Christopher Booker writes in the Telegraph:

Margaret Thatcher was the first leader to warn of global warming – but also the first to see the flaws in the climate change orthodoxy
A persistent claim made by believers in man-made global warming – they were at it again last week – is that no politician was more influential in launching the worldwide alarm over climate change than Margaret Thatcher. David Cameron, so the argument runs, is simply following in her footsteps by committing the Tory party to its present belief in the dangers of global warming, and thus showing himself in this respect, if few others, to be a loyal Thatcherite.
The truth behind this story is much more interesting than is generally realised, not least because it has a fascinating twist. Certainly, Mrs Thatcher was the first world leader to voice alarm over global warming, back in 1988, With her scientific background, she had fallen under the spell of Sir Crispin Tickell, then our man at the UN. In the 1970s, he had written a book warning that the world was cooling, but he had since become an ardent convert to the belief that it was warming, Under his influence, as she recorded in her memoirs, she made a series of speeches, in Britain and to world bodies, calling for urgent international action, and citing evidence given to the US Senate by the arch-alarmist Jim Hansen, head of Nasa’s Goddard Institute for Space Studies.

The rest here.