Maestría en Ingeniería Ambiental · 2026
Occurrence of hot, dry, and compound dry-hot events in Tropical South America: observational analysis, historical simulations and climate change projections
Extreme hydroclimatic events have increased in frequency and intensity due to climate change, generating risks for natural and human systems, especially in vulnerable regions such as South America. Hot and dry extremes have attracted growing scientific interest due to their negative impacts, which are intensified when they occur simultaneously. In this work, we characterize the occurrence of hot events (HEs), dry events (DEs), and compound dry and hot events (CDHEs) in tropical South America (TSA) during 1983–2024. We evaluate the ability of a set of CMIP6/HighResMIP models to reproduce their main characteristics (number of events, median duration, median gap between events, and median intensity), and analyze projected changes under different emission scenarios in the near and long term. During the observational period (1983-2024), a seasonal pattern was identified in HEs, with higher frequency in northern South America during December-May and in the Amazon during June–August. Meteorological droughts were more frequent, but agricultural and ecological droughts were longer in duration. CDHEs occurred less frequently than HEs, but with longer duration, increasing in frequency in recent decades. Temperature was the dominant factor during CDHEs in most of the TSA. Individual models and the ensemble median showed limitations in adequately reproducing the number, duration, and gap between events of observed extreme events. In contrast, they better reproduced the temperature intensity associated with HEs and CDHEs. The main limitations included overestimation of the number and duration of events and underestimation of the gap between events in much of TSA, with high agreement between models (> 80%) in some regions. Projections throughout the 21st century indicate that HEs and CDHEs will be more frequent, longer-lasting, and more intense in TSA under all scenarios, especially in the long term and under higher emissions. Increases in CDHEs are primarily driven by increases in HEs, even though the frequency of DEs decreases in some areas, particularly between December and May. The observation-based analysis showed that the northern Andes, Orinoco, Brazilian Amazon, and northern Cerrado were among the regions with the largest increases in the frequency of HEs, DEs, and CDHEs. For these regions, an increase in the number of hot and dry days, longer event durations, higher maximum temperature intensity, and more severe droughts is expected by the end of the century, especially under the high-emission scenario.