The latest science on the The latest science on the

climate change challengeclimate change challenge David Karoly, Univ of MelbourneDavid Karoly, Univ of Melbourne

The latest science on the The latest science on the

climate change challengeclimate change challenge David Karoly, Univ of MelbourneDavid Karoly, Univ of Melbourne

TC Larry, 2006From Bureau of Meteorology

SummarySummary Recent observed changes of several climate variables and

recent CO2 emissions have been at or above the upper range of IPCC estimates

“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 concentrations at 450 ppm CO2-eq will require removal of greenhouse gases from the atmosphere, either through natural processes or anthropogenic sequestration (not further emissions)

Delays in reducing CO2 emissions commit the world to greater magnitude, largely irreversible climate change for at least a millenium

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

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

Observed trend in annual rainfall

1970-2007

Recent emissions

1990 1995 2000 2005 2010

5

6

7

8

9

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

1850 1900 1950 2000 2050 2100

0

5

10

15

20

25

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

Global CO2 emissions from fuel consumptionComparison of IPCC emission scenarios and new growth path

From Raupach et al. 2007, PNAS

SRES (2000) growth rates in % y -1 for 2000-2010:

A1B: 2.42 A1FI: 2.71A1T: 1.63A2: 2.13B1: 1.79B2: 1.61

20062005

Observed

2000-2006 3.3%/yr

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

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

• II: CO2-eq stabilisation at 490-535 ppm, emissions peak in 2000-2020, global CO2 emissions -60% to -30% in 2050, warming of 2.4 to 2.8C 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 distribution of committed global warming (relative to preindustrial) for greenhouse gases in the atmosphere in 2005

From Ramanathan and Feng, PNAS, 2008

From www.nicholsoncartoons.com.au

Solomon et al., PNAS, 2009: “climate change that takes place due to increases in carbon dioxide concentration is largely irreversible for 1,000 years after emissions stop”

SummarySummary Recent observed changes of several climate variables and

recent CO2 emissions have been at or above the upper range of IPCC estimates

“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 concentrations at 450 ppm CO2-eq will require removal of greenhouse gases from the atmosphere, either through natural processes or anthropogenic sequestration (not further emissions)

Delays in reducing CO2 emissions commit the world to greater magnitude, largely irreversible climate change for at least a millenium