Andreas Muenchow works at the Automatic Weather Station on the surface of Petermann glacier in Greenland on Aug. 28, 2016. (Whitney Shefte/The Washington Post)

Rick Smith asked in his Dec. 20 letter, “If climate science isn’t settled, then what science is?

Well, none. Science isn’t religion. Science has many well-established areas, but by definition nothing in science is ever fully settled. Science is based on facts. A single new fact can upend decades or even centuries of well-established science. Sir Isaac Newton’s laws of motion were the well-established basis for physics for three centuries. Then, near the turn of the 20th century, sensitive experiments revealed inconsistencies between the measured speed of light and predictions based on Newton’s laws. Those inconsistencies drove Albert Einstein to formulate his theory of relativity. That has been established science for a century, but it’s far from settled.

The climate-change deniers are technically correct when they say that the science isn’t settled. But their use of the term “settled” is a clever trap that has snared more than a few scientists who ought to know better. Climate change is established science, but it’s not settled science because there is no such thing as settled science.

Tom Williams, Ocean View, Del.