Reversion to Mean

As usual, there is a lot of debate over whether warming will pick right back up, the "pause" will continue or could we see some cooling.  The warmists of course pick warming and have a delightful memory defect that let's them blank out things like models running too hot and such.  The Sun Done it bunch are planning on buying some new winter wear, but a growing number point to about neutral, at least for a few more decades.

To have some predictive power, you need to know a mean trajectory or path so you can consider reversion to that mean in a probabilistic manner.  That is poor terminology, but for now let's go with it.

I made this chart a while ago to show the number of linear trends that climate could revert to.  The warmists like the orange trend because that is the most alarming and will make oobservationscatch up with models in a decade or less.  I would be in the dark red camp, the longest trend with a caveat.

This would be the caveat.  Micheal Mann created the new composite Hockey Stick in the Background and Oppo et al the not so hockey stick in the foreground.  Mann's joke appears to be his same ol' same ol' upgraded to "Global".  Since his same ol' same ol' is based on northern hemisphere tree rings spliced to instrumental temperature starting in 1902, and the NH temperature correlation to "global" temperature sucks big time, it is joke.  The Mann has lost it.

The Oppo et al. 2009 which happens to be in a region with very high correlation to "global" temperatures is more "believable" than the Mann-O-Matic version of "Global Temperature Change".


The potential trends in this case are mainly downward, but there is an honest to goodness mean or average in blue.  That mean, plus no-feedback forcing would put us in the neutral camp.  In order to join this camp you have to think much longer term than the instrumental period.  That would exclude the warmists because of their memory problems.

There are a few other regional reconstructions that indicate a mean close to today's temperatures might be reverted to, also totally lost on the Warmists of course.

Interestingly, Emile-Geay 2012 which uses several SST data sets for calibration stops in 1995.  The contributors to that reconstruction are Emile-Geay, J.; Cobb, K.M.; Mann, M.E.; Wittenberg, A.T.

A paleo reconstruction with a fortuitous end date coauthored by Mann, M.E. is pretty much to be expected.

When you include up to date data you can get an idea of which mean the Nino3.4 region might be reverting to.  There is a new version of ERSST that makes a small difference that wasn't operational on Climate Explorer at the time in case you are wondering.  That glitch has been fixed by Geert at Climate Explorer, so I may revise this pretty soon.

If you really want to get a better idea of what mean might be reverted to you can include generic CO2 forcing.  That would be using CO2 as a reference for "all' Anthropogenic forcing.  Not very exact but a useful guestimate.

The cluster of trend lines with the CO2 reference which should be close to the longer term mean, shifted a touch various man linked effects.  The green mean line, slightly above zero is the same as the blue mean above for reference.

So should you hear someone mentioning reversion to mean in reference to future "global" temperature, this post gives you an idea of the options available.