Sunday, December 02, 2012

How scientists pull the wool over the eyes of the public 

A study just out in "Science" has already been ingested by media outlets all over the world and then pooped out in considerably altered form.  Why it has been taken so seriously is a bit of a mystery as it is in fact pretty run of the mill stuff.

It has been taken as "proving" human-caused warming but in fact it didn't address human influence at all!

What the article does is a type of meta-analysis:  It tries to combine ALL the information on the subject to produce a more reliable conclusion than any single study could do.  Such studies are often relied on in the medical literature due to the deluge of conflicting claims there.

As it happens, I know a little bit about meta-analyses and know how important goodwill is to their usefulness.  To put it bluntly, you can prove just about anything you like in a meta-anaysis by what you select to include.  Selecting the date from which you begin to assemble data is a classic dodge  -- and one that seems to have been used in the present study -- but it gets as crude as  ignoring hundreds of articles and datasets that you simply dislike.

So a good, sincere and unbiased attitude in the researcher is vital.  If you start off with (say) a Warmist bias you will usually produce Warmist results.

As it happens, the bias readily apparent in the present study is mild.  It seems to show only in the chosen starting point for the analysis.  Why 1992 and not (say) the beginning of satellite measurements in 1979?  1992 must just have produced the best results.

But, even so, the results are not spectacular.  As one summary put it:

In case that's still not clear, the sea-level rise they assert is tiny and even if it continued in a steady way (most unlikely given past known variations in polar ice) it would take 100 years or more to become noticeable.

So the only way in which the study is notable is its claim to produce pooled wisdom  -- and how influential that claim is depends very much on how much we believe in the objectivity of the researchers.  As they would not be in their jobs if they were global warming skeptics,  believing in their objectivity would be quite heroic.  It's just another dodgy appeal to authority

I append the journal abstract.













Consequently, researchers don't yet know exactly how much of the ice-sheet melt is caused by a warming atmosphere and how much by a warming ocean.  [That's easy.  There has been NO significant atmospheric warming in the atmosphere over the study period]








The shrinkage of the permanent ice sheets can't entirely be explained by any of the decades-long or century-long natural shifts in climate cycles, according to Prof. Shepherd.




A Reconciled Estimate of Ice-Sheet Mass Balance

By Andrew Shepherd et al.



Science 30 November 2012, Vol. 338 no. 6111 pp. 1183-1189


1 comment:

Doom said...

I finally made purchase of the book you suggested some while back, regarding statistics. Now, I had a general knowledge of the statistical shenanigans to start with, but this adds tools and specifics. Some harsh statistic courses, an interest, and too many grad and post-grad friends who were just as serious set me on the right path. The problem is? No matter how well you explain it, most people can't, won't, or just don't, grasp the explanation.

Isn't double the risk the same no matter where it is doubled? Well, no... Let's take a look at the... *zzz* Yeah, okay, we'll get back to that... later. Neither, I think, do most care. As long as they get their check next Friday. So Friday comes, and they go to the bar, and they order a scotch, a whiskey, and uhm beer. A triple shot of that stuff. Next! Don't even think even more than a handful of "academics" are any better than Joe-down-the-street, either. Bleh.


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