What a load of poop.
Thatcher only got (slightly) ‘green’ around 1989. Ten years into her primeministership.
The origins of the global warming scare
http://www.john-daly.com/history.htm
The hypothesis of man-made global warming has existed since the 1880s. It was an obscure scientific hypothesis that burning fossil fuels would increase CO2 in the air to enhance the greenhouse effect and thus cause global warming. Before the 1980s this hypothesis was usually regarded as a curiosity because the nineteenth century calculations indicated that mean global temperature should have risen more than 1°C by 1940, and it had not. Then, in 1979, Mrs Margaret Thatcher (now Lady Thatcher) became Prime Minister of the UK, and she elevated the hypothesis to the status of a major international policy issue.
(More details at the link.)