All Party Parliamentary Climate Change Group Is a Cross-Party ...

consequences of climate change over the next twenty, forty, a
hundred, thousands of years, what the significance of those
are for different groups of societies, different individuals in
society, are actually much more contested. So I think it is
much harder to converge on a single consensus and accept
what the consequences are for society, although again the
IPCC does make some effort to move in that direction.
PROFESSOR PIDGEON: Chris, I think you had some
comments in your written evidence on climate sensitivity. I
thought it was interesting that, regarding the climate system,
you made a statement that the 2 to 3 degrees may be higher
or there was a chance that it may be higher? Can that be
related to the forthcoming IPCC report?
DR WEST: Yes. I think the IPCC report will give a figure --
it will be hidden away in tables -- for the sensitivity; a
theoretical number that says what the global temperature does
with doubling of carbon dioxide. A hundred years ago it was
said to be between four and six. I think now people are
coming to a figure somewhere between two and three,
somewhere near there, but interesting results at the Exeter
conference a year ago suggested it was possible that the
sensitivity is much higher. I think that is a risk that is not
zero. There is a significant risk that it is higher. I would put
this in the category of uncertainties as opposed to facts which
cover, if you like, the causes and the causal relationship
between greenhouse gases, temperature rise, sea level rise,
changed climate systems, that is a quantification of all of that
of which the sensitivity of the climate system is one that, if
you like, we are approaching better and better knowledge, but
clearly we will not know what it is until it happens, if then. I
think, more importantly, there are the other uncertainties in
that sort of sensitivity of the human system to climate
change, which we do not have either any experimental
evidence for or any modelling evidence for. As Mike says,
that is very much harder to project forward. Then I think
there are uncertainties of yet another sort where we know --
this is a Donald Rumsfeld known/unknown. There are bits in
the climate system that can switch from one state to another.
What we do not know is when or how likely it is. Of course
there are the same sorts of state functional changes possible
in human systems, and I do not think we have begun to think
what those changes might mean.
PROFESSOR PIDGEON: Can you just give us a couple of
examples of both types; the climate ones?
DR WEST: A known/unknown, if you like, the North
Atlantic circulation partly driven by salinity drawdown off
Greenland. We know that in the past that circulation has
collapsed. We anticipate it is possible it collapses again. We
do not know how it might collapse -- it has been very hard to
recreate it in models -- but it is a possibility. Most models
show the flow diminishing but not stopping. If it stopped
that would be a very serious consequence. So we know
something about what it would be like if it happened, but we
cannot say anything about when or how likely it is to happen.
On the unknown unknowns on the human side; if we look at
a country like Bangladesh, which clearly is vulnerable to sea
level rise, at some point it is possible that the population no
longer put up with increased frequency of flooding and they
want to move somewhere else. May be that number of
people moving to higher ground has global geopolitical
consequences. It is a very difficult thing to investigate.
DR PARR: Could I just add a couple of comments about the
role of uncertainty in policy? My observation on the way
that the climate debate is often carried out is that the level of
certainty that seems to be sought is of a completely different
order of magnitude -- well, no, that is wrong -- but it is very
different from the sort of certainty that is expected for other
policy interventions. For example, what is the evidence base
for assuming that all class sizes in a school should be below
thirty? That is an established policy or has been an
established policy for the Labour Party. What, one might
mischievously ask, is the evidence for weapons of mass
destruction being in particular countries? What is the
evidence that certain forms of taxation stimulates certain
forms of behaviour? On many of these issues there are
actually uncertainties that seem to me to be way beyond the
uncertainties in terms of climate science . I talk here about
policies demanding mitigation rather than adaptation policies
because I think that my two colleagues have suggested they
are a different order of magnitude there. My point is that
somehow there seems to be a search for complete certainty
where it feels to me to be an inappropriate search for
certainty given that, broadly, we know that there are some
unpleasant things going to happen as a result of climate
change, and certainly our belief is that it is one of the greatest
threats to human society that there is.
PROFESSOR PIDGEON: That led on to the next question
we were interested in, which is do we need more science?
Well, we do need more science; that is a rhetorical question.
But, on the climate side, do we need more science or do we
actually need to act now? Has the balance shifted radically in
the last five years or so?
DR PARR: My view would clearly be that we need to act
now. I am certainly not saying we do not need more
research, in some cases, of a very different kind. We need
more research, but we clearly need action. Action is far more
important this point. We have the evidence base that we need
to say we need to do something.
PROFESSOR PIDGEON: Do the others have a view on
that?
DR WEST: I would support that: we have enough evidence
to act. Whether we have enough evidence to say how much
we should act, that is harder to say, but at this point in time
the action we have does not look like enough. It would be
hard to go much further than that.
PROFESSOR PIDGEON: Thank you. In a sense that leads
on to the next question that we were interested in. Given that
--
PROFESSOR WHITBY: Mike, you did not comment on
that. Do you agree?
PROFESSOR HULME: Just on the uncertainty? On
research versus action?
PROFESSOR PIDGEON: Yes.
PROFESSOR HULME: I think there is scientific evidence
that humans are often confused in ways that are potentially
damaging, or even, if they are not potentially damaging, at
least in ways that potentially society needs to respond to in
order to continue to sustain the sort of economic and social
functions that we currently have. That evidence is clear that
in some way, shape or form is necessary. I think that the
problems come -- and this is obviously what we lead on to
later on -- in actually deciding what are the appropriate types
of responses. Are they ones that can only be addressed
globally? Are they ones that actually can be implemented on
much more local scales? I think, in reality, the climate is
changing, humans are implicated, and that challenges a huge
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