In 2013, the rains soaked southern Alberta for days, unrelenting, saturating soil already sodden with melting snow. The province describes the 2013 flooding as the worst in its history, reports the Globe and Mail.
However, according to a new study by researchers at Environment Canada, the 2013 floods in Alberta may just be a foretaste of things to come.
The study, published in the journal Proceedings of the National Academy of Sciences, shows that climate change is behind more extreme rainfalls in Canada and suggests the problem is likely to get worse.
“We’re finding that in North America, we have seen an increase in the frequency and severity of heavy rainfall events. And this is largely due to global warming,” said Megan Kirchmeier-Young, a research scientist at Environment and Climate Change Canada and lead author of the study, reports CBC Canada.
Previous studies have already identified an anthropogenic influence on extreme precipitation at the hemispheric level. However, this new study finds evidence of anthropogenic influence in the continental and regional scales. This observation has implications for many facets of both the human and natural systems,
Flooding across North America has destroyed homes and businesses and caused billions of dollars in damages. But the study says it will only get worse.
“And as we continue to see warming, we will continue to see increases in the frequency and severity of extreme rainfall,” Kirchmeier-Young said. “And heavy rainfall is one of the major factors in flash flooding, particularly in urban areas.”
To make their observations, the scientists combined computer models and a plethora of observed data to get the most specific look yet at how climate change affects the kind of damaging rainfalls that turn streets to rivers across North America.
Actually, it should be your basic physics lesson. Warm air holds more moisture than cool air, while an atmosphere heated by climate change should hold more water and dump larger amounts of it – But the answer is more complex. Going beyond rainfall averages for the entire Western Hemisphere was needed.
The researchers focused on figures from a variety of locations in Canada and the U.S. 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.
“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,” Dr. Kirchmeier-Young said.
“Physics tells us that a warmer atmosphere can hold more moisture,” Kirchmeier-Young said. “That should be reflected as an increase in extreme precipitation in most locations.” And sure enough, observations and the models were consistent with one another.
Francis Zwiers, director of the Climate Impacts Consortium at the University of Victoria, said the new study is the first to link more frequent extreme rainfall and climate change in North America.
“The fact that it now can be measured on the scale of North America is significant,” he said. “When you go to smaller scales when you are able to answer the question… then it indicates that the evidence is becoming stronger and clearer.”
