The research also suggests that "mega-heatwaves", such as the prolonged extreme temperatures that struck western Europe in 2003 will become five to 10 times more likely over the next 40 years, occurring at least once a decade. But the 2010 heatwave was so extreme – 10 °C above the average for the first week of August between 1970 and 2000 – that similar events are only expected to occur once every 30 years or so.

Searing temperatures in July and August 2010 across Russia are estimated to have killed 50,000 people, say the researchers, who were led by David Barriopedro at the University of Lisbon in Portugal. Mortality rates in Moscow doubled compared with the previous year, filling morgues to capacity as people succumbed to heatstroke and respiratory problems. More heat-related deaths are expected to have occurred in the Baltic states Ukraine and Kazakhstan, though these figures have not yet been estimated.

The mega-heatwave also cut the Russian grain yield by 25%, sending food prices soaring, and left a million hectares of land burned. The nation's losses are estimated at $15 bn.

The team examined the temperature, duration and spatial extent of the 2010 heatwave and found it exceeded the previous record year of 2003, which had also caused tens of thousands of deaths. The analysis, published in the journal Science, revealed the unprecedented nature of the 2010 heatwave using temperature measurements dating back to 1871 and estimates from tree rings and other proxies going back to 1500.

Record extremes were seen over an area of two million square kilometres. The heatwave was caused by high pressure weather systems lingering over the continent.

The decade up to 2010 was also exceptional, the researchers found. Across the whole of Europe, records that had held for 500 years were broken over two-thirds of the land mass.

Climate scientists expect increasing greenhouse gas concentrations in the atmosphere to raise both average temperatures and summer variability in Europe, leading to more heatwaves. The findings of the study are consistent with this, said Barriopedro: "Under global warming this kind of event will become more common. Mega-heatwaves are going to be more frequent and more intense in the future."

Previous research has shown that global warming made the 2003 heatwave at least twice as likely, but modelling studies have not yet been done that might demonstrate the link between climate change and the 2010 heatwave. Last month, scientists showed that climate change made the 2000 floods that swamped England two to three times as likely to happen.

Barriopedro said his team's new work shows there are serious risks of major harm to people and crops in the future unless action is taken. Some countries took additional precautions after the 2003 heatwave, for example providing early warning systems, cool rooms in homes for the elderly and by creating green spaces in cities that help control temperatures.