Climate change behind increases in extreme rain danger: scientists

Climate change behind increases in extreme rain danger: scientists

The rains soaked southern Alberta for days, unrelenting, saturating soil already sodden with melting snow — and before long Calgary was awash as rivers overflowed their banks.

The province described the 2013 flood as the worst in its history, but it might not be for long. Research from Environment Canada shows that climate change is behind more extreme rainfalls in Canada and suggests the problem is likely to get worse.

“If we continue with global warming, we will see continued increase in the frequency and severity of extreme precipitation,” said Megan Kirchmeier-Young, co-author of a paper published Monday in the Proceedings of the National Academies of Sciences.

Researchers combined computer models and observed data for the most specific look yet at how climate change affects the kind of damaging rainfalls that turn streets to rivers.

The idea stems from simple physics. Because warm air holds more moisture than cool air, an atmosphere heated by climate change should hold more water and dump larger amounts of it.

Showing that, however, is more complex.

Previous research on extreme rainfall patterns hasn’t been able to achieve a finer scale than the average of the entire Western Hemisphere. Now, scientists have been able to focus on regions within the United States and Canada — what’s happening, why, and what’s coming down the road.

They began with figures from a variety of locations for the maximum amount of rain falling over a one-day period and over a five-day period.

They did four separate calculations for the probability of those rainfall amounts occurring each year over a 50-year period from 1961 to 2010. Three were based on climate models that incorporated real-world data on increasing greenhouse gas levels, while the fourth was calculated directly from observed figures.

All four calculations showed increasing chances of extreme precipitation. The result from the observed data showed the highest increase, with chances of one-day heavy rainfall increasing by more than five per cent.

Five-day rainfalls showed similar patterns, although a lower increase.

“We’re finding (that) extreme precipitation increases in the models that have this human influence (greenhouse gases) agrees well with the increases we’re seeing in the observations,” Kirchmeier-Young said.

Such studies not only help scientists understand the past. Comparing modelled results with real-world measurements increases their ability to look ahead.

“If we have that, we can have more confidence in what the model is telling us what will happen in the future.”

All three models in the study showed the chance of over-the-top rainfalls is expected to increase far into the future.

“If we continue with global warming, we will see continued increase in the frequency and severity of extreme precipitation,” Kirchmeier-Young said.

The consequences are serious, she added. A one-day deluge can create significant flash floods in an urban area; five-day downpours can swell rivers over their banks — although river floods are complicated by more factors than just rainfall.

Urban planners, builders and regulators are all going to have to take Canada’s coming climate into account.

“We have to be thinking about what impacts more heavy rainfall will have,” Kirchmeier-Young said. ”Flash flooding is something that we’re going to have to be thinking more about and be more concerned with.”

This report by The Canadian Press was first published June 1, 2020

Bob Weber, The Canadian Press

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

Sylvan Lake beachgoers spark safety concerns

‘You’re putting your life at risk,’ tweets Rachel Notley

Conservatives call for Trudeau to testify at committee on WE Charity deal

Ethics Commissioner Mario Dion is already investigating whether Trudeau violated the Conflict of Interest Act

Genetic detectives begin work to trace spread of COVID-19 in Canada

The kinds of genetic technology being used for this project did not exist when SARS hit Canada in 2003

Quebec police continue search for father, one day after missing girls found dead

Bodies were found in a wooded area of Quebec City suburb

Red Deer up to 4 active COVID-19 cases

Province announced 77 new confirmed cases across Alberta Friday

QUIZ: Are you ready for a summer road trip?

How much do you really know about roads, motor vehicles and car culture? Take this quiz to find out.

Canmore RCMP respond to multiple hiking injury calls this weekend

EMS and RCMP responded to three separate and unrelated hiking accidents in Kananaskis Country.

How Conservative leadership hopefuls would address the WE scandal if they win

The ethics commissioner has been called in to see if Trudeau broke conflict-of-interest law

With debt, deficit numbers out, experts say Liberals need plan for growth

Borrowing will push the federal debt past $1 trillion by the end of the fiscal year

Pedestrian-only downtown a hit with residents as St. John’s adapts to pandemic

‘The city really got this right this time. We’re very happy’

Bosnian-Canadians mark 25th anniversary of Srebrenica massacre

‘It’s sad for a child to think that it’s normal, actually, to … have family members killed’

PODCAST: COVID-19 and the US Election

The Expert welcomes Burman University Political Scientist Marc Froese

Sylvan Lake RCMP continue search for missing man

43-year-old Steven Hull’s last known whereabouts were in the Sylvan Lake area on May 28

Most Read