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Floods are manmade, you say now?

Posted By Joanne Nova On February 21, 2011 @ 2:27 am In Global Warming | Comments Disabled

Flood Marker in Rome 1598, when CO2 levels were extreme-(extremely low). Photo by Anthony M.

After twenty years of drought predictions that turned out to be not worth a rhinestone rune-stone,  the acolytes of the scare campaign were keen to find some evidence that they were still “right”. Two new papers came along showing that, golly, warming really “formally” “officially” caused floods after all, and they were just what the PR-doctor ordered. So the BBC, ABC, and the usual suspects rushed out to talk about how it was now “proven” that any flood was now officially man-made with a “robust” study and the “first scientific evidence” of a link. Richard Black even got excited that the study was based on “real world data”, which makes you wonder which studies used the fake sort?

If it’s all so definitively proven and obvious now that it’s a shame they didn’t think to join these dots, say, two years ago, so they could warn the world beforehand. It must be frustrating for them that they always seem to get the forecasts right two years too late. It’s another post hoc “prediction”.

And what are these two (TWO! shouted the believers) papers based on (AND don’t forget they’re from Nature)? The new-found certainty comes from about 50 years of records, interpreted by climate models, with those results then fed into precipitation models (just to magnify the error-margins even further). The handy thing about models is that if you try hard enough you can get nearly any result you want.

The Pall et al, 2011, abstract sums it up:

Here we present a multi-step, physically based ‘probabilistic event attribution’ framework showing that it is very likely that global anthropogenic greenhouse gas emissions substantially increased the risk of flood occurrence in England and Wales in autumn 2000. Using publicly volunteered distributed computing11, 12, we generate several thousand seasonal-forecast-resolution climate model simulations of autumn 2000 weather, both under realistic conditions, and under conditions as they might have been had these greenhouse gas emissions and the resulting large-scale warming never occurred. Results are fed into a precipitation-runoff model that is used to simulate severe daily river runoff events in England and Wales (proxy indicators of flood events). The precise magnitude of the anthropogenic contribution remains uncertain, but in nine out of ten cases our model results indicate that twentieth-century anthropogenic greenhouse gas emissions increased the risk of floods occurring in England and Wales in autumn 2000 by more than 20%, and in two out of three cases by more than 90%.


Note that what we are not seeing here is an empirical study that found a correlation between past high CO2 era’s and more floods.  That is difficult to get (and it’s absence doesn’t prove anything) but skeptics can point to those kinds of studies, for example, to show how cold periods kill more people.

We’re also not seeing one particular model which repeatedly has predicted (and in advance too) floods in England with a better-than-average ballpark accuracy — like Piers Corbyn has done with other events for over a decade.

Even the IPCC admits the climate models know not-much when it comes to predicting rainfall on a regional basis.

“The precise magnitude of the anthropogenic contribution remains uncertain” they say. I agree. It could be zero or something more, and it may or may not be related to CO2.

Seung-Ki Min et al 2011, in a similar vein says:

Here we show that human-induced increases in greenhouse gases have contributed to the observed intensification of heavy precipitation events found over approximately two-thirds of data-covered parts of Northern Hemisphere land areas. These results are based on a comparison of observed and multi-model simulated changes in extreme precipitation over the latter half of the twentieth century analysed with an optimal fingerprinting technique. Changes in extreme precipitation projected by models, and thus the impacts of future changes in extreme precipitation, may be underestimated because models seem to underestimate the observed increase in heavy precipitation with warming

Like all unskeptical scientists of the IPCC-ilk, they argue from ignorance:

“We can now say with some confidence that the increased rainfall intensity in the latter half of the twentieth century cannot be explained by our estimates of internal climate variability,” she says.

Nature allows an editorial writer to proffer an opinion that couldn’t possibly ever, in any known universe, be substantiated: “There is no doubt that humans are altering the climate….

Nature is not too scientific, but it does make a good advertorial newsletter for the eco-industrial-activists.

So the new “flood certainty” is based on the same models that get the upper tropospheric temperature trends wrong, disagree with 28 million weather balloons, 6000 boreholes, 3,000 ARGO floats, have little predictive success, don’t hindcast the medieval warm period, the holocene, or anything else much, and don’t match the empirical evidence, except with post hoc reanalysis. These were the same models that we relied on to build  desalination plants we didn’t need; to avoid building levees and dams that we did.

It brings to mind the saying that’s fast becoming a cliche: “It’s tough to make predictions, especially about the future.” (Attributed variously to everyone from Bohr, to Einstein, Sam Goldwyn, Mark Twain, Churchill, Confucius, and also Yogi Berra).


Pardeep Pall, Tolu Aina, Dáithí A. Stone, Peter A. Stott Toru Nozawa Arno G. J. Hilberts, Dag Lohmann & Myles R. Allen, 2011: Anthropogenic greenhouse gas contribution to flood risk in England and Wales in autumn 2000. Nature vol 470, pp 382–385 DOI:doi:10.1038/nature09762

Seung-Ki Min et al 2011, Xuebin Zhang, Francis W. Zwiers, Gabriele C. Hegerl 2011: Human contribution to more-intense precipitation extremes, Nature, vol 470 , pp 378–381

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