Human migration is increasingly recognized as a critical response to anthropogenic climate change, with far-reaching societal, economic, and geopolitical implications. However, quantitative evidence linking climate conditions to both internal and cross-border migration at the global scale remains limited. Here, we show that higher temperatures, along with temperature and precipitation extremes, significantly increase outward migration from low-income regions worldwide. This conclusion is based on a robust causal analysis that integrates annual migration data from over 3,000 subnational regions across two decades with high-resolution climate metrics, using fixed-effects panel regression models. A complementary spatial spillover analysis reveals that temperature-driven migration is primarily directed toward high-income countries, while precipitation extremes predominantly lead to movement between low-income regions. We project climate change-induced migration pressures under different emission scenarios, finding that effective emission reductions could halve the number of climate migrants by 2060. These findings highlight the need for policies that reduce greenhouse gas emissions while also strengthening the agency of climate migrants.

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