal fires reduce future global warming and sea ice loss

Significance Over the past two decades, biomass burning emissions (BBEs) from boreal forests have increased dramatically, and are expected to continue increasing. In contrast, CMIP6 models prescribe a future (2015-2100) boreal BBE scenario with low values and near-zero trends. To assess if the difference between observed and prescribed boreal BBE forcing impacts climate trends, we produced simulations using CESM2 with standard CMIP6 forcings, but increasing boreal BBEs based on observations. The increase in boreal BBEs slows down global warming by 12% and Arctic warming by 38%, reducing sea ice loss and shifting tropical precipitation southward. These impacts highlight the importance that future boreal fires may have for climate projections, and motivate revising prescribed boreal BBEs for CMIP7.