There is uncertainty in exactly how increasing CO2 will play out in the future. Some climatologists say we may nudge the atmosphere past some tipping point after which the climate will swing wildly around in a way that humanity hasn't experienced for 10,000 years.

Worrisome as that sounds, some climate "skeptics" see any uncertainty as a reason not to act. Maybe, they say, it won't be that bad. Maybe curbing emissions will cause worse trouble. That view is not science denial. Those are value judgments and opinions on policy that have no equivalent among creationists.