World's oceans hit record-high July temperatures

In the UK, meanwhile, the prolonged dry spell is increasing pressure on already-stretched water supplies.

England and Wales recorded their driest July since records began 190 years ago, according to the Met Office, while large parts of England and all of Wales have already been officially declared in drought.

The Environment Agency has warned that more areas of England could be declared in drought if dry conditions persist.

Weather that was once considered extreme is becoming the "new normal", according to the latest Met Office report on the UK's climate.

Its latest assessment found that the hottest day of the year in southern England is now 4.5C warmer than it was between 1961 and 1990.

"We are right now living in a time of historic and unprecedented change," said Mike Kendon, Met Office climate information scientist, adding that "evidence shows the climate of the 20th century has now gone".

Scientists say El Niño may temporarily push global temperatures even higher. Its effects are being felt against a backdrop of man-made warming, particularly the burning of fossil fuels.

The world is now about 1.4C warmer on average than it was in the late 19th Century.

Reporting from BBC News contributed to this story.