Figure S1. Timeline of the National Oceanic and Atmospheric Administration (NOAA) satellites, carrying the AVHRR sensors used in the GIMMS record.

Figure S2. Spectral response curves for the red and near-infrared (NIR) bands of the AVHRR, MODIS, SeaWiFS, and SPOT VGT sensors.

Figure S3. A map of lag-1 autocorrelation for the GIMMS3g GS-NDVI time series.

Figure S4. Significant trends in GS-NDVI from 1982 to 2008 in the (a) GIMMSg and (b) GIMMS3g data sets for areas north of 50°N and excluding croplands.

Figure S5. Land cover map using a combination of the Circumpolar Arctic Vegetation Map (CAVM) and the Global Land Cover 2000 (GLC2000) map.

Figure S6. Significant and non-significant trends in GS-NDVI derived from (a) GIMMSg, (b) GIMMS3g, (c) MODIS NBAR, (d) SeaWiFS, and (e) SPOT D10 using the common record (2002–2008) and estimated using the Theil-Sen approach.

Figure S7. Timeline showing the years covered by each satellite-derived NDVI product used in this study.

Figure S8. The fraction of the study area displaying greening and browning trends in GS-NDVI for each vegetation type considered in this analysis.

Figure S9. The agreement between different NDVI products (including NBAR and non-NBAR products) measured using the Mann-Kendall trend test, Cohen's kappa, and Kendall's tau.

Figure S10. The fraction of naturally vegetated areas at high northern latitudes displaying greening and browning trends in GS-NDVI for both NBAR and non-NBAR data sets.

Figure S11. Mean annual GS-NDVI for GIMMSg, GIMMS3g, MODIS NBAR, MODIS Terra, SeaWiFS, SPOT D10, and SPOT S10 in naturally vegetated areas north of 50°N.

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