What are ‘heat storms’?

Heat waves have evolved from sporadic, isolated episodes to massive, ‌cascading weather events that can blanket vast swaths of the planet for months or even years ​at a time.

To continue calling such sprawling phenomena ‘heat waves’ would be like calling a monsoon ⁠a ‘rain shower’. To understand the new reality of these immense expanses of heat, a consultation with two dozen climate researchers and an analysis of temperatures worldwide for for every hour since 1960 has yielded a new concept: heat ‌storm.

Scientists and researchers often discuss global warming in the context of risks that will arise if the planet’s average global temperature rises more than 2°C above pre-industrial levels. An ordinary person can’t make much of that. However, heat waves are the connective tissue between the science of global warming and our ‌everyday ⁠experience. And today supersized heat waves regularly swarm the planet.

Experts have also identified a ‘heat cascade’ as heat storms that run one after the other, simultaneously or both. Their duration has also swelled from around two months in the 1960s to nine months in the early 2000s.

Naming ⁠events is “a powerful way for people to understand that something is happening,” Anthony Leiserowitz, director of the Yale Program on Climate Change Communication, said. Yet “we don’t do that with heat waves,” he said, even though heat has been estimated to kill almost half a million people a year.

The largest heat storm on record, named 'Vera’, lasted for 367 days over 2023-2024 and swept over nearly 85% of the globe.