There could come a point, maybe, where nearly all folks start to believe our climate is warming. Some still will think it's natural of course. The thing is, to me, this reported 1.4°C (2.5°F) mean rise in temperatures over the past century is not readily noticeable in casual observation. I asked this question before, and most of us here do think it's a bit warmed now than when we were kids.
But of course it still gets cold in winter in most places, and it still snows at times. We had heat waves and droughts and storms in the past, the 1930s apparently.
But if we stipulate this is caused by human activity, and we end up with 90% believing the general model, it will be way too late to act seriously.
It already is in my view.