Toronto must overhaul its aging infrastructure to adapt to dramatic new climate change projections — a process that could cost billions — say some councillors and environmentalists.

But some fear the city is not taking the matter seriously enough, as the chair of the Parks and Environment Committee remains skeptical of the projections.

A study commissioned by the city and set to be discussed Tuesday by the parks committee predicts temperatures about 4.4 degrees warmer and a marked increase in extreme storms by 2040.

“If people are concerned about a crumbling Gardiner, this study makes it look like a teeny, tiny pothole,” said Franz Hartmann of the Toronto Environmental Alliance. “If we’re not paying attention, it will literally be catastrophic.”

The study, called “Toronto’s Future Weather and Climate Driver Study,” foresees Toronto’s climate 30 years in the future as marked by fewer but more intense storms, less snow in the winter and increased heat and humidity in the summer.

Torontonians have already braved three of the worst storms in the city’s recorded history in the past 12 years, and sweltered through the earliest known heat wave on June 19, 2012.

The city’s roads, sewers, storm drains and electrical grids were simply not built to withstand the new climate, said Councillor Gord Perks, a member of the committee.

“If you took Toronto and put it in another part of the world, our infrastructure would be wrong for that weather. This is the same kind of problem,” he said.

He said the study means the city has “billions of dollars of work to do,” including expanding the capacity of sewers and re-engineering green spaces to accommodate ponds of rainwater.

“We’re already experiencing severe weather. . . . We can’t delay doing this work for even one year,” he said.

Councillor Norm Kelly, chair of the committee, said climate change is a “contentious” issue and questioned the modelling process used to make the predictions.

“You know how hard it is to predict the weather for next week, let alone three decades out,” he said. “But let’s assume that they’re correct. Then what the city has to do is take stock of its infrastructure and figure out how to roll out programs of repair and replacement.”

Councillor James Pasternak said the conversation too often devolves into a debate on climate change.

“Building a city that is able to prepare for the worst is really the most prudent thing that city hall can do,” he said. “(Preventative upgrades) cost a lot less than reconstructing entire roadways or sewer systems afterwards.”

Toronto Water — which has the largest infrastructure renewal backlog of urban centres in Canada at $1.6 billion — has launched a study of 34 peak basement flooding areas and already installed new storm drainage in some.

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The model projects the impact of current carbon dioxide emissions on the atmosphere and includes the impact of so-called “climate drivers” like Lake Ontario and the polar front jet stream.

“The results are quite dramatic,” Young said. “The extremes are about to change.”

The years 2040-49 were selected because they represent a “time horizon relevant to a number of infrastructure replacement activities,” according to the study. It recommends that climate studies continue over the next three decades.