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[New at realclimate.org] Exeter conference: Avoiding Dangerous Climate Change

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  • Pat Neuman
    7 Feb 2005 Exeter conference: Avoiding Dangerous Climate Change http://www.realclimate.org/ — william @ 6:29 am The conference last week in Exeter on
    Message 1 of 1 , Feb 7, 2005
      7 Feb 2005
      Exeter conference: Avoiding Dangerous Climate Change

      — william @ 6:29 am

      The conference last week in Exeter on "Avoiding Dangerous Climate
      Change" grew out of a speech by UK Prime Minister Tony Blair. He asked
      "What level of greenhouse gases in the atmosphere is self-evidently
      too much?" and "What options do we have to avoid such levels?". The
      first question is very interesting, but also very difficult. As Roger
      Pielke has noted the conference organisers actually choose three "key

      1. For different levels of climate change what are the key impacts,
      for different regions and sectors, and for the world as a whole?
      2. What would such levels of climate change imply in terms of
      greenhouse gas stabilisation concentrations and emission pathways
      required to achieve such levels?
      3. What technological options are there for achieving stabilisation
      of greenhouse gases at different stabilisation concentrations in the
      atmosphere, taking into account costs and uncertainties?

      It is worth thinking about the difference between the initial aim and
      the "key questions" chosen. Question 1 is essentially IPCC impacts);
      question 2 is firmly WGI (how-much-climate-change); question 3 is
      fairly WG III (mitigation, including technical options). I guess they
      switched questions 1 and 2 round to avoid making the identification
      too obvious. The conference steering committe report makes it very
      clear that they are building on the IPCC TAR foundation.

      All in all it would seem that the bold vision of the politicians has
      been tempered by the conference organisers into something more
      manageable - a set of questions that can be discussed within the usual
      scientific framework and by the usual people. And probably that was
      sensible, because the initial question really is very hard - not
      merely because all the science isn't in, but because even if it was
      what is "dangerous" is probably a political rather than scientific
      question. And this was a largely scientific meeting.

      So, whats new? On the impacts front, the final report says that there
      is more clarity and less uncertainty since the TAR, which is what you
      would hope for after 4 years of research. They identify a few
      "thresholds" that are dangerous for certain processes - 2.7 oC local
      for melting Greenland; coral bleaching above 1 oC global. Extremes,
      and the 2003 european heatwave get a mention. On climate change, they
      note that restricting the global temperature change to 2 oC with a
      fair degree of confidence would require stabilisation at 400 ppm CO2
      equivalent (CO2 itself is at 380 already, but "equivalent" includes
      other GHG's and the negative effects of sulphates; see here for more).
      If you were prepared to accept more risk of exceeding 2 oC then 550
      ppm would be possible. For technical options, they note that the IEA
      predict a 63% increase in CO2 levels by 2030, in line with IPCC
      estimates. There are a whole raft of options that could be taken
      to reduce emissions, and they do mention the word "nuclear".

      All in all, it looks like progress as normal. In summary, they note
      that work is needed on both mitigation and adaption - which is to
      recognise that climate change is occuring and will continue, although
      possibilities for slowing it exist.

      To pick out some of the science, there is the perennially interesting
      "will global warming cause cooling" bit that people love so much
      because it seems paradoxical. This is the "thermohaline circulation
      (THC) shutdown" or slowdown, caused by freshening of the North
      Atlantic. Of course it wouldn't (at its worst) lead to global cooling,
      it would mostly impact Northern Europe. And the IPCC TAR said even in
      models where the THC weakens, there is still a warming over Europe
      (because the overall warming outweights the local cooling). This still
      seems to be true. The conference was presented some results showing
      what happens if THC shutdown is artifically induced (by Richard Wood),
      and various attempts to explore the probability of a collapse, but
      coupled AOGCMs seem to be quite resilient to a total collapse. From
      impacts, they mention that "resilient" societies are better able to
      survive climate stresses - for example, they downplay the
      oft-mentioned risk of malaria spreading under increasing temperature:
      the increase expected is small compared to the total number; all it
      means is that existing efforts to combat malaria should be strengthened.

      And finally, since it gets a mention in the report, there are two
      possible errors to make, apparently labelled Type 1 and Type 2. Type 1
      is excess caution, leading to damage by unnecessary action restricting
      development. Type 2 is insufficient action, leading to damage from
      climate change. In the face of uncertaintly, it is very hard to steer
      a true path avoiding these two errors, but it appears that we should
      be tilting towards taking action.

      The conference generated a lot of press coverage (thanks Het). Nature
      said UK climate meeting calls for action; New Scientist said
      Climatologists pursue greenhouse gas danger levels and Only huge
      emissions cuts will curb climate change. The BBC told us of
      Scientists' grim climate report, that "The risks from global warming
      are more serious than previously thought". The Guardian warned of A
      grim assessment of the global cost for each degree rise in temperature
      and the Manila Times says Evidence indicates climate change already
      here, which is a mild strengthening of what the IPCC TAR told us. The
      reporting seems reasonably fair - slightly sexed up headlines, as
      usual, but the text of the articles quite faithful to the conference.

      1 Comment »


      From the article:

      "So, whats new? On the impacts front, the final report says that
      there is more clarity and less uncertainty since the TAR, which is
      what you would hope for after 4 years of research."

      How much more clarity? I would like to see more regional climate
      change evidence. For example:

      "Trends showing earlier snowmelt runoff in the Upper Midwest"
      and at:


      Comment by Pat Neuman, Hydrologist — 7 Feb 2005 @ 6:47 am
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