Greening of the land surface in the world s cold regions consistent with recent warming

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1 SUPPLEMENTARY INFORMATION Letters In the format provided by the authors and unedited. Greening of the land surface in the world s cold regions consistent with recent warming T. F. Keenan,2 * and W. J. Riley Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA. 2 Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, CA, USA. * trevorkeenan@lbl.gov Nature Climate Change

2 Supplementary Information For the manuscript: Greening of the land surface in the world s cold regions consistent with recent warming Authors: Keenan, T.F. & Riley, W.J. Contents: Figures, Table. Figure S A map of the analysis spatial extent Figure S2 Temporal changes in the spatial relationship between temperature and vegetation Figure S3 A map of areas that are primarily temperature limited. Figure S4 An index map of the frequency with which a Fmax approximates F95. Figure S5 CMIP5 model functional responses Figure S6 Assessing the impact of base temperature: SWI5 vs. SWI Figure S7 The influence of the choice of percentile on the derived threshold value. Figure S8 The relationship between annual Fmax, temperature, annual summer precipitation and the ratio of actual to potential evapotranspiration. Table S Earth System models from the Coupled Model Intercomparison Project (CMIP5)

3 Fig. S A map of the analysis spatial extent. The distribution of pixels globally that are determined to be temperature limited (green). Temperature limited pixels were identified as those in which the cumulated annual temperature above 5 C (SWI5) is below the temperature limitation threshold (i.e., the breakpoint of the relationship between Fmax and SWI5).

4 8 th - 9 th a th - 9 th b Annual mean SWI 5 Annual mean SWI 5 Fig. S2 Temporal changes in the spatial relationship between temperature and vegetation. Spatial relationship between the summer warmth index (SWI5, C), which are calculated as the sum of all monthly temperatures above a threshold of 5 C, and the annual maximum fraction of absorbed photosynthetically active radiation (Fmax, %), for the threeyear period from (a) and the three-year period from 2-22 (b). The 95 th percentile of the distribution of Fmax (F95) in each C bin represents the maximum attainable Fmax for a given annual SWI5. Black lines delineate the 5 th and 95 th percentiles for the period in both (left) and (right). The red lines represent a breakpoint regression applied to the 95th percentile, which approximates the sensitivity of Fmax to spatial changes in SWI5.

5 Fig. S3 A map of areas that are primarily temperature limited. The distribution of pixels that are temperature limited (gray) and primarily temperature limited (red). Temperature limited pixels were determined to be those in which SWI5 is below the SWI5 limitation threshold identified by the breakpoint of the relationship between F95 and SWI5. Other factors also potentially limit Fmax for these pixels, as evidenced by the spread in the distribution under the SWI5 threshold (Fig. S2). Pixels were identified as primarily temperature limited if they fell within % of Fmax for at least one of the 3-year averages.

6 Fig. S4 An index map of the frequency with which Fmax approximates F95. The number of three-year windows in which average Fmax of temperature limited pixels approximates F95. Temperature limited pixels were determined to be those in which SWI5 is below the SWI5 limitation threshold identified by the breakpoint of the relationship between F95 and SWI5. Here, pixels were identified as approximating F95 if they fell within 2% of F95.

7 th - 9 th Model: bcc-csm- Model: BNU-ESM Model: CanESM Model: CCSM Model: GFDL-ESM2G Model: HadGEM2-CC Model: IPSL-CM5A-LR Model: MIROC-ESM Model: MPI-ESM-LR Model: NorESM-M Fig. S5 CMIP5 model functional responses. An analysis of spatial relationship between temperature (SWI5, C) and the annual maximum fraction of absorbed photosynthetically active radiation (Fmax) in Earth System Models from the Coupled Model Intercomparison Project (Table S), for the years Growing degree days are calculated as the sum of all monthly modeled temperatures above a threshold of 5 C. Black lines delineate the 5 th and 95 th percentiles.

8 8 th - 9 th a 8 th - 9 th b 6 4 max th - 9 th Annual mean SWI 5 c th - 9 th Annual mean SWI 5 d Annual mean SWI Annual mean SWI Fig. S6 Assessing the effect of using a base temperature of zero, versus a base temperature of 5 C. Spatial relationship between the summer warmth index (a,b: SWI5; c,d: SWI, C), which is calculated as the sum of all monthly temperatures above a threshold (here either 5 or C), and the annual maximum fraction of absorbed photosynthetically active radiation (Fmax, %), for the three-year period from (a, c) and the three-year period from 2-22 (b, d). The 95 th percentile of the distribution of Fmax (F95) in each C bin represents the maximum attainable Fmax for a given annual SWI5. Black lines delineate the 5 th and 95 th percentiles for the period in all panels. The red lines represent a breakpoint regression applied to the 95th percentile, which approximates the sensitivity of Fmax to spatial changes in SWI.

9 8 F 95 th - 9 th 95 th Percentile Temperature Not limited temperature limited F 95 th - 9 th Annual mean GDD 5 9 th Percentile Temperature Not limited temperature limited F 95 th - 9 th 75 th Percentile Annual mean GDD Temperature Not limited temperature limited F 95 Annual mean GDD 5 th - 9 th 5 th Percentile Temperature Not limited temperature limited SWI 5 Annual mean GDD 5 Figure S7 The influence of the choice of percentile on the derived threshold value. Spatial relationship between the summer warmth index (SWI5, C) and the annual maximum fraction of absorbed photosynthetically active radiation (Fmax, %), for the three-year period from A breakpoint regression is applied to each of the 95 th, 9 th, 75 th, and 5 th percentiles. The threshold value derived from each is represented as a vertical dashed line.

10 Figure S8 The relationship between annual Fmax, temperature (SWI5, left panel), annual summer precipitation (middle panel) and the ratio of actual to potential evapotranspiration (right panel), for pixels within % of F95 (Fig. S3). Monthly gridded precipitation data are from the Climate Research Unit (CRU). AET/PET, a proxy for aridity, is calculated using the approach described in Davis et al. (27), for all months and pixels.

11 Table S Models from the Coupled Model Intercomparison Project (CMIP5) included in this study. All models were used for the historical analysis (98-99) and both the RCP8.5 and RCP4.5 analyses (2-2). Model Land model Land resolution (degrees) N-cycle Dynamic Veg. Reference BCC-CSM BCC-AVIM. 2.8 x 2.8 N Y Wu et al. (23) 2 BNU-ESM CoLM + BNU-DGVM 2.8 x 2.8 N Y CanESM2 CLASS2.7 + CTEM 2.8 x 2.8 N N Arora et al. (2) 3 CCSM4 CLM4.9 x.2 Y N Lindsay et al. (24) 4 GFDL-ESM2G LM3 2.5 x 2.5 N Y Dunne et al. (23) 5 HadGEM2-CC JULES + TRIFFID.9 x.2 N Y Collins et al. (2) 6 IPSL-CM5A-LR ORCHIDEE 3.7 x.9 N N Dufresne et al. (23) 7 MIROC-ESM MATRISO + SEIB-DGVM 2.8 x 2.8 N Y Watanabe et al. (2) 8 MPI-ESM-LR JSBACH + BETHY.9 x.9 N Y Raddatz et al. (27) 9 NorESM-ME CLM4 2.5 x.9 Y N Bentsen et al. (23)

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