McLean’s folly 2: the reckoning

By Gareth Renowden 12/01/2012

Ten months ago, Aussie “sceptic” John McLean predicted that 2011 would be “the coolest year since 1956″. I pointed out at the time that this was nonsense, and so it has proven to be. I’ve taken the GISS global temperature figure for Jan – Nov 2011 (+0.51ºC compared to the 1951-80 average) and added it to the graph I created to illustrate the full extent of McLean’s folly:


Last year was warmer than 1956 by a whopping 0.68ºC — about three standard deviations, in statistical terms — making McLean’s forecast an abysmal failure. Yes, 2011 was cooler than 2010 or 2009, but still one of the top ten warm years.

ENSO does have an effect on global temperature — that’s been understood since the 1970s, if not earlier. La Niña years tend to be cooler than the years around them, as this WMO graph illustrates.


It’s clear that even cool La Niña years have been warming, with 2011 being the warmest such year in the instrumental record.

The reason McLean’s forecast failed is quite simple. He failed to take into account the warming trend that’s incredibly obvious when you look at the GISS and WMO data. Why would he do that? Well, he was lead author on a paper that “established” a link between ENSO and global temperature, but did that by filtering the global mean temp to remove any long term trend and to emphasise the ENSO time scale. Voila! The Southern Oscillation Index (SOI) suddenly accounted for most of the variability in the (filtered and detrended) global mean temperature. As pointed out in the rebuttal to McLean et al, just about any time series would be “explained” by the SOI after passing through their filter.

In order to make his unphysical forecast, McLean must have forgotten what he had done in the paper he was so keen to promote. I could perhaps be forgiven for suspecting that he didn’t know what he was doing in the first place — but then that just makes his co-authors, Chris de Freitas and Bob Carter look equally daft. They certainly didn’t rush to correct McLean’s folly. As ever, in the land of the Climate Cluelessâ„¢, anything goes.

See also: McLean, de Freitas and Carter win the Friends of Gin and Tonic’s inaugural Climate Idiots of the Year award. Richly deserved.

[A glimpse of stocking.]