[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.
The NOAA’s National Climate Data Center recently announced that the last 12 months were the warmest on record in the “contiguous” U.S., extending the 2011-12 hot streak that has now eclipsed the previous record in 1999-2000 by a half degree Fahrenheit. Apparently, that was just too much for the Heartland Institute’s James Taylor who used his regular column in Forbes magazine to accuse the NOAA of “doctoring real-world temperature data”. According to Taylor, the “alarmists” at NOAA “simply erase the actual readings and substitute their own desired readings in their place”.
But it turns out that Taylor’s source is none other than hapless climate blogger Steven Goddard, who recently leveled incoherent and unsupported false accusations against James Hansen and NASA’s Gistemp record, as well as NOAA. Goddard also relies on the same reviled NOAA data in his botched attempt to buttress his case that NASA is “hiding” an 80 year cooling trend. Never mind that the U.S. “lower 48″ represents less than 2% of the Earth’s surface area in any event, or that past attempts to show U.S. cooling have been proven utterly wrong.
If Forbes has a shred of integrity, this sorry episode will surely result in an abject retraction and apology to NOAA, along with the banishment of Heartland from the magazine’s pages. And it’s also high time reputable commentators in the mainstream media called out the irresponsible behaviour of Forbes and other right-wing media.
JetStream is an “online weather school” hosted by the Southern Region Headquarters of the U.S. National Weather Service (part of the NOAA). Great idea – except one page reads used to read like something from Marc Morano or Ian Plimer, as discovered by Philip Machanick over at RealClimate.
Not only has the page in question contained misinformation since 2003, but someone inserted highly misleading statements about the temperature record in 2007, echoing a common contrarian confusion between the U.S. and global temperature record.
[Update, Nov. 3: The dubious CO2 lesson has been removed from the overall lesson plan, although it remains unchanged and no longer exists. It used to be #10 in the Atmosphere section, right after "Canned Heat".
Update Nov. 11: The carbon dioxide lesson has been reinstated, with the previous misinformation removed from the discussion section.]
Recently, I’ve been commenting to anyone who’ll listen (or not) that short-term comparisons of global temperature trends are not very meaningful and that at least the last 20 years should be analyzed. This was based on the seemingly paradoxical observation that, while trends from 2001 to present are down or flat, long term trends increased during the same period.
Finally someone (Lucia of Blackboard fame) has listened. Unfortunately, she has compared 20-year observed trends to a model subset that has an unrealistically high projected trend.