Climate change, mitigation and adaptation: the case of the Murray–Darling Basin in Australia

water prices and availability. The results of simulation modelling of adaptation
to climate change with and without global mitigation policies are presented in
Section 4. Final comments are presented in Section 5.

1. Global Climate Change

In its Fourth Assessment Report, the IPCC (2007a,b,c) summarizes a wide range
of projections of climate change, encompassing different climatic variables, time
and spatial scales, models and scenarios. Most attention is focused on projections
of changes in global mean temperatures. However, analysis of the impact of
climate change on agriculture requires consideration of regionally specific
changes in a range of variables including temperature, rainfall and the effects of
CO2 concentrations on crop growth.

Even with aggressive strategies to stabilize atmospheric CO2 concentrations at
levels between 400 and 500 parts per million (ppm), it seems inevitable that
warming over the next century will be at least 2 degrees Celsius (C) relative to
the 20th century average.

Thus, for the purposes of policy analysis, the relevant comparison is between
warming of 2 degrees C over the 21st century and the more rapid warming that
may be expected under ‘business as usual’ projections, in which there is no policy
response to climate change. The IPCC (2007a) presents a range of ‘adaptation
only’ projections, in which estimates of warming over the period to 2100 range
from 2 degrees C to 6.4 degrees C, with a midpoint of around 4 degrees C.

The term ‘business as usual’ is somewhat misleading since it implies that
farmers and others will not change their strategies as a result of climate change.
In fact, even if there are no changes in public policy, changes in climate will lead
farmers to adapt, by changing their production plans, or perhaps by leaving
agriculture. For this reason, the term ‘adaptation only’ will be used in preference

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