Climate Transitions in the Argentine Pampas Exceed Global Rates and Reshape Crop Exposure: A Multi‐Period Köppen–Geiger Analysis (1901–2020)

ABSTRACT

Climate change is driving shifts in the spatial distribution of climate zones worldwide, with particularly strong impacts in mid‐latitude regions. The Argentine Pampas, one of the world's most important agro‐productive areas, provides a key case for assessing these dynamics. This study analyses Köppen–Geiger climate transitions across four consecutive 30‐year periods (1901–1930, 1931–1960, 1961–1990 and 1991–2020) using high‐resolution maps and a pixel‐by‐pixel approach. Transitions were classified into nine categories, distinguishing single‐driver processes—changes in aridity, summer temperature or precipitation seasonality alone—from compound transitions in which precipitation seasonality and summer temperature shifted simultaneously within the same pixel. Results reveal that climate transitions affected between 8.6% and 14.3% of the regional area across consecutive periods, consistently exceeding global averages. The temporal trajectory is non‐linear, characterised by successive reversals in the dominant process: early 20th‐century aridity increase, mid‐century aridity reduction with the retreat of semi‐arid conditions and a recent dominance of winter drought development. Compound transitions remained spatially marginal in every period (0.5% or less), indicating that hydroclimatic and thermal shifts generally operated as spatially distinct processes across the region. In the most recent period (1961–1990 to 1991–2020), transitions affected 11.6% of the Pampas, with winter drought development accounting for over two‐thirds of all changes, primarily through shifts from Cfa to Cwa climates—a pure single‐driver hydroclimatic transition. Crop exposure analysis indicates that more than 3.1 million hectares of cropland fall within transition zones, with 91% concentrated in the winter drought development belt, encompassing the core soybean–maize–wheat production system. These results demonstrate that climate change in the Pampas is expressed primarily as a reorganisation of hydroclimatic regimes and precipitation seasonality rather than as uniform trends in annual conditions. The identified transition rates and spatial patterns position the region as a mid‐latitude climate change hotspot and highlight the need for territorially differentiated adaptation strategies in highly productive agricultural systems.