How does the human body respond to rising temperatures? This one-of-a-kind lab in Ottawa is trying to find out

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The cylindrical chamber at the University of Ottawa lab looks at once like a machine from the past and the future. It swings open at a seam, splitting in half to reveal its contents. Tubes and chains dangle from the ceiling and reflect off the aluminum-sheeted walls. There’s just enough room inside for a black metal chair, rigged with wires for data collection and padding for comfort.

The chamber is the lab’s pièce de résistance. It’s the world’s only direct air calorimeter – a machine that continuously and precisely measures how much heat is gained and lost by the human body.

Originally developed in the 1970s at Memorial University of Newfoundland, the calorimeter was mothballed in 1990, until Dr. Glen Kenny brought it back to life later that decade. He likened the process to finding a rare Corvette at the dump and then refurbishing it.

More than 1,000 people have sat in the chamber over the years, lending their bodies to science in pursuit of nailing down how, exactly, the body responds to heat under various scenarios. “The reason we put the calorimeter back together is that it’s the golden key in understanding how the human system is going to react to heat exposure,” Dr. Kenny said.

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The Ottawa lab is at the forefront of research globally when it comes to the impacts of rising temperatures on human health, particularly among vulnerable populations such as the elderly and those living with chronic illness. The U.S. military, mining industry, electric utilities and others have looked to Dr. Kenny for help developing heat-management and monitoring strategies to protect people working in hot environments.

Health Canada has also turned to Dr. Kenny for advice. In late 2018, the federal department tasked him with assessing the effects of an extreme heat event on the most vulnerable Canadians. This led to the launch of a multiphase study on prolonged heat exposure, indoor temperature limits and cooling centres.

The study has not yet been published, but the data is in. It provides clear parameters for safe indoor temperatures and it dispels some commonly held views on the efficacy of cooling centres during heat waves.

The findings will inform federal guidance for health authorities across the country as they create strategies to address the growing problem of extreme heat. According to Health Canada, roughly 80 per cent of local and regional health authorities are currently working to “take a range of evidence-based action to protect health from extreme heat.” The department is aiming to develop its interim guidance this year.

Time is of the essence. When the record-setting heat dome settled over B.C. and then crept eastward last June and early July, Canadians were confronted with the reality that heat is a silent and prolific killer with the power to overwhelm emergency services. It was the deadliest weather event in Canadian history, linked to at least 619 sudden deaths in B.C.

Nearly one year later, as the clock ticks toward another summer, the province’s coroners service has shed light on the circumstances of those who died. According to a death-panel report released Tuesday, people aged 70 and older accounted for two-thirds of the deaths. Almost all – 98 per cent – died indoors. The overwhelming majority of the victims had at least one chronic disease. Most lived in socially or economically deprived neighbourhoods. More than half lived alone.

Among other recommendations, the report calls for a co-ordinated provincial heat-alert system and the adoption of community wellness checks for the most vulnerable.

It’s certainly worth looking back, because a lot went wrong last summer. People in distress couldn’t get through to 9-1-1 dispatchers. Some got a busy signal or were put on hold. Some callers who did manage to get through ended up waiting several hours for an ambulance. At one point, every fire truck in Vancouver was out on medical calls.

B.C. report on last year’s heat wave is a grim reminder that we must better protect our most vulnerable

Cooling in new buildings, tree canopy vital during heat waves: B.C. coroner report

Several emergency-services agencies in B.C. have since upgraded their heat-response plans and increased their staffing levels. B.C.’s E-Comm system, which provides dispatch services for police and fire departments, rolled out a new call-transfer process that it says has “materially improved” answering capacity. BC Emergency Health Services is piloting a new app that allows for on-scene video consultations between a patient and clinician at the dispatch centre. Vancouver Fire Services is training some of its staff in emergency medical response – a higher level of care for many firefighters.

It’s a good thing. The Pacific Northwest heat dome was a once-in-1,000-year weather event, but it won’t be 1,000 years before the next one. As the world warms, episodes of extreme weather will increase in frequency, intensity and duration.

Just last month, a heat wave in India and Pakistan killed at least 90 people. And while B.C. was in heat’s fatal crosshairs last year, other parts of Canada aren’t immune. A 2010 heat wave in Ontario and Quebec killed at least 280 people. A 2018 heat wave claimed dozens of lives in Montreal.

