Recently, during the much-needed period of recovery and imbibing after a long day of talks at a scientific conference, I found myself in the midst of a friendly – if only slightly heated – debate over climate science.  Two aspects of this realization surprised me greatly.  First, the conference had nothing whatsoever to do with climate change.  Second, my verbal adversary who seemed to be denying the science so thoroughly laid out in the IPCC reports, was a fellow scientist whom I would have thought able to see where the science was clearly pointing.  Intrigued and always up for a good debate, I dove in eager to learn what thought processes could have led him to doubt the consensus of climate scientists.

    His views quickly caught me off guard because for the most part he did not actually deny the science behind climate change; his objections were largely the result of trying to be the good scientist he was trained to be.  I have now argued at varying length with at least three scientists who have reservations about climate science, and this fellow’s point of view was representative of them all.  Granted the sample size is small, but with three points I can still draw a trend line.  Heck, I could draw a parabola if I wanted.  Given that skeptical scientists such as these provide a steady stream of skepticism into the public at large, it would be useful to understand where at least some of the points on this line are coming from.  Of course there are a few high-profile scientists who have technical problems with the science (which are often easily refuted), but in my experience the average run-of-the-mill climate-skeptic-scientist is one from outside the field who simply has a problem with the nature of the debate.  Allow me to explain.

    The first thing to realize is that any good scientist got that way with generous and continuous doses of skepticism.  While in college, we mostly learn knowledge and how to apply it.  Our textbooks and professors are sources of knowledge to be absorbed.  But upon entering graduate school, scientists in training learn how to create knowledge.  Papers and reading assignments consist of claims to be evaluated and questioned.  Facts become interpretations, proof becomes evidence.

    Science advances most dramatically when it questions commonly accepted beliefs; it stagnates when it becomes trapped in dogma.  Copernicus’s heliocentric solar system challenged the world-view of nearly everyone at his time, and resistance to Darwin’s theory of evolution persists to this day.  Einstein’s special relativity challenged not only the dogma of classical mechanics, but also the very common sense with which we perceive the world.  Yet not even Einstein was an expert with authority above question.  Remember if we had all listened to Einstein we would have no quantum mechanics.

    So every good scientist approaches any claim with his or her normal allotment of skepticism.  The problem when it comes to climate is that scientists are very busy, and the climate system is very complex.  Both of which understate the facts severely.  Many scientists from outside the climate field have read enough of the research that goes into climate models to convince themselves the work is sound, but a few, like my friend from the conference, remain unconvinced at the philosophical level, where their core skeptic lives.  They do not actually believe climate science is wrong, but the time and effort to convince themselves that it is 100% right would be far more than they have to spare.

    In fact, climate science surely is not 100% correct.  Nothing in science is certain; it must always remain open to new evidence.  This is especially true when it comes to the climate, with all of its complex interacting systems, nonlinearities, and feedback loops.  We clearly do not have all the nuances pinned down, but that does not mean we do not understand something deep about the big picture.  The evidence on climate change is beyond the scope of this rumination – the IPCC (Intergovernmental Panel on Climate Change) report contains a comprehensive and really quite frank evaluation – but as it finally concludes, “Warming of the climate system is unequivocal” and “most of [it] is very likely due to” human activity.1

    So scientists are skeptics, and the details of science are always uncertain.  Normally this natural order of things presents no problem.  The difficulty arises when science meets policy and the media.  The real hesitation many skeptical scientists have regarding climate science derives not from its conclusions, but from its communication.  When my friendly antagonist hears the media reporting definitive statements about science, his philosophical core grows uneasy.
 
Scientists speak in caveats and p-values, and we can forget that sometimes people often need a concrete yes-no, “What do I do?” type of answer.  This is especially true for climate change, where either policies will change or they will not.  “Oh I agree we should change the way we use energy,” protests the philosophically skeptical scientist, “But I fear that by speaking in absolutes we are endangering the integrity of science in the public’s eye.”

    This may be true.  Absolute statements in the media may misrepresent the process of science to the public.  But politicians do not say, “It is very likely that we have passed climate legislation.”  That is not to say that scientists should lie or hide uncertainties in their work.  But we must not be afraid – nay we have an obligation – to interpret research to the lay person so that he or she can understand what it boils down to at the end of the day.  Integrity is useless if your audience has no idea what you’re saying.

    In the case of climate change, what the pot of research boils down to is this.  First, it is as near to a scientific fact as one can get that carbon dioxide absorbs and reradiates heat in a way that would cause the Earth to warm.  Second, the past century has seen increases in both CO2 and global temperature that exceed natural variations.

    There are always a few lone iconoclasts, but within the climate field, virtually all scientists agree on these main points.  Outside the climate field, some scientists rightfully reserve the appropriate amount of doubt when they hear absolute statements in the media, but they generally agree with the take-home message on climate change.  I do not begrudge them their skepticism, but I simply ask them to be clear on what, exactly, arouses their skepticism.  Is it the general message boiled out of decades of peer-reviewed research, or is it whether rainfall in Tanzania by 2090 will drop by 20% or only 15?  Skeptical scientists must be careful that their philosophical skepticism not be misinterpreted, but at the same time the public needs to understand how a scientist really thinks in order to hear this skepticism appropriately.

    At the end of the day, we must either take action or not.  If we quibble endlessly over details and certainty, it may soon be too late and too expensive to change our course.  But if we can focus on the big picture that emerges as the closest scientists can come to consensus, we may well look back on this as we do on the ozone hole and think, “Whew, I sure am glad we nipped that problem in the bud!”

1 Intergovernmental Panel on Climate Change (2007).  Climate change 2007: Synthesis report.