With research into heat and the limits of human health Dr. Ollie Jay, Director of the Heat and Health Research Incubator at the University of Sydney. Doctor and University of Sydney Professor Adrienne Gordon explains her specialty in care of mothers and the unborn during heat waves. Then film-maker Nick Breeze wraps it up with Dr. Jack O’Connor: Tipping Points and Interconnected Disaster Risks.

Temperatures are soaring this summer in the southern hemisphere. South America is cooking, setting hundreds of new records. Recently in Australia, Sydney Airport set a new December heat record 43.5 degrees C – 110 Fahrenheit – hottest early summer day in 44 years and 18 degrees C. above average. Australians dread a “horror summer” of heat and fire.

Welcome to radio with heat. I’m Alex Smith.

Listen to or download this Radio Ecoshock show in CD Quality (57 MB) or Lo-Fi (14 MB)




Experts may underestimate human risk during extreme heat, especially as Earth reaches the hottest temperatures in more than a million years. And beyond bare survival, what do we need to really live, for basic household tasks or even physical work? A new study warns we are not protecting the most vulnerable. This includes babies, seniors, the unhoused and other risks you may not know.

We have the ideal guest to explain. Professor Ollie Jay is Director of the Heat and Health Research Incubator at the University of Sydney. He is a co-author of the paper published November 29, 2023 in Nature Communications, titled “A physiological approach for assessing human survivability and liveability to heat in a changing climate.” The paper is Open Access (free to read).

Listen to or download this 27 minute interview with Ollie Jay in CD Quality or Lo-Fi


Australia just had its first early season heat wave. The Sydney Airport hit 43.5 degrees C. (110 degrees F. in the shade). The south country cooked while a truly extreme cyclone hit the North, dumping over two feet of rain in the Cairns area! “We’ve never seen anything like it” said the local Member of Parliament (who no doubt supports coal expansion anyway).


The Australian Council of Social Services called the coming Australian months “the horror summer”. The Australian Bureau of Meteorology predicts dire heat.

Absolute temperature records were set last week in China and Korea in what should be the start of winter. People all around the world experienced extreme heat this year.

Australian research into heat and health can help us all, as the Northern Hemisphere expects even more extreme heat next Spring and Summer in this El Nino year. We all need to learn how to deal with extreme heat, and who to help and watch over first.

As this new paper explains, there are two approaches to estimating heat risk. One is to measure actual excess deaths within a few days of extreme humid heat, basically epidemiology. But that assumes a developed health system that recognizes heat-induced mortality and keeps records – not the case in many hot humid parts of the world. Instead this paper uses a physiological method – finding heat tolerance for pregnant women, babies, little kids, young adults, and seniors.


In this Abstract Tw stands for the wet bulb temperature, the “feels-like” temperature measured when a thermometer has a wet cloth around it, allowing it to cool by evaporation as humans do with sweat. Previous extreme heat guides estimate our upper limit at 35 degrees Wet Bulb Temperature (Tw). Now we know it is much lower, especially for certain age groups:

Our physiology-based survival limits show a vast underestimation of risks by the 35 °C Tw model in hot-dry conditions. Updated survivability limits correspond to Tw~25.8–34.1 °C (young) and ~21.9–33.7 °C (old) – 0.9–13.1 °C lower than Tw = 35 °C.

For older female adults, estimates are ~7.2–13.1 °C lower than 35 °C in dry conditions. Liveability declines with sun exposure and humidity, yet most dramatically with age (2.5–3.0 METs lower for older adults). Reductions in safe activity for younger and older adults between the present and future indicate a stronger impact from aging than warming.

Bad news: there is never going to be a single easy number for heat risks for public warnings by officials or on TV. As we learn, the heat limit is quite different for different ages. If you are looking for a single number, the safety barrier, no luck. There could be hundreds of different thresholds for different people and conditions.


…we model heat stroke deaths (hyperthermia) and do not model the two other common types of heat-related deaths: cardiovascular collapse and renal failure, acknowledging that heat stroke deaths are a fraction of total excess heat-related deaths.

