Bob Tisdale is rapidly becoming, for me, what Donald Trump is for John Stewart.
No matter how wrong he gets it, he won’t back down — he’ll double down. He even posted again, to say essentially the same thing he’s said so often: that the reason he accused Tom Karl at NOAA of malfeasance, saying he “mixed and matched methods until they found the results you wanted,” is that NMAT shows a different trend from ERSSTv4 since 1998. But maybe reader “Sou” said it best:
Bob has it all wrong in his now umpteenth post about this. HadNMAT2 is used to correct a bias in ship sea surface temps only. For the period he’s looking at (in fact since the early 1980s), they only comprise 10% of the observations. The rest of the data is from buoys, and HadNMAT doesn’t apply to them. They are much more accurate than ship data anyway. So much so that if ship and buoy data are together, the buoy data is given six times the weighting of ship data. So the comparison Bob thinks he’s making is completely and utterly wrong. And not just because the trends is actually quite close. He is not comparing what he thinks he is comparing.
I got sick and tired of Bob’s articles about this. He keeps insisting on making the same huge error over and over and over again. He’s repeating himself twice a day now, with yet another article hot on the heels of one just a few hours earlier. After reading lots of papers on the subject – if Tamino doesn’t mind, I wrote about it:
I’ve also done the unthinkable (only if you’re a WUWT denier) and checked it out with one of your colleagues and co-authors of Huang15, one of the main ERSSTv4 papers.
I’d rather discuss something interesting.
Here’s the data that has
The Donald The Bob in a tizzy, where I’ve computed the difference between NMAT and ERSSTv4:
I’ve circled the earliest part, from 1998, where NMAT is higher than ERSSTv4. It’s one of the main reasons that The Bob found a lower trend for NMAT than for ERSSTv4 since 1998. The difference since 1998 shows an estimated trend of -0.0044 deg.C/yr, the same value The Bob found for the difference in their individual trend rates.
What The Bob didn’t bother to do is wonder, why might that be? Just because there are differences between NMAT and sea surface temperature, that doesn’t mean the people estimating SST have rigged the game; why, there might even be an actual, physical reason for it.
What’s so special about 1998? The Bob wants us to believe it’s because of that non-existent “hiatus”. But let’s not forget that 1998 was the year of the big el Niño. Which made me wonder, might that have affected the difference between NMAT and sea surface temperature? What about aerosols from volcanic eruptions? What about changes in solar radiation?
To investigate, I took the difference between NMAT and ERSSTv4, and sought to discover how it might be related to el Niño, aerosols, and solar output. As I’ve done before, I used the multivariate el Niño index to quantify el Niño, aerosol optical depth for volcanic aerosols, and sunspot numbers as a proxy for solar output. I allowed for lagged response to each of those variables. I also allowed for an annual cycle, to account for possible annually cyclic differences between the two variables under consideration.
The available data extend from 1950 through 2010, but I started the regression in 1952 to ensure there was sufficient “prior” data for lagged variables. It turns out that all three variables affect the NMAT-ERSSTv4 difference. Here again is the difference, this time since 1952, compared to the resulting model:
It turns out that the model explains the NMAT-ERSSTv4 differences rather well, particularly the high value in 1998 as mostly due to the el Niño of that year.
Here are the residuals from the fit:
If we study only the residuals since 1998, by golly the estimated trend is still negative. But only by -0.0018 deg.C/yr (not -0.0044), a value which is not statistically significant. So much for The Bob’s “much lower.”
Is the (statistically significant) impact of these factors really affecting NMAT-SST difference? Time will tell, but the data seem to indicate so. Right or wrong, it’s a much more plausible explanation than malfeasance by Tom Karl at NOAA, and one which is founded on science, not reprehensible behavior.
Of course the salient point is what was pointed out by Sou, that the comparison Bob thinks he’s making is completely and utterly wrong.
I expect The Bob will post about this again. I expect he’ll repeat himself again. After all, the trend in NMAT is lower than that in ERSSTv4 since 1998, which can’t possibly have anything to do with el Niño or atmospheric aerosols or solar variations because that’s the time of the non-existent “hiatus”.
While you’re at it, Bob, repeat my real name as often as you can, and be sure to ask Anthony Watts to insult me because I post under a pseudonym.