Climate Change & Weather – 2 Articles

Article 1:”You’ve Got To Move Fast”: Science Learns To Quickly Link Extreme Weather And Climate


Courtesy of Barrie360.com and Canadian PressPublished: Jul 23rd, 2023

By Bob Weber

As firefighters and other first responders battle an unprecedented summer of fires, floods, tornadoes and heat waves around the country, a group of Canadian scientists are asking why they’re happening in the first place. 

“May and June were record hot months in Canada and we’ve got the record wildfire season as well,” said Nathan Gillett of Environment and Climate Change Canada. “Yes, it has been busy.”

Gillett heads the Rapid Extreme Event Attribution Project, a new federal program that uses the growing field of attribution science to promptly establish to what extent — if any — a specific flood in British Columbia or wildfire in Quebec is due to climate change.  

“The idea is to be able to make rapid extreme event attribution days or weeks after the extreme events occur,” he said. 

Twenty years ago, if you’d asked a scientist if climate change was linked to days of torrential rain or months of desiccating drought, you’d probably get an answer along the lines of “We can’t say for sure but this event is consistent with the modelling.” 

But in 2003, a paper was published suggesting science could do better. Myles Allen of Oxford University borrowed a concept from epidemiology.

“You can say that smoking increases your risk of lung cancer by a certain amount,” Gillett said. “In the same way, you can say human-induced climate change increased the risk of a certain event by a certain amount.”

Since then, hundreds of attribution papers have been peer-reviewed and published. As well as Canada, governments including the United Kingdom, Australia, the Netherlands, South Korea, Japan and the United States are using attribution science. 

Attribution science works by comparing climate models. One set of models will use data drawn from actual records while another, otherwise identical, set will be constructed with the influence of greenhouse gases removed. 

Simulations will be run using those two sets and the difference in the results reveals the impact of climate change. It allows scientists to say to what extent the presence of greenhouse gases increased the likelihood of the event in question. 

“It’s probabilistic,” Gillett said.

The process is now established enough, with peer-reviewed protocols and standards, that the calculations can be done quickly. 

“Once you’ve got the method in place and it’s validated, you really just have to get the observations from that event and you can provide a result,” said Gillett.

Some events are easier to study than others. Gillett said his group hopes to be able to come to conclusions on heat waves in about a week, but wildfires, which involve more variables, will take longer. 

Speed matters, said Clair Barnes, a researcher with the World Weather Attribution group in the U.K., which has studied the role of climate change since 2015 in more than 50 events around the world — including the finding that the heat wave preceding the fire that levelled Lytton, B.C., was made 150 times more likely by climate change.

“Our aim is to look at high-impact events that are in the news,” she said. “There was an appetite in the public and the media for more information about what’s really happening now.” 

Promptly assessing the role of climate change after extreme events brings actual insight and information to the discussion, Barnes said. 

“If you spend three years thinking about it, the media has already decided it was climate change or it wasn’t climate change and has moved on. If you want to be involved in that discussion and bring some science to that discussion, you’ve got to move quickly.”

But attribution science has more uses than just shaping public debate. Governments are using it inform their adaptation strategies. Financial institutions are using it to assess risk. It’s come up in hundreds of court cases around the world attempting to attribute climate liability. 

It does have its limitations. 

Attribution science can only work where there’s enough historical weather data to build an accurate climate model. That leaves out much of the global south, where some of the worst human impacts are occurring. As well, extremely local events are often beyond its resolving power.  

“You do have to be careful to communicate the uncertainties,” said Gillett. “We shouldn’t be overconfident.”

There’s certainly no shortage of work. Barnes said her group has had to establish a strict protocol that weighs the magnitude of the event, the amount of damage it inflicts and its effect on human lives to weed out which events merit study. 

“There are so many events that we just don’t have the time to look at them all.”

But World Weather Attribution has found the time to consider Canada’s wildfires. It’s a complex one, so results aren’t expected for another month or so. 

By then, chances are there will be a new extreme event to consider. When Barnes joined World Weather Awareness, she assumed winter and summer — the times of peak temperature highs and lows — would be the busiest. Not so. 

“We’ve had temperature records set for the last few months and it’s not even the peak of boreal summer,” she said. “It’s just been non-stop.” 

Article 2: Not All Heat Warnings Are Equal: 5 Things About Canada’s Alert System For Hot Weather


Courtesy of Barrie360.com and Canadian PressPublished: Jul 27th, 2023

By Jacob Serebrin in Montreal

Environment Canada has issued heat warnings this summer for parts of the country used to baking in the heat, but also in places unaccustomed to extended periods of hot weather. Earlier this month, the Northwest Territories and northern Quebec were under heat warnings as temperatures climbed into the 30s. On Wednesday, warnings were in effect not just in southern Ontario but in much of Nova Scotia, northeastern Newfoundland and even Old Crow, Yukon, north of the Arctic Circle.

