The 2 key points that climate skeptics miss

Arguments between climate skeptics (or whatever the hell we’re calling them now) and their opponents very frequently devolve into hypertechnical squabbles over particular scientific issues like sea surface temperatures or Milankovitch cycles (don’t ask).

Generally speaking, this is a Bad Thing. Technical scientific disputes are of limited interest the general public — especially technical disputes litigated with great partisan venom. A discussion dominated by such disputes just causes most people to tune out entirely. What’s more, it creates the illusion that the validity of climate science hinges on how these squabbles are resolved. It doesn’t.

Michael Shermer — longtime science writer, founder of the Skeptics Society, editor of the magazine Skeptic, and champion of genuine skepticism, not the funhouse mirror variety that goes by that name in climate debates — has a nice little piece in Scientific American that concisely captures why climate science is so resilient.

Why do so many scientists and scientific organizations accept that climate change is real, human-caused, and dangerous?

It’s not because of any single line of evidence or any one prediction. Rather, says Shermer, “there is a convergence of evidence from multiple lines of inquiry — pollen, tree rings, ice cores, corals, glacial and polar ice-cap melt, sea-level rise, ecological shifts, carbon dioxide increases, the unprecedented rate of temperature increase — that all converge to a singular conclusion.” Scientists call this sort of convergence of independent lines of evidence “consilience.“ Biologist E.O. Wilson wrote a very good book about it.

Climate denialists — indeed, most people — do not fully grasp the implications of consilience. The strength of consilience science does not issue from the validity of any one set of measurements or any one line of evidence. It’s not vulnerable to wholesale refutation if anomalies are found in one data set or another. Even if individual lines of evidence are weak or uncertain, their convergence, the fact that many trails keep leading to the same place, can make consilience science strong.

And the convergence also makes consilience science fecund — it suggests and structures further research.

Writes Shermer:

For [climate] skeptics to overturn the consensus, they would need to find flaws with all the lines of supportive evidence and show a consistent convergence of evidence toward a different theory that explains the data. ... This they have not done.

I’m not sure the disengaged public understands this: Climate skepticism is not an alternative theory. The climate skeptic community is a hodgepodge, a farrago of theories and conspiracies that range all over the map, from sunspots to adjustments in particular temperature data sets to hoaxes by scientists greedy for grant money. There’s no shared alternative framework, just a fixed certainty that the consensus must be wrong.

If the mainstream scientific consensus on anthropogenic climate change is wrong, then we’ll need some other theory that makes sense of present-day changes and harmonizes with data from historical record. Climate skeptics have offered no such theory. Where climate change science is fecund, climate skepticism is moribund, merely destructive.

Note that everything above is also true of evolution, which also represents the convergence of multiple independent lines of evidence and also faces no serious scientific competitor. Indeed, most of the broad theories that structure modern scientific inquiry are based on consilience, their strength less a result of any one bulletproof piece of evidence than the power of convergence.

There’s nothing wrong, in climate or any other broad area of science, with subjecting individual data sets or lines of evidence to critical scrutiny. That is the day-to-day work of science. But it is silly to think, as climate skeptics do, that debunking any individual piece of evidence is going to bring the whole superstructure crumbling down. That’s just not how climate science works.