The severe rainfall events happening on Canada’s Atlantic and Pacific coasts are a glimpse into the country’s climate future, experts say.
However, the impact of such extreme weather, like the massive flooding in British Columbia, can be managed if world leaders are able to limit climate change.
“There’s a new normal coming. … This is a glimpse into the future,” said Kent Moore, a professor of atmospheric physics at the University of Toronto.
“We’re seeing the effects of all the warming that’s happened in the last century and we’re going to continue to warm.”
This week, communities on Canada’s Atlantic and Pacific coasts are facing severe rainfall from two “atmospheric river” storms, which are giant bands of water vapour in the sky that can be several hundred kilometres long.
On the east coast, strong winds and heavy rain are hitting Atlantic Canada as part of a storm system moving its way up from the Caribbean.
Some areas, like the Halifax harbour, have recorded wind gusts of up to 107 km/h. Rainfall totals have surpassed 50 millimetres in several Maritime communities, and those numbers are expected to climb.
Environment Canada has said 100 to 150 mm of rain could fall across eastern Nova Scotia and Cape Breton, while southwestern Newfoundland could get up to 300 mm of rain over the next two days.
Meanwhile, on the west coast, parts of British Columbia will see several storms that could bring up to 100 to 200 mm of rain in central and northern B.C., said Global News’ chief meteorologist Anthony Farnell.
That system, which is expected to start late Wednesday, will move south and could drop up to 100 mm rain on parts of the province still recovering from severe flooding caused by a deluge of rain only last week, Farnell said.
“The ground is still saturated, and that’s the concern — that it now no longer takes these incredible amounts of rain to cause additional flooding,” he said.
“Also, a lot of the dyke systems around there, the pumping stations, have all been weakened. So if you get another atmospheric river or another one of these parades of storms coming in, you’re going to have problems again.”
While these so-called atmospheric rivers are nothing new — particularly for the west coast — the size and repetitiveness of them are what has experts worried.
Atmospheric rivers and changing climate
Last week, an atmospheric river hit southern B.C., triggering floods, landslides and mudslides that damaged highways, triggered evacuations and isolated thousands of people.
Typically, the west coast could see 20 to 30 atmospheric rivers on average in fall and winter, said Armel Castellan, a warning preparedness meteorologist with Environment Canada.
Furthermore, at any given time in the world, there can be four to five atmospheric rivers happening. But the severity of these atmospheric rivers is changing.
Castellan said some atmospheric rivers are holding more water and as a result, the weather event could stretch out longer. He said the trend is “consistent with climate change.”
“When it becomes a 48-hour or longer event, or even 36 hours, it can be very detrimental depending on the rain rates; then you start looking at atmospheric rivers that are not just beneficial to the ecosystem, but are absolutely devastating,” he said.
“We know that the moisture in the atmosphere is elevated as a result of a warming baseline climate post-industrial era, so you can add more moisture to the flow and that creates atmospheric rivers that are more potent in and of themselves.”
Farnell said while it’s difficult to blame climate change for one specific event, previous weather systems show that extreme events are becoming more common.
Canada’s coastal regions will be among the first to experience the effects, he added.
“One similarity is that with a warming climate, even a rise of one to two degrees over such a large ocean adds an incredible amount of energy and water vapour to these systems, so you’re going to see 20 to 30 per cent more rainfall and the first areas to feel the effects are those areas,” Farnell said.
“The flooding that happened last week — those do happen in our lifetime. But when you start to see the number of events piling up, not just in Canada but elsewhere in the world, you do take a bit of a step back and wonder … what’s happening?”
Coasts at high risk
In 2019, the Council of Canadian Academies concluded that Canada’s coasts are among the regions that face the biggest risks from climate change.
Climate change is gradually making sea levels rise, making floods more common and surges heavier and more powerful, the report said.
Infrastructure was also a concern as heavy rain, floods and high winds are growing threats to buildings like homes to hospitals.
Though Canada’s coasts are at risk to severe weather, climate change isn’t restricted to just a few provinces or territories.
“In the GTA in the last few summers, we’ve had really heavy downpours that have overtaxed the storm sewer system and basements have flooded,” he said.
“Every part of the country is experiencing the impact of climate change, and it’s different depending on where you are.”
Moore added it’s up to world leaders to manage climate change to control how severe weather events will be.
“If we increase (temperatures) by the end of the century … it’ll really determine the intensity of the events in the future,” he said.
“It’s under our control how more intense they’re going to get.”
— with files from The Canadian Press.