December 2002

Section 6bSection 6b

Canadian Impacts of Canadian Impacts of Climate Change (2)Climate Change (2)

CGCM1 results suggest very hot days across Canada will become much hotter…

…extreme cold days will become much less cold

Change in Cooling Degree Days (2090)

…and space cooling demands will risedramatically

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

There are also risks of the spread of diseases

West Nile Virus

Lyme Disease

• 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

More frequent intense rainfalls increases the risks of local floods

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

Canadian Forest Service

…and extend the duration of the annualfire season

Canada’s coastal fisheries will be affected by changes in species distribution

Ecological preserves within the national parks may be at risk