Ever since NOAA released their latest update to sea surface temperature, version ER-SSTv4 (Extended Reconstruction Sea Surface Temperature version 4), it — and they — have been the target of vicious attack. It has come not just from climate denier bloggers, but from politicians like Lamar Smith (R-TX, chairman of the House committee on Science, Space, and Technology). The accusations haven’t been limited to error, rather they have focused on claims of outright fraud by NOAA scientists, saying, without any justification whatever, that the new version was an attempt to deceive, simply because it shows faster recent warming than other versions.
But new research has not only vindicated them, it establishes that their latest update shows every sign of being the best sea surface temperature data set yet. As in, the best.
Composite sea surface temperature data sets come from numerous instruments, including shipboard measurements from buckets (both wooden and canvas), ship data from engine intakes, buoys at sea, ARGO floats, and satellite radiometry. One of the trickiest aspects of making a global historical data set is piecing together the records from all these different instruments. In the new study, Hausfather et al. compared sea surface temperature data sets to data which are instrumentally homogeneous, coming from only a single type of instrument. These were compared, for recent data (when they’re all available), to the main historical reconstructions, to see which best match the instrumentally homogeneous sea surface temperatures (IHSST). The data sets so tested include HadSST3 from the Hadley Centre/Climate Research Unit in the U.K., the Japanese Meteorological Agency’s Centennial Observation-Based Estimates of SSTs (COBE-SST), the older NOAA data set ER-SSTv3b, and the updated ER-SSTv4.
And the winner is — hands down — NOAA’s update, ER-SSTv4.
What impresses me about this research is how thorough they were. They compared data to IHSST both using only regions where data was present, and infilling to make more complete geographical coverage. They used multiple versions of IHSST for ARGO floats and for satellite radiometry. The main work was to compute the difference between the main data sets and the IHSST data sets, and estimate the trend of the difference series (by linear regression) for recent times, so that a difference trend of zero indicates a good match (no trend bias). Uncertainties in trend estimates were corrected for autocorrelation using an ARMA(1,1) model (which pleases me personally). They even applied a correction to estimates of the autocorrelation parameters (which doesn’t make a huge difference, but is still noticeable when using short time spans).
As an example, using regions with data in common (no infilling), the estimated trend rates of the difference series look like this (the second panel uses a shorter time span so comparison can be made to ARGO floats):
In every case the ER-SSTv4 data compare more favorably than its rivals. In fact, the others show a significant cool bias, underestimate the sea surface temperature trend and, because SST is a big part of global temperature estimates, contributing to the mistaken notion of a “pause” or “hiatus” in global warming. In my opinion, much of the motive for the false accusations against NOAA’s latest update is the fact that it undermines climate deniers’ favorite talking point, the “hiatus” that never was.
Of course the new research has already been criticized, but what’s striking about it is how feeble the criticism is. In part this is due to the thoroughness of the research, in part due to the desperation of deniers.
My overall opinion: the new research makes blatantly obvious that the accusers owe a huge apology to NOAA scientists, who were “rewarded” for making the best SST data yet by being slandered. The biggest apology should come from Lamar Smith, who should be removed from the House committee on Science, Space, and Technology for his gross incompetence and unethical behavior. Just my opinion.
As for any apologies, or even retraction of false accusations against NOAA scientists, my advice is: don’t hold your breath.
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