## 3 Results and Discussion
### Comparison of Globally Mapped GPP  
Figure 16 shows globally mapped FluxSat-7 and FLUXCOM-RS GPP for two eight-day periods in 2007. As expected based on [PERSON] et al. [32], large differences are shown in the U.S. Corn Belt and other highly productive agricultural areas identified with the SIF data. GPP values near the peak of the northern hemisphere growing season (for the eight-day period starting at 193) are seen to be generally higher with FluxSat-7 as compared with FLUXCOM-RS; this may be related in part to the different training datasets used. Differences in the winter hemispheres are more similar. FluxSat-7 provided mostly higher values in the tropics as compared with FLUXCOM-RS. Figure 15: Similar to Figure 14, but showing normalized interannual variations (unitless) for different plant functional types. Figure 17 shows maps of annual averaged GPP from FluxSat-7 and VPM. The average values in the Southern Hemisphere extra tropics were similar. However, mean values in both the tropics and Northern Hemisphere extra tropics were higher in FluxSat-7. To check our results in the tropics, we ran an experiment where half the sites were used for training, but the one tropical station with high GPP values from FluxSat-7, BR-Sa3, was withheld from the training set and was instead used for evaluation. Figure 18a shows that the high GPP values for this site produced by FluxSat-7 were supported by the flux tower values. This is an important finding because this region is frequently cloudy and satellite-derived GPP values have large uncertainties owing to few ground-based training sites. Figure 16: Maps of GPP (eight-day average) estimated with remote sensing data trained on eddy covariance flux tower data for Days 193–200 (**left panels**) and Days 1–8 (**right panels**) of 2007; **top panels**: FluxSat-7, **bottom panels**: FLUXCOM-RS. Averages are listed in the lower left for all grid boxes (Mean all), along with subsets from the tropics (latitudes \(<20^{\circ}\), denoted Mean trop), Northern Hemisphere extra tropics (latitudes \(>20^{\circ}\)N, denoted Mean NHET) and Southern Hemisphere extra tropics (latitudes below \(20^{\circ}\)S, denoted Mean SHET). Figure 17: Maps of annual averaged GPP estimated with remote sensing data for the year 2007; **left panel**: FluxSat-7; **right panel**: VPM. We similarly compare GPP values at four independent high latitude sites (above 60\({}^{\circ}\)N) in Figure 18b where two sites were ENF and two were wetland. We see that both FluxSat-7 and VPM underestimated GPP at the higher values for ENF sites, while FluxSat-7 somewhat overestimated for wetland sites and lower GPP values at ENF sites. VPM had a more consistent underestimation  
The annual GPP values from FluxSat-7, VPM and FLUXCOM-RS were 140.8, 125.0 (in agreement with that reported by [PERSON] et al. (2011)) and 111.6 Pg C y\({}^{-1}\), respectively for 2007. If SIF was not used for delineation of high productivity areas, and a single fit to the flux tower data was used for all areas, then FluxSat-7 reduced to 139.4 Pg C y\({}^{-1}\). It has been noted that VPM has an underestimation for ENF and EBF that is possibly related to higher light use efficiency for diffuse radiation ([PERSON] et al., 2011). It is therefore not surprising to see higher values from FluxSat-7 as compared with VPM for those PFTs that occupy a significant fraction of the vegetated land surface. FluxSat-7 is within the range of a compilation of observation-based, model, and hybrid results ([PERSON] et al., 2011), but outside the high range of values from previously reported observation-based diagnostic models ([PERSON] et al., 2011). Discussing the evaluation of global annual GPP produced by Earth system models with an earlier version of FLUXCOM (that produced a value of 119 \(\pm\) 6 Pg C y\({}^{-1}\)), [PERSON] et al. (2011) noted that higher estimates of 150-175 and 146 \(\pm\) 19 Pg C y\({}^{-1}\) were reported by [PERSON] et al. (2011) and [PERSON] et al. (2012), respectively, though there were large uncertainties associated with those estimates.