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Hiatus or Bye-atus?

Guest commentary by Stephan Lewandowsky, James Risbey and Naomi Oreskes

The idea that global warming has “stopped” has long been a contrarian talking point. This framing has found entry into the scientific literature and there are now numerous articles that address a presumed recent “pause” or “hiatus” in global warming. Moreover, the “hiatus” also featured as an accepted fact in the latest IPCC report (AR5). Notwithstanding its widespread use in public and apparent acceptance in the scientific community, there are reasons to be skeptical of the existence of a “hiatus” or “pause” in global warming [Ed: see also this previous post]. We have examined this issue in a series of three recent papers, which have converged on the conclusion that there is not now, and there never has been, a hiatus or pause in global warming.

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Reports of our demise…

Filed under: — gavin @ 23 November 2015

… have of course been greatly exaggerated. But we are having some issues with our domain name. The back story is perhaps interesting to others, so here is quick summary of the situation.

Update: The account details have been restored and the domains renewed. We should be back to normal in a couple of days.

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And the winner is…

Filed under: — group @ 17 November 2015

Remember the forecast of a temporary global cooling which made headlines around the world in 2008? We didn’t think it was reliable and offered a bet. The forecast period is now over: we were right, the forecast was not skillful.

Back around 2007/8, two high-profile papers claimed to produce, for the first time, skilful predictions of decadal climate change, based on new techniques of ocean state initialization in climate models. Both papers made forecasts of the future evolution of global mean and regional temperatures. The first paper, Smith et al. (2007), predicted “that internal variability will partially offset the anthropogenic global warming signal for the next few years. However, climate will continue to warm, with at least half of the years after 2009 predicted to exceed the warmest year currently on record.” The second, Keenlyside et al., (2008), forecast in contrast that “global surface temperature may not increase over the next decade, as natural climate variations in the North Atlantic and tropical Pacific temporarily offset the projected anthropogenic warming.”

This month marks the end of the forecast period for Keenlyside et al and so their forecasts can now be cleanly compared to what actually happened. This is particularly interesting to RealClimate, since we offered a bet to the authors on whether the results would be accurate based on our assessment of their methodology. They ignored our offer but now the time period of the bet has passed, it’s worth checking how it would have gone.

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  1. D.M. Smith, S. Cusack, A.W. Colman, C.K. Folland, G.R. Harris, and J.M. Murphy, "Improved Surface Temperature Prediction for the Coming Decade from a Global Climate Model", Science, vol. 317, pp. 796-799, 2007.
  2. N.S. Keenlyside, M. Latif, J. Jungclaus, L. Kornblueh, and E. Roeckner, "Advancing decadal-scale climate prediction in the North Atlantic sector", Nature, vol. 453, pp. 84-88, 2008.

So what is really happening in Antarctica?

Filed under: — eric @ 10 November 2015

The recent paper by Zwally et al. in the Journal of Glaciology has been widely reported as evidence that Antarctic is gaining mass, and hence lowering sea level. Is it? Expert Jonathan Bamber weighs in.

Guest post by Jonathan Bamber, University of Bristol

There have been quite few big media stories related to Antarctica recently, including a paper on the irreversible collapse of the marine portion of the West Antarctic Ice Sheet and a NASA-funded study that finds, contrary to numerous previous results, that the Antarctic ice sheet as a whole has been gaining mass between 1992 and 2008. This most recent study received a lot of media attention because it runs counter to what was said in the last IPCC Report. Certain parts of the media hailed this as another sign that the impacts of climate change had somehow been exaggerated a risk that the lead author Jay Zwally was concerned about before the research was published.

So what did Zwally and his colleagues do, what did they find, and why does it contradict a plethora of previous studies that suggest Antarctica has been losing mass over the same time period?
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Unforced Variations: Nov 2015

Filed under: — group @ 2 November 2015

This month’s open thread.

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