Where is Our SWWA Climate Headed?

transcript

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

1980 2000 2020 2040 2060 2080 2100

C) SRES high

SRES lowIPCC 450 ppm lowIPCC 450 ppm highIPCC 550 ppm lowIPCC 550 ppm high

1.21.41.5

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

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 (%)

November to April

Potential Evaporation: 7 GCMs

November to April

0 5 10 15 20 25 30 35

Evaporation Change (%)

0 5 10 15 20 25 30 35

Some Weather Types

.2 .4 1.8.6

.2 .4 .6 1.8

Probabilities 1958 - 2003

YearYear

1958 19581968 19681978 19781988 19881998 1998

Type 3: Wet West & Central Type 5: Dry Everywhere

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

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

Where is Our SWWA Climate Headed?

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