To get ready for heat, we must first understand its assault on the body. There’s a lot we already know. We know that if a person’s core body temperature reaches 40 C and continues to warm, critical systems will start shutting down. The brain will stop processing normally. The body will lose its ability to cool itself through sweating. The blood will thicken, forcing the heart to beat harder and faster. Breathing will become rapid and shallow. Organ systems will eventually fail.

We know that age is the single most important factor in terms of vulnerability to this sort of demise. With each decade, we lose roughly 5 per cent of our ability to thermoregulate – to lose heat. We know that sweating causes evaporative cooling and is key to guarding against hyperthermia; high levels of humidity inhibit that evaporative cooling process.

We know that having certain underlying conditions, such as diabetes or high blood pressure, puts people at a greater risk of heat-related illness and death. And we know that it can take a while before the accumulation of heat in the body starts affecting our cells and organs; it’s usually not until about 24 hours after the onset of a heat wave that people begin dying.

Dr. Kenny’s latest research takes our understanding further. By studying real people with real health conditions in really hot temperatures for long periods of time, his team is able to make nuanced recommendations that go beyond existing, often one-size-fits-all advice.

“This kind of work is extremely important,” said University of Washington global health professor Kristie Ebi, a lead author on the Intergovernmental Panel on Climate Change’s 2018 special report about the effects of global warming of 1.5 C above preindustrial levels. “We’re seeing heat waves at intensities we haven’t seen before. We’re not prepared. … We need to understand how to best protect people, particularly the most vulnerable.”

It’s the most vulnerable that Dr. Kenny is most concerned with. When he explains his findings, he refers to colour-coded graphs with dots representing study participants. He wants policy makers and individual Canadians to pay close attention to the dots that fall outside the clusters. “You can’t just look at the mean of a dataset,” he said. “What you need to be concerned about is the outliers. … Those are real people. They’re the ones who are going to collapse.”

Roughly 100 people participated in the federally commissioned research at the Ottawa lab. The younger, control cohort ranged in age from 18 to 31, and the older, more vulnerable group ranged from 60 to 80. Among the older demographic, a subset had either Type 2 diabetes or hypertension – an underresearched demographic in the area of prolonged heat exposure, Dr. Kenny said, owing to concerns around stress-testing vulnerable people in extreme conditions.

Three years in the making, the study has involved more than 2,400 lab hours.

On trial days, study participants put on shorts and a T-shirt, signed a consent form and got hooked up to some physiological recording devices. These included, among many others, a blood-pressure unit, an ECG machine, a body-temperature probe, a heart-rate monitor and a mask that measures oxygen consumption.

The subject then entered the study space, which consisted of two concentric cylinders (imagine one pop can inside another). The larger cylinder is about the size of a two-car garage, only taller. That’s the environmental chamber. It can be set to different temperatures and humidity levels to simulate various living and workplace scenarios. It regulates the conditions around and within the smaller, inner cylinder. That’s the calorimeter, where the nitty-gritty of the trials took place.

Here’s how it works. Researchers measure the temperature and humidity of the air entering the chamber and coming out of it. They measure two sources of heat – the heat produced by the body from simply being alive, and the dry heat the body absorbs from the hot air. Those two values, added together, equal the total amount of heat gained. Researchers then measure the moisture levels going in and out of the chamber to determine how much sweat was produced and evaporated. That’s the amount of heat lost. The difference between the heat gained and the heat lost is the amount of heat being stored in the body.

How hot is too hot?

Housed at the University of Ottawa, the world’s only direct

air calorimeter is considered the key to understanding

the impact of extreme heat on the human body. Scientists

measure the temperature and humidity of the air entering

the chamber and coming out of it. They can then calculate

how much heat the body was able to shed through thermo-

regulatory processes such as sweating, and how much it

ends up storing. Storing too much heat can lead to illness or

even death.

Monitoring station

Researchers

Direct air calorimeter

OUTFLOW

1.7 m

Temp.

Humidity

Dry

+

Evaporative

=

Total heat loss

1.9 m

Temp.

Humidity

INFLOW

Drawing not to scale

Ergometer

Participant

1. The calorimeter, which is housed in an environmental

chamber (not shown), is equipped with software that

allows researchers to monitor and record the physiologi-

cal responses of a study participant exercising or at rest.

