New Computer Fund

Tuesday, February 17, 2015

Back to the Tropics

"Surface" air temperature is the go to metric to illustrate "global" warming.  Global "surface" air temperature is a combination of roughly 2 meter measured land temperature average measured at different elevations combined with sea "surface" temperature often measured a few meters below the surface.  The data is what it is so we have to make the most of it, but it does lead to some real uncertainties that need to be addressed.

In the previous post I showed a few modeled "surface" air temperatures for the tropics (30S-30N) with SST.  There is a pretty large spread.  If you take a "historic" anomaly baseline, most of the model variance is in the future and if you take a future anomaly baseline most of the variance is in the past.  Real temperatures don't change relationships with baseline choice.

The model experiments do have a sea "surface" temperature output that should more directly compare to SST observation.  With that you can estimate an energy error using the Stefan-Boltzmann equation that neglects latent energy.

That indicates the rough "bias" of the models.  The models tend to run hot and miss cooling events like the 1910s dip by quite a bit.  In my opinion this is just error, but some repackage it as "natural" variability.  "Historic" for most models is 1861 to 2003 or so but a few it is 1850 to 2003.  One of the largest volcanic events recorded while there where thermometers was in 1815, Mount Tambora.  Most climate scientists agree that it only takes 8 to 10 years for most of the "surface" air temperature impact to be realized.

Using ocean thermal basins as a reference, there is roughly a ten year lag between the southern hemisphere ocean and the northern Pacific, but without a longer instrumental time series you have to make a number of assumptions.  I am not a big fan of lots of assumptions.  Since there is evidence of lags in the various ocean basins which would start a fairly complex recovery oscillation, I would not jump on assigning blame for the 1900 to 1920 ocean cooling on the ~1880 volcanic event.  Tambora or some other event could have started an oscillation where following events could hit in or out of phase making "forcing" appear less or more than it really should be.  If you could find a definite signature of one event, you could use that initial condition to tease out ocean inertia influence on apparent "forcing".

That lead me to tropical ocean paleo and "scaling" instrumental "surface" air temperatures in an effort to find the possible start of these longer term oscillations related to cooling events in 2000 years of climate.  According to that, circa 1700 AD is a reasonable starting point for the tropical ocean recovery.  The event(s) that caused that dip in temperature may have starting in 1200 AD.  There are potentially huge lags related to ocean heat content.

So with this you have a much more interesting puzzle than the boring debate over temperature adjustments or if model "experiments" are evidence of anything or not.  The models run hot and anomaly just let's you cheat, intentionally or not, to make the models look better.  Some real reference and some realistic starting point is needed to start solving the puzzle.

So even though this post is a bit of a rehash, I am posting it to try and get more folks involved in the pre-model and pre-Mann world of climate so perhaps something can actually move forward.

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