I think the reality is that even parties who take the issue seriously know the solutions are difficult. Making difficult decisions is a great way to get voted out in the next term.
An example from the US:
During discussions for the recent bipartisan infrastructure deals, Republicans wanted to raise the gas tax to help pay for the bill. Progressives felt it would affect the middle class too much so they pushed it out.
I think France saw something similar with the "Yellow Vest" movement. I'm definitely not knowledgeable about French politics, but I think a lot of that protest was around an increase in gas tax.
An example from the US:
During discussions for the recent bipartisan infrastructure deals, Republicans wanted to raise the gas tax to help pay for the bill. Progressives felt it would affect the middle class too much so they pushed it out.
Gas tax isn't exactly a carbon tax. But it is close. So here's a case where the party on the Right wanted a "CO2 tax" but the party on the Left scuttled it. (https://www.nytimes.com/2021/06/24/us/politics/what-is-in-th...)
I think France saw something similar with the "Yellow Vest" movement. I'm definitely not knowledgeable about French politics, but I think a lot of that protest was around an increase in gas tax.