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
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Observed global trends
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Observed national trends Climate change projections for WA
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Extremes
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Concluding remarks
Drivers of climate change
Climate has always changed
Geologic & human time scales
Past super-greenhouse conditions:
50 My BP CO 2 ~ 1,000 ppm; above present no polar ice; sea level ~ 120 m 250 My BP CO 2 ~ 10 to 20 x present level (~ 385 ppm); 95% extinction rate 50 to Advent of humans ~ 2.2 to 2.4 My BP Civilisation started ~ 12 Ky BP Current rate CO 2 650 Ky increase 200 x faster than that over last Without mitigation & abatement, burning all known coal reserves will raise atmospheric CO 2 ~ 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 CO 2 , CH 4 , N 2 O: net effect
30 25 20 15 10 Actual emissions: CDIAC 450ppm stabilisation 650ppm stabilisation A1FI A1B A1T A2 B1 B2 10 5 0
Recent emissions
1850 1900 1950 2000 2050 9 8 7 6 5 1990 2100 Actual emissions: CDIAC Actual emissions: EIA 450ppm stabilisation 650ppm stabilisation A1FI A1B A1T A2 B1 B2 1995 2006 2005 2007
Global Carbon Budget update; Raupach et al. 2007, PNAS
2000 2005 2010
SRES (2000) growth rates in % y -1 for 2000-2010: A1B: 2.42
A1FI : 2.71
A1T: 1.63
A2: 2.13
B1: 1.79
B2: 1.61
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
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)
B1 Winter A1B A1F1 B1 Summer A1B A1FI 23 GCMs; 1980 –1999 baseline Source: http://www.climatechangeinaustralia.gov.au/
Wind speed projections (2050)
B1 Winter A1B A1F1 B1 Summer A1B A1FI 23 GCMs; 1980 –1999 baseline Source: http://www.climatechangeinaustralia.gov.au/
Rainfall projections (2050)
B1 Winter A1B A1F1 B1 Summer 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
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SW summer temperatures projected to increase between 0.5 to 2.1 ºC by 2030 & 1 to 6.5 ºC by 2070
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Average annual number of days above 35 ºC in Perth to increase from 28 to 36-67 by 2070
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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
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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 Climate variable 6 8
How will changes in extremes be manifested?
Rainfall extremes ●
Occur on different scales in space-time
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intermittent processes
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poor observations Not 'resolved' by computational grids in GCMs – need 'downscaling' methods
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topographic effects coastal effects subgrid-scale processes (e.g. convection)
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Changes do not scale with specific humidity changes: more complex
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Statistics vary over a range of time scales (temporal clustering)
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Changes in rainfall means cannot be used to reliably infer changes in extremes
2030
Value added by dynamical downscaling
200 km 65 km 4 km fraction 2070
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 – an active area of research difficult topic & Believe/disbelieve – stay informed & manage the risk
Future management strategies will need to be:
adaptive rather than static
based on a scenario & portfolio approach