BlueSkiesResearch.org.uk: Could the Pliocene constrain the Equilibrium Climate Sensitivity?

The long-awaited prequel to "Can the Last Glacial Maximum constrain climate sensitivity?" is now up on CPD and open for comment. This latest episode is set back in the mid-Pliocene warm period 3-3.3Ma BP (MPWP, sometimes also called mid-Piacenzian by people who care deeply about the conventions for paleoclimate nomenclature). The particular reason for looking at the MPWP is that it’s the most recent period when CO2 was relatively high (at least compared to pre-industrial, though perhaps not so high compared to today) and the climate was correspondingly warm. This means that it avoids some of the major complications that arise when studying the Last Glacial Maximum, where there is the question of how directly a strong cooling informs about a strong warming, and large ice sheets provide a substantial forcing to the atmosphere-ocean system that does not necessarily combine linearly with other forcings such as GHGs. Thus, PlioMIP was born around 2009, and by 2015 lots of different modelling groups had produced simulations of the MPWP to compare with each other and with the data assembled by the USGS. Being much further back in time than the LGM, the data are much more sparse (even though the interval of time is also far broader) and more uncertain. Also, the boundary conditions such as atmospheric CO2 level are not known with great precision. One might be suspicious that choice of value used in the simulations, 405ppm, could have been been influenced by political considerations :-)

Although theres been a fair bit of analysis of the model results, no-one had looked directly at how the simulations depended on the equilibrium climate sensitivities of the models. So we did the usual thing, of comparing the tropical temperature change at the MPWP, to the equilibrium sensitivity of the models. It looks like there might be some sort of relationship there, though it’s far from certain.

Here’s the main result, with the model results represented by red dots.

The temperature data for the MPWP is a bit less well developed than for the LGM, so we didn’t really have a good uncertainty estimate but instead just tried a few possible values as a sensitivity test. It is also notable that the model ensemble seems to generally show more warming here than the data, although with substantial overlap if uncertainty is taken into account. It is possible that the forcing is too strong, or that the models are too sensitive in this region, or it may be that the data are wrong, or to be more precise, misinterpreted in terms of climate. I try to be avoid saying things like "the data are wrong" especially when talking to the data specialists, as at some level the data are definitely correct, real stuff has been measured and the measurements themselves are not in any real doubt. It’s how these real measurements are translated into a putative climate variable that is where the difficulties lie. Another interesting and possibly disconcerting aspect of this result is that the regression line does not pass through (or close to) the origin, implying that a hypothetical model with zero sensitivity to CO2 would show a significant tropical cooling at the MPWP. It is hard to see how that might arise, although it is also hard to see how a model with zero sensitivity to CO2 could arise anyway. It is perhaps not completely impossible that increased latitudinal transport would result in a tropical cooling accompanied by a high latitude warming so as to cancel out the change on the global average. After all, there has to be some explanation as to why a small change in model sensitivity seems to correspond to such a large change in MPWP tropical warming in this sample. We've presented this work a few times and no-one has come up with any great ideas about it.

Anyway, we don’t have any strong conclusions, it might be possible to generate a meaningful constraint out of this, but we don’t have any real confidence in the specific result presented here. PlioMIP2 is being planned, with various improvements over the original PlioMIP. Most importantly perhaps, the researchers are aiming for a true "time slice" in which orbital and other forcings are near enough constant (and so, hopefully, the climate was in some sort of equilibrium with this), rather than aiming for some sort of average over the warm peaks within a longer interval, as PlioMIP did. The main problem with this is that the data become even more sparse, but it should in principle enable a more meaningful model-data comparison. Watch this space!

No, Terence Mills does not believe his “forecast”

Another day, another bit of clickbait climate sceptic trash in the Times. Hidden behind a paywall, which saves you from having to read it, though some of it is republished here and the underlying report (not peer reviewed) is on the GWPF site here. The basic premise is that if you fit a nonsense model with no trend or drift, you generate a forecast with no trend or drift (though with huge uncertainty intervals, necessary to allow for the historical warming we've already seen). Amusingly, even with those huge uncertainty intervals, the temperature is already outside them as tweeted here by Gavin.

