"Global warming is a big topic. On the internet, there is great debate about the causes of global warming and fact mingles with myth in heated and sometimes vitriolic discussion.

"When UKTV asked us to do a programme on global warming, David was clear about the direction it should take: he had already set out the scientific evidence for human-led warming in his Climate Chaos programmes; now he wanted look at how species and habitats are being affected by a warming planet.

"We decided to make Britain the focal point of the programme with the occasional look at the global picture. Britain boasts a long history of nature observation, which is of great benefit to scientists today.

"The timing of natural events, such as flowering and egg-laying, have been recorded in detail by amateur and professional naturalists for more than a century. Using this historical data as a reference, it's possible to compare the timing of today's natural events with the past and detect any unusual changes."