Defining the present climate:

Why does it matter? What help exists?

Pandora Hope (BMRC) and Ian Foster (DAWA)

Acknowledgements: Colin Terry (Water Corp), Andrew Watkins (NCC), Jay Lawrimore (NCDC), Lynda Chambers (BMRC),

Peter Powers (BMRC)

Outline

• ‘Standard’ meteorological climatology

• Observed Trends and Breakpoints

• Examples of the issues and responses in various sectors

• Available help

Defining the present climate1961-1990

http://www.bom.gov.au/silo/products/cli_chg/

Defining the present climate1961-1990

http://www.bom.gov.au/silo/products/cli_chg/

Trends – A reason to change the ‘baseline’ definition?

Combined global land-surface air and sea surface temperatures (degrees Centigrade) 1861 to 1998, relative to 1961 to1990; University of East Anglia, UKhttp://www.grida.no/climate/vital/17.htm

http://lwf.ncdc.noaa.gov/oa/climate/research/trends.html

National Climatic Data Centerhttp://lwf.ncdc.noaa.gov/oa/climate/research/trends.htm

l

National Climate Centre, Australian Bureau of Meteorology

http://www.bom.gov.au/silo/products/cli_chg/

Annual Temperature SWWAAnnual Maximum Temperature SWWA catchment

22.5

23

23.5

24

24.5

25

1952 1956 1960 1964 1968 1972 1976 1980 1984 1988 1993 1997 2001 2005

Year

deg

rees

C

Annual Minimum Temperature SWWA catchment

9

9.5

10

10.5

11

11.5

12

12.5

1952 1956 1960 1964 1968 1972 1976 1980 1984 1988 1993 1997 2001 2005

Year

deg

rees

C

Created using

“Diagnose”

Summer Temperature SWWADJF Maximum Temperature SWWA

27

27.5

28

28.5

29

29.5

30

30.5

31

1952 1956 1960 1964 1968 1972 1976 1980 1984 1988 1993 1997 2001 2005

Year

deg

rees

C

DJF Minimum Temperature SWWA

12

12.5

13

13.5

14

14.5

15

15.5

16

16.5

17

1952 1956 1960 1964 1968 1972 1976 1980 1984 1988 1993 1997 2001 2005

Year

deg

rees

C

Early Winter Temperature SWWAMJJ Maximum Temperature SWWA

15

15.5

16

16.5

17

17.5

18

18.5

19

19.5

1952 1956 1960 1964 1968 1972 1976 1980 1984 1988 1993 1997 2001 2005

Year

deg

rees

C

MJJ Minimum Temperature SWWA

6

6.5

7

7.5

8

8.5

9

1952 1956 1960 1964 1968 1972 1976 1980 1984 1988 1993 1997 2001 2005

Year

deg

rees

C

http://www.grida.no/climate/vital/18.htm

National Climate Centre, Australian Bureau of Meteorology

http://www.bom.gov.au/silo/products/cli_chg/

Seasonality of SWWA Rainfall Decrease

0

20

40

60

80

100

120

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

mm

1925-1975 1976-2003

Figure 1 Average monthly rainfall for the south west. (The area south west of the line in

Early Winter SWWA RainfallSouthwest May, June and July rainfall

100

200

300

400

500

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Year

Rai

nfal

l (m

m)

Annual

1901-75

1976-04

Break-point in time series at 1968/69NB: IOCI in general uses a breakpoint of 1975/76, which is the

breakpoint of the sea-level pressure data in the region

Changes to the ‘baseline’

• WMO suggested 1971-2000, but this was not adopted

• Some agencies are using the full period, e.g. NCDC uses 1880-2004

• Many sectors use the time-period most relevant to their purpose

Major System Impacts

http://www.watercorporation.com.au/Integrated water supply scheme – source development

plan

• 2001 had 2nd worst inflow to Perth dams

• 8 year sequence of lowered streamflow to 2005

Changes to Streamflow Probability

Period No. Yrs > 177 GL

%

1948-75 23 77

1976-2003 9 30

177 GL is the mean over 1975-96

Response of Water Corp.

• Major desalination of seawater

• Recycling of treated wastewater

• Better management of dam catchments to improve inflows

• Trading for water from irrigation cooperatives

Salt risk and land-useNB: This is an example only. The data is from station data interpolated onto a grid (Jones and Weymouth 1997). There will be differences from

maps produced using other methods of interpolation

1950-1979 1980-2004

< 900 mm < 900 mm

900-1100 mm

> 1100 mm 900-1100 mm

Forestry, Mining

Isohyet limits from Colin Terry, maps plotted using NCC gridded rainfall data by Pandora Hope

System Response - Waterlogging FrequencyWaterlogging at Katanning for a Duplex Soil 100mm

0

10

20

30

40

50

60

70

80

90

01-Mar 30-Apr 29-Jun 28-Aug 27-Oct

Occ

urr

ence

(%

)

1925-75

1976-03

Wheat Yield Trend

Source: ABS state averages

WA Wheat Yields 1950-2003

0

0.5

1

1.5

2

2.5

3

1950 1960 1970 1980 1990 2000

t /

ha

Agricultural Responses

• Fewer very wet years may have affected rates of salinity spread

• Sowing opportunities tend to occur later• Decreased waterlogging in susceptible areas.

This may have improved conditions for cropping in higher rainfall areas

• Technology changes have improved productivity despite generally drier years

Tools available

• http://www.bom.gov.au/silo/products/cli_chg/• Australian Rainman (QDNR, BoM et al)• DIAGNOSE; CD or website (v. large):

ftp://ftp.bom.gov.au/anon/home/bmrc/perm/append/install_v3/

• MetAccess (CSIRO et al)• Climate Calculator – Dept Ag• Future projections – IOCI, CSIRO

Conclusions

• There have been strong trends in rainfall in Western Australia, causing sectors to re-examine the climate ‘baseline’

• Impacts have been strong in some sectors, and variable in others

• There is a range of tools that can help define climatology, opportunities and risks.

Climate Calculator – DAWARisk Charts

Agriculture- Altered rainfall pattern

Corrigin

0

10

20

30

40

50

60

70

80

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Mo

nth

ly R

ain

fall

(mm

)

Mean 1925-75

Mean 1976-2003