There have been record-breaking heat waves from Delhi to the Pacific Northwest and the number of deaths is expected to increase. Depending on future emissions of greenhouse gases, a range of heat impacts will be given by the University of Washington and Harvard University.
The study was published in August.
"The record-breaking heat events of recent summers will become much more common in places like North America and Europe," said the lead author, who was a PhD student at the University of Washington. "For many places close to the equator, more than half the year will be a challenge to work outside if we don't curb emissions."
He said that the study shows a wide range of possibilities. It shows that the emissions choices we make are still important.
The heat index is a combination of air temperature and humidity that is used to measure impact on the human body. The National Weather Service defines a heat index as 103 F. The heat index is unsafe to humans for any length of time.
The standards were not thought of as conditions that would happen in outdoor environments when they were first created. We are seeing them now.
Even if the Paris Agreement goal of keeping warming to 2 C is met, crossing the "dangerous" threshold will be more common in the US, Western Europe, China and Japan by the year 2200. By the year 2200, dangerous days could double in the tropics.
In countries closer to the equator, such as India and sub-Saharan Africa, "extremely dangerous" conditions, in which humans should not be outside for any amount of time, could become common.
If 30 to 40 days a year were exceeding the extremely dangerous threshold, what would happen? We have the ability to prevent these scenarios. The study shows us that we have some agency to prevent these scenarios from happening.
The range of future conditions is calculated using a probability based method. The authors used a statistical approach that combines historical data with population projections, economic growth and carbon intensity to predict the likely range of future CO
Adrian Raftery, a professor of statistics and sociology with an appointment in atmospheric sciences, said that the statistical approach gave plausible ranges for carbon emissions and future temperature.
The authors looked at how rising carbon dioxide levels would affect global monthly weather patterns.
According to co-author David Battisti, the number of days with dangerous levels of heat in the mid-latitudes will more than double by century's end. Much of the tropics will experience dangerous levels of heat stress for nearly half the year by the year 2200.
The results show the need for both to reduce future greenhouse gas emissions and to protect populations.
More information: Lucas Vargas Zeppetello, Probabilistic projections of increased heat stress driven by climate change, Communications Earth & Environment (2022). DOI: 10.1038/s43247-022-00524-4. www.nature.com/articles/s43247-022-00524-4 Journal information: Communications Earth & Environment
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