Well my first thought is that considering it was written by Richard Curtis, its not actually very funny, either in script or in concept.
It is however quite a cleverly subversive/neutral film.
Pro climate measure supporters will see it as a powerful message of how devastating ignoring environmental issues actually is.
Those who believe its not our problem will see it as a satire on the bully-boy scare-mongering of some political and media groups on the issue.
I can see why it got complaints, but I enjoyed the gore - very Rambo IV