Un-natural variability


Extraordinary persistent rainfall is behind the flooding in the UK.

As with Russia and Pakistan 2010, Texas 2011, and Australia pretty much constantly for the last decade, this is so far out of the ordinary that “natural variability” seems inadequate as an explanation. How many freak seasons do we need before we say there’s a pattern?

Thanks to Dan Olner for the pointer and the UKMO for the image.

Figure 8(b) on the Right

Screen shot 2013-09-29 at 1.21.09 PM

I’ve just had my first look over the first and most important piece of IPCC AR5. I think an exposition for the previously inattentive is in order, but that will take some time. At Planet3.0, we mostly leave the fast news to others.

As someone who was fairly well steeped in the community a decade ago, the image which most struck me as novel was the right half of figure 8(b), which shows increased detail of the prognosed precipitation anomaly in the 2081-2100 period under a high emissions scenario.

It’s a nice, high-information figure.

The orange colors indicate drying, and the blues and greens, moistening (in percentage change in annual precipitation, ranging in 10% bands from over -30% to over +50%. (That is (-30%, … -20%), (-20%, … -10%), … (+50%, … +60%] )

The stripes indicate where the change is small compared to variability and/or the sign is disputed among models used. The dots (“stipples”) indicate where the change is not small and 90% of the model runs agree. The extreme wetting outside the equatorial convergence zone occurs in a couple of very dry places and may just be a sort of noise. In any case those areas are sparsely settled.

The most salient feature over populated areas is the extraordinary drying out of the Mediterranean.