Fig. 3: Spatial patterns of RMSE from reconstructed temperature relative to instrumental reanalyses.

Spatial distributions of RMSE from OEnKF (a–c), HGAOEnKF (d–f), their differences (g–i), and corresponding zonal mean RMSE (j–l) relative to the BE data set. The reconstructions using PAGES2k, PAGES2k + M08, and the comprehensive database are shown in left column, middle column, and right column, respectively. In (j–l), the blue lines represent the zonal mean RMSE from OEnKF, and red lines represent zonal mean RMSE from HGAOEnKF. The differences between OEnKF and HGAOEnKF are shown in green lines. The circle indicates the difference is significant at 0.05 level.