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confidence that human-caused climate change was already observable. The scientists argued that “the
balance of evidence suggests an
appreciable
human influence on climate” because only when human
impacts were included could the rise in temperature over the past century be accounted for. The Saudi
delegate complained that the word
appreciable
was too strong. He demanded weaker wording.
For two whole days, the scientists haggled with the Saudi delegate over this single word in the
“Summary for Policy Makers.” They debated, by one estimate, nearly thirty different alternatives
before IPCC chair Bert Bolin finally found a word that both sides could accept: “the balance of
evidence suggests a
discernible
human influence on climate.” The term
discernible
established a
middle ground by suggesting that climate change was indeed detectable, as the scientists argued,
while acknowledging that humanity's precise role in that change and its magnitude were still subject
to dispute—a concession that no doubt pleased the Saudi delegate. This sentence would go on to
become famous or, in some circles, infamous. The fact that two entire days at the final plenary were
devoted to debating a single word in the report's summary gives you some idea of how contentious
the debate over the reality of human-caused climate change had become by 1995.
Why did the scientists care so much about the wording? What would be the harm, after all, if the
wording were weakened a bit? I suppose it comes down to how deeply scientists care about getting
things right. Details matter, and we argue passionately with each other about them. We don't suffer
perceived inaccuracies lightly, and more than anything else, we don't like being misrepresented. The
fact that the science in this case might have deep real-world consequences only amplified these
natural inclinations.
Among the scientists who fought hard against any watering down of the report's key conclusion
was Ben Santer, a climate specialist who works for the Department of Energy's Lawrence Livermore
National Laboratory in California. The recipient of a coveted McArthur “genius” award in
recognition of his groundbreaking contributions to our understanding of climate change, Santer was a
primary author on a series of important papers establishing the human role in observed climate
change. As such, Santer was in a better position than anyone—and certainly than a bureaucrat with a
political agenda—to assess the level of scientific confidence in concluding that human activity was
changing the climate.
As it happens, I had met Santer for the first time a little more than a year earlier, in July 1994, at
a two-week workshop on climate science at the National Center for Atmospheric Research. I was
attending the workshop as a graduate student invitee, and Santer was one of the invited speakers. I
asked him a question about certain details of his analysis following his presentation. His response
came across as a bit defensive, as if he perceived my question as an attack. Only later would I
understand why.
Santer's work on climate change detection, unbeknownst to me, had been under increasing attack
from contrarians in the climate change debate. In 1994, for example, his findings regarding the match
newsletter with fossil fuel industry funding
6
that featured criticisms of mainstream climate change
research.
The attacks against Santer were ratcheted up dramatically following the November 1995 IPCC
plenary. In February 1996, for example, S. Fred Singer, the founder of the Science and Environmental
