From The Australian:
Lord Lawson -- energy secretary from 1981 to 1983 and then chancellor until 1989 -- said that he was not surprised by Mr Cameron's letter to Julia Gillard last week praising her for sending a "strong and clear signal that Australia is determined to make its contribution to address this challenge".
Comments in Australia about Baroness Thatcher's position as one of the pioneers of action against climate change were "not an accurate portrayal", he said.
"I was as close to Margaret Thatcher as anybody at the time. The fact is initially she felt this issue needed to be looked into, but she was agnostic as to whether it was a serious problem or not.
"She was instrumental in having the IPCC set up, but it has changed greatly from what she intended as a fact finding organisation to become a lobby group."
Lord Lawson said Baroness Thatcher made her position clear in her memoirs and her later book Statecraft.
"She did have reason for highlighting the possibility of global warming because the biggest threat to the UK energy security at the time was the stranglehold the Marxist National Union of Mine Workers had on the coal industry.
"She felt Britain should not be so dependent on coal. She was in favour of building up nuclear energy to break the dependence on coal and the main opposition to nuclear came from the environment movement. Mrs Thatcher thought she could trap them with the carbon emissions argument."
So that was Thatcher's excuse. What's Cameron's?