Elevated CO ₂ advances vegetation phenology

The continuous rise in atmospheric CO 2 concentration has profoundly altered vegetation structure and function across terrestrial ecosystems. Among various indicators, vegetation phenology is conventionally considered an early warning indicator of changes in other ecosystem processes. However, the relationship between vegetation phenology and elevated CO 2 (eCO 2 ) remains highly elusive. Here, we conducted a comprehensive meta‐analysis of 624 experimental records from 39 published studies to evaluate eCO 2 effects on vegetation phenology and quantify the relative importance of climate variables, soil factors, eCO 2 magnitude and experimental duration. The findings showed that eCO 2 significantly advanced overall vegetation phenology by 2.50 days (−1.99%), with leaf‐out advancing by 3.00 days (−2.38%) and maturity by 4.09 days (−3.24%). Elevated CO 2 exerted a negligible overall effect on plant growing season length. Importantly, model selection showed that plant functional groups were not essential predictors of phenological shifts. Instead, phenological shifts were primarily predicted by mean annual temperature (MAT) and eCO 2 magnitude. These results provide new insights into the mechanisms linking atmospheric change with plant developmental timing and highlight the need to explicitly incorporate CO 2 ‐driven phenological responses into ecosystem and Earth system models. Read the free Plain Language Summary for this article on the Journal blog.