The heatwave that struck parts of North America’s Pacific coast in 2021 propelled temperatures in Lytton, a village in British Columbia, to 49.6°C—4.6° higher than the previous record. On the fourth day of this torment the place erupted in flames and was almost completely destroyed. These events were so out of the ordinary that, in a press conference held some weeks later by climate modelers, they struggled to explain how circumstances had conjured them.

Climatologists reckon the North American heatwave of 2021 was one of the most extreme deviations from meteorological norms ever recorded, anywhere. But others have come close. As the world gets hotter, phenomena once considered rare are becoming common and others, believed impossible, are happening.

This shift in weather patterns has inspired modelers to pay more attention to the tails of the frequency distributions of meteorological possibility which their models generate (see chart), in search of such unprecedented extremes. One recent exercise, led by Erich Fischer at eth Zurich, a technology university in Switzerland, shows how the heatwave that destroyed Lytton could have been foreseen with data available at the time….The approach Dr Fischer used is one of several developed recently. Another, from Britain’s Met Office, is UNSEEN  (Unprecedented Simulation of Extremes with Ensembles)…Researchers in the UK are looking at another sort of extreme event—the risk of “wind droughts” which would wipe out a lot of the country’s wind-turbine-base electricity supply. It would be ironic indeed if Britain’s huge effort to combat climate change in this way were, itself, to fall victim to a changing climate.

The Paris Olympics, to be held in 2024, will take place during that city’s hottest weeks. A group of meteorologists from various French research institutes therefore wondered just how bad a heatwave manifesting itself then might be. Using yet another approach, they found a chance of temperatures being more than 4°C higher than they were during a catastrophic heatwave in 2003, in which tens of thousands died. Since that happened, France has built a “heat plan” which includes an early-warning system and provisions for opening cool spaces if needed.

Excerpts from How to predict record-shattering weather events, Economist, Feb. 11, 2023