Forest fire threatens global carbon sinks and population centres under rising atmospheric water demand

Levels of fire activity and severity unprecedented in the instrumental record have recently been observed in forested regions worldwide. Using a large sample of daily fire events and hourly climate data, the study shows that forest fire activity across all global forest biomes responds strongly and predictably to exceedance of thresholds in atmospheric water demand, measured by maximum daily vapour pressure deficit (VPD). The climatology of VPD can thus reliably predict forest fire risk under projected future climates. Climate change is projected to cause widespread increases in risk, with at least 30 additional days above critical thresholds for forested biomes on every continent by 2100 under rising emissions scenarios. Escalating forest fire risk threatens catastrophic carbon losses in the Amazon and major population health risks from wildfire smoke in South Asia and East Africa.