DAILY NEWS Jan 29, 2013 2:59 PM - 2 comments

Consultant's report predicts Toronto climate in 2040s, forecasting more intense rain storms

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Summer storms in Toronto are going to be more intense 30 years from now and warmer weather will increase the demand for air conditioning, according to a consultant's report discussed Tuesday at the city council's parks and environment committee.


"The operation of critical infrastructure such as the electrical grid, water treatment plants, sewers and culverts, public transport and roads are sensitive to particular temperature and weather thresholds," according to the report, titled Toronto's Future Weather and Climate Driver Study: Outcomes Report. "Beyond these thresholds infrastructure may have reduced capacity or may not function at all."

The report, completed by SENES Consultants Ltd. and commissioned by the Toronto Environment office, was submitted last year to the parks and environment committee for information by John Livey, the deputy city manager of planning and public works. It projects climate patterns for Toronto for 2040-49. At press time, the meeting was still in session. Depending on the outcome of Tuesday's meeting, the report is scheduled for submission to full council Feb. 20.

The city commissioned the study "to provide a window on the conditions that our public infrastructure will be operating in over the course of its service life," according to the committee agenda.

The report predicts that the average number of winter storms per year between 2040 and 2049 will be six, down from 14 per year in 2000 to 2009. The average number of summer storms per year will be 17, up from 16 in 2000 to 2009.

But the maximum amount of rainfall in summer storms per hour would double, according to the report. It also suggested the maximum amount of precipitation in one day could be expected to increase, from 66 mm in the decade from 2000 to 2009, to 166 mm in the 2040 to 2049 time frame.

Although fewer storms will product more than 25 mm per day of precipitation in 2040 to 2049 than in 2000 to 2009, "a small number of those 'heavy storms' will produce 'very intense' storms and produce much greater amounts of rainfall in short periods than previously seen with clear impacts on city infrastructure (culverts and drainage management) and an increased potential for flooding."

The report cited several extreme weather events in 2000 to 2009, including a storm Aug. 19, 2005, which washed out the bridge on Finch Avenue crossing Black Creek, about a kilometre southwest of York University.

"The storm left a trail of damage that, according to the Insurance Bureau of Canada, represented the highest insured loss in the province's history, exceeding $500 million," the report said. "That's more than two and a half times Ontario's losses during the ice storm of 1998 and the second largest loss event in Canadian history."

That storm, according to the report, produced wind gusts of 72 km/h and 103 mm of rain in one hour across the northern part of the city.

"That compares to 53 mm in one hour from Hurricane Hazel in 1954," according to the report.

In addition to more intense summer rain storms, the report also predicts warmer summer days, putting an increased demand on air conditioning.

The average number of days per year with a temperature greater than 30 degrees Celsius is expected to increase from 20 (in 2000 to 2009) to 66 during the 10-year period starting in 2040. The report also projected the number of "degree days per year" greater than 24 Celsius, when the temperature is higher than 24 degrees for 24 hours.  That figure is expected to increase to 180 by 2040, from 31 in 2000 to 2009.

The agenda for the Jan. 29 committee meeting noted it is important to design public infrastructure to operate under extreme weather.

"Key points of concern are public transit, roads, energy, water supply, sewage treatment, storm water management and for those members of our community who are vulnerable to heat waves and cold winter temperatures."

The agenda also stated there are "no financial impacts resulting from the receipt of this report for information purposes," but that "there are financial implications for capital works and operating budgets due to changing weather patterns in the Toronto area resulting from climate change."

The report used a global climate model, regional climate model and the U.S. Weather Research Forecasting model, developed jointly by the National Centre of Atmospheric Research and the National Oceanic and the Atmospheric Agency.

It was written in consultation with climatologists, meteorologists and hydrologists from agencies including the Ontario Ministry of the Environment and the Toronto Region Conservation Authority.

It also used data from the Hadley Centre, a climate research unit operated by Britain's public weather service and funded by the British government.

Other climate predictions for Toronto for 2040-2049 included:

  • An average annual temperature increase of 4.4 degrees Celsius;
  • Twenty-six fewer snow days per year;
  • An average increase in winter temperature by 5.7 degrees Celsius;
  • An average summer temperature increase by 3.8 degrees Celsius; and
  • An increase by 13 degrees Celsius of the extreme daily minimum temperature
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