Rapid Increases in Heat-Driven Extreme Moisture Demand in the Southern Amazon

Extreme vapor pressure deficit (EVPD), representing the 5% hottest and driest surface air conditions, has risen rapidly over the Southern Amazon during the dry season, especially over forested areas. Its frequency has increased by 7 ±
1.5% (or 11 more dry season days) per decade, and its intensity has increased at rates faster than that of mean vapor pressure deficit (VPD), primarily due to rising extreme surface temperatures. Our observation-based attribution analysis shows that anthropogenic forcings are primarily responsible for 93% and 64% of the increases in EVPD frequency and intensity, respectively. Under a scenario close to current greenhouse gas emission trends (SSP 2–4.5), climate models project that dry season EVPD intensities will reach 7–15 standard deviations above climatological levels by the end of the century, substantially increasing the risks of extreme weather conditions conducive to wildfires in the Southern Amazon.