Observed increases in extreme fire weather driven by atmospheric humidity and temperature

Recent increases in regional wildfire activity have been linked to climate change. Here, we analyse trends observed global extreme fire weather and their meteorological drivers from 1979 2020 using the ERA5 reanalysis. Trends annual (95th percentile) values of index (FWI95), initial spread (ISI95) vapour pressure deficit (VPD95) varied regionally, with mean 14, 12 12%, respectively. Significant occurred over a quarter almost half burnable land mass. Decreasing relative humidity was driver three-quarters significant FWI95 ISI95, while increasing temperature for 40% trends. VPD95 were predominantly associated temperature. These are likely continue, as change projections suggest decreases that may increase future risk where fuels remain abundant. Climate has led increased parts globe due extremes. driven by decreasing