Not long ago Willis Eschenbach did a post at WUWT about USCRN, the U.S. Climate Reference Network. It’s the best collection of quality-controlled, properly sited, state-of-the-art instrumentation for weather data in the U.S. Its only drawback is that it hasn’t been in operation very long. If we want to form a nationwide temperature average (for the “lower 48” states), we can only do so using USCRN since 2005. With just a little more than 12 years’ data, that’s not nearly long enough to get a useful estimate of what the trend is.
Here’s that USCRN data, from January 2005 through September of 2017, and I’ve added (in red) a trend line estimated by linear regression:
The estimated trend is upward, but its uncertainty is large because the time covered is so short. I estimate the warming rate at 10 ± 14 °F/century (95% confidence limits). Because the uncertainty is so large, we say that the claim the trend is upward fails to reach “statistical significance.”
If this was the only data we had, we would know that the trend was highly uncertain; it could be as low as cooling at 4 °F/century, but it could be warming at a whopping 24 °F/century.
But we do have more data for the “lower 48” states of the U.S., from the National Climate Data Center, all the way from 1895 to the present. Here it is:
I’ve added an estimated trend which is not a straight line, because the trend over this entire time span is not linear.
It is at least approximately linear since 1975, which enables us to estimate the recent trend rate. Here’s the data since 1975 with a trend line according to linear regression:
The estimated trend is upward, and this time it is statistically significant at 5.5 ± 2.2 °F/century. We can plot the estimated rates together with their uncertainties:
This makes it abundantly clear that ignoring the trend from NCDC data, mentioning only the USCRN data, helps our understanding not at all. It only serves one purpose: to muddy the waters.
The upshot is that, as good as the USCRN data are, they don’t cover a long enough time span to give us any useful information about the trend. Let’s face facts: “between -4 and +24 °F/century” tells us just about nothing we didn’t already know. If you were to tout the trend estimate from USCRN data alone, to draw any conclusion or even to imply any conclusion, you’d be wrong.
Yet Eschenbach’s post declares (in its title no less) “no significant warming in the USA in 12 years.” It’s a follow-up to an earlier post by Anthony Watts which also declared “no significant warming,” based at that time on less than 10 years’ data. Watts even declares that USCRN data shows “the pause.” Based on less than 10 years’ data. Not long after, he did essentially the same thing again.
If someone I knew nothing about posted that on his blog, I might regard it as “good-faith dissent.” Horribly misguided, amazingly ignorant, but I like to give the benefit of the doubt so I’d assume good faith. After all, most people aren’t statisticians, don’t know how to compute probable error ranges for trend estimates (let alone trend estimates themselves), and aren’t fully aware of just how completely, totally, utterly, astoundingly meaningless and misleading are conclusions based on trend estimates using such a way-too-short time span. You can’t blame people for simple ignorance, especially on scientific topics (like statistics) that take years to get good at.
But when it come to Anthony Watts and Willis Eschenbach, the “just ignorance” defense doesn’t hold water. Watts has been blogging about climate change for over 10 years (longer than the USCRN data he used to declare the “pause”!). He has often discussed, and has hosted many posts about, temperature trends. Some of them have explored some of the subtleties involved.
When it comes to knowing that trends based on such short time spans are useless and misleading, Anthony Watts has been told. Many times. Many, many times. Many, many, many, …, many times. By me, by his critics, even by his own readers and supporters. There is no excuse for him not to know this. Willis Eschenbach too.
There’s a legal concept called “culpable negligence.” We’re all susceptible to accidents, you might even shoot and kill someone by accident. Ordinarily the law doesn’t punish people for accidents, and this is as it should be. But sometimes, the accident happens because someone was so negligent, so oblivious to what he should have known, that it goes beyond mere accident. It’s culpable negligence.
To ignore what he has been told so often, what he has himself acknowledged, and continue to both write and host posts exploiting readers’ ignorance by flouting useless, meaningless “trend” estimates, he has stepped far, far beyond simple ignorance. As far as I can see, there are only two possibilities. 1) He is deliberately misleading his readers. 2) He is culpably and willfully ignorant.
I don’t blame people for ignorance. I do blame them for repeatedly ignoring the truth after it has been pointed out so many times.
My opinion: Anthony Watts has gone beyond “skepticism” to “denial.” That’s why I call him a climate denier. Eschenbach too; he actually uses the phrase, “Many people, including scientists who should know better …” Willis, you should know better.
This blog is made possible by readers like you; join others by donating at My Wee Dragon.