Transcript Presentation Title, Arial Regular 29pt Sub title

Climate Change : The State of Knowledge
Climate Adaptation National Research Flagship
Bryson Bates
Leader, Pathways to Adaptation Theme
22 April 2009
Presentation outline
● Human vs geological time scales
● Observed global trends
● Observed national trends
● Climate change projections for WA
● Extremes
● Concluding remarks
Drivers of climate change
Climate has always changed
NewScientist, 2008
Geologic & human time scales

Past super-greenhouse conditions:
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50 My BP CO2~ 1,000 ppm; no polar ice; sea level ~ 120 m
above present

250 My BP CO2~ 10 to 20 x present level (~ 385 ppm); 50 to
95% extinction rate
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Advent of humans ~ 2.2 to 2.4 My BP

Civilisation started ~ 12 Ky BP



Current rate CO2 increase 200 x faster than that over last
650 Ky
Without mitigation & abatement, burning all known coal
reserves will raise atmospheric CO2 ~ 2,000 ppm
Estimated arrival time for next ice age: ‘now’ to 20 Ky
Enhanced greenhouse effect

GHGs are a natural part of the atmosphere: support life

Water vapour is most abundant GHG: humans have little impact

Humans have most impact on CO2, CH4, N2O: net effect
5
Recent
emissions
Global
fossil
fuel
emissions
0
1850
1900
1950
2000
2050
2100
CO2 Emissions (GtC y-1)
10
9
8
7
Actual emissions: CDIAC
Actual emissions: EIA
450ppm stabilisation
650ppm stabilisation
A1FI
A1B
A1T
A2
B1
B2
SRES (2000)
growth rates
in % y -1 for
2000-2010:
2007
2006
2005
A1B: 2.42
A1FI: 2.71
A1T: 1.63
A2: 2.13
B1: 1.79
B2: 1.61
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Global Carbon Budget update; Raupach et al. 2007, PNAS
5
1990
1995
2000
2005
2010
Observed
2000-2006
3.3%
Observations vs IPCC projections
Rahmstorf et al. (2007)
Observations vs IPCC projections
Rahmstorf et al. (2007)
Global average temperatures are rising
CRU, UEA
Global average temperatures are rising
Global average temperatures are rising
Lags in the response of climate to emissions
IPCC 2001, SYM, Figure 8.3
Past 12 years have been unusual
Very wet in the north & west
Very dry over southeast Qld,
southern NSW and SA, Victoria,
eastern Tas and southwest WA
CSIRO Climate change: the latest science
Feb 1997 – Jan 2009
Minimum & maximum temperatures
Temperature projections (2050)
Winter
B1
A1B A1F1
Summer
B1
A1B A1FI
23 GCMs; 1980–1999 baseline
Source: http://www.climatechangeinaustralia.gov.au/
Wind speed projections (2050)
Winter
B1
A1B A1F1
Summer
B1
A1B A1FI
23 GCMs; 1980–1999 baseline
Source: http://www.climatechangeinaustralia.gov.au/
Rainfall projections (2050)
Winter
B1
A1B A1F1
Summer
B1
A1B A1FI
23 GCMs; 1980–1999 baseline
Source: http://www.climatechangeinaustralia.gov.au/
Specific projections
● SW rainfall projected to decrease by 2 to 20% by
2030 & 5 to 60% by 2070
● SW summer temperatures projected to increase
between 0.5 to 2.1 ºC by 2030 & 1 to 6.5 ºC by
2070
● Average annual number of days above 35 ºC in
Perth to increase from 28 to 36-67 by 2070
● SW winter temperatures projected to increase
between 0.5 & 2 ºC by 2030 & 1 & 5.5 ºC by 2070
Potential impacts of climate change
Greater risks to major infrastructure due
to increases in extreme weather events
More damage to buildings; transport,
energy & water services; telecommunications
More heat-related deaths
for people aged over 65
1115 deaths per year at present in
the 5 largest capital cities, increasing
to 2300-2500 per year by 2020
Greater risks for coastal flooding
from sea-level rise and storm surges
(global sea level rise of 1 metre or more
possible by 2100)
Key points on weather & climate extremes
● Infrequent events at either the low or high end of a variable
of interest – low probability, high impact
● Small change in average of a variable can be accompanied
by large changes in I-F-D characteristics
● Wide range possible within unchanging climate – difficult to
attribute individual event to climate change
0.1
0.2
0.3
How will
changes in
extremes be
manifested?
0.0
Frequency
0.4
0.5
Climate change & extremes
0
2
4
Climate variable
6
8
Rainfall extremes
● Occur on different scales in space-time
● intermittent processes
● poor observations
● Not 'resolved' by computational grids in GCMs – need
'downscaling' methods
● topographic effects
● coastal effects
● subgrid-scale processes (e.g. convection)
● Changes do not scale with specific humidity changes:
more complex
● Statistics vary over a range of time scales (temporal
clustering)
● Changes in rainfall means cannot be used to reliably
infer changes in extremes
Value added by dynamical downscaling
200 km
2030
2070
65 km
4 km
fraction
Concluding remarks

Our climate will continue to change due to
natural & human-induced forcing

Present evidence for climate change is
compelling

Prognosis for WA is hotter, & drier for SW
(NW uncertain)
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Climate/weather extremes – difficult topic &
an active area of research
Believe/disbelieve – stay informed & manage
the risk
Future management strategies will need to
be:

adaptive rather than static

based on a scenario & portfolio approach