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anomalous nature of recent warming.
Figure 12.1: Expanding Spaghetti Plot
Figure from the IPCC AR4 assessment (working group 1 report, chapter 6) showing a dozen different reconstructions of Northern
Hemisphere average temperature in past centuries along with the instrumental record through 2006.
Falling Pillars
By the time the AR4 report was published in summer 2007, the case for legitimate climate change
skepticism was on thin ice, so to speak. The four main pillars of denial that contrarians continued to
cling to were:
1. Climate models are crude, untested, and unvalidated.
2. The instrumental record of global temperature is unreliable
3. Other data contradict the claim that Earth is warming.
4. Even if Earth is warming, it could be due to natural factors.
Various strands of purported evidence had been used to support these broader pillars. By 2007, most
of those strands had weakened, and the pillars mostly crumbled, or toppled entirely.
PILLAR 1
Let us consider, as things stood then in 2007, the first pillar: the claim that climate models are
unreliable. As the statistician George Box famously once put it, “all models are wrong, but some are
