Didn’t need the adobe fort after all.

Less-ancient history

The Skeptical Environmentalist came out in 2001 — right after the imminent collapse of civilization caused by Y2K computer bugs — and I found it fascinating. The author, Bjørn Lomborg, had started out a believer, but in trying to analyze the work of Julian L Simon, he had realized that an awful lot of the imminent crises either weren’t supported by real data, or were much less harmful than the solutions that were being proposed.

Still, I was only a sort of mildly interested skeptic myself; I proposed a pair of articles to PJM in 2007, one taking the pro-AGW position and one the anti, and I was finding the pro-AGW article hard to write. There were too many questions, and I was already seeing the way that the science and the politics had combined in 2004 and were shaping up for the 2008 election. Now, though, I was interested and reading much more widely.

Then, in 2010, was the Climategate bombshell; we at PJM were among the first non-specialist media to break the story of the purloined files that showed how a relatively small clique were working to suppress research that contradicted the imminent environmental crisis predictions, while concealing the fact that they themselves had real problems even replicating their own research.

This whole history is a (possibly too long) lead-in to suggest that we can take a careful and appropriately skeptical look at the science, and also at the reasoning behind the science, and make our own decisions, without being seduced by the press release science.

What is the hypothesis?

Basically, what I suggest is that we think about what chain of things must be true for the whole climate change hypothesis to be probable. Technically, this is called a chain of implications.

To start with, let’s set out the hypothesis clearly. The hypothesis of the Intergovernmental Panel on Climate Change has been that the evidence supports several statements:

  • that the Earth’s overall average temperature is increasing and we can measure the magnitude of that warming with sufficient accuracy to reason further
  • that the Earth’s climate is changing as the result of an overall increase in the global average surface temperature
  • that the magnitude of this change is greater than can be accounted for by natural processes
  • that the primary mechanism responsible for this warming is the change in radiative balance caused by increased CO2 content in the atmosphere (the “greenhouse effect”)
  • that humans are responsible for this warming
  • that this warming will continue