Science and decision-making

Ian Lowe

21 May 2007

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Projected global warming

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An example of non-linear change

Millennium Assessment Report 2005

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Possible non-linear changes

• North Atlantic circulation

• Methane from Arctic tundra

• Melting of [polar] ice

• Drying of rainforests

• Clearing and burning of peatlands

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What is “dangerous” climate change ?

• Two degrees of warming might be dangerous

• Three degrees almost certainly is

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How close is this ?

• Current CO2 380 ppm

• With other GHG, ~ 460 ppm CO2 equiv

• 510 ppm, 67 % chance warming > 20

• 590 ppm, 90 % chance warming > 20

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UK Government estimates

• 2003: 550 ppm, temperatures are expected to rise between 2 and 5 0C

• 2006: “a limit closer to 450ppm or even lower might be more appropriate to meet a 20 C stabilisation limit”

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“If emissions and concentrations grow according to mid-range projections… the cumulative warming by 2100 would be approximately 3o to 5o C above pre-industrial conditions… scientific evidence suggests that changes of this magnitude are likely to be associated with large and perhaps abrupt changes in climatic patterns … will adversely impact agriculture, forestry, fisheries, availability of fresh water, the geography of disease, the liveability of human settlements…”

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0

200

400

600

800

1000

1200

1990 2000 2010 2020 2030 2040 2050

Energy Transport Fugitive, waste and industrial processes)Agriculture Land clearing

Kyoto target

60 - 90% reductions

Business As Usual

Source: Adapted from the Australian Greenhouse Gas Inventory and ABARE projections

Australia’s Emissions (Mt)

Where we are going

What we need to achieve

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It’s Achievable and Affordable

Source: The Allen Consulting Group (2006)

Real GDP

($b 2005)

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S O C I E TY E N V I R T

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S O C I E T Y

E C O N O M Y

E C O L O G Y

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Conclusion• Even when the science is

clear, decision-makers will tend to focus on the economy

• Science can inform and shape the policy debate: CFCs, water ? Forests ??

• Scientists need to be policy - literate

• Policy-makers must be science- literate

Ian Lowe 17Photo: NASA