TORONTO – Extraordinary weather continued this week in parts of North America, bringing thunder and hail storms, flooding and heatwaves to parts of Canada and the U.S.
Severe storms hit southern Ontario as record-setting hot and humid weather moved into the region Wednesday.
While apocalyptic storm clouds gathered over Toronto, residents in other parts of the province endured hail the size of ping pong balls and gusty winds that brought down power lines and tree branches.
A heatwave sweeping through the northeastern U.S. peaked Wednesday. Hundreds of cities reported breaking or matching record-high temperatures while at least five possible heat-related deaths were reported, all involving people 60 years or older with pre-existing medical conditions.
The extreme, volatile weather points to “global weirding,” an appraisal of climate conditions that finds previously believed irregular weather patterns becoming the standard worldwide.
Global weirding examines a variety of weather changes that accompany global warming, essentially shifting the conditions for what we perceive as normal weather.
“What we’re used to, our normals, are changing,” says Katharine Hayhoe, an atmospheric scientist at Texas Tech University.
The term refers to “a change in the conditions we’re used to, a different climate than (what) we grew up with,” Hayhoe explains.
Originally from Etobicoke, Ontario, Hayhoe now studies climate change issues in west Texas, a hotbed of wild weather activity from wildfires and snowstorms to dust storms that paint the sky a shade of burnt sienna reminiscent of a Star Wears movie.
“We have weather conditions I'd never seen before… At least once a week from April to June we have tornado watches,” she says.
“It's certainly true that we have an enormous diversity of weather on our planet and that's why we have to be careful not to immediately jump to conclusions about what could be causing a specific weather event.”
Hayhoe explains how global weirding differs from global warming, the latter being just one factor in climate change.
“Warming implies rising global temperatures, but weather is a lot more than just temperature,” she says.
Weirding considers how individual weather events—heat waves, cold spells, blizzards, hurricanes and tornadoes—coupled with long-term trends—frequency of drought, reduced crop yield, insect infestation—paints a portrait of the overall change in the weather we’re used to experiencing in our daily lives.
“Where we live today does not feel the same as it did when we were growing up. Spring is arriving on average one to two weeks earlier each year across the entire northern hemisphere. Summer heat is becoming more frequent and more severe. Heavy rainfall events are increasing in strength and frequency,” Hayhoe explains.
While weirding cannot totally account for the recent spate of extreme and devastating storms across North America, what it can do is isolate a weather event as exceptional, allowing scientists to identify larger-scale trends that can be linked to global climate change.
Hayhoe explains with a dice analogy.
“When we throw a pair of dice, we always have a chance of rolling two sixes. That's the natural variability. What climate change is doing, however, is slowly, one by one, removing one other number at a time and replacing it with an identical six. So our chances of rolling double sixes for many extreme events have slowly been increasing,” she says.
The recent spree of killer tornadoes spawned by severe storms in the U.S. midwest cannot be characterized by the double six dice analogy.
In Joplin, Missouri, over 100 people were killed when the deadliest single tornado in recorded history tore through the area in May.
"It is too early to tell if this is simply an unusual year, or the beginning of a new trend," Hayhoe says.
“We can never tell for sure if a single event is because of climate change. We can say, however, that the long-term statistics, or chances, of rolling a double six are increasing. And that's what's happening with many, but not all, of our weather extremes.”
Copyright (c) Shaw Media Inc.