[New at realclimate.org] Exeter conference: Avoiding Dangerous Climate Change
- 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"
Comment by Pat Neuman, Hydrologist 7 Feb 2005 @ 6:47 am