Bob Tisdale has a new post at WUWT about a supposed “divergence” between temperature at Earth’s surface and in the lower troposphere.
The “money graph” is this one:
Note that the linear trend rate since 2000 for surface data is +0.0181 deg.C/yr, while for lower-troposphere data it’s merely +0.0096 deg.C/yr. On that basis, “the Bob” concludes that the lower troposphere is definitely warming more slowly than the surface, because, as he says, “The average global surface temperature data almost double the warming rate of the average global lower troposphere temperature data during this period.”
But does it really?
What, one might wonder, is the uncertainty in those trend estimates? The data sets show strong autocorrelation, so we can’t just take the naive uncertainty estimates from linear regression. We can approach that issue in two ways: 1) apply an autocorrelation correction, e.g. as in Foster & Rahmstorf, or 2) transform monthly data to annual averages to reduce the autocorrelation to manageable levels. Let’s do both.
Rather than use an average of 3 surface data sets and 2 lower-troposphere data sets, let’s just use one of each. For the surface I’ll use NASA data, for the lower troposphere I’ll use RSS TLT v3. The NASA data give a linear trend rate since 2000 of +0.0188 deg.C/yr, the RSS data a mere +0.0089 deg.C/yr — a “divergence” even greater than for Tisdale’s combined data.
But when we add “error bars” to those estimates, we find that they’re not necessarily different at all!
I’m guessing that either Tisdale doesn’t know how to do it right, or he just saw what he wanted to see and fired from the hip. Or both.
And by the way … when you compute the trend rate since 2000 by ignoring the data before that, even though we actually have that data, you end up fitting a “broken trend” model, yet another foolish mistake.
He does suggest three possible explanations for his supposed “divergence”:
Of course, there are three possible reasons why the global lower troposphere and surface temperature products do not agree with the hypothesis of human-induced global warming:
- First, the global lower troposphere data are flawed, causing warming rates that are too low.
- Second, the surface temperature data are flawed, causing warming rates that are too high.
- Third, the hypothesis of human-induced global warming is flawed, along with the computer models that support it.
How about this: Fourth: Bob Tisdale’s analysis showing this disagreement is flawed. I’ll go with #4.
And while we’re at it, how about #1? The troposphere data sets used by Tisdale are indeed flawed, in a significant way, according to recent revision by none other than the RSS team itself. That’s why they’ve produced a new product, v4, which shows more warming that the older v3. They haven’t yet published an updated “TLT” (lower-troposphere) product, but the best representative of the troposphere is their “TTT” product, which now looks like this from 2000 to the present:
The linear trend estimate it gives is +0.0171 deg.C/yr. Bye-bye to even a hint of Tisdale’s “divergence.”
And of course there’s the much-vaunted balloon data, the one consistently claimed to confirm the UAH TLT data even though it doesn’t. Here’s what the balloon data say, according to the RATPAC (Radiosonde Atmospheric Temperature Product for Assessing Climate) data set:
The linear trend rate, using only the data since 2000, comes in at +0.0281 deg.C/yr, faster than the rate for surface data. But again, some error analysis would be useful before one declares any sweeping jump-the-gun conclusion.
Bob Tisdale ingored the data he didn’t like (the new RSS version 4 and the RATPAC balloon data) in favor of the data that gave him the answer he wanted, he implied a definitive “divergence” when even the data he selected doesn’t confirm that conclusion, and did it so he could imply that “human-induced global warming is flawed.” And, he threw in a snipe about computer models to boot.
That’s my opinion.
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