Wednesday, 19 December 2012

IPCC AR5 - is the truth finally slipping out?

WG1 chapter 1 contains the following graphic (click to enlarge)

Figure 1.11: Estimated changes in the observed global annual sea level since 1990. Estimated changes in global annual sea level anomalies from tide gauge data (Church and White, 2011; available at (black error bars showing 1s uncertainty) and based on annual averages from TOPEX and Jason satellites (Nerem et al., 2010; available at (blue dots) starting in 1992 (the values have been aligned to fit the 1993 value of the tide gauge data). The shading shows the largest model projected range of global annual sea level rise from 1990 to 2015 for FAR (Scenario D and business-as-usual), SAR (IS92c and IS92e), TAR (A2 and A1FI) and for Church et al. (2011) based on the CMIP3 model results available at the time of AR4 using the SRES A1B scenario.

A couple of things immediately struck me; first that the blue dots (annual average from TOPEX and JASON) show a tailing-off on the right (2011) to almost exactly 5cm above the 1993 value of a smidgen (that's a technical term used by us statistical experts [ha! - ed.] for a very small quantity) above zero. That gives 5/19 = 0.263 or 2.63 mm/year, rather less than the 3.2 mm/year over the satellite era (since the beginning of 1993) we've been fed to date. In order to get that 3.2 rate, the 2011 value would have to be 6cm above that for 1993 which clearly it's not. I think they've got a cheek assigning a zero value to 1992; observations didn't start until well into the latter half of that year.

Small potatoes maybe but is the truth (or something approaching the truth) finally slipping out?

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