Guest Post by Bob Tisdale
A few days ago, we showed that global ocean surfaces are, just barely, at record warm levels in 2014, according to the two NOAA sea surface temperature datasets. But the two UKMO sea surface temperature datasets are split. One is pointing to 2014 as warmest, but, with the other, 1998 looks like it will remain the highest…by a hair. (Thanks to wbrozek for advising me of the HADSST3 update.)
We recently presented the Meteorological Annual Mean (December to November) sea surface temperatures for 1997 through 2014, using the two sea surface temperature datasets furnished by NOAA: ERSST.v3b and Reynolds OI.v2. See the post Meteorological Annual Mean (Dec-Nov) Global Sea Surface Temperatures Set a Record High in 2014 By a Whopping… For the ERSST.v3b dataset, 2014 was 0.02 deg C warmer than the previous record high in 1998, and for the Reynolds OI.v2 data, 2014 was 0.01 deg C warmer than in 1998. It didn’t matter with those two datasets whether we included the polar oceans; the difference was the same.
The UKMO Hadley Centre also has two sea surface temperature products. First, the HADSST3 dataset is the sea surface temperature component of the HADCRUT4 combined land+ocean product. Unlike the NOAA ERSST.v3b data used by NCDC and GISS, HADSST3 is not infilled. That is, if a 5-deg latitude by 5-deg longitude grid contains no data for a month, that grid is left blank in HADSST3…same as the CRUTEM4 land surface air temperature component of the HADCRUT4 product.
Second, their HADISST dataset is a statistically infilled dataset that incorporates satellite data from 1982 to present. It is preferred by many scientists for short-term and long-term studies of global sea surface temperatures. In fact, if you were to perform a Google Scholar search of HADISST, you’d get about 2900 results, which is more than the 2500 results shown for NOAA’s ERSST dataset. The Hadley Centre has been in the process of updating the HADISST dataset for a couple of years. If memory serves, HADISST2 was expected to be released in 2013. It’s now approaching the end of 2014.
So let’s take a look at the two UKMO Hadley Centre products and see which is expected to show record-high sea surface temperatures in 2014.
HADSST3 is only available on an anomaly basis, compared to the base years of 1961-1990. The November 2014 global sea surface temperature anomaly value from the Hadley Centre was published recently, so we can show the HADSST3 data on a (December to November) Meteorological Annual Mean basis. See Figure 1. According to the HADSST3 dataset, the surfaces of the global oceans were 0.04 deg C warmer in 2014 than in 1998.
The data has not been updated since this summer for the HADSST3 product at the KNMI Climate Explorer, so I had to use the data direct from the UKMO website here, with the format discussion here. That also means we can’t provide a graph showing the data without the polar oceans (60S-60N), as I had for the two NOAA products in the last post.
The updates of the HADISST data have always lagged a few months. Currently, September 2014 is the most current month. As a result, I’ll present annual average anomalies (January to December) with the year-to-date (September) for 2014. The source this time is the KNMI Climate Explorer. For the global HADISST-based global sea surface temperature anomalies, year-to-date 2014 is 0.01 deg C less than the full year of 1998. See Figure 2.
And as shown in Figure 3, looking at the global HADISST data without the polar oceans (60S-60N), 1998 was warmer than YTD 2014 by 0.02 deg C.
Like the NOAA sea surface temperature datasets, the differences between 1998 and 2014 using the UKMO Hadley Centre datasets are minimal, measured in hundredths of a deg C. Even so, I suspect alarmists will choose to present HADSST3 data, not HADISST data.