Global urban vegetation exhibits divergent thermal effects: From cooling to warming as aridity increases

Urban vegetation, a key nature-based solution for mitigating heat stress, is critical as global warming, and urban heat islands amplify high temperatures in cities, affecting over half the global population. Yet, its potential warming effects remain unquantified globally, with mechanisms unclear. Using high-resolution satellite and climate data, we provide the first global assessment of vegetation’s temperature regulation across 761 megacities across 105 countries, uncovering a paradox: cooling weakens in arid environments; and in 22% of cities with