Except it is the case in the joke I was replying to:

> "What if it's a big hoax and we create a better world for nothing?" https://en.m.wikipedia.org/wiki/What_if_it%27s_a_big_hoax_an...

This joke asserts that climate change mitigation measures would be justified even if climate change was a hoax. And that joke only works if you assume that those measures are free, or at least very cheap.

That isn't necessarily true if the benefits unrelated to climate change are also high, which it seems to me that they are. If millions of premature deaths are prevented yearly the measures can actually be pretty darn costly and still worth taking. And that is just one of many upsides.