The Court of Appeal’s decision in R (Plan B. Earth) v Secretary of State for Transport, and other appeals  EWCA Civ 214 paves the way for future climate change challenges based on the Paris Agreement.
Outside the Royal Courts of Justice on 27 February 2020, there was something unusual about the scenes of celebration. Among those punching the air were the Conservative MP for Windsor, Adam Afriyie, the shadow chancellor, John McDonnell, the Mayor of London, Sadiq Khan, and Caroline Russell, Green Party member of the London Assembly. Most immediately, the cause of this unlikely alliance, transcending the political spectrum, was the Court of Appeal’s ruling that the government’s Airports National Policy Statement (ANPS) in support of a third runway at Heathrow was unlawful. It is the legal basis for that decision, however, that is potentially even more significant than the fact that plans to expand Heathrow Airport have now been stopped dead in their tracks.
In December 2015, there had likewise been scenes of jubilation as world leaders embraced following the adoption of the Paris Agreement on Climate Change, which many of them hailed as a landmark moment in the battle against climate breakdown. One hundred and ninety-seven governments (including the UK) had committed to limiting average global warming to ‘well below’ 2˚C, while aiming for 1.5˚C. Many scientists consider that even 1.5˚C is too much, but following decades of inaction and the despair at Copenhagen in 2009, the Paris Agreement was generally regarded as a significant advance. A key concern, however, was the absence of effective enforcement mechanisms. If governments could not be held to account for their commitments, was the Paris Agreement any more than a dangerous delusion?
Until 27 February, it had seemed likely that the answer to that question was ‘No’. Since 2015, the trajectory of global emissions of greenhouse gases has continued to rise. Governments, while claiming commitment to the Paris Agreement temperature limit, have simultaneously maintained courses of action that are blatantly inconsistent with it.
Since the government negotiates international treaties, treaties do not, in our dualist legal system, have ‘direct effect’. That would infringe the sovereignty of parliament. The government tried to argue that we were seeking to give effect to the Paris Agreement ‘through the back door’. In fact, it is the Planning Act 2008 itself, which is an Act of Parliament, which requires the secretary of state, in designating a national policy statement, to factor in the climate change implications of a project in two ways. First, s5(7)–(8) states:
(7) A national policy statement must give reasons for the policy set out in the statement.
(8) The reasons must (in particular) include an explanation of how the policy set out in the statement takes account of government policy relating to the mitigation of, and adaptation to, climate change.
Second, s10(2) of the Act requires the secretary of state to exercise his functions ‘with the objective of contributing to the achievement of sustainable development’ and s10(3) states specifically that ‘[f]or the purposes of subsection (2) the secretary of state must (in particular) have regard to the desirability of— (a) mitigating, and adapting to, climate change’.
In the original Detailed Grounds of Defence, the government claimed that: ‘the secretary of state considered the Paris Agreement in producing the ANPS and explained his position …’ Following disclosure of his witness statements, however, it emerged that the secretary of state had in fact taken a conscious decision not to assess Heathrow expansion against the Paris temperature limit. He had used as a benchmark the historic temperature limit of 2˚C, which had been rejected by governments in 2015 as inadequate and dangerous. The secretary of state was required by the Divisional Court to amend his pleadings to state that the Paris Agreement was ‘not relevant’, either to s5 or s10 of the 2008 Act.
The Court of Appeal disagreed with the secretary of state on both counts, finding in favour of both Plan B. Earth (which had focused on section 5) and Friends of the Earth, which emphasised s10:
It is clear, therefore, that it was the government’s expressly stated policy that it was committed to adhering to the Paris Agreement to limit the rise in global temperature to well below 2˚C and to pursue efforts to limit it to 1.5˚C (para 216).
Secondly, and in any event, if he had appreciated he had any discretion in the matter, we agree that the only reasonable view open to him was that the Paris Agreement was so obviously material that it had to be taken into account (para 237).
In essence, the Court of Appeal’s ruling is a conservative proposition: the government, in developing major infrastructure plans, should take into account its own policy commitment to the Paris Agreement temperature limit. It simply requires the government to be honest: is it serious about limiting warming to 1.5˚C or not? If not, it should let us all know.
That’s why the ruling sets such a powerful precedent, both in the UK and beyond. The message has gone out loud and clear that governments can no longer do what they’ve been doing for decades: claiming to be serious about tackling the climate crisis while marching us headlong towards disaster.