The UK Court of Appeal has ordered a stop to a third runway at Heathrow because of the UK Government's failure to consider its climate change obligations under the Paris Agreement. It shows the power of using the courts to hold governments to their international climate change commitments.

Key points

In 2018 the UK Government announced it would develop a third runway at Heathrow. The 'Airports National Policy Statement' summarised the benefits and detriments which the Government considered before deciding to support the third runway.

The ANPS was deliberately silent on the Paris Agreement. It gave extensive consideration to the relationship between the third runway and the UK's Climate Change Act 2008, which at the time set the target to reduce emissions by 80% on 1990 levels. However, the obligations imposed on the Government by that Act lagged behind the Paris Agreement's requirement to restrict global average temperature increases to well below 2°C (but ideally 1.5°C) above pre-industrial levels.

Under UK planning law, the Government was required to explain how the ANPS took account of Government policy relating to the mitigation of, and adaptation to, climate change. The Paris Agreement was 'clearly' part of Government policy. Because it ignored the Paris Agreement, the ANPS did not comply with UK planning law and the Court declared it unlawful.

This means for the third runway to go ahead, the Government needs to redraft the ANPS to consider the impact of the runway on its Paris Agreement obligations. It may come to precisely the same decision, but its reasons will be under even more intense scrutiny.

What does it mean for Australia?

The case is another example of a court enforcing its government's international climate commitments. In 2019 the Netherlands was successfully sued for failing to take action to sufficiently cut its greenhouse emissions. That same year an Australian court refused to approve a Newcastle coal mine as its impacts on climate change and Australia's Paris targets meant it was not (on balance) in the public interest. Whether the UK decision could lead to action against the Australian government for failing to consider or achieve its international commitments is less clear – the High Court is not settled on whether a government decision is unlawful if it ignores or is contrary to its international agreements.

The decision comes at a key time in Australia's own climate law debate. MP Zali Steggall's Climate Change Bill (modelled off the UK law, see here) is seeking to set a 2050 net zero emission target for Australia. This target is in line with global government and (increasingly) industry standard – Rio Tinto is the latest multinational to adopt the target. If the target became law in Australia it would add an additional layer to what the Australian government needs to consider when making a lawful decision.

We do not disclaim anything about this article. We're quite proud of it really.