One of the things about the global warming/climate change debate that annoys me is the claim that there is a scientific consensus about global warming/climate change, hence it must be true. The problem is that scientific theories/hypotheses can fall with new data. Take for example the idea of six degrees of separation.
Six degrees of separation is the hypothesis that anyone on Earth can be connected to any other person on the planet through a chain of acquaintances with no more than five intermediaries.
The hypothesis was first proposed in 1929 by the Hungarian writer Karinthy Frigyes in a short story called Chains. The concept is based on the idea that the number of acquaintances grows exponentially with the number of links in the chain, and so only a small number of links is required for the set of acquaintances to become the whole human population.
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In the 1950s, Ithiel de Sola Pool (MIT) and Manfred Kochen (IBM) set out to prove the theory mathematically. Although they were able to phrase the question (given a set N of people, what is the probability that each member of N is connected to another member via k1, k2, k3…kn links?), after twenty years they were still unable to solve the problem to their own satisfaction.
In 1967, American social psychologist Stanley Milgram (see Small world phenomenon) devised a new way to test the hypothesis, which he called “the small-world problem”. He randomly selected people from various places in the United States to send postcards to one of two targets: one in Massachusetts and one in the American Midwest. The senders knew the recipient’s name, occupation, and general location. They were instructed to send the card to a person they knew on a first-name basis who they thought was most likely, out of all their friends, to know the target personally. That person would do the same, and so on, until it was delivered to the target himself/herself.
Although the participants expected the chain to include at least a hundred intermediaries, 80% of the successfully delivered packages were delivered after four or fewer steps. Almost all the chains were less than six steps. Milgram’s findings were published in Psychology Today, and his findings inspired the phrase six degrees of separation.
However, now there is this story in at the BBC.
The phrase was coined by an American academic, Stanley Milgram, after experiments in which he asked people to pass a letter only to others they knew by name. The aim was to get it, eventually, to a named person they did not know living in another city.
The average number of times it was passed on, he said, was six. Hence, the six degrees of separation.
It is a seductive idea.
Films have been made about it, there are parlour games based on it and mathematics has begun to propose theories for why it should be true. But is it?
Judith Kleinfeld, a professor psychology at Alaska Fairbanks University, went back to Milgram’s original research notes and found something surprising.
It turned out, she told us, that 95% of the letters sent out had failed to reach the target.
Not only did they fail to get there in six steps, they failed to get there at all.
Milgram was a giant figure in his world of research, but here was evidence that the claim he was famously associated with was not supported by his experiments.
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And when she looked for other studies, none of those matched up to the claim either.
In the most recent, two years ago, only 3% of letters reached their target.
“If 95 or 97 letters out of 100 never reached their target, would you say it was proof of six degrees of separation? So why do we want to believe this?”
Take a look at the quote from Wikipedia, note that it refers to 80% of the letter that made it to the target. To claim there is six degrees of separation when 95% or more of the letters never arrive at all is evidence against the claim, not evidence in favor of it. By looking just at the letters that arrive the sample is severely biased.
And this isn’t even new evidence, but a more complete look at the initial evidence in favor of the hypothesis. Now this doesn’t mean that the global warming/climate change hypothesis is not true, but it does highlight that scientific consensus is not a fact and it can change when new evidence comes available, or even with a better look at old evidence.
Via Climate Audit.