2. The temperature in the chamber is tightly controlled to

simulate hot conditions. Study subjects wear monitoring

devices, including a mask that collects expired gases and

helps determine the amount of heat produced by the

body due to metabolism.

3-4. By precisely monitoring air temperatures and humidi-

ty levels flowing into (3) and out of (4) the calorimeter,

researchers can measure the rate of heat-exchange

between the body and the environment. Using these

measurements and the rate of heat production described

in (2), the calorimeter can be used to quantify the

real-time accumulation of heat within the body.

kathryn blaze baum and john sopinski /

the globe and Mail, Source: Dr. Glen P. Kenny,

University of Ottawa, Human and Environmental

Physiology Research Unit

How hot is too hot?

Housed at the University of Ottawa, the world’s only direct

air calorimeter is considered the key to understanding

the impact of extreme heat on the human body. Scientists

measure the temperature and humidity of the air entering

the chamber and coming out of it. They can then calculate

how much heat the body was able to shed through thermo-

regulatory processes such as sweating, and how much it

ends up storing. Storing too much heat can lead to illness

or even death.

Monitoring station

Researchers

Direct air calorimeter

OUTFLOW

Temp.

Humidity

Dry

+

Evaporative

=

Total heat loss

Temp.

Humidity

INFLOW

Drawing not to scale

Ergometer

Participant

1. The calorimeter, which is housed in an environmental

chamber (not shown), is equipped with software that

allows researchers to monitor and record the physiologi-

cal responses of a study participant exercising or at rest.

2. The temperature in the chamber is tightly controlled to

simulate hot conditions. Study subjects wear monitoring

devices, including a mask that collects expired gases and

helps determine the amount of heat produced by the

body due to metabolism.

3-4. By precisely monitoring air temperatures and humidi-

ty levels flowing into (3) and out of (4) the calorimeter,

researchers can measure the rate of heat-exchange

between the body and the environment. Using these

measurements and the rate of heat production described

in (2), the calorimeter can be used to quantify the

real-time accumulation of heat within the body.

kathryn blaze baum and john sopinski / the globe and Mail,

Source: Dr. Glen P. Kenny, University of Ottawa, Human

and Environmental Physiology Research Unit

How hot is too hot?

Housed at the University of Ottawa, the world’s only direct air calorimeter is considered the key to

understanding the impact of extreme heat on the human body. Scientists measure the temperature and

humidity of the air entering the chamber and coming out of it. They can then calculate how much heat

the body was able to shed through thermoregulatory processes such as sweating, and how much it ends

up storing. Storing too much heat can lead to illness or even death.

Monitoring station

Direct air calorimeter

OUTFLOW

Temperature

Humidity

Dry

+

Evaporative

=

Total heat loss

Temperature

Humidity

INFLOW

Researchers

Drawing not to scale

Ergometer

Participant

1. The calorimeter, which

is housed in an environ-

mental chamber (not

shown), is equipped with

software that allows

researchers to monitor

and record the physiologi-

cal responses of a study

participant exercising or

at rest.

2. The temperature in the

chamber is tightly controlled to

simulate hot conditions. Study

subjects wear monitoring

devices, including a mask that

collects expired gases and

helps determine the amount of

heat produced by the body

due to metabolism.

3-4. By precisely monitoring air tem-

peratures and humidity levels flowing

into (3) and out of (4) the calorimeter,

researchers can measure the rate of

heat-exchange between the body and

the environment. Using these mea-

surements and the rate of heat pro-

duction described in (2), the calorime

ter can be used to quantify the

real-time accumulation of heat within

the body.

kathryn blaze baum and john sopinski / the globe and Mail, Source: Dr. Glen P. Kenny,

University of Ottawa, Human and Environmental Physiology Research Unit

The conditions inside the calorimeter and the duration of the heat exposure depended on the aspect of the study at hand. In the case of the work on prolonged heat exposure, subjects endured a total of roughly nine hours in 40-degree heat at a relative humidity level of 15 per cent. That’s a dry heat, which is comparatively easier on the body.

Most of their time was spent at rest, watching Netflix on an iPad or reading a book. At three-hour intervals, several basic tests were performed to understand the impact of mundane, quotidian movements that people would do at home during a heat wave, such as moving from sitting to standing.

