Western amazon 2020 extreme heatwave

Abstract

Between September and November 2020, an extreme climate event characterized by the co-occurrence of severe drought, extreme heat stress, widespread burning, and respiratory health impacts affected southwestern Amazonia. This study investigated the event using an integrated framework combining meteorological observations, reanalysis products, burned area data, climate attribution methods, and health records. Heat extremes were characterized using the CTX90pct index and Wet Bulb Globe Temperature (WBGT), while drought conditions were assessed using the 3-month Standardized Precipitation–Evapotranspiration Index (SPEI-3). Anthropogenic influence was quantified using HadGEM3-A attribution experiments and CMIP6 simulations through probability ratio (PR) and Fraction of Attributable Risk (FAR) metrics. Results showed persistent drought conditions and WBGT anomalies exceeding the 95th percentile during September to November 2020. Attribution analyses consistently indicated a strong anthropogenic contribution to the event, with PR estimates ranging from approximately 129 to values exceeding 1000 across climate-model ensembles and FAR values approaching unity. Wildfire activity was strongly concentrated in non-forest land cover classes, which accounted for approximately 80% of the total burned area, while forest formations represented about 20%. Health records indicated 39,453 respiratory disease notifications during the peak fire season, corresponding to 5.4% of Acre’s population, with substantial spatial heterogeneity among municipalities and 159 reported deaths in Rio Branco. Spatial analyses revealed that respiratory outcomes were associated with multiple environmental drivers, including atmospheric pollution from fires and meteorological conditions, although these relationships varied considerably across municipalities. The results demonstrate that anthropogenic climate change substantially increased the likelihood of the 2020 extreme heat event and contributed to environmental conditions favorable to wildfire activity and smoke exposure. These findings highlight the importance of integrated adaptation strategies combining climate-risk management, wildfire prevention, air-quality monitoring, and public health preparedness in this region. Anthropogenic climate change greatly increased the likelihood of the 2020 extreme heat-stress event, as indicated by a large Probability Ratio in HadGEM3-A simulations and CMIP6 PR estimates ranging from 129 to more than 1000. The event combined drought, extreme heat, widespread wildfires, and respiratory health impacts. Approximately 80% of the burned area occurred in non-forest land cover classes during the peak fire season. Environmental drivers of respiratory outcomes showed strong spatial heterogeneity across municipalities. Anthropogenic climate change greatly increased the likelihood of the 2020 extreme heat-stress event, as indicated by a large Probability Ratio in HadGEM3-A simulations and CMIP6 PR estimates ranging from 129 to more than 1000. The event combined drought, extreme heat, widespread wildfires, and respiratory health impacts. Approximately 80% of the burned area occurred in non-forest land cover classes during the peak fire season. Environmental drivers of respiratory outcomes showed strong spatial heterogeneity across municipalities.