As signatories to the Paris climate accord, the countries have agreed to cut their emissions rates to help prevent global temperatures rising by more than 2˚C.
The children will ask the European Court of Human Rights to tell the nations to enforce stronger emission-cutting policies, and to stop mining fossil fuel reserves.
Lead counsel Marc Willers QC, from London’s Garden Court Chambers, says the legal action is a landmark case. If successful, it would set a historic precedent and be binding across Europe.
‘Country in mourning’
The seven children bringing the action are from the Leiria region of Portugal, but have yet to meet in person, and correspond chiefly over the WhatsApp messaging service.
Claudia, 18, the oldest member of the group, is in the first year of a nursing degree. She told CNN she felt compelled to do something.
“I think its time to do something and fight for our future and the future of the next generations.
“Whether we like it or not we (children and adolescents) are going to be the main ones affected by the consequences that climate change entails.”
Martim, 14, says he has become increasingly worried by recent heatwaves and fires in Portugal and elsewhere.
“Climate change causes many problems,” he said in a recorded interview made available to CNN by the NGO Global legal action network (GLAN), which is supporting the children’s case.
“But if I had to name the ones that worry me the most, it would be the sea level rise … and also the increase in the number of forest fires that we’ve been observing lately — especially this summer, as the fires caused many deaths and left our country in mourning.”
CNN’s Duarte Mendonca contributed to this report.