By the way, living in a very hot dry place, like Arizona or the Middle East, does NOT protect vulnerable people from heat stroke or death. The paper says: “… impossibly high sweat rates are needed for survivability in very hot and dry conditions, resulting in Tw survivability values considerably lower than 35 °C”


At last official count, Australia has over a quarter of a million homeless people. It is probably more. They may not find shelter during the heat wave. As in America and every country, the homeless are a special category of social risk. A University of Sydney press release says “In a 2020 Sydney heatwave, the cost of treating heat illness in just two people who were homeless was A$70,184.” [about $47,000 USD]

It surprised me to learn certain medications also lower the amount of heat people can stand, as well as obesity and probably mental illness.


We can’t just focus on mortality. Everyone has to live, doing a job, getting groceries and all that. About a quarter of world population still has to work outdoors to grow crops. We recently heard from our guest Dr. Connor Dunn Diaz about possible crop losses – meaning food shortages – when agricultural workers can’t work outside. This team also tested limits to livability, and those limits are reached at much lower temperature/humidity combinations than fatality-only guidelines.

Global projections for end of century indicate next generations will be able to do less during humid heat waves, i.e. lower productivity. Various studies have tried to put a monetary value on that labor loss due to climate change.

From the Jay et al. paper:

..by end-of-century, select areas (Arabian Peninsula, Northern India, Bangladesh) are projected to see a significant increase in conditions that are survivable but not livable for young adults, reaching a frequency of 5–7% (6 months/decade) for SSP5-8.5 …

…For regions around Riyadh, Cartagena, New Delhi, and Dhaka, there is already a high frequency of time where an older adult cannot presently perform more than 2.5 METs of activity (slow walking). Thus, moving forward, these locations will increasingly become unliveable despite being survivable.”


The Australian Council of Social Services found even before the summer begins 74% of people on income support are cutting back on cooling and heating due to increasing energy costs. That happens in America and Europe too. So there is a socio-economic aspect to who lives and who dies during extreme heat waves.

From my light research, it seems Australia does not have a complete plan for emergency cooling shelters. The University of Technology Sydney just announced the first mobile cooling hub, but that is just a start. Dr. Ollie Jay says cooling centers set up in Australia did not really work. People did not use them. What works in North America or Europe may not be the best way to go in Australia, he says.

We know Earth is getting hotter. We try to sweat through heat never seen before. Yet governments around the world, including Australia, continue to fund and approve big expansions of fossil fuel production. Perhaps there is back-pressure against warning the public about the real risks scientists find. Why are we so slow to prepare?


Vecellio, D., Kong, Q., Kenney, L. & Huber, M. Greatly enhanced risk to humans as a consequence of empirically determined lower moist heat stress tolerance. Proc. Natl Acad. Sci. 120, e2305427120 (2023).

Covered here on Radio Ecoshock October 18, 2023

Destabilized Weather in an Unstable World

Daniel Vecellio interview (Lo-Fi)



Sydney Ideas – Extreme heat and human health – Dec 15, 2022




Extreme heat is risky for pregnant women and babies in the womb. It can be fatal – or may increase chances of diseases in the child. Adrienne Gordon is a Clinical Professor in Obstetrics with special knowledge of neonatology and heat. She leads clinical research and co-authored over a hundred peer-reviewed papers.  From Faculty of Medicine and Health, University of Sydney we welcome Adrienne Gordon to Radio Ecoshock.

Listen to or download this 14 minute interview with Adrienne Gordon in CD Quality



From Science.org August 13: “A 2020 literature review found that each 1°C increase brought a 5% increase in the risk of prematurity in hot areas or seasons – and a 16% increase during heat waves. That means climate change could exacerbate a major risk: Globally, prematurity is already the leading cause of death for children younger than 5.” Premature birth can affect later childhood health, and even lifetime health outcomes.

Adrienne also specializes in stillbirths. She is also Chief Investigator for the National Health and Medical Research Council with the Stillbirth Centre of Research Excellence. Extreme heat increase the tragic risk of stillbirths. It is difficult to imaging the pain of losing a baby right from the womb. Men can’t really understand, although fathers hurt too.

Dr. Gordon’s work reminds me of my feature in 2006 with Dr. Francisca Perera of Columbia. Their team strapped backpacks on women in Harlem New York – to measure air pollution coming into their lungs during pregnancy. They found actual changes to DNA in the womb due to smog. Now in Australia, Canada, and around the world, we have heavy wildfire smoke as well. I ask Adrienne about the effects of wildfire smoke on babies in the womb.

