The Impacts and Costs of Climate Change

The Impacts and Costs of Climate Change
Figure 13. Social Cost of Climate Change responses grouped as low, medium & high
temperature change

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Model Analysis with the PAGE Model
The PAGE model, run by Chris Hope at the Judge Institute at the University of Cambridge has been
used to examine a number of different stabilisation targets, as part of work commissioned for this
study.
PAGE2002 is an updated version of the PAGE95 integrated assessment model (Plambeck, Hope and
Anderson, 1997, Plambeck and Hope, 1995 and Plambeck and Hope, 1996). The main structural
changes in PAGE2002 are the introduction of a third greenhouse gas and the incorporation of possible
future large-scale discontinuities into the impact calculations of the model (IPCC, 2001a, p5). Default
parameter values have also been updated to reflect changes since the IPCC Second Assessment Report
in 1995. The full set of equations and default parameter values in PAGE2002 are given in Hope,
2004. Most parameter values are taken directly from the IPCC Third Assessment Report (IPCC,
2001 b). Rather than only give single estimates, PAGE builds up probability distributions of results by
representing 31 key inputs to the marginal impact calculations by probability distributions.
The basic assumptions that go into the model, such as that the economic and non-economic impacts in
the EU before adaptation, are given in the following table
Mean Min Mode Max
Econ impact in EU(%GDP for 2.5 degC) 0.5 -0.1 0.6 1
Non-econ imp EU (%GDP for 2.5 degC) 0.73 0 0.7 1.5
Impact function exponent 1.76 1 1.3 3
And the following climate sensitivity/range:
Mean Min Mode Max
Equilibrium warming for 2xCO2 (degC) 3 1.5 2.5 5
In relation to adaptation, a 2'C rise in temperature can be tolerated before economic impacts in
developed regions occur, and adaptation can reduce these by 90% after 10 years. For economic
impacts in developing regions there is no tolerable temperature rise, but adaptation can decrease the

AEA Technology Environment, August 2005

44

Watkiss, Paul; Downing, Tom; Handley, Claire & Butterfield, Ruth. The Impacts and Costs of Climate Change. Oxford, England. UNT Digital Library. http://digital.library.unt.edu/ark:/67531/metadc29337/. Accessed October 1, 2014.