Earth greening mitigates hot temperature extremes despite the effect being dampened by rising CO2

The escalating threat of climate-induced hot temperature extremes poses a global sustainability challenge that impacts ecosystems and public health. Although the enhancement of leaf area index (LAI; also known as Earth greening) is known to cool global mean air temperature, knowledge gaps exist regarding its mitigation effect on hot temperature extremes, particularly under rising CO2 during the past three decades. Our study, combining coupled land-atmosphere climate model (IPSL-CM) simulations with global observations, suggests that Earth greening has reduced the hot day frequency index (TX90p) and warm night frequency index (TN90p) by −0.26 ± 0.10 days decade−1 and −0.38 ± 0.11 days decade−1, respectively, offsetting 4.7% and 5.8% of observed trends globally. However, rising CO2 levels partly diminished these mitigation effects, without which Earth greening might have offset 7.7% of TX90p and 10.0% of TN90p. Our findings illuminate Earth greening’s potential to mitigate hot temperature extremes, offering a pathway toward more resilient and sustainable climate adaptation and mitigation.