The wisdom of crowds, and why we shouldn't dismiss the validity of personal experience with climate

Over at Tamino (and Rabett), they're discussing how to talk to the general public, genuine skeptics, and insincere denialists about climate change. I'd generally agree with Rabett's statement regarding denialists and skeptics "that the separation is between those who have filled the trough of denial and those who, wandering by have supped from it." With maybe two types of exceptions, I don't think anyone who stayed and spent alot of time looking at the evidence can remain a genuine skeptic. The first exception is someone who develops a monomaniac obsession with an alternative theory like cosmic rays that allows them to blind themselves to the mountains of evidence. The second exception type is someone willing to put their money where their mouths are and bet against warming, and these people are few.

But that's not what got me going on this post - instead I was thinking about the true general public, not those who occasionally blog about climate change. There's this comment by inel:

I think more time needs to be spent on listening to the views of the general public (as opposed to the denialists and sceptics who undoubtedly influence them), and reflecting back the average person’s concerns in an empathetic way. Then our focus should be on educating, reassuring and encouraging the vast majority of people who (potentially) inhabit the middle ground on the climate challenge: let’s gain their trust, then reinforce their basic knowledge, now that Al Gore has got their attention, so they feel compelled to act and vote for action.

John and Jane Public, I think, are heavily influenced by the basic knowledge of what they personally experienced, remembering recent heat waves or feeling like the weather's screwy compared to when they were kids. Scientists and hangers-on like me don't like this reasoning very much because we know there's a low signal-to-noise ratio in the randomness of individual experience of weather. Still, there is a signal there - climate change has increased record heat events, made winters milder, and affected some kinds of weather.

If you think of understanding information at the aggregate level, rather than the individual, then much of the noise problem cancels out, and the signal from personal experience becomes stronger. Millions of people are walking around, and the ones who experience record heat and mild winters outnumber those with the reverse experience. Yes, real scientific data is better,* but this isn't all that bad a way for the general public to understand things.

So if someone I meet on the street says "I believe in global warming now, after last week's heat," then the appropriate response is "well, it's unlikely but possible that global warming made the heat even worse." If they say, "what global warming? It was freezing last night," then I'd say "yeah, but it can still get cold sometimes even if the average is going up."

The denialists who should know better, deserve a much stronger response.


*For once, there is a viable argument here about the Urban Heat Island effect when combined with increasing urbanization to affect perceived experience. Maybe people account for it in their own assessment, and there's a reverse trend from the post-World War II migration from cities to suburbs. Again, I'm not arguing that personal experience is perfect, but just that it has some validity at the aggregate level.