Unfortunately this isn't the win he's making it out to be.
By my understanding they are not saying that they were wrong about climate change, just that their projection of how bad it's going to get by the end of the century was wrong.
And they're saying their projection was wrong specifically because usage of fossil fuels has declined quicker than they thought it would thanks to lowered costs of renewable energy and their climate policies.
They still think it's real and even worse they think their policies are working.