Hundreds of millions of people live in the new too-hot-to-live danger zones. Most have no electricity or air-conditioning. If we keep on our high emissions path, this sounds like a recipe for large-scale tragedy for women, babies and toddlers – many who emit practically nothing in greenhouse gases. Maybe as part of climate reparations from big fossil fuel burning countries, we need to incorporate a special program for child-bearing women globally.

SEE ALSO: This PBS specialExtreme heat exposure during pregnancy can raise risk of severe delivery complications, new study finds” September 10, 2023. That is based on this recent paper “Analysis of Heat Exposure During Pregnancy and Severe Maternal Morbidity” September 7, 2023.

SEE ALSO: “How extreme heat can hinder effectiveness of pregnancy tests, some contraception
August 13, 2023.



In extreme heat and a grid-down situation, many Canadians and Americans can retreat to their cooler basements. But very few homes in Australia have basements because (a) the frost line is barely a meter (3 feet) down; (b) flooding may be a problem, so homes are often raised to allow water to flow under. So there is no built-in cooling shelter in Australian homes. What is the plan for people in Sydney, Melbourne, Adelaide or Perth if electricity is lost during a high heat wave? Are there adequate cooling centers or other buildings with backup generators? No.

Even those who can afford to run an air conditioner can be vulnerable if the power goes out – as happened to hundreds of thousands in Victoria during a heatwave in 2009.”


Here is a quick report on what happened in 2009.

“In southern South Australia maximum temperatures widely reached their highest levels since at least 1939. Adelaide peaked at 45.7 °C on 28 January and South Australia’s highest temperature was 48.2 °C at Kyancutta.

There were widespread power outages across both states. In Victoria, up to 500,000 homes and businesses were left without electricity. There were also major disruptions to train services with more than 1300 trains cancelled as rails buckled and air-conditioning failed.

A Department of Human Services report from the Victorian Government found that the heatwave contributed to 374 deaths.

A Department of Health report from the South Australian Government found that the 13-day heatwave contributed to 32 deaths above the expected number for this period.


Conditions such as these are listed on death certificates, whereas environmental factors like extreme heat or air pollution often aren’t. This means researchers and policymakers have to estimate heat-associated hospitalizations and deaths using models, or piece them together from multiple sources. The estimates can vary greatly.

South Australian coroners recorded 58 deaths during the 2009 southern Australian heatwave, for instance. Victorian coroners estimated 374 “excess deaths” in Victoria during this period. But the Australian Bureau of Statistics recorded just 54 excess natural heat deaths across the country for the entire year.

HEAT IS BIGGEST NATURAL KILLER IN AUSTRALIA (more fatalities from heat than all other natural causes combined, including cold, floods, storms, and lightening.



Here are some quick tips to watch during extreme heat – from healthline.com:

“Heat emergencies have three stages: heat cramps, heat exhaustion, and heatstroke.

With heatstroke, all the symptoms of heat exhaustion may be present, plus:

body temperature over 104°F
irrational behavior or hallucinations
rapid, shallow breathing
rapid, weak pulse
loss of consciousness
dry skin”


Whereas heat exhaustion is related to dehydration and a cardiovascular system struggling to pump blood through the body, heatstroke occurs when a person’s body temperature gets so dangerously high that it begins overheating their tissues and organs, says William Roberts, MD, a professor of family medicine and community …” May 4, 2023




We just have time for a sample from the ClimateGenn podcast with host UK film-maker Nick Breeze. Nick interviews leading scientists for his members and then posts them on YouTube. Find out more at www.genn.cc.

Nick Breeze speaks with Dr Jack O’Connor, at the UN University’s Institute for Environment and Human Security. Jack is the author of the “Interconnected Disaster Risks Report” on tipping points, human security and the Earth System. My thanks to Nick for sharing his work.



That’s it for this week. Tune in again next week for more Radio Ecoshock. I’m Alex Smith. Thank you for listening, and caring about our world.  A special thanks to those who stepped up and donated last week.  Expenses for the program will be covered until February 2024.  Your help is still needed, please donate if you can.