Climate Parallax

Why different views of the surface temperature record should always be regarded as a good thing.

Parallax: Channel 4 title sequence (Source: http://www.tvwhirl.co.uk)

Parallax – noun: the apparent change in the position of an object due to a change in the position of the observer.

(Famously used by UK Channel 4 in a series of animations of their title sequences where landscape features line up at a certain point to form “4”).

Zeke Hausfather’s recent post Agreeing at the Blackboard begins:

My personal pet peeve in the climate debate is how much time is wasted on arguments that are largely spurious, while more substantive and interesting subjects receive short shrift. While I’m sure a number of folks will disagree with me on what is spurious vs. substantive, I think it would be useful to outline which parts of the debate I feel are relatively certain, are somewhat uncertain, and quite uncertain.

I found myself agreeing mostly with Jeff Id’s post about it,  but much of that is gut feeling.  There are a couple of Zeke’s statements where my opinion is based on having looked in detail at data. In Zeke’s category What I think is likely he says:

Land and ocean temperature measurements over the past century are largely accurate at a global level, though there are some regions that have limited data, especially toward the earlier part of the century. That said, factors like UHI, instrument change, siting issue, and other data quality issues could potentially change the global trend modestly.

For the first sentence, well, no, I can’t agree. Why? Because of what he says in the second; I have seen enough of the data and the adjustments to think that these ‘factors’ could reduce the calculated warming dramatically. But then it might not; either way I can’t assign it to ‘likely’.

In the past year countless hours have been spent perfecting reproductions of the GISS and CRU global average anomalies (e.g. this post at WUWT). There has been some sterling work done by Zeke, Ron Broberg, Nick Stokes, Steven Mosher and others.  It is reassuring in a way and I applaud them for it.  Each analysis has taken very similar data processed it using small variations in the input data and methods but with the same approach – that of averaging it with spatial weightings to account for changes in the number and location of the thermometers.  Their analysis is equivalent to looking at the data from one angle, a single viewpoint.  It is one where slight variations in data produce an almost identical graph.  What we need to do is take a few more steps sideways, away from the CRU/GISS ‘line of sight’.

A look at the data itself – measuring it, poking it, prodding it and generally chopping it into little bits and examining it, shows inconsistencies, omissions and errors.  Looking from different angles generally shows up ‘stuff’.  I don’t know if this will matter but at least looking at it with ‘fresh eyes’ has to be a good thing.

Anthony Watts’ today mentions a new approach – the Berkeley Earth Surface Temperature project (BEST).  He expresses confidence in their methods and says:

But as the famous saying goes, “there’s more than one way to skin a cat”. Different methods yield different results. In science, sometimes methods are tried, published, and then discarded when superior methods become known and accepted. I think, based on what I’ve seen, that BEST has a superior method. Of course that is just my opinion, with all of it’s baggage; it remains to be seen how the rest of the scientific community will react when they publish.

WM Briggs, also discussing BEST, makes a very good point about the treatment of uncertainty in predictive vs parameter based statistics. In a linked post which I have now read several times (Global Average Temperature: An Exceedingly Brief Introduction To Bayesian Predictive Inference)  there is quite an insight into the traps and pitfalls that analysis of climate data has fallen into (and I gained more insight with each reading).

We all await the BEST output with interest, not least because the GISS, NCDC and CRU analyses are so closely related that one can only worry about the fitness of their offspring. New blood is needed – new ideas and a lack of groupthink.  If it is possible to ‘walk around’ the data and, seeing it from all angles, still come to the conclusion that the warming is something to worry about and that man-made “CO2 did it” then so be it.  I remain to be convinced.