There are lots of green parties in Europe and they have always been against mass AC because of their energy use and because it lets poor city design and poor insulation off the hook. There's also the fact that the ACs have to compensate for making it cooler indoors, so outdoors gets even hotter. It's an argument I'm sympathetic to, honestly.

But I suspect that the real reason AC isn't widespread is because there isn't capacity on the electric grid and high electricity prices scares people off, in short a complete failure of European energy policy, for which the Greens are partly to blame with their hasty shutdowns of polluting and nuclear plants while the renewables rollout keeps getting stalled by political winds and NIMBYism.

And because the left parties typically pool from the same voter base as the Greens they believe the same, even a self-declared Marxist party like the Belgian PVDA/PTB is still against nuclear although not as adamant about it.