Heatwaves in Europe are likely to become much hotter and much more frequent during the course of this century, a study suggests.

The study, by researchers at Met Office's Hadley Centre, found that extreme summer temperatures are expected to increase if atmospheric CO2 concentration doubles, as it is expected to over the course of the century.

North and South America and East Asia are also expected to be affected, the study revealed.

"Using multiple simulations to quantify uncertainty, Met Office scientists obtained some sobering results," the Met Office said in a press release.

"These simulations indicate that European heatwaves could become hotter by between 4 and 10C - an increase greater than that expected for normal summer days."

In the UK, severe heatwaves lasting five days or more, such as occurred in July 2006, happen now approximately once every 20 years, according to the Met Office.

However, by 2100, the study shows such heatwaves are likely almost every year, and could even occur several times each summer.

Met Office scientists also examined possible mechanisms behind the worrying increases, finding that drier soils resulting from drier summers and reduced cooling at night were largely responsible.

The study is published in the Journal of Climate.