Projected spatial reorganization of Köppen–Geiger climate zones under climate change and consequences for population and economic exposure

Climate change is expected to reorganize macro-climatic regimes at the planetary scale, with implications that extend beyond physical climate variables to the spatial configuration of human systems. While projected shifts in temperature and precipitation are well documented, their translation into categorical climate-regime transitions and associated socio-economic exposure remains insufficiently quantified within a spatial planning perspective. This study provides a global assessment of projected Köppen–Geiger climate zone transitions and their implications for population and economic exposure by the end of the 21st century. Using bias-corrected CMIP6 projections aggregated at 0.1° resolution and a categorical multi-model ensemble, we map climate-regime changes between 1991–2020 and 2071–2100 under SSP1–2.6, SSP2–4.5, and SSP5–8.5. Gridded population and GDP datasets consistent with the Shared Socioeconomic Pathways are spatially harmonized with the climate classifications to quantify exposure under both fixed baseline and scenario-consistent frameworks. Results indicate that climate-zone redistribution is spatially structured and dominated by a limited set of directional transitions, notably cold-to-temperate (D→C), temperate-to-arid (C→B), and temperate-to-tropical (C→A) pathways. Under SSP5--8.5, approximately 13.6\% of global land surface undergoes a shift in primary climate group by the late 21st century (2071–2100), corresponding to nearly 3.5 billion people and more than 40 trillion USD of economic activity operating within regions experiencing a macro-climatic regime transition. Differences across emissions pathways highlight the strong mitigation dependence of large-scale territorial reorganization. Rather than representing isolated local changes, projected Köppen–Geiger transitions constitute a coherent spatial restructuring of macro-climatic envelopes that intersect directly with patterns of settlement, economic production, and regional development. By linking categorical climate-regime migration with spatially explicit demographic and economic projections, this study provides an operational framework for examining long-term territorial transformation under climate change and supports applied geographical assessments of adaptation and planning under alternative futures.