Human-made global heating caused two in every three heat deaths in Europe during this year’s scorching summer, an early analysis of mortality in 854 big cities has found.

Epidemiologists and climate scientists attributed 16,500 out of 24,400 heat deaths from June to August to the extra hot weather brought on by greenhouse gases.

The rapid analysis, which relies on established methods but has not yet been submitted for peer review, found climate breakdown made the cities 2.2C hotter on average, greatly increasing the death toll from dangerously warm weather.

“The causal chain from fossil fuel burning to rising heat and increased mortality is undeniable,” said Friederike Otto, a climate scientist at Imperial College London and a co-author of the report. “If we had not continued to burn fossil fuels over the last decades, most of the estimated 24,400 people in Europe wouldn’t have died this summer.”