Increased Start‐to‐Peak Vegetation Growth is Associated With Spring Phenology Across the Northern Hemisphere

Shifts in vegetation phenology affect photosynthesis and productivity, further influencing ecosystem carbon and hydrological cycles. Over recent decades, widespread advancements in the start of the growing season (SOS) have been found to advance the peak of the growing season (POS) and enhance vegetation growth under global warming. Understanding vegetation growth dynamics from SOS to POS (i.e., start‐to‐peak growth) is crucial because this period represents a critical phase of carbon uptake and ecosystem productivity, directly impacting seasonal and annual climate‐biosphere feedback. However, the effect of SOS on vegetation growth, especially start‐to‐peak growth, remains largely unknown. Using MODIS NDVI, ground FLUXNET data set, and meteorological data (2001–2022) across the Northern Hemisphere (>30°N), we found that SOS advanced by 0.11 days per year, while start‐to‐peak growth, indicated by the sum of daily NDVI from SOS to POS, increased by 0.13 units per year. Notably, earlier SOS significantly enhanced start‐to‐peak growth in 55.64% of vegetated pixels ( p < 0.05). Critically, the earlier SOS was associated with a longer SOS‐POS duration and lower vegetation growth rates, suggesting that the extended SOS‐POS duration contributed to the observed increased start‐to‐peak growth. Climatic conditions, especially colder temperatures, slowed growth rates, particularly at mid‐latitudes. This slowing of growth rates was observed across various vegetation types, although the magnitudes of the reduction varied among them. Overall, these findings enrich our understanding of how start‐to‐peak growth responded to spring phenology and climate change, offering valuable insights into future predictions of terrestrial ecosystem dynamics under global change.