One, there's still 8.5 months to go with the year.
Two, this is just a doomsday prediction that is extreme because it is only if we weren't doing anything about climate change.
But, Greta Thunberg in my opinion is radical with her climate change views, not just your average centre-left views but left wing (only with Climate Change). But Thunberg said that she doesn't want to be involved in politics because it is too "toxic".
https://www.bbc.com/news/science-environment-63130705