Trees still have leaves

So I live in Michigan and right now quite a few of the trees still have leaves and some of them are actually still green. The majority of them have fallen yes but there are still many remaining. I thought maybe it had just always been like this and I just didn’t notice but I’ve heard several people comment about how it was unusual to see this many leaves this time of year. Is this something that global warming has an effect on or is it just a weird fluke?