Climate Change and Variability: Climate Change and Variability: Observed trends for Australia, Observed trends for Australia, NSW and the NSW and the Namoi Namoi Perry Wiles NSW Climate Services Centre Climate Change and Agriculture Climate Change and Agriculture 21 & 22 March 2007 21 & 22 March 2007
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Climate Change and Variability:Climate Change and Variability:
Observed trends for Australia, Observed trends for Australia,
NSW and the NSW and the NamoiNamoi
Perry Wiles
NSW Climate Services Centre
Climate Change and Agriculture Climate Change and Agriculture
21 & 22 March 200721 & 22 March 2007
Outline
� Climate variability in Australia and NSW
� Observed temperature trends
� Observed rainfall trends
“…of droughts and flooding rains”
Australian climate variability
Driest inhabited continent
High annual rainfall variability
Variability of Annual rainfall
0
2
4
6
8
10
12
14
16
18
20
Australia S. Africa Germany France NZ India UK Canada China USA Russia
Country
Co
eff
icie
nt
(%)
Seasonal rainfall zones
Global atmospheric circulation
Source: The Greenhouse Effect and Climate Change, Bureau of Meteorology
Some sources of rainfall variability
Inter-decadalInter-decadal Pacific Oscillation
Inter-annualIndian Ocean Dipole
Inter-annualEl Niño (Southern Oscillation)
SeasonalSeasonal shifts in circulations
Month/sMadden-Julian Oscillation
WeeksSouthern Annular Mode
Day/weekWeather patterns
Approximate Time scaleKnown major causes
Observed climate change trends
� Detection
o Finding a trend “signal” in the variability “noise”
� Attribution
o What is causing any trend?
Observed Temperature Trends
Australian Temperature Trends
1910-2006 trends - Max T: 0.06°C/decade, Min T 0.12°C/decade
� Project currently underway in NSW Climate Services Centre to seek to better understand what changed meteorologically and therefore get clues as to why
Change in annual average rainfall between the two periods 1900-1946 & 1947-2000 (%)
Clinton Rakich, NSW Climate Services Centre, Bureau of Meteorology
Change in annual average rainfall between the two periods 1900-1946 and 1947-2000
Change in annual average rainfall betweenthe two periods 1900-1946 and 1947-2000
Local Rainfall Trends
Annual Rainfall Timeseries for District 55
0
200
400
600
800
1000
1200
1400
18
90
19
00
19
10
19
20
19
30
19
40
19
50
19
60
19
70
19
80
19
90
20
00
Year
An
nu
al R
ain
fall
Local Area Seasonal Rainfall Trends
Seasonal Rainfall Timeseries for District 55
0
50
100
150
200
250
300
350
4001890/1
891
1900/1
901
1910/1
911
1920/1
921
1930/1
931
1940/1
941
1950/1
951
1960/1
961
1970/1
971
1980/1
981
1990/1
991
2000/2
001
Year
Ra
infa
ll (
mm
)
11 per. Mov.
Avg.
(Summer)
11 per. Mov.
Avg.
(Autumn)
11 per. Mov.
Avg. (Spring)
11 per. Mov.
Avg. (Winter)
Trends in extreme events
Average NSW Stations (25)
Number of heavy rainfall days
0
5
10
15
20
25
30
35
40
1870
1876
1882
1888
1894
1900
1906
1912
1918
1924
1930
1936
1942
1948
1954
1960
1966
1972
1978
1984
1990
1996
2002
Year
Nu
mb
er
of
da
ys
/ y
ea
rNumber of days with more than 10 mm's of rainfall / year20 mm's of rainfall / year30 mm's of rainfall / year11 per. Mov. Avg. (20 mm's of rainfall / year)
South-coastal Australian April-July Pressure (hPa)
••Southern Australia has been experiencing increasing Southern Australia has been experiencing increasing summer/autumn pressures since 1950, delaying the summer/autumn pressures since 1950, delaying the winter rainfall season. winter rainfall season.
Observed changes in pressure/weather systems
Observed changes in pressure/weather systems
�� This is believed to be the driver for both the SW WA and This is believed to be the driver for both the SW WA and
SE (Vic and SE (Vic and SthSth NSW) autumn/winter rainfall declines NSW) autumn/winter rainfall declines
(although research is ongoing to understand the (although research is ongoing to understand the
underlying mechanisms)underlying mechanisms)
�� Latest modeling studies suggest that this is being driven Latest modeling studies suggest that this is being driven