Fog engulfed the city of Ipswich yesterday morning as commuters made their way to work.
Fog engulfed the city of Ipswich yesterday morning as commuters made their way to work. Rob Williams

Extreme hot weather to become killer within 50 years: study

Choking. Stifling. Inescapable. If you think humidity's abhorrent, it's going to get much worse. And researchers are warning it will become a major killer within 50 years.

A research paper released today warns extreme hot and humid weather events will begin to exceed the upper limits of human survivability by the late 21st century.

This will be a particular problem for Australia's nearest neighbours in densely-populated South East Asia. But an Australian academic says it also has dire implications closer to home.

THE HEAT IS ON

"There are many studies now coming out from South East Asia and India where they're starting to realise heat is becoming a serious concern," says Associate Professor Lidia Mayner, who is researching the health implications of extreme weather events at Flinders University's College of Nursing and Health Sciences.

"Similar conditions are reflected in parts of Australia, such as Darwin, Cairns and Broome,"  Prof Mayner said.

Put simply, the weather events combining extreme heat and humidity in these tropical zones are set to surpass the human body's ability to cool itself.

The new study published today in Science Advances projects extreme heat events, which for the moment are mostly an inconvenience, are set to become increasingly regular and fatal in South Asia - home to one fifth of the world's population.

And that's in a region where heat is already a serious problem.

In 2015, the fifth deadliest heatwave in recorded history hit large parts of India and Pakistan, claiming around 3500 lives.

In this Oct. 22, 2014 photo, waste pickers look for recyclable items at a landfill on the outskirts of New Delhi, India. India says it is taking bold steps against climate change with plans for a five-fold increase in renewable energy capacity. However, Environment Minister Prakash Javadekar said the country won't act to curb carbon emissions because it first must pursue economic growth to eradicate poverty. (AP Photo/Altaf Qadri)
In this Oct. 22, 2014 photo, waste pickers look for recyclable items at a landfill on the outskirts of New Delhi, India. India says it is taking bold steps against climate change with plans for a five-fold increase in renewable energy capacity. However, Environment Minister Prakash Javadekar said the country won't act to curb carbon emissions because it first must pursue economic growth to eradicate poverty. (AP Photo/Altaf Qadri) Altaf Qadri

BOILING POINT

The northern parts of Australia also potentially have a deadly mix of humidity and heat, with monsoonal rains and high sea temperatures.

"If you have high humidity, the body will not perspire," Prof Mayner said.

"Normally this will help keep you cool, but with high humidity that simply doesn't happen."

High humidity makes heat stress more dangerous and intolerable. The body is more prone to overheat. This can lead to heat stroke and a variety of other problems.

And stifling humidity's not the only threat.

"People need to realise their body temperature is about 37C, so once you get above that you will start feeling effects," Prof Mayner said.

"Temperatures of 40-42C, which we regularly have in summer, will have an impact on your health - for all age groups."

While older people will be more vulnerable, those in the 18-64 age groups also suffer heat-stress related issues, especially if they already have a medical condition.

RED ALERT

"If you already have heart, renal or respiratory conditions, the heat will make it worse," Prof Mayner said.

"That's a pretty big group of people. And if you look at anyone from 65 onwards, such conditions are really quite prevalent."

ALL BASES COVERED: A paramedic comforts a house cat while another prepares to assess an elderly relative of the man.
ALL BASES COVERED: A paramedic comforts a house cat while another prepares to assess an elderly relative of the man. Andrew Thorpe

But a less-well known threat, even in existing hot weather, is the impact dehydration has on medications.

"When you do perspire, the body doesn't have the normal level of fluid," Prof Mayner said..

"So whatever medication you're taking could have a higher impact on the body."

This is because, once they enter the body, medications are more concentrated than they should be. There's not enough fluid in the body to properly dilute them.

"When there are these extreme conditions, people that have medical conditions or are on medication to maintain normal daily activity must go see a doctor," Prof Mayner said.

"Ask your doctor what you need to do to balance out your effective dose."

CLIMATE ALERT

The Science Advances report ran high-resolution simulations under two climate change scenarios.

Wet-bulb temperatures - calculated as a combination of humidity, heat and the human ability to cope with both - are projected to approach the survivability threshold (35C) over most of South Asia, and exceed it at a few locations, by the end of the century under a business-as-usual scenario.

Under a mitigation scenario (roughly comparable to the goals pledged by the 2015 UN Conference on Climate Change), temperatures are still expected to reach dangerous levels (over 31C).

"The increase in humid heat raises important questions of environmental justice in agricultural areas where the inhabitants - the majority of whom work outdoors and have poor access to air conditioning - are most vulnerable," the authors say.

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