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Where is Our SWWA Climate
Headed?
Bryson C. BatesDirector, CSIRO CLIMATE
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Talk Outline
• Background
• GHG emissions
• Time scale and context
• Planning for climate change
• Scenarios
• Global climate models (GCMs)
• Climate change scenarios for SWWA
• Concluding remarks
Indian O cean C limate Initiative
Informed A daptation
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GHG Emissions CO2 concentrations have grown from 280 ppm in
1750 to 375 ppm in 2003
Half of CO2 emitted by human activities absorbed by oceans & biosphere, leaving half in atmosphere where it has a lifetime of 50 to 100 years
Impossible to stabilise GHG concentrations at current level
Stabilization at 450 ppm requires reductions of 40% by 2050 & 60% by 2090, limiting global warming to 1.2 to 2.3 ºC by 2100
Regardless of reductions in GHG emissions, some climate change is inevitable
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Time Scale & Context
Super-greenhouse conditions have existed before – well before advent of humans
Estimates of arrival time for next ice age vary from 100s to 20,000 years
Population: 5M@35,000BC; 1.2B@1850; 2.5B @1950; 5.3B@1990; 6.3B@2000; 10B by 2050?
In 200 years, world's urban population has grown from 2% to nearly 50%
Megacities: 4@1975, 19@2000, 23@2015?
Infrastructure designed on assumption of a stationary climate
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Planning for Climate Change
Rather than extrapolating observed trends, we use computer models of climate system driven by scenarios of GHG & aerosol emissions, & ozone depletion
Future GHG emissions will depend on demographic, economic, technological, & political factors that are likely to evolve discontinuously in coming decades
Reliable prediction of Australia’s climate over next few decades is impossible
Better not to select one future & hope it comes to pass, nor to find the most probable future & adapt to it
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Scenarios
Series of events that could lead from the present to plausible but not assured future situations
Exemplify what might happen with/without actions to reduce GHG emissions
Provide baseline against which need for, and effectiveness of, adaptation measures & emission reductions can be measured
Not the same as predictions or forecasts! Usually consider at most 6 to 7 scenarios (e.g.
likely, pessimistic, optimistic) Acknowledge presence of uncertainty
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IPCC SRES Scenarios
A2 – population growth to 15 billion by 2100; rather slow economic and technological development
B2 – population growth to 10.4 billion by 2100; more rapidly evolving economy and more emphasis on environmental protection
There are also 5 IPCC CO2 stabilisation scenarios (450-1000 ppm)
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Global Warming Scenarios
0
1
2
3
4
5
6
1980 2000 2020 2040 2060 2080 2100
Year
Tem
pera
ture
ch
ang
e (o
C) SRES high
SRES lowIPCC 450 ppm lowIPCC 450 ppm highIPCC 550 ppm lowIPCC 550 ppm high
1.21.41.5
2.3
2.9
5.8
50% of uncertainty due to GCMs; 50% to emission scenarios
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Global Climate Models
Main components: atmosphere, land surface, biosphere, oceans, and polar ice
Simulate water & energy fluxes at 30-minute time steps over 3-D computational grid
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A Perspective on GCMs Current GCMs do good job at simulating
most of essential climate-forming processes in atmosphere & oceans, & behaviour of total climate system at global scale
Best GCMs not yet sophisticated enough to capture all of the processes that influence climate at regional scales
We have several well-tested technologies for inferring climatic information at local & regional scales from GCM simulations
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IPCC SRES Scenarios
Scenarios used: A2, A1B & B1
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Mean Temp: 9 GCMs
SRES 550 ppm 450 ppmMay to October
November to April
0 1 2 3 4 5 6 7 8
Temperature Change (oC)
0 1 2 3 4 5 6 7 8
Temperature Change (oC)
0 1 2 3 4 5 6 7 8
Temperature Change (oC)
0 1 2 3 4 5 6 7 8
Temperature Change (oC)
0 1 2 3 4 5 6 7 8
Temperature Change (oC)
0 1 2 3 4 5 6 7 8
Temperature Change (oC)
2030
2070
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Precipitation: 9 GCMs
-80 -60 -40 -20 0 20 40 60 80
Rainfall Change (%)
-80 -60 -40 -20 0 20 40 60 80
Rainfall Change (%)
-80 -60 -40 -20 0 20 40 60 80
Rainfall Change (%)
-80 -60 -40 -20 0 20 40 60 80
Rainfall Change (%)
-80 -60 -40 -20 0 20 40 60 80
Rainfall Change (%)
-80 -60 -40 -20 0 20 40 60 80
Rainfall Change (%)
SRES 550 ppm 450 ppmMay to October
November to April
2030
2070
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Potential Evaporation: 7 GCMs
SRES 550 ppm 450 ppmMay to October
November to April
2030
2070
0 5 10 15 20 25 30 35
Evaporation Change (%)
0 5 10 15 20 25 30 35
Evaporation Change (%)
0 5 10 15 20 25 30 35
Evaporation Change (%)
0 5 10 15 20 25 30 35
Evaporation Change (%)
0 5 10 15 20 25 30 35
Evaporation Change (%)
0 5 10 15 20 25 30 35
Evaporation Change (%)
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Some Weather Types
1016
1000
1012
1008
1016
1004
1012
Typ
e 5
Typ
e 3
.2 .4 1.8.6
.2 .4 .6 1.8
H H
L
1016
1016
1012
1020
1012
H
L
Indian O cean C limate Initiative
Informed A daptation
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Probabilities 1958 - 2003
YearYear
Pro
bab
ility
Pro
bab
ility
0.4
00.
10.
20.
3
0.2
0.3
1958 19581968 19681978 19781988 19881998 1998
Type 3: Wet West & Central Type 5: Dry Everywhere
Indian O cean C limate Initiative
Informed A daptation
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Coupled GCM Runs
CSIRO Mk 3 AGCM: T63 (1.875o x 1.875o approx); 18 vertical levels
OGCM: 1.875o longitude x 0.9375o latitude; 31 vertical levels
Transient run (380 years): observed GHG forcing 1871-present; A2 SRES scenario to 2100; stable GHG 2100-2250
Control run (323 years): 330 ppm equivalent CO2 for 1871-2193; no other historical forcing
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Margaret River
Current rainfall decrease, as recorded by
speleothem P, is well-outside
range of natural rainfall variability of last 200 years
Indian O cean C limate Initiative
Informed A daptation
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A New Way of Thinking!
Climate is non-stationary: changed rapidly in the past; changing now; & will change in the future
Future climate will exhibit wet and dry periods due to natural variability – this variability will be superimposed upon continued warming & changes in mean rainfall
We cannot wait for full scientific certainty: it may never come, or it may be too late!
We must take a balance of evidence approach for the time being (just like medical science)
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A New Way of Thinking!
Mitigation & adaptation are necessary & complementary
Developing policies & plans that are robust across a range of plausible futures will improve environmental, food & water security
Planning for the future can lead to beneficial outcomes in the present
We need to find fair & cost-effective measures to minimise adverse impacts & maximise benefits (must consider communities, not just economics)
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13-17 November 2005, Melbourne
www.greenhouse2005.com
AwarenessAwareness
AdaptationAdaptation
AbatementAbatement
ActionAction
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The End