Expected Changes from Global Warming

Have you noticed a distinct change in the rhetoric around global warming? Seems like revisionism going on in the mainstream media in the form of shift in focus to the most likely values, or expectations of global warming, rather than emphasizing the low probability, worse possible scenario.

For example, this one on sea level from nature.com.

Sea level rise – not so fast.

In the latest salvo of the scientific debate over future sea level rise, a new report counters claims that rapidly swelling seas will soak estimates published by the UN climate planel in 2007.

A major “it’s worse than we thought” story out of March’s Copenhagen Climate Congress, for example, was that sea level could climb more than a metre by 2100 – seemingly far worse than the rise of up to 59 centimetres indicated in the 2007 report from the Intergivernmental Panel on Climate Change (IPCC). This was in fact something of a straw-man comparison, since the IPCC total explicitly excluded the impacts of accelerated glacier melt, and the new studies were attempting to add these impacts in.

But the latest study suggests that even considering glacier effects, the 2100 rise is likely to be well under a metre. A trio of researchers – Mark Siddall of Columbia University in New York, Thomas Stocker of the University of Bern (current co-chair of IPCC Working Group I) and Peter Clark of Oregon State University – used a new method that looks to the past to inform this future projection.

Here is a letter to the Australian, commenting on qualifications by Andrew Ash,

ANDREW Ash of the CSIRO said that a projected 1.1m sea-level rise by the end of the century was “certainly plausible” (“Sea levels threaten 250,000 homes”, 14-15/11). Playing safe, he went on to say that “the only variation will be exactly when we reach that level”. So he’s certain of the level but doubtful of the timing.

In fact, absolutely no one can predict with certainty either what level the sea will reach or the rate at which it will rise. Predictions can be based only on informed supposition, otherwise known as modelling.
Graham Dick, St Ives, NSW

Similar articles here about the sea level frenzy in Australia.

Could it be hoped that the message is finally getting through that exploitation of the long tail of extremely low probability high consequence events is counter productive, damaging to science, and we will start to see more focus on the expected values — the most likely, but less alarming, future?

And are the alarmists going to be off the hook by claiming that ‘worst case scenario’ analysis is a virtue. Maybe not. Below are links to newspaper clipping on a forthcoming article by Stewart Franks, claiming proof that the recent drought in the Murray Darling Basin was not caused by AGW.

here and here.

About the fourth assessmenrt report of the Intelgovernmental Panel on
Climate Change he says:

It seems the physics of evaporation remains misunderstood by those we would hope would understand it the most.

Thanks to cohenite for scans.

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0 thoughts on “Expected Changes from Global Warming

    • Aslak,
      I know there are a number of papers
      using the same general assumptions,
      though the details vary. From my empirical
      perspective I have noted:

      1. There little evidence for ‘acceleration’ of
      sea level WRT temperature. Plot SL and T and
      the best fit is a straight line, suggesting
      empirical support is for SL = aT+c not
      dSL/dt=aT , the rate related relationship
      where sea level rises faster when as it gets
      hotter.

      2. The SL stopped increasing mid century
      just when temperature stopped increasing.
      This suggest at most a 10 year lag is
      justified by the data. Could it also be that
      the current low rate of SL increase is
      because temperature has stopped increasing?
      So if temperature does not increase much
      then SL may not increase much either.

      3. The estimates of 1m are based on IPCC
      projections which are running way too high.
      Current warming after subtracting out PDO
      are about 0.5C Century. Anyway, if IPCC
      projections are high side, the is sea level
      will be too.

  1. Aslak,I know there are a number of papersusing the same general assumptions,though the details vary. From my empiricalperspective I have noted:1. There little evidence for 'acceleration' ofsea level WRT temperature. Plot SL and T andthe best fit is a straight line, suggestingempirical support is for SL = aT+c notdSL/dt=aT , the rate related relationshipwhere sea level rises faster when as it getshotter.2. The SL stopped increasing mid centuryjust when temperature stopped increasing.This suggest at most a 10 year lag isjustified by the data. Could it also be thatthe current low rate of SL increase isbecause temperature has stopped increasing?So if temperature does not increase muchthen SL may not increase much either.3. The estimates of 1m are based on IPCCprojections which are running way too high.Current warming after subtracting out PDOare about 0.5C Century. Anyway, if IPCC projections are high side, the is sea levelwill be too.

  2. Aslak,I know there are a number of papersusing the same general assumptions,though the details vary. From my empiricalperspective I have noted:1. There little evidence for 'acceleration' ofsea level WRT temperature. Plot SL and T andthe best fit is a straight line, suggestingempirical support is for SL = aT+c notdSL/dt=aT , the rate related relationshipwhere sea level rises faster when as it getshotter.2. The SL stopped increasing mid centuryjust when temperature stopped increasing.This suggest at most a 10 year lag isjustified by the data. Could it also be thatthe current low rate of SL increase isbecause temperature has stopped increasing?So if temperature does not increase muchthen SL may not increase much either.3. The estimates of 1m are based on IPCCprojections which are running way too high.Current warming after subtracting out PDOare about 0.5C Century. Anyway, if IPCC projections are high side, the is sea levelwill be too.

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