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 CO 2 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 CO 2 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

Global CO 2 emissions from fuel consumption From Raupach et al. 2007, PNAS IPCC SRES (2000) growth rates in %/yr for : A1B: 2.42 A1FI: 2.71 A1T: 1.63 A2: 2.13 B1: 1.79 B2: Observed %/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  C 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 million 100 year storm surge height around Cairns increases 22%; area flooded doubles 25% increase in 100-year storm tides along eastern Vic coast % 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 CO 2 -eq. A large part of the warming influence was masked by aerosols. WGI Fig SPM.2

Stabilisation scenarios 455 ppm CO 2 -eq in 2005, 379 ppm CO 2 conc I: CO 2 -eq stabilisation at ppm, emissions peak in , global CO 2 emissions -85% to -50% in 2050, warming of 2.0 to 2.4  C 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

Summary Recent observed changes of several climate variables and recent CO 2 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 CO 2 -e is needed to minimise the risk of dangerous climate change ( 2  C) This requires removal of ghgs from the atmosphere, either through natural processes or anthropogenic sequestration (not further emissions)