Global Compound Events Interplay: Impacts on Fires and Air Pollution

Recently, there has been increasing attention on the complex interactions among environmental and climatic stressors, including heatwaves, droughts, and poor air quality or fires, which are intensified by climate change. These stressors, classically considered individually, are now understood to be interconnected phenomena with far-reaching global impacts. Moreover, the cumulative effects of these events have often higher impacts than isolated events, with far-reaching consequences for ecosystems, economies, and public health on a global scale. This study provides a detailed examination of compound events involving heatwaves, droughts, fires, and poor air quality worldwide, elucidating their interconnected nature, triggering drivers, and consequences for ecosystems and societies.To conduct this analysis, meteorological data from ERA5 were utilized to identify droughts using the Standardized Precipitation-Evapotranspiration Index (SPEI) and heatwaves, while Fire Radiative Power (FRP) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard Terra and Aqua satellites was selected, along with air quality data (specifically particulate matter PM2.5) obtained from the Copernicus Atmosphere Monitoring Service (CAMS) global reanalysis (EAC4). Compound events were identified based on the detection of pollution events, heatwaves, droughts, or FRP occurring in various combinations.The analysis revealed hotspots of compound events concentrated in different regions worldwide. For example, instances of pollution and heatwaves were predominantly observed in India, the Arabian Peninsula, and eastern China, while heatwaves and fires were more common in the Brazilian Cerrado, northern Australia, and South African Savannas. The Mediterranean region is particularly affected by hot and dry events, whereas Greece, Portugal, and Italy are those more affected by the compound of hot, dry, fire and pollution hazards. The impacts of single and simultaneous occurrences of hot, dry, and fire events on particulate matter PM2.5 levels varied significantly by continent, with North America and Asia experiencing notably higher pollution levels during simultaneous events compared to isolated pollution events.The intersection of compound hot and dry events with wildfires presents a significant public health challenge, highlighting the interrelation of climate change, extreme weather events, and air pollution. Addressing these complex relationships requires comprehensive strategies that integrate climate resilience, wildfire management, and air quality regulations to protect human health and well-being in the face of a changing climate.This work was funded by the Portuguese Fundao para a Cincia e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020). This work was performed under the scope of project https://doi.org/10.54499/2022.09185.PTDC (DHEFEUS) and supported by national funds through FCT. DL and AR acknowledge FCT I.P./MCTES (Fundao para a Cincia e a Tecnologia) for the FCT https://doi.org/10.54499/2022.03183.CEECIND/CP1715/CT0004 and https://doi.org/10.54499/2022.01167.CEECIND/CP1722/CT0006, respectively.