Saturday, July 06, 2013

Fear Pressure

In his Mind and Matters column in today's WSJ, Matt Ridley reminds us that that science is about evidence not consensus:

And that is where the problem lies with climate change. A decade ago, I was persuaded by two pieces of data to drop my skepticism and accept that dangerous climate change was likely. The first, based on the Vostok ice core, was a graph showing carbon dioxide and temperature varying in lock step over the last half million years. The second, the famous "hockey stick" graph, showed recent temperatures shooting up faster and higher than at any time in the past millennium.

Within a few years, however, I discovered that the first of these graphs told the opposite story from what I had inferred. In the ice cores, it is now clear that temperature drives changes in the level of carbon dioxide, not vice versa.

As for the "hockey stick" graph, it was effectively critiqued by Steven McIntyre, a Canadian businessman with a mathematical interest in climatology. He showed that the graph depended heavily on unreliable data, especially samples of tree rings from bristlecone pine trees, the growth patterns of which were often not responding to temperature at all. It also depended on a type of statistical filter that overweighted any samples showing sharp rises in the 20th century.

I followed the story after that and was not persuaded by those defending the various hockey-stick graphs. They brought in a lake-sediment sample from Finland, which had to be turned upside down to show a temperature spike in the 20th century; they added a sample of larch trees from Siberia that turned out to be affected by one tree that had grown faster in recent decades, perhaps because its neighbor had died. Just last week, the Siberian larch data were finally corrected by the University of East Anglia to remove all signs of hockey-stick upticks, quietly conceding that Mr. McIntyre was right about that, too.

So, yes, it is the evidence that persuades me whether a theory is right or wrong, and no, I could not care less what the "consensus" says.

Mr. Ridley has also announced that this is his last Mind and Matters column which is a shame. His perspective and willingness to approach topics with an open mind will definitely be missed.