A senior American climate scientist has spoken of the fear he experienced when US intelligence services apparently asked him about the possibility of weaponising the weather as a major report on geo-engineering is to be published this week.

Professor Alan Robock stated that three years ago, two men claiming to be from the CIA had called him to ask whether experts would be able to tell if hostile forces had begun manipulating the US's weather, though he suspected the purpose of the call was to find out if American forces could meddle with other countries' climates instead.

During a debate on the use of geo-engineering to combat climate change, at the annual meeting of the American Association for the Advancement of Science in San Jose, California, Prof Robock said: "I got a phone call from two men who said we work as consultants for the CIA and we'd like to know if some other country was controlling our climate, would we know about it?