Do the math, PM

Estimates of Global Mean Sea Level changes

The Prime Min­is­ter wants to re-engage with the evi­dence. Good! But she is appar­ent­ly unable to read the advice of her own “experts”. Or add-up: 

…Glob­al warm­ing will see seas rise by pos­si­bly up to a metre by the end of the cen­tu­ry — that’s a huge risk to many parts of our coun­try” Extract from Julia Gillard’s 4 July press con­fer­ence, quot­ed in The Australian

Sev­er­al nation­al sci­ence author­i­ties includ­ing CSIRO have esti­mat­ed the glob­al mean sea lev­el (GMSL) rise since 1992—when the cru­cial satel­lite mea­sure­ments began— to be approx­i­mate­ly 3.2 mm per year. That works out at 29 cm by the year 2100; or just under one foot in the impe­r­i­al scale. Not even close to a metre. 

Yes, sea-lev­el varies from place to place: but that is irrel­e­vant to the case for a Labor/Greens coal tax. The pro­posed tax address­es a glob­al emis­sions “prob­lem” because there is no way to affect the local atmos­pher­ic com­po­si­tion or the local sea-lev­el.

Note, inci­den­tal­ly, the incon­ve­nient side­ways track in graph for the past few years? Warm­ing of the top lay­ers of the ocean has slowed to a stop since about 2001. It may even­tu­al­ly resume warm­ing because the cli­mate is vari­able over mul­ti-decade peri­ods (ho-hum!).

Update: In Ques­tion Time, today, the PM accused the Mem­ber for Hasluck (Ken Wyatt) of ask­ing a ques­tion about the Labor/Green coal tax in which he “made up the num­bers, in order to fright­en the Aus­tralian peo­ple”. Oh the irony!


  1. Do the Eng­lish Peter?  Shouldn’t that be ‘do the maths’?

    Any­way you seem to have a pret­ty thin grasp of the maths your­self — for starters the state­ment was ‘up to’, and if i’m not mis­tak­en any­thing less than 1m is also ‘up to 1m’.  And past trends do not relate direct­ly to the future, if evi­dence points to accel­er­at­ed warm­ing, then you would need to mul­ti­ply the rate and not use it directly.

    Every­one seems to have per­fect arith­metic when it comes to petrol prices or inter­est rates but seem to go a bit thick when it comes to sci­ence or push­ing their own barrows.

  2. Hi Mike,

    You and I agree on your last para 🙂

    As for “up to 1m”… On that log­ic it could be “up to 1km”, too. I think it would have been more rea­son­able of JG to have said “up to 30cm” or even, “up to 1 foot.”

    Accel­er­a­tion of the sea-lev­el rise? Where? Do you see any accel­er­a­tion in the CSIRO data I referred to? The oppo­site seems to be true, for rea­sons to which I referred in the post. I believe the PM was quot­ing Will Stef­fen, who is a ded­i­cat­ed hyperbollist.

    As for “math”, my OED recog­nis­es the word as a 19th Cen­tu­ry abbre­vi­a­tion of “math­e­mat­i­cal” (it doesn’t recog­nise ‘hyper­bolist’).



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