But the temperature that leads to a heat warning in one province could be lower than the temperature that triggers an alert in another part of the country.

Here are five things to know about heat warnings in Canada:

What exactly is a heat warning?

Environment Canada issues heat warnings when temperatures begin posing a health risk. Generally, the warnings act as forecasts that include daytime highs and nighttime lows above a specific threshold for two consecutive days.

Heat can be dangerous because it forces the body to work harder than normal to maintain its internal temperature, says Ray Bustinza, a scientific adviser on environmental health at Quebec’s public health institute. Older people, those with chronic medical conditions and young children are particularly at risk because their bodies have to work even harder, Bustinza says.

How hot is too hot?

Provinces have different thresholds, and the levels warranting an alert can even vary within a province. In general, there are only a few degrees difference in the threshold between provinces.

For example, heat warnings are issued in Nova Scotia when daytime high temperatures are expected to reach 29 C or warmer for two or more consecutive days, and when nighttime low temperatures aren’t expected to fall below 16 C. In southwestern British Columbia, it takes two days at 33 C or warmer with nighttime lows of 17 C or warmer to trigger an alert.

As well, British Columbia has a second extreme-heat warning system that is used when temperatures get so high everyone is at risk.

Sarah Henderson, scientific director of environmental health services at the British Columbia Centre for Disease Control, said the Environment Canada system is intended to alert people when there is risk associated with higher temperatures, especially for vulnerable people. The extreme-heat warning is issued when conditions become really dangerous, she said.

Quebec, like B.C., also has an extreme-heat warning system in addition to the Environment Canada-issued warnings. The levels that trigger those alerts vary from region to region and are based on temperatures that have been associated with significant increases in mortality.

Why are heat warnings triggered at different temperatures in different provinces?

Environment Canada has 15 heat warning regions across Canada, with different criteria for each one — though those criteria often differ by just a few degrees.

Jean-Philippe Bégin, a meteorologist with Environment Canada, says the criteria were developed in conjunction with provincial and territorial health departments, which are responsible for setting the thresholds.

Henderson, who is also a professor in the medical faculty at University of British Columbia, said people’s susceptibility to higher temperatures is based on what they’re used to. “That’s partially because they’re physiologically adapted to the climate that they live in, partially because they’re behaviourally adapted to the climate they live in and partially because the built environment reflects the climate,” she said.

In B.C., there are five different heat regions to account for its varied topography and climate. In each of those regions, the threshold for a warning is based on the minimal temperature that leads to an increase in mortality of around five per cent.

How does the humidex factor in?

In every province, except B.C. and Alberta, heat alerts can also be triggered if the humidex reaches a specific level. 

The humidex is an attempt to link the temperature with the relative humidity, a measure of how much moisture is in the air, said Djordje Romanic, a professor of atmospheric and oceanic sciences at McGill University.

As temperatures rise, people start sweating, which cools the body when the sweat evaporates. But that process doesn’t work as well if there’s a lot of moisture in the air. “We are sweating, but that sweat is not evaporating, and our body is not capable of reducing its temperature,” Romanic said.

Humidex readings quantify the combined effect of humidity and temperature on a healthy person at rest in the shade, Romanic said, adding that high humidex levels can cause heatstroke.

The Canadian Centre for Occupational Health and Safety says humidex levels of 46 and higher are dangerous and that people should avoid exertion when the humidex rating is over 40.

In western Canada, hot weather tends to be drier than in eastern and central Canada, Henderson said. B.C., she added, considered adding the humidex to its thresholds when they were updated in 2018, “but we didn’t see any meaningful differences between the temperature and humidex models.”

With climate change, will heat warnings become more common and could people stop caring? 

B.C. is currently evaluating whether to update its thresholds, Henderson said, as warnings become more common. “We worry constantly about over-alerting,” Henderson said, adding that last summer some parts of B.C. had six heat warnings, a frequency she worries will lead people to become desensitized to the warnings.

One of the challenges to maintaining people’s attention to the health risks of heat warnings is that many people enjoy hot weather, she said.

While poor air quality caused by wildfire smoke, for example, isn’t pleasant for anyone — even those who may not be at risk of serious health effects — temperatures that can kill vulnerable people can also lead to a pleasant day at the beach for others.

“It really is a very challenging communications problem,” she said.

Patricia Dent

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