Two related, but contrasting, items on Brexit.
The climate change connection to Brexit is unclear and mostly negative. It is simply true that we benefit from international unity when addressing a global problem, and the EU is a powerful forward looking entity that could address climate change more effectively than the collection of individual nations in the EU otherwise might. With the UK out of the EU, AGW may be somewhat harder to address.
Or, maybe not so much. The EU is still only one entity among several dozen, so having this small shift may not be that big of a deal.