If global temperatures rise by one degree Celsius or more from current levels each year Billions of people will be exposed extreme temperature and humidity Those who cannot cool themselves naturallyAccording to research by Purdue University School of Science and Purdue Sustainable Future Institute in the United States.
The results of the research were published in the journal Proceedings of the National Academy of Sciencesshows that global warming is happening 1.5°C above pre-industrial levels will increasingly harm human health across the planet.
People can only withstand certain combinations of heat and humidity before their bodies begin to experience heat-related health problems such as heat stroke or heart attack. While climate change increases temperatures around the world, billions of people could be pushed beyond these limits.
The research team modeled increases in global temperature between 1.5°C and 4°C (considered the worst possible scenario) to identify areas of the planet where warming would occur. Heat and humidity levels that exceed human limits.
“To understand how complex real-world problems like climate change will affect human health,” says W. Larry Kenney, professor of physiology and kinesiology at Pennsylvania State University and co-author of the new study. knowledge of both the planet and the human body is required“.
Temperatures and humidity above human limits
The ambient wet-bulb temperature limit for young, healthy people is about 31°C, according to the study published last year by Penn State researchers. However, besides temperature and humidity, any individual’s specific threshold at a given time also depends on the individual’s level of effort and other environmental factors. such as wind speed and solar radiation.
According to the researchers, in human history, temperatures and humidity above human limits have been recorded only on a limited number of occasions and for only a few hours in the Middle East and Southeast Asia.
India, Pakistan, Eastern China and Sub-Saharan Africa
This map shows the expected annual heat hours beyond human limits, depending on how global warming increases:
The results of the study suggest that if global temperatures rise by 2°C above pre-industrial levels, 2.2 billion people in the Indus River Valley in Pakistan and India, 1 billion people in eastern China, and 800 million people in sub-Saharan Africa Each year, they will be exposed to hours of heat that will exceed human tolerance.
The researchers also note that these regions are located in lower-middle-income countries, so many of the affected people may not have access to air conditioning or any effective means of reducing the negative effects of heat on health.
Will reach the United States, South America and Australia at 3°C
Researchers conclude: If global warming persists at 3°C above pre-industrial levelsTemperature and humidity levels that exceed human tolerance will begin to affect the east coast and central United States, as well as South America and Australia.
“Such models are good at predicting trends, but they cannot predict specific events, such as the 2021 heatwave that killed more than 700 people in Oregon or London reaching 40°C last summer,” warns the lead author in a statement Bioclimatologist Daniel Vecellio, who completed a postdoctoral fellowship with Kenney at Penn State.
Millions, billions of people will try to migrate
“If temperatures continue to rise, we will live in a world where crops will fail and millions or billions of people will try to migrate because their areas of origin are uninhabitable,” he warns.
Over the past several years, Kenney and his colleagues conducted 462 separate experiments to document the total levels of heat, humidity and physical exertion that people could tolerate before their bodies could no longer maintain a constant core temperature.
“As people get warmer, they sweat and lose heat to the environment, pumping more blood through the skin to maintain their body temperature,” Kenney explains. At certain temperature and humidity levels, these settings are no longer sufficient and the body’s core temperature begins to rise.“.
In 2022, Kenney, Vecellio and their colleagues showed that the heat and humidity limits that humans can tolerate are lower than suggested in theory.
“The data provided much-needed empirical evidence about the human body’s ability to tolerate heat. These studies formed the basis for these new predictions about where climate change will create the conditions humans will face.” They won’t be able to tolerate it for long.” says co-author Matthew Huber, professor of earth, atmospheric and planetary sciences at Purdue University.
The researchers, together with Huber’s graduate student Qinqin Kong, decided to investigate how people in different parts of the world would be affected if the planet warmed between 1.5°C and 4°C. Researchers say the best estimate for how warm the planet will be by 2100 if no action is taken is 3°C.
Humid heat will pose a threat
“Official climate adaptation strategies around the world focus only on temperature,” says Kong. But this research shows that moist heat will be a much greater threat than dry heat. “Governments and policymakers should re-evaluate the effectiveness of heat reduction strategies to invest in programs that address the greatest hazards people face.”
Researchers say people should always worry about extremes of heat and humidity, regardless of how much the planet is warming. Although it remains below the determined human limits. In preliminary studies of the elderly population, Kenney found that older adults experience heat stress and health problems associated with lower heat and humidity levels than younger people.
The data used in this study examines core body temperatures, but researchers say people also experience health problems from other causes during heat waves.
To stop rising temperatures, researchers cite decades of research showing that humans need to reduce greenhouse gas emissions. especially carbon dioxide from burning fossil fuels.
“The worst heat stress will be experienced in non-rich regions, with rapid population growth expected in the coming decades,” warns Huber. “This is despite the fact that these countries produce much less greenhouse gas emissions than the rich.” As a result, billions of poor people will suffer and many will die, but rich nations will also suffer from the heat, and in this interconnected world, everyone can expect to be negatively affected in some way“.
Reference work: https://www.pnas.org/doi/10.1073/pnas.2305427120
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