I was interested in whether the author really believed it, whether he'd been conned or misrepresented by the GWPF, or whatever else his explanation might be. So I emailed him, proposing a simple bet: for every month where the temperature lies above the red 50% line, he pays me £50. For every month where the temperature lies below the line, I pay him £60. Expected win for him: £5 per month, indefinitely. Assuming he believes the forecast, that is. Expected win for me, knowing his forecast to be junk: £50 per month, though I might lose a few at the outset :-)

There followed a fruitless exchange in which he declined to comment on whether he thought the forecast was credible and refused to even discuss any possible bet. I'm still baffled as to what might motivate a statistics professor to put their name to such obvious drivel, it's hardly something that will enhance his reputation in the academic community, or that he can feel proud to have written.

sunshine and BlueSkies

In January there was one day of blue skies and sunshine when it did not rain, so on that day we cycled to Kirkby Lonsdale for breakfast (Kirkby Lonsdale is very 21st century - they let you eat breakfast until noon!!!). Stupidly I did not take a camera. In February it has also rained a great deal. For example, on Sunday we did a fell race in the wind and rain and mud. Running is probably one of the better things to do in the rain, but it was still unpleasant. However, it is hard not to feel an immense sense of glowing achievement just for completing such a stupid thing. Then yesterday it dared to be sunny when I was too tired from the race to go on a long ride. Very annoying. The whole point of BlueSkiesResearch is that we can go and research the blue skies when they appear rather than being stuck inside staring sadly out of the window. Unbelievably, today it also dawned bright! We cycled one of the several off-road routes to Litton, and this time did not forget a camera.

And to prove it was also sunny at home... one of GingerNut's main hobbies is seeking out sun patches. Presumably he does this in order to make his fur look as orange as possible.
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Posted by jules from jules' pics.

"If I was better at mathematics I would have liked to have been an engineer."

Spotted by chance, and the article is mostly irrelevant but I did like the refreshingly honest quote from a fund manager who has woefully underperformed the FTSE over the past 5 years, no doubt drawing a massive salary in the process.

There are those in the skeptic community who argue (based on who knows what, salary perhaps?) that scientists are basically the dregs left behind once the financial parasite industry has skimmed off the cream of the crop of the university leavers. This wasn't my experience, as in fact the top few in the year mostly queued up for the handful of DPhil grants available, but it's a good shtick to beat climate scientists with.

Ginger Nuts

When stocking a pond, it is usual to consider inches of fish. The inches can be in many little tiddlers or a smaller number of bigger fish. It turns out that the same applies to cats, only you measure it in feet rather than inches. Spice and Pepper didn't find their new home yet and were a bit lost in our large pond of a house. So we asked the cat rescue for some more feet of cat. His name is not actually Ginger Nuts, but Hobbes. But he is definitely a lot of feet of cat. 

A weaponised marmalade seal pup, his purr is a husky breathing sound. When he kneads, it is a real massage. He actually likes to have his tummy tickled (which is quite rare) but one mis-stroke and his tendency is to bite and swat. Thwap! He likes playing games too, in between the hours spent plotting our deaths. Of course, all cats spend much of the day plotting the death of their human parents, whether foster or adoptive, but it is a little more concerning when the cat is over 6kg of enthusiasm.  Now I know why tigers are so dangerous to keep as pets. Well, at least he doesn't have to choose which of us to sit on - on the sofa he can easily spread across both of us. 

So now we have Ginger Nuts, Ginger Tits and Poppet staying in our cat pond house. Funny how quickly cats lose their names (...should be Ginger Wot-No-Nuts? of course).

More Catniss

Should probably be blogging about our little paper in review at Climate of the Past.

But bugger that:  new catz have arrived!

Archie and Alfie grew to be large and elegant beasts, and went to a new home in mid-January. They went together, which was fortunate, as they were highly entangled. Hopefully they will provide many years of fun and friendship for their new Ma and Pa in Kendal.

After this, we got to rest from cats, as the rescue itself was on hols. They put all 25 kitties into kennels for a month. Fair enough - it is important that their primary carer doesn't get compassion fatigue! Holidays over, new cats arrived hot from the kennels two days ago. They were grubby, but luckily they like being brushed and are polishing up nicely. They are also eating like anything considering their minuscule size. I guess they didn't enjoy the kennels much. These ones are females and are of the QUIET kind. shhhh.

Prettiest ever is probably Spice (3.45kg).

But, if I were picking one, it might be time Pepper (2.75kg), as she seems friendlier and perhaps a bit more bent on having fun. She certainly won't cost much to feed! Rat sized, really. She looks quite stupidly small sitting on James' huge lap.

They are friendly, but seem unadventurous, spending most of their time in their room playing about in the cat tree. Early days, but I reckon they don't need their new owner to have a large house! 

Someone saw them advertised at the vets yesterday and she came to visit them last night. They were on good form (830pm is a great time to visit cats!). They really liked her, and so they have got their paws crossed that they may have new real parents very soon.