[UPDATE 08/17: In comments, Berkeley Earth team member Zeke Hausfather reveals that most of the discrepancy between the Berkeley Earth 2011 and 2012 results is due to a previously unreported error in latitudinal weighting in the earlier version.
UPDATE 08/20: The 2012 GHCN-only series has been uploaded by Zeke Hausfather. Also, I have added clarifications concerning absolute temperature uncertainty and data availability. The summary has been updated accordingly.]
The recent Berkeley Earth land-surface average temperature series is based on a greatly expanded database of station temperature data, along with a completely automated statistical averaging process. In contrast, established average temperature series from NOAA, NASA and HadCrut are based primarily on the smaller Global Historical Climate Network (GHCN) database, and use empirically derived homogenization methods to remove known biases, albeit supplemented by pure statistical methods.
Here, the post-1950 Berkeley Earth “complete” land series is compared to the preliminary Berkeley series released in 2011, as well as to GHCN-only simulated series, based on overall attributes of those unreleased series provided in the Berkeley Earth companion “methods” paper. The 2011 and 2012 “full” (ALL) series Berkeley versions both fall squarely in the range of the latest comparable series from the three other groups post-1950. However, the two Berkeley ALL series diverge over the 1980-2010 period, and lie completely outside each others’ 95% confidence intervals in the 2000s, when baselined to 1950-1979. This turns out to be due to a significant error in latitudinal weighting in the 2011 ALL series; the error was not publicly disclosed at the time of correction. The GHCN 2012 series falls halfway between the 2012 ALL and 2011 ALL series in the 2000s; 2012 GHCN and 2012 ALL each appear to diverge outside the other’s confidence interval in the 2000s. As well, there is an increasing widening between the 2012 GHCN and ALL series the further one goes back before the 1950-1979 baseline period, with the ALL series about 0.3 C cooler in the early 1800s.
Other issues requiring further analysis are also identified, particularly a reported reversal in the long-term trend of narrowing diurnal temperature range starting in 1987, which contradicts previous GHCN-based analyses.Taken together, these issues cast doubt on the robustness of the present Berkeley Earth analysis, and point up the need for more open data access and improved diagnostics in order to further assess the reliability of the Berkeley Earth approach to surface temperature analysis.
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Over the past few weeks, there has been much discussion of global surface temperatures, as 2016 broke the previous 2015 record in all surface temperature series. Here I will place 2016 in context, highlighting the role of rapid Arctic warming in recent surface temperature evolution as seen in a comparison of four operational data sets. The 2016 increase over 2015 was much larger in the analyses that account for missing areas, especially the Arctic, providing additional impetus to address coverage bias among research groups that still have not done so. I’ll also take a quick look at the growing effect of residual biases from ship-buoy measurement adjustments in sea surface temperature (SST) analyses in recent years, which has led to some additional divergence between the two major operational SST series underlying these four global series.
Deep Climate 
