There’s a very important distinction to be made here - scientists aren’t activists. The main difference is that when science is generally speaking in the language of probability, activism speaks in language of certainty, hype and simplification.
Scientific evidence for climate change being caused by human CO2 emissions is vast, I would consider it nearly as solid as law of universal gravitation today - the theory behind it is sound and consistent, and it’s consistent with experimental observations.
My problem with “environmental” activism is that it’s selective and often completely wrong. Where science -represented by IPCC - clearly says nuclear power and CRISPR are enablers to decarbonisation, activism - represented by #Greenpeace, #WWF etc - says exactly the opposite. They do say climate change is real, which is consistent with IPCC, but then they reject the whole IPCC package and selectively pick parts they like and those they don’t, in an entirely arbitrary manner.
And by their fierce insistence on doing things their way, they effectively only prevent actual decarbonisation.