Tropics at risk of ‘dangerous’ heatwaves, study finds

Many people in the tropics are at risk of experiencing ‘dangerous’ heatwaves more than half the year by the end of the century, a study has found. They will happen even if the goals of the Paris climate agreement are met.

If this goal of limiting temperature rises to less than 2 degrees Celsius compared to pre-industrial times is breached, the tropics could face longer ‘brutal’ heat waves, according to work by US researchers, published Thursday in the journal Climate Change. Communication Earth and Environment.

Under the effect of global warming, heat waves are already increasing, most recently in Western Europe or currently in China, with consequences such as droughts, poor harvests or fires, and endangering health and biodiversity.

Based on statistical projections of warming induced by different scenarios of greenhouse gas emissions associated with human activities, the researchers evaluated potential exposure to dangerous levels of heat and humidity.

India and Africa are at risk

Consequence: In tropical regions, even if the Paris target is met, heat could reach dangerous levels for humans “on most days of a typical year”. Otherwise, the temperature may reach a very dangerous level for a long time. All tropical regions are involved, with the Indian subcontinent and sub-Saharan Africa being the most exposed.

Outside the tropics, catastrophic heat waves could become annual events, the study found. “If we don’t pull ourselves together, billions of people will be exposed to more dangerous temperatures than ever before,” said lead author Lucas Vargas Zebbedello of Harvard University.

The study is based on a scale that defines ‘dangerous’ for humans from 39.4 degrees Celsius and ‘extremely dangerous’ at 51 degrees.

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Very high limits were initially defined in relation to certain working environments (for example boilers) and have not yet been observed in the outdoor atmosphere. But by 2100, some tropical regions are ‘almost certain’ to face it, Mr Zeppetello notes, unless emissions fall sharply. ‘It’s very scary’.

In the worst-case scenario, extreme temperatures can last for two months of the year in the most affected areas.

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