97–98% of the most actively publishing climate scientists believe climate change is real, is caused by human emissions and is dangerous. The prominence and expertise of climate scientists who don't believe this is significantly lower than those who do.
So what? If I said that 97-98% of cancer researchers believed that smoking caused cancer, or if 97-98% of astronomers believed that the Earth revolved around the Sun, you would all be laughing at how trivially obvious it is. But when we discuss climate change, consensus plays a big (and controversial) role in the debate.
|Response to the survey question "Do you think human activity is a significant contributing factor in changing mean global temperatures?" (Doran 2009) General public data come from a 2008 Gallup poll. Image from SkepticalScience.com|
It should be first noticed that it is an invalid argument to claim that "because 97-98% of experts something is true, it must be true". This argumentum ad numerum implies the truth of a proposition from only the popularity of its belief. It is not difficult for anyone to think of counterexamples which show that popularity does not determine truth. Science, itself, is full of such anecdotal counterexamples. Some of the most famous examples are those of the Scientific Revolution, where rebellious scientist-philosophers such as Galileo fought against the tide of commonly accepted 'truth' and won. If anywhere, science is where one can stand against the majority and emerge victorious and vindicated.
Looking even only briefly at the popular discussion of climate science, one quickly stumbles upon the oft-repeated argument of "There is a consensus of scientists who believe that climate change is real" to which the response is always "Science does not work by consensus!" If you're trying to explain how you know that climate change is real, the argument from consensus falls flat. The scientific method does not work by consensus. When a scientist is trying to determine how much Arctic sea ice has been lost during the summer melt this year, their answers come from the scientific evidence, not from assessing how much sea ice the majority of scientists believe has been lost. So, if you're going to argue about knowledge, you need to argue from the scientific evidence.
That all said, consensus does appear to play a role in the institution of scientific progress. My understanding of science as an advancing body of work and a congregation of like-minded investigators has been influenced by Thomas Kuhn's writings on scientific research paradigms. Kuhn, who was not without his detractors, argued that scientists are also humans bound by subjective biases which affect their scientific work. Although the Baconian scientific method does a spectacular job of focusing a scientist's work through a prism of objectivity, the work is still defined by the world view within which the scientist was trained. When the world view produces a theory which fails to explain fundamental phenomena, the world view slowly becomes challenged and eventually rejected. At this point, when a new paradigm and accompanying world view successfully arises, the consensus of scientific acceptance shifts appropriately. At this 'macro' level of science, consensus appears to play an important role. The world view is established by the consensus of scientists. When older scientists train younger scientists, the younger scientists are adopted into the consensus by being taught the world view of the older scientists.
This consensus is tested, however, when the world view is clearly plagued with inconsistencies of theory and experiment. But without this consensus, the scientific community could not function. The consensus of world view determines the terminology, methodology and even purpose of a particular scientific discipline. Without a consensus, scientists would be stuck arguing first principles and not actually performing any research. Scientists accept the consensus position, even if slightly flawed, in order to proceed with the dirty business of extending research. If the consensus position was too outrageous (e.g. if predictions clearly did not match the data) the consensus would be rejected and redrawn as a new paradigm. So while we can see that consensus does not play a role in the 'micro' level of scientific research, consensus does play a role in the 'macro' level of scientific progress. But I don't believe this level of acceptance of consensus in scientific paradigms constitutes anything fallacious or akin to 'groupthink' because scientists are trained (more than anybody else) to challenge the consensus. Consensus is accepted because it works.
When it comes to communicating climate science, however, consensus is an important talking point. Climate change is incredibly complicated. Climate scientists have known about climate change for decades and have understood the physics for over a hundred years. But only in the last decade or so has the public really started to catch onto this issue. Why? Other than political obstruction (which is a story for another day), the big issue seems to be the difficulty of communicating the science. Naturally, when a journalist has neither the time nor expertise to appropriately convey the complex science, an argument appealing to the trustworthy authority of the scientific majority is made instead. Is it fallacious? Yes. But is it fair? I think so. We should trust our scientists on complex issues concerning the health of our climate just as we would trust our doctors on complex issues concerning the health of our children.