Another attempt to kill the "Pause"
It is perfectly proper to re-analyse an existing body of data, though the analysis is likely to be of interrest only if all steps in the reanalysis are revealed. Revising the data itself, however, is an intrinsically dubious enterprise -- particularly if each revision to the data leads to a result more satisfactory to theory in circumstances where the original data were not in line with theory
But that is the situation with Warmism. The actual climate data conflict strongly with the global warming theory. Particularly pesky was the apparent stasis in temperature during the first 14 years of C21. CO2 levels rose but global temperatures did not. And that is a fatal flaw. CO2 molecules don't have a little timer in them that tells them when to reflect heat. They just start reflecting whatever heat they are going to heat immediately they arrive in the atmosphere. So C21 temperatures should have reflected rising CO2 levels but did not.
So the C21 pause is basically quite fatal to Warmism. But that doesn't dent the beliefs of Warmists of course. They set about finding a way around the problem. And data revision is one possibility. Reanalysing the existing data is harder but is also sometimes attempted.
The first such data revision was by Thomas Karl, the former head of a major NOAA technical center. He noted that the data on ocean temperature was pretty wobbly and applied "corrections" to it which tended to show that the "missing" C21 heat was still generated but had been swallowed up by the oceans. Why the oceans started doing that only at the turn of the century was unexplained.
There were however enough infelicities in Karl's work to disturb even a lot of Warmists. It was a too obvious "fix" with too little attention to all the data. The work was, in a word, too open to derision. So some prominent Warmists, including Michael Mann got together as co-authors of the Fyfe paper, which re-admitted a C21 temperature slowdown. The Fyfe paper was however a ramble rather than a proper scientific report and ended up admitting that they did not know why the slowdown occurred, though various theoretical explanations were suggested. They spoke of "the EMBRYONIC field of decadal climate prediction" in their conclusions.
But now a gaggle of the old hands have tried again in an article headed by Risbey and including in its co-authrs Stefan Rahmstorf, who believes that temperature changes of thousandths of one degree are significant. The paper claims that "pauses" in warming are common and the early C21 pause is therefore wrongly focused. They present analyses that give results very different from results presented in hundreds of other papers.
An obvious reason why they get different results is that they use data "through 2016", where 2016 was the height of the El Nino effect. So they include natural warming into CO2-based warming, a handy conflation but a completely illegitimate one
In a second article by Lewandowsky, Michael Mann and others, much the same gaggle of authors rely on a fresh lot of data from the Arctic. But that is very suspect. There is furious volcanic activity under the Arctic sea-ice, particularly along the Gakkel ridge -- so attributing warming there to atmospheric influences is very tendentious. The fact that the Arctic warms irregularly and is often out of sync with temperatures elsewhere is in fact pretty clear evidence that temperatures there are not part of anything global. Incorporating Arctic data into atmospheric climate models is therefore simply unscientific.
Below is a popular presentation of the latest shenanigans
The United Nations panel of climate science experts mentioned it in a 2013 report, scientists have published more than 200 papers analyzing it, and climate deniers said it was proof that climate change didn't exist, but in reality the global warming "pause" or "hiatus" never occurred.
That is the conclusion of a pair of studies, published Tuesday in the scientific journal Environmental Research Letters, based on statistical reassessments of a recent 10-year period that appeared at the time to evince a flattened warming curve.
These are the latest of several assessments to caution that the hiatus theory has no real significance either for climate science or for science-based policy. Even so, they seem unlikely to stamp out the discussion, which has become a deeply embedded meme in some circles.
"In hindsight, with current GMST [Global Mean Surface Temperature] datasets, there is no statistical evidence for a 'pause,'" concluded one of the two studies, which reassessed temperature monitoring from the late 1990s and early 2000s.
The second study, which focused on what appeared to be a difference in observed temperatures and earlier projections from climate models, reached a similar conclusion.
"There was a natural slowdown in the rate of warming during roughly the decade of the 2000s due to a combination of volcanic influences and internal climate variability, but there was no actual 'hiatus' or 'pause' in warming," Michael Mann, director of the Earth System Science Center at Pennsylvania State University and an author of the climate modeling study, said.
A Lack of Arctic Data
The notion of a pause in warming from approximately 1998 to 2012, was fueled in part by incomplete data and erroneous projections that have since been corrected, the studies conclude.
It's long been obvious that if there had been any blip in the trends it was temporary. The years that followed have hit new temperature records. And new evidence has made clear why some were fooled.
Scientists know, for example, that the Arctic is warming at a faster rate than the planet as a whole, but there weren't enough temperature observations from the Arctic in the early 2000s to accurately measure the changes that were occurring there. As a result, data sets on global temperature tended to omit the Arctic until recently, when researchers came up with a better way to extrapolate data from the region.
"We simply didn't have all the information available at the time," Stephan Lewandowsky, a researcher at the University of Bristol and lead author of the climate modeling report said.
Natural phenomena, including increased volcanic activity and decreased solar activity, also masked human-caused warming during the late '90s and early 2000s, seemingly deviating from what climate models had projected, Lewandowsky said.