The mayor of London, five local authorities and environmental campaigners Greenpeace and Friends of the Earth are among those challenging the decision to build a third runway.
They are appealing the High Court’s decision in May that the government had not breached sustainable development duties. This was before the Climate Change Act had been amended to incorporate the target of net zero by 2050.
Paul McGuinness, chair of the No 3rd Runway Coalition, said: “If the unavoidable increases in noise pollution and poorer air quality were not enough, the recent inclusion of a net zero carbon target in the Climate Change Act has tightened the noose around Heathrow expansion even further.
“The Committee on Climate Change [CCC] has highlighted that demand for aviation must be limited and that a third runway at Heathrow would inevitably mean restrictions on capacity at other airports across the UK.”
Under current laws, the government has a legal obligation to reach net zero emissions by 2050 compared to 1990 levels. However, the CCC, which is the government’s advisory body, said demand for flights must be curbed to tackle greenhouse gas emissions as part of the UK’s climate targets.
Current planned additional capacity in London, including a third runway at Heathrow “is likely to leave at most very limited room for growth at non-London airports”, the committee said.
The UK needs to limit the growth in demand for flights to no more than 25 per cent above current levels by 2050, according to the CCC, yet Heathrow expansion plans could see the number of passengers using the airport rise to 132 million, an increase of 60 per cent.
John Sauven, executive director of Greenpeace UK, said the government continues to be making the right noises about the climate emergency but is still not doing the right thing.
He said: “Heathrow’s third runway is the poster child for this huge disconnect between official rhetoric and action. An enormous expansion of carbon emissions and pollution at the exact moment they agreed to do the opposite is unacceptable. The government needs to curb emissions now by tackling the growth in aviation.”
The other part of the argument is about the absence of plans to address commitments under the Habitats Directive, which means expansion expansion must not have significant negative impacts on the local environment.
Jenny Bates, campaigner at Friends of the Earth, said expanding Heathrow would see a huge increase in emissions.
“Declaring a climate emergency while backing Heathrow’s third runway project shows the climate hypocrisy of our government,” she said.
“It’s time the government is held to account over the third runway, and for more thought to go into what a third runway would mean for the planet. We need to be cutting down the number of planes in our skies, not giving them a massive daily boost.”
The House of Commons overwhelmingly voted in favour of the £18bn third runway plans at Heathrow last year, approving transport secretary Chris Grayling’s plans by 415 votes to 119.
The defendant in this legal challenge is the Department for Transport. A spokesperson said: “We do not comment on ongoing legal proceedings.”
A Heathrow spokesperson said: “Judicial reviews are common in infrastructure projects of this size. Our plans remain on track and we will support the Department for Transport throughout this process.
“We remain totally confident in the robust process that has got us to this point, including the extensive evidence gathered by the independent Airports Commission, multiple rounds of public consultation and the overwhelming cross-party support of parliament.”
The hearing – which starts on Thursday morning at 8.45am – is expected to last six days.
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