Download Climate change and water

Policy Brief – May 2008
Climate change and water
Australia is one of the must vulnerable developed countries to the impacts of climate change
(Garnaut, 2008). The Intergovernmental Panel on Climate Change (IPCC) report that Australia
natural and economic systems are already becoming stressed by changes in climate, in particular
from impacts on water supply and agriculture (Hennessy, Fitzharris, Bates, et al., 2007). They also
report that as a result of reduced rainfall and increased evaporation, water security problems are
projected to intensify by 2030, particularly in southern and eastern Australia. Increases in the
severity and frequency of drought are also projected and global warming of more then 2oC
threatens to overwhelm the known adaptive capacity of water supplies.
This briefing note outlines a number of assessments undertaken by CSIRO on climate change,
catchment runoff and drought since the release of the IPCC’s assessment in 2007.
Catchments under threat
Soon-to-be-published risk assessments of Australia’s 325 surface water management areas by the
CSIRO shows that Australia's major capital cities and the Murray-Riverina region are at "high” to
“very high” risk from climate change. (Figure 1. Preston, Jones, 2008a). Other factors include recent
30-year trends in rainfall, the condition of catchments and population growth.
Figure 1: Catchments at risk
Assessments from CSIRO also project significant declines in runoff across many of Australia’s key
catchments (Preston, Jones, 2008b, Table 1). In the selected catchments in Table 1, by 2030, runoff
declines are projected to be in the order of 3-9 per cent and possibly up to 11-25 per cent. By 2070,
runoff declines are expected to be in the order of 7-26 per cent but in the worst case are up to 3173 per cent.
Table 1: Projected change in runoff in selected catchments – 2030 and 2070
Catchment
2030
2070
Blackwood River (WA)
-9% (-25 to -2)
-26% (-73 to -6)
Brisbane River (Qld)
-5% (-19 to +7)
-14% (-53 to +18)
Hawkesbury River (NSW)
-3% (-12 to +1)
-7% (-34 to +4)
Murray-Riverina (NSW)
-7% (-17 to -2)
-20% (-49 to -3)
Thomson River (Vic)
-5% (-11 to -2)
-14% (-31 to -4)
Torrens River (SA)
-6% (-16 to -1)
-16% (-45 to -4)
These assessments assume no action to reduce greenhouse pollution. However, in the MurrayRiverina region, urgent and concerted action to reduce emissions could reduce runoff declines by
around a third to 50 per cent in 2070 (Preston, Jones, 2008b, Table 2).
*
Table 2: Change in runoff in Murray-Riverina: No climate action vs climate action
GHG stabilization
2030
2070
No climate action (SRES)
-7% (-17 to -1)
-20% (-50 to -4)
550 ppm
-7% (-15 to -1)
-16% (-38 to -3)
450 ppm
-6% (-14 to -1)
-14% (-31 to -3)
350 ppm
-6% (-13 to -1)
-11% (-25 to -2)
Climate change and drought
New research by CSIRO on the impact of climate change on the length of severe droughts in
Australia indicates it may double or triple in some parts of Australia after 2050 (Mpelasoka, Collier,
Suppiah et al. (2007), Table 3). Other studies suggest by 2030, soil-moisture-based drought
frequency increases 20–40 per cent over most of Australia and up to 80 per cent over the Indian
Ocean and south east coast catchments by 2070 (Mpelasoka, Hennessy, Jones et al., 2007).†
Table 3: Change in severe drought intensity and frequency - 2051-2100‡
Region
Change in severe drought
intensity
Duration of severe drought
Queensland
+18%
+100%
New South Wales
+5%
+33%
Victoria
+16%
+200%
Tasmania
+23%
+140%
Western Australia
+21%
+88%
*
Climate action scenarios represent action to stabilise atmospheric concentrations of greenhouse gases
at various levels. For example, under the 450 ppm scenario, global fossil fuel CO2 emissions peak by
around 2010 and would be around 15% below 1990 levels by 2050. Note that newer stabilisation
scenarios show higher fossil fuel emissions early this century largely due to stronger action to reduce
deforestation emissions. See Meinshausen, Hare, Wigley, et al. (2006).
†
Change on 1975–2004 levels.
‡
Change on 1951-2000 levels.
References
Garnaut (2008a), Interim Report to the Commonwealth, State and Territory Governments of
Australia, The Garnaut Climate Change Review, Melbourne, Australia.
Hennessy, Fitzharris, Bates, et al. (2007), Australia and New Zealand, in Climate Change 2007:
Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment
Report of the Intergovernmental Panel on Climate Change [Parry, Canziani, Palutikof, et al. (eds)],
Cambridge University Press, Cambridge, UK.
Meinshausen, Hare, Wigley, et al. (2006), Multi-gas emission pathways to meet climate
targets, Climatic Change 75: 151–194.
Mpelasoka, Collier, Suppiah et al. (2007), Application of Palmer Drought Severity Index to
Observed and Enhanced Greenhouse Conditions using CSIRO Mk3 GCM Simulations, in
Proceedings from MODSIM 2007. International Congress on Modelling and Simulation, 10-13
December 2007.
Mpelasoka, Hennessy, Jones et al. (2007), Comparison of suitable drought indices for climate
change impacts assessment over Australia towards resource management, International Journal of
Climatology, DOI: 10.1002/joc.1649.
Preston, Jones (2008a), Screening climatic and non-climatic risks to Australian catchments,
Geographical Research, in press.
Preston, Jones (2008b), Evaluating sources of uncertainty in Australian runoff projections,
Advances in Water Resources 31: 758–775.