The environmentalist movement has long been dogged by a sizeable aura of people who dilute the message with craziness and false claims. They are the major reason why progress is so slow - very few people trust them anywhere near anything important. I've yet to see an English-speaking Green party that I'd accept as competent to set policy even assuming they have the correct problems identified.
Surely you must mean "false" claims?
Maybe .. but on the other hand, craziness and false claims emanating from right-wingers and even the Presidential Twitter Account seem to get taken seriously and make progress.
Scottish Green Party (separate from the Green Party of England And Wales, who do indeed have a bit of a lunatic fringe and ended up picketing their own council at one point) seem to be pretty good to me. Including sensible but difficult to implement policies like "how about we don't have a hundred-foot column of gas flame over Fife all the time".
https://www.bbc.co.uk/news/uk-scotland-edinburgh-east-fife-5... (yes, this is a pet issue, but I can see a lot of CO2 right there)
I don't know if you're in the US, but this is untrue here.
Our most-watched media outlet spreads climate-change denial, as does the (minority) party that has controlled our federal -- and most state -- governments for the last few years.
One of their tactics is literally to say that there is still snow, so global warming can't be real[1].
Articles like this are the counterpoints to that narrative, and there is evidence that individual data points are convincing[2] to people who are not able (or willing) to understand long-term statistical information.
1. https://www.motherjones.com/environment/2018/02/3-years-ago-...
2. https://www.theguardian.com/us-news/2019/feb/03/climate-chan...