Earlier leaf-out warms air in the north


Earlier leaf-out in response to climate warming has been recorded in northern temperate and boreal regions. In turn, this shift modifies climate by altering seasonal cycles of surface energy, water and carbon budgets. Here, we use the Community Earth System Model 1.2 to investigate climate feedbacks from advanced leaf-out in northern temperate and boreal vegetation. An imposed 12-day earlier leaf-out in this region, consistent with recent observations, enhances annual surface warming in the Northern Hemisphere. We identify warming hotspots in the Canadian Arctic Archipelago (~0.7 °C), east and west edges of Siberia (~0.4 °C) and southeastern Tibetan Plateau (~0.3 °C). We attribute this enhanced warming to combined effects of indirect water vapour, cloud and snow-albedo radiative feedbacks through intensified poleward water vapour transport rather than direct vegetation albedo and latent heat biophysical feedbacks. With continued warming, positive feedbacks between climate and leaf phenology are likely to amplify warming in the northern high latitudes.

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Fig. 1: The leaf area change and temperature anomalies due to advanced leaf-out.
Fig. 2: Latitudinally averaged temperature anomalies and radiative forcing.
Fig. 3: The relationships of latitudinally averaged anomalies in radiative forcing and its drivers.
Fig. 4: Vertically integrated water vapour accumulation and transport anomalies.
Fig. 5: A schematic diagram of the dipole temperature anomaly pattern in Eurasia.

Data availability

The authors declare that the simulation results that support the findings of this study are available upon request from Xiyan Xu or Gensuo Jia. The input data for CESM1.2 simulations are available on https://svn-ccsm-inputdata.cgd.ucar.edu/trunk/inputdata/. Source data for Figs. 1–5 are provided via 10.6084/m9.figshare.11626965.

Code availability

CESM1.2 used in this study is available from the National Center of Atmospheric Research, distributed through a public subversion code repository following the release information on http://www.cesm.ucar.edu/models/cesm1.2/.


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This study is funded by Strategic Priority Research Program of the Chinese Academy of Sciences, CASEarth (XDA19070203) and the Natural Science Foundation of China (#41875107). W.J.R. and C.D.K were supported by the US Department of Energy, Office of Science, Biological and Environmental Research, Regional and Global Climate Modeling Program through the RUBISCO Scientific Focus Area under contract DE-AC02-05CH11231 to Lawrence Berkeley National Laboratory. This research used resources of the National Energy Research Scientific Computing Center (NERSC), a US Department of Energy Office of Science user facility operated under contract no. DE-AC02-05CH11231, and the Lawrencium computational cluster resource provided by the IT Division at the Lawrence Berkeley National Laboratory.

Author information

X.X. designed the study, performed the simulations, analysed the model output and wrote the paper. W.J.R. and C.D.K. provided important insight on aspects of the CESM model and study design. G.J. provided important insight on the land surfaces processes and contributed to the analysis of the result. X.Z. contributed to the analysis of the result. All authors contributed to the results discussion.

Correspondence to Gensuo Jia.

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Peer review information Nature Climate Change thanks Marysa Laguë and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Xu, X., Riley, W.J., Koven, C.D. et al. Earlier leaf-out warms air in the north. Nat. Clim. Chang. (2020). https://doi.org/10.1038/s41558-020-0713-4

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