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.