Thank you for asking:
"Here are some questions to ask a creationist or climate change denier:
(1) If they don't want to be guided by scientific consensus in matters of science, what alternative guide would they like to use?"
Evidence. The divide between "consensus" and "deniers" seems to be along what evidence they find acceptable. No one will argue that "numbers of believers" makes evidence more compelling. In fact, consensus-holders' resorting to name-calling the unconvinced, "deniers", can be offered as its own evidence that they've run out of arguments. (However, the more likely explanation is that it arises from frustration at not being able to eliminate dissenting opinions which too now appear to be "guiding people who are not scientists.")
Persuade me. Don't order me to follow because there's a herd. If it's difficult, and you don't want to bother, and deem it not worth the effort, I understand, but my response to being written off and called names won't be warm acceptance.
"(2) What standard of proof do they think is appropriate, and why?"
Seems to suggest that the consensus position has been proved, in which case there would be no room for alternate interpretations of evidence, only "denial" of proof. There is no proof, only interpretations of the evidence, more or less persuasive.
"(3) On the issue being discussed, is there an alternative theory that fits the evidence?"
Yes, but being already persuaded by an alternative explanation, you would likely "deny" its arguments. ;^)
I agree that it should be harder to form consensus around a bad theory today, but people are still people and are not immune to wanting to be in the "in" group, esp. if there's monetary incentive (as in research dollars, resulting in increased fame and salaries).
I could even agree with your statement:
"...even if it's only a 99% chance that it's right, it seems to me to make sense to take strong action to keep from driving our planet off a cliff."
if we could agree on the definition of the word "strong." I would be averse for example to capital punishment (exc. for the people on what W.S. Gilbert called "my little list" [must see Mikado]) or to replacing the U.S. Constitution with something more flexible for implementing government policies (unless I managed to get into the Senate by that time).
What makes me a skeptic?
Given the track record of experts, I simply cannot accept that they can predict the future. Given my personal association with scientists, I cannot accept that they are, some how, more "pure" than, say, bankers. People are people. Greed is greed. The money is going to research proving human-caused climate change.
The consensus do their work in institutions, like the one I did, that are air-conditioned and with refrigerated drinking water, and the most energy-hogging supercomputers on the planet (which subsequently require extra cooling/heat-disposal measures). Once a year they preside over piling up waste in "spend-it-or-lose-it" end-of-budget-year orgies and then plead poverty. Been there. Seen it. Participated myself under orders from superiors.
They have not persuaded themselves.
When I see the consensus wearing sackcloth and ashes and moving out of their upscale lifestyles, I'll start shopping for a similar outfit on Amazon.
The story of J. Harlen Bretz was first to cause me to question consensus-as-truth. He was sorely treated by establishment scientists in his day, but doggedly pressed on.
Even if we disagree, let us agree to try to understand each other. I hope we can agree that, even if things go the way of the consensus, that "denial" doesn't have to become a capital crime; you know, for the "sake of the consensus."
Atheism is the elephant in the scientific room: "There is no god but fact." I have also not been persuaded that there is nothing more to humanity than what we can sense. However if atheism is true, I cannot understand the angst of atheistic scientists over the disappearance of meaningless, after all, human life. Why not party on to the end?
Here's the thing, Adrian Monk would begin, I'm willing to accept that the earth is now warming, now cooling, ...changing. I'm willing to accept that mankind can do better at being stewards of their home (remember that Genesis-era concept before growth-fueled consumerism?). If we have waited too long to be able to do enough to reverse our doom--short of draconian measures--so be it, and R.I.P. human race.
Respectfully, I very much hope, and have labored to try to assure,