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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 - PowerPoint PPT Presentation
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Climate Change : The State of Knowledge
Bryson Bates
Leader, Pathways to Adaptation Theme
22 April 2009
Climate Adaptation National Research Flagship
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
New
Scientist, 2008
Geologic & human time scales
Past super-greenhouse conditions: 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
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
Global fossil fuel emissions
SRES (2000) growth rates in % y -1 for 2000-2010:
A1B: 2.42 A1FI: 2.71A1T: 1.63A2: 2.13B1: 1.79B2: 1.61
Observed 2000-2006 3.3%
Recent emissions
1990 1995 2000 2005 2010
CO
2 E
mis
sion
s (G
tC y
-1)
5
6
7
8
9
10Actual emissions: CDIACActual emissions: EIA450ppm stabilisation650ppm stabilisationA1FI A1B A1T A2 B1 B2
1850 1900 1950 2000 2050 2100C
O2 E
mis
sion
s (G
tC y
-1)
0
5
10
15
20
25
30Actual emissions: CDIAC450ppm stabilisation650ppm stabilisationA1FI A1B A1T A2 B1 B2
20062005
2007
Global Carbon Budget update; Raupach et al. 2007, PNAS
Observations vs IPCC projections
Rahmstorf et al. (2007)
Rahmstorf et al. (2007)
Observations vs IPCC projections
Global average temperatures are rising
CR
U, U
EA
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
CSIRO Climate change: the latest science
Very wet in the north & west
Very dry over southeast Qld, southern NSW and SA, Victoria, eastern Tas and southwest WA
Feb 1997 – Jan 2009
Minimum & maximum temperatures
Temperature projections (2050)
Winter Summer
B1 B1A1B A1BA1F1 A1FI
23 GCMs; 1980–1999 baselineSource: http://www.climatechangeinaustralia.gov.au/
Wind speed projections (2050)
Winter Summer
B1 B1A1B A1BA1F1 A1FI
23 GCMs; 1980–1999 baselineSource: http://www.climatechangeinaustralia.gov.au/
Rainfall projections (2050)
Winter Summer
B1 B1A1B A1BA1F1 A1FI
23 GCMs; 1980–1999 baselineSource: 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 eventsMore 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
Climate change & extremes
0 2 4 6 8
0.0
0.1
0.2
0.3
0.4
0.5
Climate variable
Fre
quen
cy
How will changes in
extremes be manifested?
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 65 km 4 km
2030
2070
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)
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