Sometimes…often…many of the scientific rebuttals to climate change deniers amount to pep-talking the base (an Americanism for rallying those who are already loyal to the cause). Well, sometimes the base needs a good pep-talk. Like now, when the voices of global warming denialism are being orchestrated into a general anti-science chorus. That’s what 255 members of the National Academy of Sciences (speaking for themselves, not officially for the academy), including 11 Nobel Prize winners, arguably can accomplish with their open letter released May 6. The original is well worth reading: Climate Change and the Integrity of Science

There is a sense that the members are speaking from hurt, from a wound inflicted by clever manipulation of a world media all too willing to be manipulated. There is also outrage, submerged perhaps, but deeply felt – so much effort, so much time, the human capital of lifetimes – cheapened by the shallow jibes and empty challenges being hurled at climate science, all science – at scientists themselves.

No ‘letter’ of a few thousand words can deliver either the precise arguments or the years of data, scientific process and publication that went into the consensus view of global warming. I doubt this letter would change many minds or convince those not already convinced. What it does is condense the argument for the significance of scientific consensus with no little force and some creativity, and why, in the case of global warming, the significance of consensus needs to be not just understood but paramount.

Here’s a key passage:

Scientific conclusions derive from an understanding of basic laws supported by laboratory experiments, observations of nature, and mathematical and computer modeling. Like all human beings, scientists make mistakes, but the scientific process is designed to find and correct them. This process is inherently adversarial — scientists build reputations and gain recognition not only for supporting conventional wisdom, but even more so for demonstrating that the scientific consensus is wrong and that there is a better explanation. That’s what Galileo, Pasteur, Darwin, and Einstein did. But when some conclusions have been thoroughly and deeply tested, questioned, and examined, they gain the status of “well-established theories” and are often spoken of as “facts.”

For instance, there is compelling scientific evidence that our planet is about 4.5bn years old (the theory of the origin of Earth), that our universe was born from a single event about 14bn years ago (the Big Bang theory), and that today’s organisms evolved from ones living in the past (the theory of evolution). Even as these are overwhelmingly accepted by the scientific community, fame still awaits anyone who could show these theories to be wrong. Climate change now falls into this category: there is compelling, comprehensive, and consistent objective evidence that humans are changing the climate in ways that threaten our societies and the ecosystems on which we depend.

[Source: The Guardian (UK): Full text of letter]

In science there is always a place for skepticism and counter evidence. “Fame awaits anyone who could show these theories to be wrong.” Until then, there is consensus: Climate change caused by human activity is real and dangerous.

Unfortunately, appealing to consensus may not be a very strong argument. Can 255 scientists be wrong? The response will tend to be a binary, yes or no. What about 3,000 scientists (more like the actual consensus on climate change) can they be wrong? “Probably not” or “They’ve been wrong before!” People find it relatively easy to reject an argument from authority – and by itself an appeal to consensus is really a variation of appealing to authority. This is a reason why so many climate change deniers attack individual scientists and ‘experts’ as a whole – discrediting them makes the consensus seem suspect.

Perhaps the scientific consensus on climate change is a talking point. I like putting it into the context of the origin of the Earth, the Big Bang, and evolution, that’s good company for those who support science. That grouping won’t help much with the deniers; they tend to deny these theories as well. However, the point may be not to convert the deniers or even win arguments with them, but to help the supporters of science take the offense (for a change). Couple the scientific consensus with a consistent demand that the deniers provide credible evidence for alternative explanations – that’s a good start.