The decision to expand Heathrow airport with a third runway was unlawful because it failed to consider the full impacts of climate change and the need for more stringent targets to avoid catastrophic global warming, the high court has been told.

Friends of the Earth on Wednesday accused the transport secretary, Chris Grayling, of acting unlawfully when he agreed to the expansion, which is contained in the government’s airports national policy statement.

“Friends of the Earth is concerned that the expansion of Heathrow airport by adding a third runway will jeopardise the UK’s ability to make the very deep reductions in greenhouse gases that are necessary to prevent global warming from causing catastrophic, irreversible impacts for people and ecosystems,” the NGO said in documents submitted to the court.

The allegation that the third runway is not compatible with climate change targets in UK domestic law, and agreed under international obligations in the Paris agreement, is one of five legal challenges to the third runway at Heathrow from local councils, environmentalists and the London mayor, Sadiq Khan.

The court heard that the government knew when it approved the third runway that the Paris agreement, which UK ministers have signed, was likely to involve more stringent emissions targets than domestic law required under the UK Climate Change Act of 2008.

Under domestic law, the government has a legal commitment to reduce greenhouse gas emissions by 80%, compared with 1990 levels, by 2050. But since the government signed the Paris agreement, it has been made aware that the reductions in emissions have to be deeper. The agreement has increased the demand for nations to tackle emissions, with its ambition to limit global warming to well below 2C above pre-industrial levels and to pursue efforts to limit it to 1.5C.

David Wolfe QC, for Friends of the Earth, said ministers were told by the climate change committee in January 2018 that as a result it was “essential that actions are taken now to enable these deeper reductions to be achieved”.

But he said Grayling failed to legally take both domestic law and international obligations into account when approving the third runway after receiving this advice.

The court heard that the ability of the UK to meet the lower 2050 aviation emissions target already required other industries and sectors to reduce their emissions by 85%, which was “at the limit of what is feasible [for other sectors], with limited confidence about the scope for going beyond this”.

The House of Commons voted in favour of building a third runway at Heathrow last year, approving Grayling’s national policy statement by 415 votes to 119.

Nigel Pleming QC, for a coalition of local councils, Greenpeace and the London mayor, has told the high court the development, if it goes ahead, will in effect add a new airport with the capacity of Gatwick to the north of Heathrow.

He said building a third runway at Heathrow would have “severe” negative consequences for residents and Grayling had ignored the “high risk” that expansion would breach air quality standards.

The planned expansion would enable Heathrow to add 260,000 flights a year to its current 480,000 capacity.

The legal challenges come as new scientific analysis found there was only a narrow window to keep global warming levels to less than 2C as required in the Paris agreement. The study published in Nature Climate Change suggested carbon emissions must reach zero by 2030 in every country in the world to meet the below 2C target for warming by 2100.