Plans for a third runway at Heathrow airport have been ruled illegal by the court of appeal because ministers did not adequately take into account the government’s climate change commitments.
The ruling is a major blow to the project at a time when public concern about the climate emergency is rising fast and the government has set a target in law of net zero emissions by 2050. The prime minister, Boris Johnson, could use the ruling to abandon the project, or the government could draw up a new policy document to approve the runway. The judge said ministers had not sought permission to appeal.
Johnson has opposed the runway, saying in 2015 that he would “lie down in front of those bulldozers and stop the construction”. Heathrow is already one the busiest airports in the world, with 80 million passengers a year. The £14bn third runway could be built by 2028 and would bring 700 more planes per day and a big rise in carbon emissions.
The court’s ruling is the first in the world to be based on the Paris agreement and may have an impact both in the UK and around the globe by inspiring challenges against other high carbon projects.
Lord Justice Lindblom said: “The Paris Agreement ought to have been taken into account by the Secretary of State. The National Planning Statement was not produced as the law requires.” He said the government had seen the ruling in advance but did not seek permission to appeal to the supreme court.
“The court ruling is bad news for all businesses and investors in the carbon economy, who will have to factor in the increasing risks of legal challenges,” said Tim Crosland, at legal charity Plan B, which brought the challenge. “But really it is good news for everyone, since all of us – including businesses and investors – depend on maintaining the conditions which keep the planet habitable.”
Plan B’s challenge was one of a number of legal challenges against the government’s national policy statement, which gave the go-ahead for the new runway in 2018 after MPs backed it by a large majority. Others were brought by local residents, councils, the mayor of London, and environmental groups including Friends of the Earth and Greenpeace.
The challenges were dismissed in the high court in May 2019 but the complainants took their cases to the court of appeal, which delivered its verdicts on Thursday.
Plan B argued that the Paris agreement target, which the government had ratified, was an essential part of government climate policy and that ministers had failed to assess how a third runway could be consistent the Paris target of keeping global temperature rise well below 2C, and close to 1.5C if possible.
In a witness statement, the then transport secretary, Chris Grayling, said the 2015 Paris agreement was “not relevant” to climate policy and assessing the plans against the earlier and less strict Climate Change Act of 2008 was sufficient. But the court of appeal disagreed.
“This is an opportunity for Boris Johnson to put Heathrow expansion to bed and focus on the most important diplomatic event of his premiership, the UN climate summit in Glasgow in November,” said Lord Randall, a former Conservative MP and climate adviser to the former prime minister Theresa May. “It’s his chance to shine on the world stage.” On 12 February, Johnson said in parliament: “I wait to see the outcome of the various legal processes that are currently under way.”
The court of appeal did not overturn the high court’s dismissal of the other challenges on Thursday, which related to air and noise pollution, traffic, and the multibillion pound cost of the runway.
But the Paris agreement ruling is far-reaching, according to Margaretha Wewerinke-Singh, an international public law expert at Leiden University, in the Netherlands. “Its implications are global,” she said.
“For the first time, a court has confirmed that the Paris agreement temperature goal has binding effect. This goal was based on overwhelming evidence about the catastrophic risk of exceeding 1.5C of warming. Yet some have argued that the goal is aspirational only, leaving governments free to ignore it in practice.”
Heathrow and proponents of the third runway say it would provide an economic boost and is important for international business, particularly after Brexit. John Holland-Kaye, chief executive of Heathrow airport, said on Wednesday: “Let’s be clear, no Heathrow expansion, no global Britain.”
However, most flights are taken for pleasure and just 20% of the UK population take more than two-thirds of international flights. Critics say the economic benefits are illusory given, for example, the estimated £10bn of taxpayers’ money needed to alter road and rail links to the airport, and would draw investment towards the south-east.
Justine Greening, the former transport secretary who represented the south-west London seat of Putney until the election, said: “The decision to expand Heathrow was both environmentally and economically ill-judged. The Heathrow third runway proposal [also] significantly undermines Boris Johnson’s ‘levelling up’ strategy and it should be stopped.”
Justine Bayley, from local campaign group Stop Heathrow Expansion, said: “No one should bear the misery [the third runway] would bring.”
The Department for Transport and Heathrow airport have been approached for comment.