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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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References

  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. http://dx.doi.org/10.1126/science.1139540
  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. http://dx.doi.org/10.1038/nature06921

Debate in the noise

Last week there was an international media debate on climate data which appeared to be rather surreal to me. It was claimed that the global temperature data had so far shown a “hiatus” of global warming from 1998-2012, which was now suddenly gone after a data correction. So what happened?

One of the data centers that compile the data on global surface temperatures – NOAA – reported in the journal Science on an update of their data. Some artifacts due to changed measurement methods (especially for sea surface temperatures) were corrected and additional data of previously not included weather stations were added. All data centers are continually working to improve their database and they therefore occasionally present version updates of their global series (NASA data are currently at version 3, the British Hadley Centre data at version 4). There is nothing unusual about this, and the corrections are in the range of a few hundredths of a degree – see Figure 1. This really is just about fine details. More »

Global warming and unforced variability: Clarifications on recent Duke study

Filed under: — group @ 13 May 2015

Guest Commentary from Patrick Brown and Wenhong Li, Duke University

We recently published a study in Scientific Reports titled Comparing the model-simulated global warming signal to observations using empirical estimates of unforced noise. Our study seemed to generated a lot of interest and we have received many inquires regarding its findings. We were pleased with some of coverage of our study (e.g., here) but we were disappointed that some outlets published particularly misleading articles (e.g, here, here, and here). Since there appears to be some confusion regarding our study’s findings, we would like to clarify some points (see also MM4A’s discussion).

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References

  1. P.T. Brown, W. Li, E.C. Cordero, and S.A. Mauget, "Comparing the model-simulated global warming signal to observations using empirical estimates of unforced noise", Scientific Reports, vol. 5, 2015. http://dx.doi.org/10.1038/srep09957

Reflections on Ringberg

As previewed last weekend, I spent most of last week at a workshop on Climate Sensitivity hosted by the Max Planck Institute at Schloss Ringberg. It was undoubtedly one of the better workshops I’ve attended – it was focussed, deep and with much new information to digest (some feel for the discussion can be seen from the #ringberg15 tweets). I’ll give a brief overview of my impressions below.

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Climate Sensitivity Week

Some of you will be aware that there is a workshop on Climate Sensitivity this week at Schloss Ringberg in southern Germany. The topics to be covered include how sensitivity is defined (and whether it is even meaningful (Spoiler, yes it is)), what it means, how it can be constrained, what the different flavours signify etc. There is an impressive list of attendees with a very diverse range of views on just about everything, and so I am looking forward to very stimulating discussions.

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