INDEPTH: SUMMER SENSE
Heat waves
CBC News Online | June 30, 2005
While there is no formal definition for the term heat wave, we all know
what it feels like – hot, humid and energy-sapping.
The definition of an extreme heat emergency on the other hand, is a little more formal. It's up to each municipality to come up with its own, but generally it's declared during a period of sustained, excessively hot weather. In Toronto, health authorities add to that definition that the likelihood of weather-related mortality exceeds 90 per cent.
Indeed, during the June 2005 heat wave in Ontario and western Quebec, the coroner's office in Toronto identified three heat-related deaths.
The skyline of Toronto is masked by pollution, Monday, Aug. 12, 2002. (CP Photo/Kevin Frayer)
The reason heat kills is that is pushes the body beyond its limits. When overheated, we produce perspiration, which evaporates and brings down our internal temperature. But when the mercury rises along with the humidity, then evaporation becomes more difficult and we're more likely to overheat.
Those at greatest risk for overheating include elderly people, young children and those who work, exercise or live outdoors, such as homeless people. According to the American Red Cross, heat-related illness rises significantly when excessive heat lasts more than two days. It says spending at least two hours per day in air conditioning significantly cuts down on the number of heat-related illnesses.
City people are at greater risk of heat-related illnesses and death than their rural neighbours. That's because stagnant hot air traps the pollution in cities instead of allowing it to disperse, leading to increased breathing problems. And cities, with their concrete and asphalt, trap heat, gradually releasing it at night. That means there's no break from high temperatures.
That may explain why Toronto, the biggest city in Canada, experienced the most
significant increase in normal June temperatures for 2005. The normal mean
monthly average temperature for June – including daytime and nighttime temperatures – is
17.8 C. For June 2005, it was 22.5.
"We've smashed the normal temperature by almost five degrees. It's a significant record. The previous record was 21.7 C in 1949," said
Environment Canada meteorologist Peter Kimbell.
Ottawa also broke records with a mean monthly average of 21.1 in June 2005, compared to a normal of 18.3. The previous record was 20.6 in 1999. In Montreal, the June 2005 average was 21.4, compared to a normal average of 17.9. That breaks the previous record of 21 in 1999.
And in Windsor, a different hot weather record was broken. Residents there suffered through 16 days of temperatures over 30 in June 2005. The previous June record of 15 days over 30 was set in 1949.
While Environment Canada does not keep records about humidex advisories, certainly June 2005 was full of them. It issues the advisories when the temperature is above 30 and the humidity makes if feel like it's above 40.
Kimbell warns June's hot weather may extend throughout the rest of the summer.
"We are forecasting the temperature to be above average for June, July and August. But you have to take that with a grain of salt because of our record. Three-month forecasts are very difficult to do," he said.
But if the summer of 2005 does in fact turn out to be one of the hottest on
record, does that prove that we’re truly in the throes of climate change? The short answer is no, but it’s a qualified no.
“Climate change is something that is long-term and happens over decades,” said
Kimbell. In other words, one hot summer does not equal climate change.
Still, climatologists say we are in a sustained, relatively rapid period
of global warming, which could have significant effects on animal, plant and
human life. The 1990s contained some of the warmest years since 1861, when
scientists began keeping records. The year 2004 was the fourth-warmest on record.
Some scientists suggest that global warming will increase the number of extreme weather events such as El Nino and the European heat wave of 2003. Many researchers note the increase in temperature coincides with the industrial revolution, and the resulting increase of carbon dioxide released into the atmosphere from the burning of fossil fuels and the cutting of forests.
Researchers with the Intergovernmental Panel on Climate Change say the Earth's
average surface temperature has gone up about 0.6 C since the start of the
20th century. And that may be just the beginning. The IPCC projects an average
global temperature increase of 0.6-2.5 C in the next 50 years, and 1.4-5.8
C by 2100.
Intergovernmental Panel on Climate Change
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