Some are trying to defend Judith Curry’s claim that early 20th century global warming (i.e. between 1900 and 1950) was “almost as large as the warming since 1950.” An ardent attempt from Jaime Jessup reveals a mind hard at work, trying to make the evidence fit belief.
Let me explain.
When trying to measure climate change (whether natural or man-made), we have to separate the signal from the noise, that up-and-down jiggling and wiggling that never ceases but never really gets anywhere. The signal we’ll call climate, when we add the noise to it we get the weather.
I looked into the issue by using a smoothing method (modified lowess smooth) to estimate what the signal was, which I’ll show here as a solid black line for NASA data (first on my list, I did all five major global data sets):
I don’t think the early 20th century warming qualifies as “almost as large” when the warming since 1950 is 2.8 times as big. Do you?
I didn’t just use NASA data. I used NOAA, and HadCRU, and Cowtan & Way , and Berkeley Earth, and they all gave the same answer. “Modern warming” was bigger than “early warming” by a factor ranging from a low of 1.8 times the size (for the HadCRUT4 data), to a high of 2.8 times the size (NASA data). Any data set you choose, including HadCRUT4, the early warming is not “almost as large” as the warming since 1950. So, I stated outright that Judith Curry’s claim is bullshit.
Jaime Jessup takes exception with my analysis. He shares a graph with us:
Then he makes sure we know it’s a real graph:
This is not a fake graph. It is actual data via Tim Osborn of the UEA. The blue line is a decadally smoothed average. What it shows is that between 1910 and about 1945, global temperature increased by just over 0.5C. Between 1950 and now, global temperature has increased by approximately 0.75C, looking at the decadal average. 0.75 is 1.5 times 0.5C, …
He seems to think I’m showing fake graphs. But the graphs I showed are real too, featuring real data from NASA and NOAA and Cowtan & Way and Berkeley Earth and yes, from UEA too (that’s the HadCRUT4 data, the same data he’s using).
He used a 10-year smoothing filter (which? one wonders). But we’ve studied global temperature data enough to know that a 10-year filter is too short, it’ll show too much fluctuation that’s really due to noise, not signal. This is method #1: help noise obscure the signal.
No matter. I’ll do my own 10-year filter, a Gaussian filter, and mine sure looks a lot like his:
He estimates the early warming was “just over 0.5C.” My calculation puts it at 0.48. He gets a ratio, late to early warming, of ~1.5. I get 1.54.
And that’s giving the early warming every chance, using a smooth with too much noise and allowing only the data set with the lowest ratio of the five available. The late warming is still 54% bigger, early warming just is not “almost as large.”
Now the most fascinating part. The factor of 1.5 (the absolute lowest he could get it) wasn’t good enough to satisfy Jaime Jessup, so he changes it yet again, but in bizarre fashion.
If we look at the anomalies only, notice that 1910 was a little less than -0.5C, 1945 was about +0.1C, 1950 was about -0.05C and 2018 – the latest year in the series – is +0.6C (January to November). So, very similar warming 1910 to 1945 and from 1950 to 2018. Whichever way you look at it, the warming from 1950 (or 1979 if you prefer, which I do, because it was uninterrupted rapid warming, just like the E20C warming) to present is of similar magnitude and rate to the early 20th century warming. They are not vastly dissimilar as claimed by Tamino.
Jessup resorts to basing his estimates by “eyeballing” values, based on individual points — which of course maximizes the impact of noise. This is method #2: Cherry-pick times and values to enhance your case. It enables him to claim that the range covered by global warming in the early 20th century is given by the dashed blue lines in this graph:
Look at the red line, showing Jessup’s already-too-wiggly smooth. Look at the range it covers prior to 1950. Look at the range Jessup uses to estimate early warming. Do you think he’s being honest? I don’t.
As for the later warming, Jessup is using these values (again, the dashed blue lines):
Look at the red line. Look at the range it covers after 1950. Look at the range Jessup uses to estimate late warming. Do you think he’s being honest? I don’t.
If you want to know whether or not I’d call the early and late warming “vastly dissimilar,” you’ll have to define precisely what you mean by “vastly dissimilar.”
But I can tell you this: the idea that early 20th century warming was “almost as large” as recent warming, in all its forms and with all its dressings, is not just bullshit, it’s dim-witted bullshit!
This blog is made possible by readers like you; join others by donating at My Wee Dragon.