The truth is that global climate change is not even surprising. What is substantially more surprising is that our climate ever cooled as much as it did. We have a long way to go before we reach the Paleocene-Eocene thermal maximum or even the lowest temperature the planet ever reached during the Cretaceous.
That does not mean that humans would enjoy living in a Cretaceous climate. It might not be the end of the world, but I doubt that humans would find it to be either comfortable or convenient.