These trials showed that the older study participants not only gained heat at a faster rate, but they also saw their temperatures plateau at a higher level than the younger subjects. The younger cohort’s temperatures increased by an average of 0.5 degrees before levelling off, whereas the older group’s rose by a full degree, with some climbing more than 1.5 degrees. Most public-health authorities say that, when it comes to heat exposure, core body temperatures shouldn’t rise more than one degree above resting, or 38 C, for prolonged periods.

There’s good reason for this. When the body gets warm, the brain activates two critical heat-loss mechanisms: an increase in blood flow to the skin, which transfers heat to the surface and helps prevent heat gain from the surrounding air; and an increase in sweating, which causes evaporative cooling and is the primary avenue for heat dissipation. Over a sustained period under these conditions, the heart will be straining to send blood to the skin while at the same time trying to maintain a healthy blood pressure.

Sometimes the cardiovascular system is simply unable to maintain that healthy blood pressure. Some older trial participants saw their blood pressure tank by as much as 40 per cent, putting them at a much greater risk of fainting and, in turn, head injury from a fall. Basic movements around the house – such as going from sitting to standing, as was tested in the calorimeter – could prove fatal, particularly for those with blood-pressure issues to begin with.

Effects of extreme heat on the

human body

The team at the University of Ottawa research unit conducted a multi-phase study looking at the impact of various extreme-heat scenarios on younger and older adults. The findings have not yet been published, but the below represents some of the early data from one of the prolonged heat trials. The research showed that older study participants not only gained heat at a faster rate, but they also saw their temperatures plateau at a higher temperature than the younger subjects. Some participants were unable to complete the daylong heat exposure because their temperatures just kept climbing and they felt unwell, including a 77-year-old participant who stopped the trial at hour six.

Prolonged heatwave simulation

40˚C, 15 per cent relative humidity

39.8˚C

77 years

39.4

39.0

74 years

38.6

38.2

37.8

20 years

37.4

37.0

0

1

2

3

4

5

6

7

8

9

Exposure time (hours)

The Globe and Mail, figure published with permission from Elsevier (Environment International, DOI.ORG/10.1016/J.ENVINT.2020.105909)

Effects of extreme heat on the human body

The team at the University of Ottawa research unit conducted a multi-phase study looking at the impact of various extreme-heat scenarios on younger and older adults. The findings have not yet been published, but the below represents some of the early data from one of the prolonged heat trials. The research showed that older study participants not only gained heat at a faster rate, but they also saw their temperatures plateau at a higher temperature than the younger subjects. Some participants were unable to complete the daylong heat exposure because their temperatures just kept climbing and they felt unwell, including a 77-year-old participant who stopped the trial at hour six.

Prolonged heatwave simulation

40˚C, 15 per cent relative humidity

39.8˚C

77 years

39.4

39.0

74 years

38.6

38.2

37.8

20 years

37.4

37.0

0

1

2

3

4

5

6

7

8

9

Exposure time (hours)

The Globe and Mail, figure published with permission from Elsevier (Environment International, DOI.ORG/10.1016/J.ENVINT.2020.105909)

Effects of extreme heat on the human body

The team at the University of Ottawa research unit conducted a multi-phase study looking at the impact of various extreme-heat scenarios on younger and older adults. The findings have not yet been published, but the below represents some of the early data from one of the prolonged heat trials. The research showed that older study participants not only gained heat at a faster rate, but they also saw their temperatures plateau at a higher temperature than the younger subjects. Some participants were unable to complete the daylong heat exposure because their temperatures just kept climbing and they felt unwell, including a 77-year-old participant who stopped the trial at hour six.

Prolonged heatwave simulation

40˚C, 15 per cent relative humidity

39.8˚C

77 years

39.4

39.0

74 years

38.6

38.2

37.8

20 years

37.4

37.0

0

1

2

3

4

5

6

7

8

9

Exposure time (hours)

The Globe and Mail, figure published with permission from Elsevier (Environment International, DOI.ORG/10.1016/J.ENVINT.2020.105909)

As heat exposure drags on, older adults will get hotter and hotter, but they’ll be unable to perceive the threat in the same way younger adults do. They have a weaker thirst drive and don’t sweat as readily. This is why it’s so important to check on older loved ones on hot days, ideally in person. “These elderly people will tell you they’re okay,” Dr. Kenny said. “It’s very late in the game, after eight hours or so, that they’ll start to say, ‘I’m not feeling well.’”

