december 2002 section 6b canadian impacts of climate change (2)
TRANSCRIPT
December 2002
Section 6bSection 6b
Canadian Impacts of Canadian Impacts of Climate Change (2)Climate Change (2)
0 20 40 60 80
Victoria
Calgary
Winnipeg
London
Toronto
Quebec
Fredericton 2080-2100
2041-2069
2020-2040
1961-1990
Number of hot days above 30C
Heat waves in Canadian cities are expected become more frequent
0
10
20
30
40
50
60
1961-90 2020s 2050s 2080s
Scenario Period
Da
ys
>=30
>=32
>=35
By 2080, Toronto could experience more than 30 “Hot Days” in excess of 32C each year
Toronto
Increased heat stress and related degradation in air quality will have major health effects
Air quality
• Normally defined on basis of statistical frequency – e.g. 2 SD, 3 SD, upper/lower decile or percentile, return period– Can apply to intensity, duration, areal extent and/or frequency– can also often be considered as weather that is out-of-place
• By definition, these events rarely occur– Infrequency makes probabilities hard to estimate
• An extreme becomes a disaster when it causes large ecological or socio-economic damages
– Human factors are important– Greatest disasters often linked to 2 or more unusual weather features
occurring at same place/time
Defining extreme events and related disasters
In some ways, the risks of extreme events are like
the odds in games of chance
Game of Chance Analogy Probability
1 in 6
1 in 36
1 in 216
1 in 1296
Extreme events can cause many types of disasters
Lightning damage
Floodlosses
Ecologicaldisaster
Structural damage
Wind damage
Loss oflife
Factors involved in two recent Canadian disastersFactors involved in two recent Canadian disasters
The 1997 Red River Flood• wet fall in 1996• unusually high snow accumulation in headwaters during winter• major April snow storm in Manitoba• moderate rate of melt• large, moderately populated area
The 1998 Ice Storm • Warm, moist air mass related to El Nino event• unusual atmospheric blocking/duration of event related to NAO• cold air in valley• followed by cold weather• large, heavily populated area
Climate change and natural variations in climate can change the risks of extreme events
• Changes in NAO and ENSO patterns with time can change the probability of unusual weather– The intense El Nino and unusual NAO behaviour in 1997-98 were
important factor in the 1998 ice storm
• Climate change may change the behaviour of NAO and ENSO
• Climate change can also directly cause large changes in weather behaviour and hence in probability of extremes – Much like playing with loaded dice
Total expendituresfor 1982-99
Federal:$8.3 billion
Other:$20 billion
Weather related disasters alone cost Canadians more than an average $1 billion per year
• Analyses suggest increases have occurred in some types of weather extremes in some, but not all areas
• Individual extreme events occur rarely and hence are difficult to link directly to specific “causes”
• However, many of the events are broadly consistent with climate change projections
• Hence these events are good examples of what may happen more often in the future
Are recent weather extremes due to natural variability or to climate change?
Climate change will also increase the risks of forest fires across much of Canada
Canadian Forest Service