AcknowledgementsIOCI Colleagues Bureau of Meteorology, CSIRO Marine and Atmospheric Research,CSIRO Land and Water, CSIRO Mathematics and Information Sciences,Brian Sadler and Ed HauckAnd specifically Roger Jones (CMAR) for work on impact of climate change on water resources in Australia

Impact of Climate Change on Water ResourcesHow has climate change?Is the evidence for anthropogenic climate change? (Greenhouse Gases and Aerosols)What can we say about the future climate?What is the likely impact of climate change on water resources?What are the threats to the water sector of climate change?

IPCC Third Assessment Report

An increasing body of observations give a collective picture of a warming world and other changes to the climate system

How have surface temperatures changed?

How have sea surface temperatures in the Indian Ocean Basin changed?

How has Australian rainfall changed?http://www.bom.gov.au/silo/products/cli_chg/index.shtml

Abrupt shifts in Australian annual rainfall1890-991940-451967-69

May-July SW WA RainfallHow has the rainfall of South-western Western Australia changed? Time series of SWWA rainfall (mm). Solid trace depicts early winter (May to July) totals and dotted trace late winter (August to October) totals. Means for the periods 1900 to 1974 and 1975 to 2004 are represented by horizontal lines.

How has the frequency of wet synoptic patterns (& June-July rainfall) changed?Decrease in frequency of wet types accounts for ~50% of rainfall decrease

Decrease in rainfall associated with troughs to west types accounts for ~30%

Summary of how the Regional Climate of SWWA has changed.Temperatures have increased by about 0.8C since 1910 with most of increase since 1950Daily minimums have increased more than daily maximumsSea surface temperatures in the averaged over the Indian Ocean basin have increased by 0.6CSince 1970 the number of storms have decreased and they bring less rainAnnual rainfall has decreased by 10% since 1970sMay-July rainfall has decreased by 15% since 1970sReduced rainfall has resulted in 50% less runoff Key Message: Water managers can not assume that the climate baselines of the 20th century will be valid in the 21st century

Is it possible to model the observed temperature and rainfall changes?

What can we say about the attribution of the drying in SWWAThe decline in the number of storms is linked with large-scale global circulation changes (in about 1970); It is feasible that the drying trend could have been the result of unforced climate variability;However, the decline in rainfall is also consistent with the modelled effect of anthropogenic forcing;Changes in land cover may also have contributed to the rainfall decline.

What can we say about the future?Emission scenarios

Global Temperature RiseGlobal temperatures and sea level are projected to rise under all IPCC emission scenarios

Projected warming of 1.4-5.8oC between 1990 and 2100Projected warming of 0.54-1.24oC between 1990 and 2030Projected warming of 1.17-3.77oC between 1990 and 2070At least half of uncertainly relates to uncertainties in emissions, the rest to uncertainties in climate scienceChanges will persist for centuries

SWWA: Range of projections for changes of temperature from nine international models

SWWA: Range of projections for changes of rainfall from nine international models

Some Weather Types1016100010121008101610041012Type 5Type 3.2.41.8.6.2.4.61.8HHL

SWWA winter weather state probabilities from stochastic downscaling of Mk3 (A2 dots, B2 small dash, B1 medium dash, A1B long dash and committed dot-dash). Winter Seasonal Totals(% of median for 30 SWWA rainfall station)Scenario 2030-2064A2 80-90%B2 84-91%A1B 87-91% B1 97-99%S(20) 96-99% Baseline 1975-2004

Key MessageThe climate change simulations show that even with the lowest conceivable greenhouse gas emission scenarios, the south-west of Western Australia is projected to be drier and warmer later in the century, with an increasing probability of dry weather patterns and a decreased probability of wet weather patterns

P and Ep changes for south-western AustraliaChange per degree global warming

P and Ep change over Australia(per degree global warming)

What is the likely impact of climate change on water resources?Hydrological model sensitivityRelate change in mean annual rainfall and potential evaporation to mean annual change in runoff (%)

Q = P A + Ep B

The further A and B are from zero, the more sensitive that factor is

Hydrological model sensitivityModel comparison

Simple model of mean flow changes MDB (2030)Vertical lines measure range from ten models with a global warming range from 0.54-1.24C. The central box is range of change at 0.85C (median) global warming

Provisional results relating runoff response to climate change for the MDB

Simple model of mean flow changes SW WA (2030)Vertical lines measure range from ten models with a global warming range from 0.54-1.24C. The central box is range of change at 0.85C (median) global warming

Reduction in mean monthly inflow to Stirling Dam (Berti et al 2004) using the current (1982-2002)and future (2042-2062) GCM simulations Annual % decrease in stream flow is 31%

IOCI Living with our changing climate workshopKey Impacts on Water SectorReduced reliability of public supplyReduced reliability of private supplyReduced stream and estuary flow and water quality reducing ecological and social valuesDrying of ground water reliant systemsReduced water availability for fire fighting Challenged regulatory and management systemsSeasonally variable floodingStranded underperforming assets and infra structure

IOCI Living with our changing climate workshopWater Sector Climate Science PrioritiesBetter understanding of the dynamics of climate change and variability, including rainfall for south-west WA, to provide data for policy and planning;Developing of probabilities around climate scenario estimates;Distinguishing between climate change and climate variability;Differentiating effects on summer and winter rainfall; Breaking down spatial trends between north to south and east and west, and even within the south-west; andUnderstanding of meteorological shifts that have or will occur.

www.csiro.au

Thank You ContactName:Dr Brian Ryan Phone:61 3 9333 6554 Email:brian.ryan@csiro.au Web:www.marine.csiro.auContact CSIROPhone:1300 363 400 +61 3 9545 2176 Email:enquiries@csiro.au Web:www.csiro.au

The climate change projections indicate an increase in temperature under enhanced greenhouse conditions.

Inland regions show warming between 0.5 and 2.1C by 2030 and between 1 and 6.5C by 2070 during the summer-half of the year for SRES emission scenarios. Relatively less increases are projected for stabilized scenarios for 550 and 450 ppm.

During the winter-half of the year, increases are between 0.5 and 2C by 2030 and between 1 and 5.5C by 2070. Southern coastal regions show relatively less warming. Projected rainfall decreases are between 2 and 20% by 2030 and 5 and 60% by 2070 in the extreme southwestern Western during the winter-half of the year for SRES emission scenarios, but magnitudes of decreases are relatively smaller for stabilized emission scenarios. Rainfall changes during the summer-half of the year show decreases and some increases, particularly in the inland regions.

Steve Charles and Bryson Bates have used a local scale statistical downscaling method to determines the dominant spatial patterns of SWWA station rainfall using the signals from a number of atmospheric predictors.

The downscaling method produced six dominant patterns, and the prevailing MSLP patterns on the days corresponding to each rainfall pattern. The self-organising map discussed earlier by Pandora Hope give results consistent with this technique. The patterns corresponding to wet conditions across SWWA has decreased over time while the frequency of the dry pattern has increased consistent with the observed record.