Guest Post by Bob Tisdale

The new 2015 paper by Cai et al Increased frequency of extreme La Niña events under greenhouse warming has been getting a lot of alarmist attention recently. Examples: see the CBS News story Climate change expected to bring more La Niñas, and the BBC News article Study: Global warming ‘doubles risk’ of extreme weather, and, for those of you who are multilingual, see the German journal Bild der Wissenschaft post Mehr Besuche der kalten Schwester von „El Niño”. [Thanks to bloggers Alec aka Daffy Duck, Paul Homewood and Werner Kohl for the heads-up.] Also see Paul Homewood’s post BBC – Global Warming Doubles Risk Of Extreme Weather at NotALotOfPeopleKnowThat.<.

Cai et al. (2015) 14 co-authors are a who’s-who of climate scientists, including Michael McPhaden of NOAA’s PMEL, who’s written numerous papers about ENSO; and Eric Guilyardi, who’s the lead author of Guilyardi et al. (2009) Understanding El Niño in Ocean-Atmosphere General Circulation Models: progress and challenges.

We discussed Guilyardi et al. (2009) back in July 2012 in the post here. As you may recall, it was a study of how poorly the CMIP3-archived climate models simulated ENSO…that the models basically simulated no ENSO processes correctly. Thus one of their conclusions was:

Because ENSO is the dominant mode of climate variability at interannual time scales, the lack of consistency in the model predictions of the response of ENSO to global warming currently limits our confidence in using these predictions to address adaptive societal concerns, such as regional impacts or extremes (Joseph and Nigam 2006; Power et al. 2006).

Cai et al (2015) Increased frequency of extreme La Niña events under greenhouse warming is a companion paper to Cai et al (2013) Increasing frequency of extreme El Niño events due to greenhouse warming. We discussed the earlier paper in the post Our Climate Models Are Aglow with Whirling, Transient Nodes of Thought Careening through a Cosmic Vapor of Invention. It included a link to and discussion of Bellenger et al. (2012), which described how poorly the CMIP5-archived models simulated ENSO. Once again, the models simulate little if anything correctly. The same arguments apply to the newer paper Cai et al (2015), so there’s no need to repeat them, so please see the “Climate Models are Aglow” post.

The following is from an update to the “Climate Models are Aglow” post about the earlier paper. It should also apply to the newer paper:

Brian Kahn also covered Cai et al. (2013) in his ClimateCentral post Climate Change Could Double Likelihood of Super El Ninos. (Thanks again Andrew for the link to the post at HockeySchtick.) Brian Kahn’s article included the following and a remarkable quote from Kevin Trenberth: The core of Cai’s results, that more super El Ninos are likely, was disputed by Kevin Trenberth, a senior scientist at the National Corporation [sic] for Atmospheric Research. He said some of the models used in the study overestimate the past number of El Nino events by a wide margin and do a poor job of representing them and their impacts. “This seriously undermines the confidence that the models do an adequate job in ENSO (El Nino-Southern Oscillation) simulations and so why should we trust their future projections?” he said in an email. Trenberth also said that some long-range climate models also fail to adequately simulate other natural climate patterns that influence El Nino let alone how they might also shift in a warming world.

Trenberth asked,“…so why should we trust their [climate models’] future projections?”

The obvious answer is ____________________ [I’ll let you fill in the blank].

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