The Phenology-Climate Feedback Loop: Current Understanding and Future Directions

Résumé fourni par la source

Land surface phenology–the seasonal rhythm of leaf emergence and senescence–is shifting in response to climatic changes. These shifts modify how the land and atmosphere exchange energy, water, and carbon, feeding back onto the climate system. This article synthesizes current understanding of phenology-climate interactions and provides a perspective on how to address key uncertainties across biogeophysical and biogeochemical pathways, including changes in surface albedo, turbulent heat fluxes, carbon cycling, and cloud formation. To bridge synthesis and perspective, we complement the review with new fully coupled Earth system model simulations in which satellite-derived leaf area index (LAI) changes serve as an observationally constrained proxy for recent phenological trends, corresponding to approximately 2.1 days per decade earlier spring onset and 1.8 days per decade later autumn senescence. Under these idealized pre-industrial conditions, a 10-day growing-season extension triggers a global surface cooling of -0.10 +/- 0.03 °C, strongest in northern high latitudes. These results identify a potentially important feedback mechanism; as outputs of an idealized single-model setup, however, these simulations only serve as hypothesis-generating tools, not definitive predictions. This first-order quantification motivates a research pathway forward focused on: (1) coordinated integration of multi-stream observations and experimental networks; (2) model-data fusion via causal and hybrid approaches; and (3) a hierarchy of mechanistic models, from single-column frameworks to next-generation Earth system models capable of resolving phenology-climate feedbacks across scales. Emerging priorities include phenological saturation and acclimation, improved representation of autumn phenology and legacy effects, and characterization of non-linear compensation mechanisms. Phenology thus emerges not only as a climate responder but as an active regulator of the Earth system.

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