Sigh. Fine. OK, I wasn't very clear. Let me try again.
Some people say things like "Global warming? Ha! It's May and we've all got coats on! So much for global warming!"
(Some American bloke who came to preach at our church literally did say that, pretty much verbatim)
They act like they've made a good point and totally disproved all this global warming nonsense. They haven't. For several reasons.
1) Cold snaps in Spring or warm spells in Autumn aren't "proof" of anything. You need to look at long term trends, not one off events. It's like using the NLD result as "proof" that we are better than Spurs this season. One could argue that it's evidence that we are - you would expect us to beat them if we're better than them - but it is just a one off result. We'll see over 38 games who comes out on top.
2) Strictly speaking, scientific ideas can't be proven. Only mathematical theorems can. In science you make a hypothesis and then test it. As more evidence is gathered the likelihood of the hypothesis being true becomes higher, but it's never proven in the strictest sense. So if my hypothesis is "the world is getting warmer and will continue to and it's caused by human activity" then warm weekends in October like this one could be part of the evidence for that but it's not proof. And even if the world does continue to get warmer (it certainly has in my lifetime), it's impossible to prove conclusively that it's human activity causing it although there does seem to be a lot of evidence pointing that way right now.
3) Global Warming is an effect of Climate Change but it's not the only one. Climate Change also means more extreme weather events generally which can mean colder winters. So cold snaps aren't evidence against Climate Change, they're evidence for it.