Dear Jonathan,
These are very much more difficult questions to answer than those in your
previous email. Your first question basically boils down to "How much is
too much?" The answer to that question depends on the values that one
holds. Some radical greens hold that any change whatsoever in nature is
unjustifiable. Many today have vague ideas about "sustainability"; in other
words, we can change nature and use its products provided we do not reduce
the earth's capacity to supply humanity with its needs.
This latter approach (there are many more!) is the one that has come into
favour in political circles as being the definition that does most to
promote economic growth in the long run. So the UN Framework Convention on
Climate Change (UN/FCCC) article 2 (1992) states that:
"The ultimate objective of this convention ... is to achieve ...
stabilisation of greenhouse gas concentrations at a level that would
prevent dangerous antrhopogenic interference with the climate system. Such
a level should be achieved within a time frame sufficient to allow
ecosystems to adapt naturally to climate change, to ensure that food
production is not threatened, and to enable economic development to proceed
in a sustainable manner."
The priorities agreed by the world's nations at the political level seem
very clear! Many climate scientists regard their job as being to develop
the knowledge that will enable us to put those priorities into practice.
For climate scientists, that means understand what the future effects will
be of emitting greenhouse gases (and other pollutants) into the atmosphere.
However, the job of discovering the levels of change that are acceptable as
well as those that are not acceptable require the close involvement of
other disciplines, such as ecology (to tell us what effects a given climate
change will have on agriculture) and economics (to tell us what the costs
are of changes in agriculture, both now and in the future).
In other words, in answer to your question "How much is too much?"... We
don't know. But we are trying very hard to discover all that we can about
the effects of oour pollution, so that those in society to whom we have
entrusted decision-making can be as well informed as possible about the
likely consequences of their actions.
I think that this also begins to answer your question about the way forward
in science concerning this issue. It is a real, genuine issue, with great
practical importance for billions of people. We owe it to the Lord and to
them to discover all that we can about the likely effects of our pollution,
so that we can take appropriate mitigative actions (reducing emissions) and
adaptive actions (building better sea defences, for example).
What do I do? I use models in order to enhance our abilities to predict
what will happen to the climate in the future in specific regions of the
world, rather than over the globe in general. There is more information on
my web site.
regards
Tim
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Tim Mitchell
Climatic Research Unit
post: CRU, UEA, Norwich, NR4 7TJ, UK
email: t.mitchell@uea.ac.uk
web: http://www.uea.ac.uk/~f709762
phone: +44 (0)1603 593161
fax: +44 (0)1603 507784
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