Readers will recall my posts on two recent papers which looked at how climate models simulated various aspects of the climate system, using these to draw inferences about our future. The Sherwood et al paper picked the models that best simulated clouds and showed that these predicted that the future would be hot. "Planet likely to warm by 4C by 2100", wailed the Guardian. Meanwhile, the Cai et al paper picked the models that best simulated extreme rainfall and showed that these predicted more frequent extreme El Nino events. "Unchecked global warming 'will double extreme El Niño weather events'", the Guardian lamented.
Reader Patagon wondered, not unreasonably, which models fell at the intersection of "best climate model simulation of clouds" and "best climate model simulation of extreme rainfall", and his question prompted the following response from Nic Lewis:
I was also wondering that. So I've cross-referred between the new Cai et al. ENSO/extreme rainfall paper, and the recent Sherwood et al. paper tracing the spread in climate sensitivity to atmospheric convective mixing and implying therefrom that climate sensitivity is over 3°C.
The Cai paper analyses 40 CMIP3(last generation - AR4) and CMIP5 (latest generation - AR5) models. Out of those 40, it selects 20 that are able to produce the high rainfall skewness and high rainfall over the Nino3 region (Supplementary Tables 1 and 2). It finds that those 20 models generate twice as many extreme ENSO events in the 100 years after 1990 than the 100 years before 1990.
The Sherwood paper shows 7 CMIP3 and CMIP5 models that have a lower-tropospheric mixing index, their chosen measure, falling within their observational uncertainty range (Figure 5(c)). It takes a little effort to work out which models they are, as some of the colour codes used differ little. For the record, I make them to be: ACCESS1-3, CSIRO-Mk3-6-0, FGOALS-s2, HadGEM1, IPSL-CM5A-LR, MIROC3-2-HIRES and MIROC-ESM.
Two of the seven models that Sherwood's analysis favours are not included in the Cai paper. Of the other five, by chance you might typically expect two or three to be in the 50% (20 out of 40) of models that Cai's analysis favours. But in fact not one of those five models is.
So the answer is that there are NO MODELS at the intersection of "best lower-tropospheric mixing" and "best simulation of extreme rainfall etc".So, if the Sherwood and Cai analyses are valid, it looks as if with CMIP3 and CMIP5 models you have a choice. You can find selected models that have realistic lower-tropospheric mixing, strong positive low cloud feedback and high climate sensitivity. Or you can choose models that produce realistically high rainfall skewness and rainfall over the Nino3 region and generate a large increase in extreme ENSO events with global warming. But you can't have both at once.
Of course, the real world climate system may differ so much from that simulated by any CMIP3 or CMIP5 model that the Sherwood and Cai results have little relevance.
FWIW, if one assumes a binomial distribution with each of the five models favoured by Sherwood's analysis having a 50% chance of being favoured by Cai's analysis (no better or worse than average), then I calculate there would be only a 3% probability of none of the five models being so favoured.
Pure climate comedy gold.