Long-Term Temperature and Precipitation Trends Across South America, Urban Centers, and Brazilian Biomes

This study analyzes long-term trends in maximum (Tmax) and minimum (Tmin) near-surface air temperatures and precipitation across South America. The analysis focuses on Brazilian biomes and the capitals of South American countries, using ERA5 reanalysis data from 1979 to 2024. Seasonal cycles were removed using Seasonal-Trend decomposition based on Loess (STL) to isolate underlying climate signals. Temperature trends were quantified using ordinary least squares regression (OLS), with statistical significance assessed through the Student’s t-test. Precipitation trends were assessed using the Mann–Kendall test with Theil–Sen slope estimation, ensuring robustness against serial correlation. Results show a robust but spatially heterogeneous warming, with Tmax increasing more rapidly than Tmin. This asymmetry is consistent with mechanisms reported in the literature, such as reduced cloudiness and evaporative cooling. A meridional dipole is evident in precipitation: drying across central and southern regions, including the Cerrado, Pantanal, Caatinga, and Pampa, contrasted with rainfall increases in northern South America linked to ITCZ dynamics. Among Brazilian biomes, the Pantanal emerges as the most vulnerable, combining intense warming (+0.51 °C decade⁻¹) with the steepest rainfall decline (–10.45 mm decade⁻¹), while even the relatively weaker changes in the Pampa (+0.20 °C decade⁻¹ and –4.09 mm decade⁻¹) raise concerns for pasture productivity and livestock sustainability. In South American capitals, warming is widespread, though precipitation trends display a clear north–south contrast. Converging changes in temperature and rainfall are likely to intensify ecosystem stress, biodiversity loss, and threats to water and agricultural security. These impacts underscore the urgent need for biome-specific adaptation and conservation strategies under accelerating climate change.