An item from the Union of Concerned Scientists:
Certainty vs. Uncertainty
Understanding Scientific Terms About Climate Change
Uncertainty is ubiquitous in our daily lives. We are uncertain about where to go to college, when and if to get married, who will play in the World Series, and so on.
To most of us, uncertainty means not knowing. To scientists, however, uncertainty is how well something is known. And, therein lies an important difference, especially when trying to understand what is known about climate change.
In science, there’s no such thing as absolute certainty. But, research reduces uncertainty. In many cases, theories have been tested and analyzed and examined so thoroughly that their chance of being wrong is infinitesimal. Other times, uncertainties linger despite lengthy research. In those cases, scientists make it their job to explain how well something is known. When gaps in knowledge exist, scientists qualify the evidence to ensure others don’t form conclusions that go beyond what is known.