News of the sentencing reached the public broadcaster here in Estonia, including Dale Vince's comment that "this resembles Russia or maybe North Korea" and Chris Packham's assessment that "this is a threat against freedom of speech".
I hope the judgement gets overturned on appeal, and the law that enabled the judgement gets scrapped or rewritten.
I also suspect that the next people who want to stop traffic will not choose peaceful assembly as their method, but will use far more dangerous methods - sabotage from distance, e.g. no more traffic lights on a big intersection. Needless to say, state will cry "terrorism" then, and that is not a desirable outcome, so I hope nobody feels compelled to prove the point.
As an anarchist who would welcome other anarchists - sadly, I doubt if that's a reliable recipe to stop climate change.
Limiting (hopefully stopping) climate change can be done under almost any political system... except perhaps dictatorial petro-states. However, it takes years of work to tranform the economy. Transport, heating, food production - many things must change. Perhaps the simplest individual choices are:
The rest - creating infrastructure to produce energy cleanly and store sufficient quantities - are typically societal choices.
As for corals - I would start by preserving their biodiversity, sampling the genes of all coral and coral-related species and growing many of them in human-made habitats. If we're about to cause their extinction, it's our obligation to provide them life support until the environment has been fixed.
Also, I would consider genetically engineering corals to tolerate higher temperatures. Since I understand that this is their critical weakness, providing a solution could save ecosystems. If a solution is feasible, that is.
Corals reproduce sexually so a useful gene obtained from who knows where would spread among them (but slowly - because typical colonies grow bigger asexually). Also, I would keep in mind that this could have side effects.
As for tempeature - it will be rising for some time before things can be stopped. Short of geoengineering, nothing to be done but reduce emissions, adapt, and help others adapt. The predictable outcome - it will get worse for a long while before it starts getting any better.