I understood what you said, but in my view you were painting a false dichotomy: it's not a matter of "either climate change or all-these-other-useful-things", it's a matter of "all-these-other-useful-things because of our inability to address climate change directly".
what do we do when people treat their opposition as faith, i.e. belief despite lack of evidence.
for some people it will never be real. what do we do about that? is that a legitimate thing to take into account? does that faith mean we cannot act as though climate change is largely human-driven?
You don't wait until you've proven it beyond doubt. But you say "this is our best model, we're pretty confident it's right in the essentials, and we're going to act on it but remain open to being wrong; here are our policy proposals". You don't say "this is our best model, and here are our policy proposals based on it, but even if our model is wrong we would make the same proposals anyway".
I have no particular insights into the other questions.
'what do you mean you don't know, you're not sure? you could be wrong?!'
that's how people see that. that's why climate science needs to give concrete beyond doubt proof. anything less and people ignore it.
But I'll respond anyway. From http://www.who.int/mediacentre/factsheets/fs266/en/:
> climate change is expected to cause approximately 250 000 additional deaths per year between 2030 and 2050; 38 000 due to heat exposure in elderly people, 48 000 due to diarrhoea, 60 000 due to malaria, and 95 000 due to childhood undernutrition
Meanwhile, today malaria is killing around 600 000 people a year (ten times that number), and malnutrition around 3 million (thirty times). So, while I'm open to convincing, color me skeptical that today, climate change is the "biggest cause" of those things, for any reasonable definition of "biggest cause".
(Granted, you said "spreading of the malaria mosquitos beyond the tropics". To the extent that this problem is different from the problem of malaria in general, it's moving the goalposts.)
(I also note that even if climate change were the biggest cause of those problems, the best solution to those specific problems might not be to fight climate change. Perhaps instead we should work on growing more resistant wheat, or eradicating mosquitos.)
I'm not arguing that climate change isn't real or that we shouldn't try to solve it. But I categorically reject the idea that if it weren't real, we should nevertheless act as though it were.