Anthropogenic climate change, evolution, and scientific theories

One of the common misconceptions about science is the nature of scientific theories.  Much of the confusion stems from the word "theory" having two very different definitions.  Among non-scientists, a theory is a guess, possibly an educated guess based on some facts, but a guess nonetheless.  It's little more than an opinion and less than a known fact (itself is usually taken to mean the unchanging truth) on the hierarchy of truth.  Skeptics often dismiss climate change and evolution with statements like "Human-caused global warming is just a theory, not a fact" or "Evolution is just a theory."  Those statements reveal that the person stating or writing them are using the non-scientific definition.

In science, "fact" and "theory" have very different meanings from their nonscientific definitions.  "Facts" are data, discovered and verified via repeated observations and experiments to the point where it's ridiculous to at least not acknowledge their existence.  Note that "fact" in science doesn't mean unchanging truth.  As technology advances and new experiments and observations are done, what is known as fact today can change, usually being shown to be a subset of a larger set of facts.  Some data is obvious to anyone without any equipment needed: Objects fall toward the ground at an accelerating rate of speed; certain trees grow in floodplains whereas others grow on hilltops; hot air rises; the Earth is a sphere; the order of fossils in the geologic column (first worked out in the 1790s).  Other facts are not so obvious: The speed of neutrinos; the change in DNA over time due to mutations; the infrared absorption properties of CO2; the change from visible light to infrared at the Earth's surface.

"Theories" are ideas that combine known facts to explain how part of the world works.   Newton's laws of motion and gravity explained the then-known facts and still do quite well despite now being recognized as special cases of Einstein's theory of general relativity.  The sliding filament theory of muscle contraction explains the observed bands within a muscle cell and changes in the positions of those bands as a muscle contracts.  Optimal foraging theory explains choices animals make when selecting food.  Scientists test theories by using them to predict the results of experiments yet to be conducted and observations yet to be taken, then do the experiments and take the observations and compare the actual results with the predicted results.  If the predicted and actual results match reasonably well, great.  If the predicted do not match the actual, it's time to modify the theory until they do match or time to come up with an entirely new theory that matches the known facts and predicts the existence of new facts better than the old theory.

What does this mean for the theories of anthropogenic climate change and evolution?  Simple.  They are both scientific theories based on long-known facts (the order of the fossil record was elucidated in the late 1700s and the greenhouse effect was first proposed in the 1820s) and which have been successfully predicting the results of experiments and observations since the 19th century.  If skeptics really want to debunk those theories, they wouldn't be relying on the ignorance of the general population as to the definition of theory and fact in science.  If they really wanted to debunk those theories, they would come up with theories that fit the known facts just as well as those theories and predict the results of new experiments and observations better than those theories.  Then they would actually do experiments and take observations to show that their new theory fits the known facts and predicts experimental/observational results better.  Of course, that would actually mean learning the known facts about climate change and evolution in the first place and being willing to actually test their ideas against reality.  And that's something most aren't willing to do.  It's much easier to just take ignorant potshots from an armchair than to do the actual work required to create and validate their own theory.


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