There are a couple of new papers that essentially analyse the various analyses of the supposed “pause” in global warming. One, lead by James Risbey considers fluctuation[s] in surface temperature in historical context: reassessment and retrospective on the evidence. The other, lead by Stephan Lewandowsky, considers the “pause” in the context of model-observation comparisons.

The basic results are that there isn’t really any indication of a model-observation discrepancy, and that global warming didn’t “pause”, at least not in the sense of it having done anything unusual, given our understanding of how surface temperature are expected respond to increasing external forcings. I wrote quite a few posts about the “pause” and it always seemed pretty clear that it wasn’t anything particularly unusual, even if it did provide an opportunity to study variability in the temperature record.

As Gavin Schmidt pointed out on Twitter there were some interesting analyses in the papers. For example, the figure on the right shows the trends from a start year of 1998 to whatever end year is shown on the x-axis, for the different surface temperature datasets. The only one showing a trend of 0 was HadCRUT3, which suddenly jumps up when HadCRUT4 is released in 2012. So, much of the “pause” narrative originated from one dataset that had problems that were later corrected.

The papers also highlight a number of other issues. For example, it was never entirely clear what was meant by a “pause” in global warming. Was it an actual pause? Did it just mean that the trend was lower than the long-term trend? Was it based on the uncertainty being large enough that we couldn’t rule out that there had been no warming? Did it refer mainly to a model-observation mismatch? In fact, there wasn’t even a clear definition of what time period was being considered; papers considered quite a wide range of different start dates and durations. This is in addition to the “pause” referring only to the surface temperature datasets, and not to warming of the entire climate system.

Probably the most controversial aspect of these new papers is the suggestion that the declaration of a “pause” created additional confusion for the public and policy-system about the pace and urgency of climate change and that constant public and political pressure by climate contrarians may have caused scientists to take positions that they would not have taken in the absence of such opposition. I can see why some might be irritated by this, but I don’t see why it’s not an unreasonable thing to consider. I also think there is some truth to these suggestions.

We don’t do research only because it’s interesting, we also do it to have some kind of broader impact. There’s therefore nothing wrong with later considering the impact of some research. We also don’t do research in a vacuum; we often do what seems interesting at the time. There’s nothing wrong with this, but there’s also nothing wrong with considering what might have influenced some research direction. Even though researchers should be (mostly) free to research whatever they wish, there is also nothing wrong with thinking about how it should be presented. I never liked the term “pause” because it implied something that probably wasn’t true. It would seem important to frame research in a way that minimises the chance of it being interpreted in a way that isn’t consistent with what is actually being presented.

Of course, a lot of the research associated with the “pause” was very interesting; I wrote about quite a bit of it. It was also a good opportunity to better understand how variability influences surface temperatures. Even though the “pause” narrative did influence the public/policy discourse, I don’t think it really had all that much overall impact. The Paris agreement still aimed for quite a stringent target. Also, if it there hadn’t been a focus on the “pause”, there would probably have been something else. I don’t think that our lack of policy action is really due to scientists studying something that provided a convenient narrative for those who oppose doing anything. That doesn’t mean, however, that there isn’t any merit in reflecting on this.

Links:

John Kennedy has a post about the Risbey et al. and Lewandowsky et al. papers.