Where is Our SWWA Climate

Headed?

Bryson C. BatesDirector, CSIRO CLIMATE

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

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

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

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

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

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)

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

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

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

IPCC SRES Scenarios

Scenarios used: A2, A1B & B1

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

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

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 (%)

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

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

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

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

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)

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)

13-17 November 2005, Melbourne

www.greenhouse2005.com

AwarenessAwareness

AdaptationAdaptation

AbatementAbatement

ActionAction

The End