“Had Chris Grayling assessed Heathrow expansion against the 1.5C temperature goal in the Paris Agreement he could not have approved it,” he said.
“The pandemic has reminded us of our subjection to natural laws. The Paris temperature limit is all that divides us from a grim future of crisis upon crisis.
“The Supreme Court’s judgement, which has legitimised Mr Grayling’s use of the deadly two degree threshold, has betrayed us all.”
Under the 2015 Paris Agreement, almost all countries – including the UK – agreed to try to limit global warming to 1.5C above pre-industrial levels and “well below” two degrees of warming.
At a Court of Appeal ruling in February, three judges concluded Mr Grayling failed to take account of the government’s commitments to tackling climate change when setting out support for the Heathrow project in an Airports National Policy Statement (ANPS).
The ANPS was set out in 2018 – three years after the Paris Agreement, but a year before the UK made a legally-binding commitment to bring all greenhouse gas emissions to net zero by 2050,
At a two-day appeal hearing in October, a panel of five Supreme Court justices heard the challenge brought by Heathrow Airport Ltd.
The government and developers have stepped back from the legal process, saying they do not support a further appeal of the case.
Lawyers for Heathrow Airport Ltd told the court that the firm, which owns and operates the airport in west London, still wishes to go ahead with the expansion project.
It is the latest in 17 years of wrangling over whether or not to build a third runway at Heathrow.
Prior to becoming prime minister, Boris Johnson had vowed to “lie down in front of bulldozers” to stop it being built.
The decision is seen as hugely significant because it could influence other legal challenges on policies that aren’t seen as being compatible with tackling climate change.