Geoscience Reference
In-Depth Information
Other impacts are being felt indirectly, for example through pressures on
global food prices from the intensification of extreme weather events (Garnaut,
2011b: 132-3; Tolero, 2011). These have contributed to failures of state stability
in and to displacement of people from some countries and regions, applying
pressures on refugee and immigration policies in many countries.
The range of possible climate outcomes that flow from Australia's and other
countries' mitigation efforts remains wide. There is still a chance that global
mitigation efforts will hold the atmospheric concentration of greenhouse gases
to 450 ppm of CO
2
equivalent, corresponding to a reasonable chance of holding
global warming to something near 2°C.
The climate outcomes from processes initiated at the Copenhagen Climate
Conference in 2009 and taken forward in Cancun in 2010 and Durban in 2011
cannot yet be defined even in broad brush because existing commitments and
promises of future agreements say little about what happens after 2020. They
have been interpreted to suggest that atmospheric concentrations of greenhouse
gases of 550 or 650 ppm are possible - most likely leading eventually to global
average temperature increases of 4°C or more. However, depending on what
we all do next on mitigation, much better and much worse outcomes remain
possible.
There is some uncertainty about the amount of warming associated with
any given increase in greenhouse gas concentrations, and about some of the
important impacts from any extent of warming. This means that Australians now
and in the future face uncertainty about the level of their adaptation challenge.
But for all the uncertainty, when we compare the most likely physical
and biophysical effects of 4°C warming as described elsewhere in this topic
- including shocks of magnitudes that have in the past turned out to be unman-
ageable for modern human social, economic and political systems - planning for
adaptation to a Four Degree World within established state structures seems an
indulgence of fantasy.
So, current adaptation policy is necessarily about preparation for the 2°C
warming - or a bit more - that would be an inevitable accompaniment of
successful global mitigation policies. The rest for now is for hopes and prayers,
and not for policy planning. If our generation fails to mitigate emissions and
bequeaths a temperature increase of 4°C or more to future generations, present
discussions about how they should try to manage their circumstances are unlikely
to be of much worth.
The difference in impact between 2°C and 3°C was examined in detail in the
2008 Garnaut Climate Change Review (Garnaut, 2008:
Chapters 4
,
5
,
6
and
11
). It is large enough for it to be in Australia's interests to make the extra effort
required, as its fair share of a global mitigation effort, to hold or to bring back
greenhouse gas concentrations to 450ppm (Garnaut 2008:
Chapter 11
).
Temperature increases beyond 3°C would be associated with increasing risks to
the stability of state and society. But whatever happens to the state and ordered
society, humans will continue to make their lives as best they can. The extent of
climate change will shape their chances of salvaging more rather than less from
