ideas.unimelb.edu.au

The Warning of the Warming World

Professor David Karoly, School of Earth Sciences

Overview

• Recent observed changes of some climate variables and recent CO2 emissions

• Impacts of climate change globally and in Australia

• Stabilisation of greenhouse gas concentrations to minimise dangerous climate change

Recent variations

Top to bottom: observed CO2 concentrations,

global mean surface temperature,

and sea level change,

compared to IPCC (2001) projections, from 1990 (Rahmstorf et al., 2007).

From Stroeve et al, GRL, 2007

Observations to 2005

Sea ice in Sept 2007

From Stroeve et al, GRL, 2007

Sept 2005

Observed and projected Australian rainfall

Best estimate projected rainfall change for 2070(from “Climate change in Australia”)

Observed trend in annual rainfall

1970-2008

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Recent emissions

1990 1995 2000 2005 2010

5

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10Actual emissions: CDIACActual emissions: EIA450ppm stabilisation650ppm stabilisationA1FI A1B A1T A2 B1 B2

1850 1900 1950 2000 2050 2100

0

5

10

15

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30Actual emissions: CDIAC450ppm stabilisation650ppm stabilisationA1FI A1B A1T A2 B1 B2

Global CO2 emissions from fuel consumption

From Raupach et al. 2007, PNAS

IPCC SRES (2000) growth rates in %/yr for 2000-2010:A1B: 2.42 A1FI: 2.71A1T: 1.63A2: 2.13B1: 1.79B2: 1.61

20062005

Observed 2000-2006 3.3%/yr

IPCC WGII Fig SPM.2

Impacts are greater in developing countries and in low income groups in developed countries

IPCC WGII Fig SPM.2

Impacts are greater in developing countries and in low income groups in developed countries

Projected climate change hotspots in Australia (from IPCC AR4 WGII, chapt 11)

Climate change impacts on Australia for 1 - 2C warming relative to 1990

• Hard coral reef communities are widely replaced by algal

• 100% of Acacia species are eliminated in SW Australia• 40% of core habitat lost for Eucalyptus• 12-25% decrease in flow in the Murray Darling Basin • Population at risk of dengue fever increases from 0.17

million to 0.75 - 1.6 million• 100 year storm surge height around Cairns increases

22%; area flooded doubles• 25% increase in 100-year storm tides along eastern Vic

coast• 15 - 65% increase in very high and extreme fire danger

days in SE Australia (Lucas et al, 2007)

(from Preston and Jones, 2006; may be underestimates)

Causes of climate change

In 2005, greenhouse gas concentration was 455 ppm CO2-eq. A large part of the warming influence was masked by aerosols.

WGI Fig SPM.2

Stabilisation scenarios

• 455 ppm CO2-eq in 2005, 379 ppm CO2 conc

• I: CO2-eq stabilisation at 445-490 ppm, emissions peak in 2000-2015, global CO2 emissions -85% to -50% in 2050, warming of 2.0 to 2.4C above pi

• Assuming equal per capita emissions, 50% global emission reduction in 2050 means ~90% emission reduction for Australia

IPCC SyR Fig SPM.11

Probability of committed global warming for greenhouse gases in the atmosphere in 2005

From Ramanathan and Feng, PNAS, 2008

From www.nicholsoncartoons.com.au

Summary

• Recent observed changes of several climate variables and recent CO2 emissions have been at or above the upper range of earlier projections

• “Australia has a larger interest in a strong mitigation outcome than other developed countries; small variations in climate are more damaging to us than to other developed countries” (Garnaut, 2008)

• Stabilisation of greenhouse gas (ghg) concentrations at lower than 450 ppm CO2-e is needed to minimise the risk of

dangerous climate change (<10% chance of warming >2C)

• This requires removal of ghgs from the atmosphere, either through natural processes or anthropogenic sequestration (not further emissions)