State of Wildfires 2025-26: Present-Day Attribution using HadGEM3-A large ensemble.

This dataset supports the State of Wildfires 2025-26 report submitting to Earth System Science Data (Burton et al., under review). The dataset quantifies changes in the likelihood of fire weather extremes (represented by the Canadian Fire Weather Index) associated with the focal events by assessing how their likelihood has changed relative to past (1850-1900; preindustrial baseline) climate condition based on the 95th percentile of the Fire Weather Index (FWI95). This analysis is based on a combination of HadGEM3-A large attribution ensemble (525 Members) relying on historical validation of the HadGEM3-A Historical ensemble (15 members) in addition to the ERA5 Reanlaysis FWI95 values. Files and Descriptions: Probability ratio estimates for extreme fires occurred in Chilean Temperate Forests and Matorral in 2026 using: ERA5_FWI_1980-2013-Chile.nc - Baseline period reanalysis derived values. This is used as the ground truth for bias correcting the large attribution ensemble. HadGEM3-A_FWI_1980_2013_Chile.nc - Baseline period used to bias correct the large attribution ensemble. HadGEM3-A_FWI_2020-2024_Chile_CounterFactual.nc - Natural only ('Pre-industrial derived') climate simulation used as a proxy for 2026 based on early 2020s climatology. HadGEM3-A_FWI_2020-2024_Chile_Factual.nc - Human influenced climate simulation ('Post-Industrial/Present Day') used as a proxy for 2026 based on early 2020s climatology. Probability ratio estimates for extreme fires occurred in Midwestern Canadian Shield Forests in 2025 using: ERA5_FWI_1980-2013-Canada.nc - Baseline period reanalysis derived values. This is used as the ground truth for bias correcting the large attribution ensemble. HadGEM3-A_FWI_1980_2013_Canada.nc - Baseline period used to bias correct the large attribution ensemble. HadGEM3-A_FWI_2020-2024_Canada_CounterFactual.nc - Natural only ('Pre-industrial derived') climate simulation used as a proxy for 2025 based on early 2020s climatology. HadGEM3-A_FWI_2020-2024_Canada_Factual.nc - Human influenced climate simulation ('Post-Industrial/Present Day') used as a proxy for 2025 based on early 2020s climatology. Probability ratio estimates for extreme fires occurred in Northwest Iberia in 2025 using: ERA5_FWI_1980-2013-Iberia.nc - Baseline period reanalysis derived values. This is used as the ground truth for bias correcting the large attribution ensemble. HadGEM3-A_FWI_1980_2013_Iberia.nc - Baseline period used to bias correct the large attribution ensemble. HadGEM3-A_FWI_2020-2024_Iberia_CounterFactual.nc - Natural only ('Pre-industrial derived') climate simulation used as a proxy for 2025 based on early 2020s climatology. HadGEM3-A_FWI_2020-2024_Iberia_Factual.nc - Human influenced climate simulation ('Post-Industrial/Present Day') used as a proxy for 2025 based on early 2020s climatology. Analysis Scripts: Scripts used in the producution and analysis of this data can be found at https://github.com/douglask3/State_of_Wildfires_report