By Imogen Foulkes
BBC News, Geneva
A new report from the Worldwide Fund for Nature (WWF) warns that temperatures in Europe's major cities are rising.
The report analysed summer temperatures in 16 European cities over the last 30 years and found that in most of them, average summer temperatures were at least one degree Celsius higher over the last five years than they were 30 years ago.
The rising temperatures mean more than just sunbathing
WWF says the increase is caused primarily by greenhouse gases, such as carbon dioxide, which is released into the atmosphere by coal and gas-fired power stations and by cars.
Heat waves, drought and torrential rains are all things Europe can expect to see more of, the WWF says.
Rising temperatures will mean more extreme weather conditions and cities may be especially hard hit.
The WWF study shows that Europe's big cities are getting hotter faster than expected.
Serious health risks
London showed the biggest increase.
Its average maximum temperatures now are two degrees higher than in the 1970s.
Madrid, Paris, Stockholm, Lisbon and Athens are suffering in the heat too.
Average summer temperatures have risen by one-and-a-half to two degrees in all of them, and such increases don't just mean more nights out in the open-air cafes.
They mean heat exhaustion for those struggling to work and serious health risks for the very young and the very old.
But the WWF warns we shouldn't look to short-term measures to cool things down.
Air conditioning, which uses up electricity, will simply add to the problem.
Most scientists now agree the root cause of the rising temperatures is carbon dioxide.
It is created by fossil fuels, like coal, which are burned to create electricity.
WWF is calling on European countries to cut CO2 emissions and invest in alternative forms of power generation - because if the temperatures continue to rise at this rate, Europe's great cities may become unliveable.