From The Garnaut
Report
2. The Climate Science
Climate change policy must begin with the science. When
people who have no
background in climate science seek to apply scientific
perspectives to policy, they
are struck by the qualified and contested nature of the
material with which they have
to work. Part of the uncertainty derives from the
complexity of the scientific issues.
Part derives from the enormity of the possible
consequences of anthropogenic
global warming, which encourages a millennial perspective
on it. Part derives from
the large effects of possible policy responses on levels
and distributions of incomes,
inviting intense and focussed involvement in the
discussion by vested interests.
2.1 A growing body of evidence that the world is warming
The Intergovernmental Panel on Climate Change (IPCC)
Fourth Assessment Report
(2007), recognised an improvement in the scientific
understanding of anthropogenic
influences on climate change, and concluded that the
warming of the climate system
is ‘unequivocal’, and that there was a ‘very high
confidence’ - a greater than 90 per
cent chance – that ‘the global average net effect of
human activities since 1750 has
been one of warming’1.
There is statistical evidence that the global temperature
has been on an upward
trend in recent times. This would seem to confirm the
science that anticipated such
warming as a result of increased concentrations of
greenhouse gases. However,
some people with relevant scientific credentials (and
many who lack them) argue
that the warming trend may be mainly the result of
factors independent of human
activity that have been responsible for continuously
changing global climate since
homo sapiens have been on earth.
If there were natural as well as anthropogenic
causes of recent global warming, it is not obvious that
this would reduce the urgency
or importance of reducing anthropogenic greenhouse gas
emissions. It could be
argued that the presence of additional sources of warming
actually increased the
importance of early and strong action to moderate the
contributions over which
humans have some control.
Be that as it may, the Review is in no position to
adjudicate on the relative merits of
various expert scientific opinions. The Review has
neither the time nor the resources
to do so. The large majority of the relevant scientific
opinion, and of the leadership of
the learned academies of science in the countries of
great scientific
accomplishment, hold the view that human-induced climate
change is with us, and
that it is already affecting natural and human systems
and will increasingly create
risks to current patterns of human settlement and
activity. The Review takes as a
starting point, on the balance of probabilities and not
as a matter of belief, the
majority opinion of the Australian and international
scientific communities.
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