Assessing Garnaut’s recommendations

I dis­agree with the rec­om­men­da­tions of the Review because it bases its apoc­a­lyp­tic assess­ments (Table 5.1) on cli­mate mod­els whose pro­jec­tions, so far, are appar­ent­ly false. If the ques­tions posed by cli­mate change are about sci­ence (they are), then we must address the­mas sci­en­tif­ic ques­tions. The only way to do that is to fol­low the Galilean empiricist’s roy­al road.

  1. Form an hypoth­e­sis (the IPCC’s AGW hypoth­e­sis, for exam­ple);
  2. Makepre­dic­tions based on the hypoth­e­sis (the IPCC’s 2007 Assess­ment Report, for exam­ple), and;
  3. Test the pre­dic­tions against the facts.

There’s noth­ing nov­el about this. It works for sim­ple prob­lems (like geo­cen­trism) and equal­ly well for ‘dia­bol­i­cal’ prob­lems like cli­mate change (Review Report Chap­ter 1) or quan­tum mechan­ics.

The empir­i­cal evi­dence rel­e­vant to the IPCC pro­jec­tions appears to show that their hypoth­e­sis about glob­al warm­ing is false. The tem­per­a­ture ris­es that their mod­els project have not hap­pened, despite the high­er-than-pro­ject­ed eco­nom­ic growth rates and CO2 emis­sions to which the Gar­naut Report referrs. The data over the peri­od 2001–2008 falls out­side (below) the two-stan­dard-devi­a­tions range for their mod­el pro­jec­tions. While they are pro­ject­ing a trend in this decade of 2°/century the trend since the start of their pro­ject­ed peri­od is -1.1°/century. This is most clear­ly illus­trat­ed by Lucia Lil­je­gren here although her orig­i­nal work is here.

These results make the case for the IPCC AGW mod­el look very doubt­ful. The IPCC may still be right that the globe will warm at an alarm­ing rate; but there is now very lit­tle rea­son to be con­fi­dent in this pro­jec­tion and, accord­ing­ly, very lit­tle rea­son to take dras­tic action that will harm our econ­o­my and wealth in response to the IPCC view.

I am sure many peo­ple feel unease, or maybe scorn, for the idea that an elab­o­rate ‘sci­en­tif­ic con­sen­sus’ on AGW, con­struct­ed over 20 years, that claims wide­spread sup­port could be over-turned by a sim­ple sta­tis­ti­cal pro­ce­dure. But here’s the nub of the prob­lem: the IPCC case is unusu­al­ly vul­ner­a­ble to a sta­tis­ti­cal weak­ness­es because it has lit­tle oth­er than mod­els and hypothe­ses drawn from the time-series to offer. Their AGW case turns on a mech­a­nism derived, in their lat­est (2007) report by sub­trac­tion, as Ross Garnaut’s report points out (Sec­tion 5.1.5). They say, in essence: “if you remove forc­ings relat­ed to human activ­i­ty then there’s no warm­ing in our mod­els. So warm­ing must be due to human activ­i­ty. QED”. Their actu­al culprit—as the Review Report briefly acknowl­edges at Sec­tion 3.3.1—is not CO2: it’s water-vapour which dri­ves the green­house effect in a feed­back-looped rela­tion­ship to CO2. The IPCC does not have phys­i­cal evi­dence to demon­strate that this feed-back is suf­fi­cient­ly pow­er­ful to be the cause of recent warm­ing. The only evi­dence they have is their mod­els; which is OK if the mod­el pro­jec­tions are con­firmed. But, if the IPCC mod­els aren’t get­ting it right, then their mod­el-derived mech­a­nism starts to look ques­tion­able at best.

I do not say that this means the asser­tion of glob­al warm­ing is wrong. Every empiri­cist has to acknowl­edge that things that hap­pen only 5% of the time (actu­al tem­per­a­tures falling out­side the 2σ bounds of the IPCC pro­jec­tions) are in fact like­ly to occur 5% of the time. There is a very small chance that the IPCC’s mod­els are still on track, and even if they weren’t there is no doubt that it’s been warmer recent­ly than, say, in the 1950s. You don’t need a mod­el to tell you that.

But the fal­si­fi­ca­tion of the pro­jec­tions by the tem­per­a­ture data only adds to a grow­ing body of pub­li­ca­tions by sci­en­tists with sound rep­u­ta­tions that the CO2 sto­ry is a crock that may be divert­ing atten­tion from much more impor­tant fac­tors in the cli­mate. I have been espe­cial­ly impressed recent­ly by the data pre­sent­ed in this arti­cle by Zbig­niew Jaworows­ki, a researcher with spe­cif­ic expe­ri­ence in the mea­sure­ment of CO2 in the paleo-cli­mate. But there are many oth­er trou­bling crit­i­cisms of the cen­tral AGW the­o­ry.

One final point, for now. The Gar­naut Review Report appropriately—and at some length—acknowledges both the chal­lenge of man­ag­ing pub­lic pol­i­cy under uncer­tain­ty (Chap­ter 2) and the over­lap­ping uncer­tain­ties in the IPCC AGW the­o­ry (Chap­ter 3). So am I just belly­ach­ing because they don’t come to the same con­clu­sion that I do? My answer is ‘no’. The con­vic­tion (whether on faith or on the ‘bal­ance of prob­a­bil­i­ties’) that the AGW the­o­ry of the IPCC is cor­rect per­vades the assess­ments in the report, weak­en­ing its con­sid­er­a­tion of both kinds of uncer­tain­ty. In brief:

  1. The Report, in my view, is so inter­est­ed in the most extreme pre­dic­tions of this the­o­ry being valid that dread over­whelms the assess­ment of the appro­pri­ate pub­lic pol­i­cy response in Chap­ter 2. I agree with a lot of things in this chap­ter, includ­ing the con­clu­sion that it is sen­si­ble to do some­thing now. But the Report’s assess­ment is col­ored, at every point, by the con­vic­tion that at one end of the risk dis­tri­b­u­tion is an illim­itable dis­as­ter of our own mak­ing that is real­ly impend­ing. The Report seems inca­pable of mak­ing a cool eval­u­a­tion of the uncer­tain­ty.
  2. The assess­ment of the uncer­tain­ty about the mech­a­nisms of AGW warm­ing in Sec­tion 3.5 (fig­ure 3.9 illus­trates) is rel­e­vant only if the under­ly­ing theory—the basic pre­miss of dom­i­nant human forc­ings due to the CO2-water vapor cycle—is valid. Just as it doesn’t real­ly mat­ter how Phlo­gis­ton is incor­po­rat­ed in com­bustible mate­ri­als, so the uncer­tain­ty in the AGW mech­a­nisms is moot if the expla­na­tion is wrong (which is what the data is now telling us).

For anoth­er time: what we should do now to mit­i­gate the risk and what role mul­ti­lat­er­al agree­ments will play in that mit­i­ga­tion strat­e­gy.

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