A new post on WUWT by S. I. Outcalt concludes that “the modern warming regime ended in 1997.” Outcalt transforms various data sets, and although he refers to his transformation as the “Hurst rescaling” (in order to associate it with the “Hurst exponent”) it’s really just a rescaled version of something statisticians were familiar with long before Hurst, called cumulative sums.
Cumulative sums can show very interesting behavior. They can also be extremely tricky to deal with statistically. That’s not a problem for Outcalt, his post doesn’t seem to have any statistics.
The heart of his claim that “the modern warming regime ended in 1997″ is this graph:
It’s the rescaled version of the cumulative sums of deviations from average, for various global temperature data sets from 1976 through 2008. It begins what seems like a steady rise right around 1997, which Outcalt concludes is the start of a new regime, with modern warming coming to a halt.
One wonders why he stopped at 2008 — it’s 2012 already, data are easy to get, and the “analysis” is pretty simple. Let’s bring things up to date.
I retrieved a different data set (but which one? it’s a mystery) for global average temperature 1976 through 2011 and computed the rescaled cumulative sums of deviations from average:
Wow! This also shows what seems like a steady rise starting in 1997. Could that be a “regime shift”? Could Outcalt be right that modern warming stopped then?
It also indicates a “regime shift” starting in 1984. What could have caused that? Is it the AMO? The PDO? A novel by George Orwell?
Here, by the way, is the same graph but with the result for data from NASA GISS superimposed in red:
The GISS data don’t seem to show the 1984 regime shift. Is it just an artifact of the other data set, or have the bad boys at NASA tampered with their data to eliminate the 1984 regime shift?
Kudos to the first reader who can identify the origin of the mystery data set.
UPDATE UPDATE UPDATE
We have a winner, folks. Reader “L. Hamilton” states
I can get something pretty similar, regime shifts and all, from random data, taking the 1978-2011 GISTEMP trend plus white noise with the residual sd.
It kinda shows how ridiculous is the claim of a “regime shift in 1997″ based on Outcalt’s “analysis.”