Why engage? “The thing humans fear more than anything else is the inability to care for our children," says Auden Schendler (*). Caring would seem to include protecting their home and life support system.
For a succinct all-purpose rejoinder to doubter objections, see what Peter Thomson would say (skip down to "I’d tell ...[them] that every major national scientific academy in the world...")
If someone stresses uncertainty but doesn't point out its implications, remind him or her that uncertainty cuts both ways, and in risk management it's actually cause for greater urgency - "As uncertainty increases, the probability of a truly catastrophic
outcome [goes up much more: an increase in]...the standard
deviation of our distribution...from .5 to 2.5 increases the likelihood
of catastrophe by a factor of 200." (link). Plus uncertainty doesn't hobble us elsewhere: "there is more certainty about climate change than around most of the issues we choose to act on as individuals or in our society." (*). And, in models projecting the future climate, the biggest uncertainty actually lies in what we'll decide (or not decide) to do. (link)
For folks who think climate change can be fought effectively without putting a price on carbon, see this "hot topic" post ('...economist William Nordhaus says, "If economics provides a single bottom line for policy, it is that we need to correct this market failure by ensuring that all people, everywhere, and for the indefinite future are confronted with a market price for the use of carbon that reflects the social costs of their activities. ..."')
(I'm sure I'm duplicating Skeptical Science content here, since this is extremely well-trodden turf; best to go there for more.)
An account of a problem should always end by offering an action, so -
What can you do? Ask yourself, what's your biggest lever? Then pull on it.