Rising temperatures threaten survival of Belgium’s sour lambic beer, study warns.

Climate change is putting one of the world’s oldest beer varieties at risk, environmental scientists and one of Belgium’s leading artisan brewers have said.

A study into temperatures in Brussels and the Pajottenland region south-west of the Belgian capital has raised doubts over the future of the sour lambic beer produced exclusively in the region.

Lambic is fermented in the open air through exposure to wild yeasts and airborne native bacteria. It relies on night-time temperatures of between -8C and 8C (18F-46F) for cooling and inoculation.

The traditional brewing season runs from October to April, with bezomerd – Brussels dialect for a beer that has had “too much summer” – a possibility if it is produced any later.