Abstract:

The Amazon rainforest, a vital component of Earth’s carbon and hydrological cycles, has undergone significant changes to its climate in recent decades. These include increases in vapor pressure deficit (VPD) that reflect greater atmospheric moisture demand, delays in the wet season onset (WSO) that result in longer dry seasons, and increases in the frequency and intensity of compound hot-dry-windy (HDW) extremes. Consequently, the Amazon has experienced increased ecosystem stresses and elevated wildfire risks from these changes. Through a combination of observation-based attributions and climate model simulations provided by the Coupled Model Intercomparison Project Phase 6 (CMIP6), we determine the mechanisms behind the VPD increases, WSO delays, and increases in HDW extremes; and we also determine whether they are primarily attributable to climate change or natural variability.