04 April 2011

Global Warming: It's Worse Than You Think

My favorite climate scientist and several of his colleagues have a new paper out on global land surface temperature trends (Montandon et al. 2011).  They perform an interesting analysis in asking the degree to which the spatial distribution of land surface stations is representative of land surface types found on Earth.

They find that the major surface temperature records (i.e., NCDC, GISS, CRU, GHCN) are not spatially representative (see their Figure 2 above).

What happens if you weight the land surface record to account for this bias? Their preliminary result (which they emphasize is preliminary) is that land surface trends would actually increase if properly weighted. If this is the case then it potentially presents a headache for the climate modeling community because it would exacerbate the divergence between land surface and tropospheric trends that we documented in Klotzbach et al. 2009 (see this, this, and this).

Does this study have policy implications? Not for me, but it does show that there remain interesting scientific questions to ask and maybe surprises yet to be found in the greenhouse.

6 comments:

Abdul Abulbul Amir said...

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What this says in spades, is that climate "science" is way too immature and untested to trust when making weighty decisions.

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DeWitt said...

Doesn't that analysis beg the question of how confident we are in the trends in the under sampled regions. If you change the weighting to increase the representation of under sampled regions, you're bound to increase the confidence limits so it's not at all clear that a new trend would be statistically significantly different even if it's nominally higher.

Roger said...

About ten years ago, back in my “denier” days, I spent a lot of time analyzing GISTEMP records in a determined attempt to prove that the GISS global surface air temperature time series was wrong. But try as I might I always got the same answer as GISS, so eventually I was forced to admit that the GISS series was substantially correct. There’s nothing in the Montandon et al. results that would cause me to change this opinion, so my conclusion is still that global warming isn’t any worse than we think - provided we look only at surface air temperatures.

But while everyone in the blogosphere fixates on a surface air temperature series that probably has nothing much wrong with it the big problem - sea surface temperatures - continues to be ignored. There are in fact good reasons to believe that existing SST series understate sea surface warming since 1940 by 0.3-0.4C, which if so would indeed make global warming look a lot worse (although I hasten to add that it wouldn’t necessarily make the case for AGW any stronger - it would just mean that we understand it even less than we think.) It might even have some policy implications too.

markbahner said...

"About ten years ago, back in my “denier” days, I spent a lot of time analyzing GISTEMP records in a determined attempt to prove that the GISS global surface air temperature time series was wrong."

Why even bother with the global surface temperature record...at least since 1979, when the satellite measurements have been available?

DeWitt said...

While the satellite record is in nominal agreement with surface records, that's a problem in itself. The atmosphere should be warming faster than the surface. Making the surface warmer makes that discrepancy worse. The real problem may be that SST measurements don't, in fact, measure the surface temperature. They measure the temperature some distance below the surface. That was true even in the bucket days. The actual surface is about the same as the subsurface at night, but is cooler during the day.

Roger Pielke, Jr. said...

-3-Roger et al.

Someone emailed to ask if your comments were made by me ... no, that Roger is not this Roger.

I comment as "Roger Pielke, Jr.".

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