There is a "real national risk of death, disease and coastal flooding" if the Irish Government does not tackle the country's rising emissions, the High Court in Dublin has heard.
On the second day of the landmark historic case against the state, the court heard claims it is breaching the human rights of its citizens over its inability to reduce carbon emissions and tackle climate change.
It was also claimed the Government is breaching the constitutional right to life, bodily integrity and a healthy environment as set out in the European Convention on Human Rights.
In 2017, Friends of the Irish Environment obtained leave from the High Court for a judicial review of the Government's approval of its National Mitigation Plan (NMP) on the basis that the decision was inconsistent with national, EU and international obligations.
It came after the Government published its mitigation plan detailing its goal to achieve an 80% reduction in emissions by 2050 compared to 1990 levels.
The so-called Climate Case Ireland is calling for the Government to be more ambitious in its plans to tackle climate change, and is asking the court "to quash and remit the inadequate" NMP and review its plans and policies.
Eoin McCullough, senior counsel for Friends of the Irish Environment, said the state must show it has taken all steps to preserve the right to life.
He said: "This is a case of right to life (and) on the face of it, it is threatened by the actions of the Government and therefore the Government must show it has taken all steps to preserving it.
"I say the undisputed evidence shows the real threat to life, and if the court agrees with the evidence it shows the (NMP) is not adequate to address that risk and it is, on the face of it, a breach of a right."
He said the Government's plan is a "flagrant breach" which has potentially "extraordinary consequences".
Mr McCullough added it would require an "extreme level of justification" to stand over a plan which fails to provide substantial reduction in emissions.
"We are not asking the court to impose certain amount of measures. This plan is not in accordance with the constitution," he added.
He accused the Government of producing a plan that ignores measures which countries across the world signed up to in the Paris Agreement.
Mr McCullough said if the court agrees with these findings, then the failure to stop Ireland's increasing emissions will have a "serious threat" to human life.
Summing up his argument, Mr McCullough said there "can be only one answer" and that is to quash the State's plan and send it back for reform.