Climate Change Is Real, of Course

William M. Briggs, on “Of Course Human Caused Climate Change is Real”:

Given our knowledge of physics, it is not just true, but trivially and obviously true that humans cause the climate to change.

But then so do ants cause climate change, and their arch rivals the aardvarks.  As do yellow perch and their meals the nightcrawlers.  Any species that moves or engages in respiration, or in eructation after a good meal, changes the climate.

It would be impossible for them not to.  Why?  Because any move through the atmosphere changes its state, just as any exchange of gases changes the state, and any change of state of the atmosphere is a change of climate.  And that is that. Humans, ants, and every other damn creature cause the climate to change.

The only question is how much?  A worm wiggling across the surface of a sidewalk after a rainstorm is not moving fast, and thus not causing large changes of state of the atmosphere.  But it’s not as simple as that: the birds who dive bomb the worms cause larger changes, changes that would not have taken place had the worms not been there.

And when the worm begins to rot after you squish it, its dissolving body changes the chemical composition of the atmosphere, and changes it in a different way than if it were processed through the gut of a robin.

Don’t scoff!  We read that the biomass of worms outweighs that of humans.  Worms are unimaginably important critters, aerating—get it?—soil, feeding fish, and crawling trillions of miles.  How can we say authoritatively the exact effect worms have on climate?  We cannot, not exactly; but perhaps we can approximate it.  [...]

Humans and worms do cause the weather to change, even cause it to change measurably; thus they also cause the average of the weather—the climate—to change measurably.  For instance, your author lives on a small island upon which is dumped a great, tangled mass of concrete, through which scurry motorized vehicles, rats, cockroaches, and even people.  These static and movable objects cause great changes in the weather, and thus in its average.

Humans, on the island and off, also pump various gases and other effluvia into the atmosphere.  These gases also cause changes in the weather, thus climate.  So much is indisputable.

What is disputable is how much.  We can ask—it is an intelligible question—what the weather (thus climate) would be like on the small island given the concrete, vermin, and people were removed.  We might cobble together a mixed physical-statistical model which gives an answer.  But the answer won’t necessarily be the right answer.  And we’ll never be able to tell if it’s right or wrong because we’ll never be able to shift all that stuff off the isle to check.  [...]