I meant to write about this particular smoking gun some time ago, but I didn’t want to take away attention from Steve’s travails with the NAS Panel and with Geophysical Research Letters. Willis Eschenbach did the actual replication so really it’s his story.
If you cast your minds back to last year, a modelling study by James Hansen and Gavin Schmidt was touted as yet another "smoking gun" proving that the dire warnings of future warming were justified as they could now model the past – or at least a few years of it.
The BBC was at the forefront of the publicity for this new result.
The Earth is absorbing more energy from the Sun than it is giving back into space, according to a new study by climate scientists in the US.
They base their findings on computer models of climate, and on measurements of temperature in the oceans.
The group describes its results as "the smoking gun that we were looking for", removing any doubt that human activities are warming the planet.
I always find it disturbing that in an experimental setup involving many variables which are as poorly understood as the climate system, the bold scientists should be looking for a particular result and being exultant at finding what they were looking for.
If it was me, and I’d thought I’d got the right answer, I’d know that I’d be asking for a monster custard pie in the face to announce it in such categoric terms if no-one had first checked my work and replicated it. But this is climate science, where replication is not the done thing.
Let’s see what Hanson and Schmidt managed to produce:
Now I try to get excited about this close replication but I’m sure that Dave Stockwell could come up with much better correspondence with his red noise simulations if he wanted to.
However, if you’re going to show that your simulations are robust, then what finer way of doing so than to backtest against someone else’s data, in this case Levitus et al.
Hansen didn’t show that he did this even though he quoted Levitus in his references, but Willis Eschenbach has stepped up and done it for him.
Here’s the backtest:
1. "Earth’s Energy Imbalance: Confirmation and Implications"
James Hansen, Larissa Nazarenko, Reto Ruedy, Makiko Sato, Josh Willis, Anthony Del Genio, Dorothy Koch, Andrew Lacis, Ken Lo, Surabi Menon, Tica Novakov, Judith Perlwitz, Gary Russell, Gavin A. Schmidt, Nicholas Tausnev
http://www.sciencexpress.org / 28 April 2004 / Page 6/ 10.1126/science.1110252
2. "Warming of the World Ocean"
Sydney Levitus, John I. Antonov, Timothy P. Boyer, Cathy Stephens
24 MARCH 2000 VOL 2228 287 SCIENCE
3. Hansen data used in simulation: http://www.climateaudit.org/wp-content/hansen graph data.xls