One study participant – a 77-year-old woman with no pre-existing health conditions – started to complain of light nausea after nearly six hours of heat exposure. The lab scientists, who were in constant communication with the woman and monitoring the physiological data streaming onto their computers, could see her core body temperature had reached 39.4 degrees. The researchers moved the woman into a cooler space and, within about 20 minutes, she felt much better. Her day in the lab, however, was over.

Open this photo in gallery:

Even though the 77-year-old’s body temperature had cooled to a normal level, it wouldn’t have been a good idea for her to return to the heat. This rationale was proved true through the trials related to cooling centres.

Those experiments were similar to the ones on prolonged heat exposure, except that the study subjects got a two-hour break from the heat in a 22-degree space. The research found that while time in a cool space does indeed give people reprieve from the heat and briefly stops the unabated rise of core body temperature, it can also provide a false sense of security. When the person returns to the hot environment, the threat goes right back up to the same level within just a couple of hours.

“People will get what’s called an after-rise,” Dr. Kenny explained. Although a person may feel cooler while in the cooling centre, lots of heat is still being stored in the muscles. Upon return to the hot conditions, that heat gets shunted back to the core, causing a rapid increase in body temperature. “The solution can’t just be, ‘Put them in the cold and then let them go home thinking they’re safe.’ Because they’re not.”

Does this mean cooling centres are bad? No. But they’re not the straightforward panacea that governments and others may believe them to be. The cities of Vancouver, Toronto and Montreal all pointed to a network of cooling centres as a feature of their current heat-response plans.

Dr. Kenny said if people are going to rely on cooling centres as a way to beat the heat, they should visit them multiple times throughout a heat event. And governments, he said, should communicate this proviso to their citizens. They should also consider 24/7 cooling centres, so the most vulnerable have a safe place to sleep when overnight temperatures haven’t dropped enough to mitigate the risk. Some B.C. municipalities did this for the first time last year, when a heat wave hit about a month after the Pacific Northwest heat dome.

Another effective way to shed heat is to go from a very hot place to a warm one. This allows the body to cool down a bit, but not so much that the body’s heat-loss responses shut down. That’s helpful because when the person returns to the very hot place, their thermoregulatory functions are still ramped up and ready to fire. This is particularly critical for people who work outdoors in the heat. It’s better to find some shade on the grass under a tree, Dr. Kenny said, than to go sit in an air-conditioned space and then return to work in the extreme heat.

People can also immerse their lower limbs in cool or even lukewarm water, Dr. Kenny said, since there’s a greater transfer of heat through water molecules than air molecules.

And then there’s the matter of fans, which is particularly important to consider in typically temperate locations with low rates of air conditioning. According to the coroners report, the majority of heat-dome victims died indoors in places without AC. At least 149 people died in a location where a fan was in use.

The prevailing international public-health guidance has long been that fans are advised when the air temperature is at or below 35 degrees – the average skin temperature. Because thermal energy naturally flows from hot toward cold, the body will shed heat to the environment. But if the surrounding air is warmer than the skin, a fan will actually force hot air over the body and could cause the person to gain heat.

This is where age comes into play. While the rise in body temperature will cause a younger person to compensate by sweating more, an elderly person’s body won’t sweat enough to offset the increase in heat gained from the environment. A fan, basically, could turn a room into a convection oven. “The fan may keep the elderly person feeling okay,” Dr. Kenny said, “but feeling okay and not dying are two different things.”

The prevalent advice on safe fan use doesn’t take into account vulnerabilities related to age or underlying health conditions, Dr. Kenny said. The University of Ottawa team is on a mission to fill that gap in knowledge.

Robert Meade, a senior postdoctoral fellow in the lab and Dr. Kenny’s co-investigator on the research for Health Canada, is currently working on a biophysical model – a type of study that doesn’t involve human trials but rather uses mathematical formulations to simulate what happens in the body under certain circumstances. That soon-to-be completed work, Dr. Meade said, will call into question recent recommendations suggesting fans could be used to help cool the body during hot weather above 35 degrees.

