Ciarán Cuffe hopes the next EU Commission will take climate change seriously.
The Green MEP was speaking after the incoming Commission President Ursula von der Leyen made bold pledges on the issue.
The promises include an aim to make the EU carbon-neutral by 2050.
Ms Von der Leyen was backed by Greens and Socialists in the Parliament but only at the 11th hour.
Dublin MEP Cuffe hopes she sticks to her commitments:
"We'll see what kind of cabinet she proposes (but) I'd say the hearings will be quite rigorous," he said.
Mr Cuffe added that the European's Parliament's "swing to the centre-left" will lead to progress "on both social and environmental issues".