Global sea surface temperature and model projections, with Bob Tisdale

A couple of days ago at WUWT Bob Tisdale posted a whole heap of charts of sea surface temperature and compared them to CMIP5 models (archived here). He was doing his usual thing of complaining the climate models don't model weather. He wrote:

The climate models used by the Intergovernmental Panel on Climate Change (IPCC) are not simulating climate as it exists on Earth. 

What he was really complaining about was that:

The multi-model mean of climate models used by the Intergovernmental Panel on Climate Change (IPCC) are not simulating climate as it exists on Earth. year to year variations in the weather as recorded by the older version of Reynold's OI v2 data, when looking at some sections of the ocean. 

Well, they aren't meant to do that. Climate models are for, you guessed it, climate not weather. The CMIP5 models are used for climate projections as well as learning more about particular aspects of climate. They are pretty good when it comes to global projections. Not as good (but not that bad) when looking at large areas like entire oceans. They are not intended to be used for weather forecasts. (Bob wants them to time ENSO events at the same time as they happen. That won't happen. There are other models specially developed for localised projections looking ahead a few months.)

There were some charts that were noticeable by their absence, so I figured I'd fill in the gaps in his article.

Bob Tisdale goes AMO-ing to a big chill - not!

Update: The University of Southampton has issued a clarification. It doesn't address the substantive issues raised here. There's also no mention of 0.5C.

Also see Gerard McCarthy's replies to my query to him via Twitter - here and here and here.

Sou 2 June 2015

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There was a new paper that came out this week in Nature, which had a bit of coverage around the traps. Deniers rather liked it not so much because of what was in the paper itself, but because of what was in the press release.

The paper was by a team from the University of Southampton, led by Dr. Gerard D. McCarthy. The paper was about the Atlantic Multidecadal Oscillation or AMO and ocean heat transport, and related.

The AMO is used to indicate changes in sea surface temperature in the North Atlantic. It is of such long duration that there aren't instrumental records going back far enough to show multiple repeating patterns. It's probably not a regular cycle with a fixed period. Estimates seem to place the latest period at around 70 years (from the beginning of a warm phase in the 1920s to the end of a cool phase in the 1990s - see here). The latest IPCC report had this to say about it (page TS-25):

A number of studies have investigated the effects of the Atlantic Multidecadal Oscillation (AMO) on global mean surface temperature. While some studies find a significant role for the AMO in driving multi-decadal variability in GMST, the AMO exhibited little trend over the period 1951-2010 on which these assessments are based, and the AMO is assessed with high confidence to have made little contribution to the GMST trend between 1951 and 2010 (considerably less than 0.1°C). {2.4, 9.8.1, 10.3; FAQ 9.1}.

From the above paragraph I take it that the nature of the AMO is not all that well agreed upon - by some at least.

A short pause: Bob Tisdale thinks climate models are weather forecasts of the Northern Hemisphere

There's a new paper out in Science mag, which is another one looking at the so-called hiatus. This time it's from a different angle. The researchers, Byron A. Steinman, Michael E. Mann and Sonya K. Miller, were exploring climate models and observations in relation to natural variation. They studied surface temperature variations in the northern hemisphere over the past 150 years.

A temporary respite before more heat kicks in

The abstract sums up the research. The study suggests the supposed pause is merely a coincidence of two features of natural oceanic fluctuations - a peak in the Atlantic Multidecadal Oscillation (AMO) and a strongly negative-trending Pacific Multidecadal Oscillation (PMO). That it is the combined effect of these (in other words, natural variability) that partly offset the ongoing greenhouse warming.

The paper suggests that it may not be long before we get a lot hotter.