It's frustrating really, as you so often get people who are a bit bonkers put in front of the media, and they're made to sound bonkers and naive and all of those things, because they pretty much are. Neill talks about the IPCC models and the scientific community, but it would be a great start if America hadn't withdrawn from the Paris accord, and there was more teeth given to it to police it so that Brazil (as an example) weren't burning the Amazon with abandon. The danger is that because these people are so far out, we use that as a reason not to do anything at all.
This is the lefts real difficulty currently. There is an absence of intellectual leadership in most aspects.
There's a lot of potential reasons for this. I think labour under Blair did a very good job at developing cadres away from such thinking. The breakdown of the trade union movement has had a knock on affect too. However there's little doubt there's an absence of intellectual ideas and far too few people who can convey them with any degree of effectiveness.
I remember reading about why the Revolution was in Russia not Germany (who had the most advanced, and sizeable working class) and it was essentially reduced down to Russia having Trotsky, Lenin, Kamenev, Zinoviev, Bukharin, Bogdanov etc. All fantastic intellects and communicaters. Sometimes it's as simple as that.

