Extreme weather such as intense storms, droughts and heat waves will cause more frequent and severe food shortages as the global climate and food supply systems change, British and American experts warned Friday.

The pressure on the world's food supplies is so great, and the increase in extreme weather events so rapid, they said, that food shortages on a scale likely to occur once a century under past conditions may in future hit as often as once every 30 years.

"The chance of having a weather-related food shock is increasing, and the size of that shock is also increasing," said Tim Benton, a professor of population ecology at Leeds University who presented a report commissioned by the British government.