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A model isn’t enough to support a change in international guidance on safe fan use. That’s why Dr. Kenny applied for a grant from the Canadian Institutes of Health Research to fund 600 day-long human trials on the topic. Approved in March, the nearly $1-million, five-year project will evaluate heat-mitigation strategies, including the use of readily available, store-bought fans in older adults and those with chronic disease.

“Fans have never been comprehensively studied under simulated heat-wave conditions, like those experienced during the B.C. heat dome,” Dr. Kenny said. “We’re just getting started.”

Among those most affected by the heat dome in B.C. last summer were people living in residential homes. While the death rate in long-term care facilities and hospitals was 30 and 35 per cent higher than normal, respectively, the death rate in residential dwellings, such as apartments, houses and mobile homes, was a whopping 205 per cent higher. This, scientists and doctors have said, was likely due to extremely high indoor temperatures in residences without air conditioning.

Anonymized, voluntarily provided data collected from users of Ecobee smart thermostats in Abbotsford, B.C., showed that the hottest home without air conditioning was nearly 17 degrees hotter at the peak of the heat dome than the coolest home with air conditioning. There were also times when it was cooler outside than it was in the hottest residence without air conditioning.

Melissa Lem, a family doctor in Vancouver and president-elect of the Canadian Association of Physicians for the Environment, said temperatures reached the low-30s inside her home in Kitsilano. She remembers doing live television interviews about the heat dome with an ice pack pressed against her abdomen.

Heading into the summer, Dr. Lem is concerned for the most vulnerable of her patients. “I’m worried,” she said. “I think the heat dome has made it so clear that we need to view cool and clean indoor air as a human right.”

But how hot is too hot when it comes to indoor temperatures? To answer that question, Dr. Kenny’s team ran trials in which participants spent roughly eight hours in each of two or four temperature settings, depending on their age and health condition: 22 C, 26 C, 31 C, and 36 C, all set to 45-per-cent humidity.

Open this photo in gallery:

That’s the sticky kind of heat, the kind that’s harder for your body to shed. The reason for that is perhaps best explained this way: If you take a shower and step out into a dry room, you’ll feel much cooler than if you shower and step out into a steamy room. In the high-humidity scenario, the moisture in the air is preventing water from evaporating from your skin, thwarting your body’s key cooling process and causing you to instead retain heat.

The research showed that at indoor temperatures under 26 degrees, people are safe. But when the thermostat hits somewhere between 26 and 31 degrees for hours at a time, health problems may arise for some adults. Temperatures over 31 degrees, Dr. Kenny said, should be avoided for prolonged periods, especially for high-risk people.

Heeding such advice will require us to adapt our environments. The federal government recently launched public consultations and released a discussion paper on a National Adaptation Strategy, which is aimed at transforming everything from emergency services to infrastructure and supply chains to mitigate the risks of a warming world. Environment and Climate Change Canada said the strategy will “provide a framework for concrete action to address climate-related hazards, including extreme heat.”

Dr. Kenny is eager to publicize the team’s latest findings, but he also knows there’s much more to be learned about the body’s ability to thermoregulate. A couple of years ago, he applied for funding through the Canada Innovation Foundation to support a $5-million project dubbed Operation Heat Shield Canada: Protecting Human Health on a Warming Planet. The vision is to create a global hub where scientists can conduct studies using the calorimeter and, ideally, a new transformable chamber that would allow for more complex heat simulations.

But while the federal government and the University of Ottawa agreed to kick in $2-million and $1-million, respectively, the Ontario government declined to provide the remaining $2-million in funding. The Ministry of Colleges and Universities, which reviews applications to the provincial research fund, said in an e-mail that submissions are “evaluated to assess scientific excellence, strategic value to Ontario and potential economic and/or geopolitical risks.”

Dr. Kenny is still hoping to somehow secure the money he needs to get Operation Heat Shield off the ground. “This kind of work is critical,” he said. “We can’t be playing games with people’s lives.”

This article is part of No Safe Place, a year-long Globe project on climate adaptation in Canada. Last year’s catastrophic and deadly heat dome, fires and floods in British Columbia revealed a hard truth about how ill-equipped Canadians are to respond to the devastating effects of climate change. No Safe Place focuses on issues and solutions related to adapting societies and economies to a hotter climate. Coverage includes digital interactives, data-driven investigations and engaging features. https://tgam.ca/NoSafePlace

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