"These are separate events, not a single heat wave event sweeping across the Northern Hemisphere," said Julien Nicolas, senior scientist at the Copernicus Climate Change Service. "Affected regions are often separated by areas with colder-than-average conditions."

Despite their geographic separation, these events share a common underlying cause — human-induced climate change.

The still-unbroken trend of rising temperatures, largely attributed to anthropogenic greenhouse gases, has led to record-high sea surface temperatures, further warming the lower atmosphere, said Andreas Walter, spokesman for the German Meteorological Service.

Heat waves are often triggered and sustained by stationary high-pressure systems, sometimes referred to as "heat domes". These systems trap hot air near the surface and block the formation of cooling clouds and precipitation, leading to prolonged periods of extreme heat, Nicolas said.