At the outset I want to say that I believe that human activities have increased the amount of greenhouse gases in the atmosphere and, as a result, have strengthened the naturally occurring greenhouse effect. My belief is based on results of research carried out by a wide range of scientists in a wide range of physical, biological and social science disciplines over at least the past 60 years. Their research has been calibrated in part by observations: worldwide melting of glaciers, sea level rise, warm climate ecosystems moving upslope to higher altitudes, tropical disease vectors moving into the mid-latitudes and the disappearance of Arctic Sea ice.

There are other suggested changes that are not yet confirmed as global warming FAQs (facts) but, to me, seem credible — even foreseeable, but they are not necessarily reliable as predictions of what will occur. These include but are not limited to the following: changes in the characteristics of seasonality; a change (weaker or stronger) in frequency and intensity of extreme meteorological events (droughts, floods, fires, disease outbreaks); shifts in the location of ecosystems; disappearance of various glaciers; trend toward ice-free Arctic Ocean; changes in the various atmospheric oscillations and ocean currents, and so forth.

Despite this mountain of scientific data, information, analogues, anecdotes and guesstimates about climate change, I still harbor some doubts about some of the “evidence” of anthropogenic influences on the global climate system. I would not be totally surprised whichever direction the temperature trend goes. Aren’t all scientists supposed to be skeptical about their research findings and those of others, until their scientific research efforts reduce remaining uncertainties to an acceptable level (e.g., beyond a doubt)? I guess that makes me a skeptic of sorts. In fact, anyone can be a good skeptic. Some movies and books that use the word “good” to mean opposing things: “The Good Son” was about a bad son; “The Good Wife” on TV was about a jailed politician’s wife who served to uphold the law. Here I use the adjective “good,” in a positive sense.

I wonder how much we really know or how much we really understand about the workings of the global climate system. There will always be uncertainties, as the climate of the planet is always changing. And there are uncertainties about the uncertainties: though the temperature will increase, how, when and where will the rain fall? There are glitches in the scientific information: missing data, cooling episodes and cold extremes in the midst of warming, and changes in the naturally occurring quasi-cycles in the atmosphere. Science skeptics are sure to find other problems in the data, models and interpretations of modeling assumptions.

Let’s look at climate change skeptics. It is interesting to look at the evolution of the names used by believers in global warming to label those who have shown a reluctance to accept their view that human activities could influence the atmosphere. I remember Will Kellogg a super senior atmospheric scientist at the National Center for Atmospheric Research in the mid 1970s referring to those people as naysayers. They were also referred to as doubters and non-believers. Some time in the 1980s they became referred to as the skeptics. After 2000 they seem to be collectively and pejoratively referred to as deniers. Let’s sort this out.

Naysayers, doubters, skeptics, contrarians, denier: what a difference a word makes

A naysayer is one who does not agree with the scientific findings as they currently exist. It is not necessarily so that s/he does not believe in science but that the scientific evidence for human induced global warming is unconvincing. Skeptics are those who are a mix of those who reject the scientific findings and those who reject the science (e.g., those who do not believe humans can influence the global climate). Now, in the first decade of the 2000s, it seems that those who do not agree with the scientific findings of the IPCC have been labeled as deniers by those scientists who believe in global warming. This is an unfortunate turn of events.

I liken the true deniers to be like the flat-earthers whose minds are closed to any possibility of their views being wrong; damn the scientific findings. They play on the fact that there are uncertainties in the science, and there likely always will be. However, they seem to have lumped good skeptics in with the true deniers; good skeptics have legitimate doubts about the data, models and interpretations of climate change science.

I have worked in the midst of physical scientists on a daily basis for almost 40 years; I know some of the weaknesses in their scientific presentations as well as their strengths and successes. So do many of us. We tend to believe to varying degrees that it is quite possible (or likely) for human activities to influence global temperatures (we know we can do it at the local, urban and regional levels; why not the global level?) but we are not 100 percent convinced about many of the projections of future climate changes. However, we still choose to err on the side of precaution and support the climate change “yeasayers.” Some “good” skeptics are still neutral or lean toward the naysayers. Their questions and concerns are often legitimate. They are different than the deniers.

In fact there are climate deniers on both sides of the climate change issue. By that I mean that deniers on either side cannot readily come up with a list of climate characteristics that would get them to change their minds about whether or not global warming is human-induced. To one set of deniers, the climate is warming because of anthropogenic factors and they are 100 percent convinced of that. To the other set humans cannot possibly influence the temperature of the atmosphere: they believe without a doubt that natural variability will overshadow whatever humans might be doing.

Those who label people as yeasayers or naysayers, skeptics or “good” skeptics, doubters or contrarians, or hardened deniers must apply those labels much more carefully than they are doing to the range of perspectives of people debating global warming. The failure to do so has created more closed minds and resulting polarization about climate change than have the validity of the scientific findings.

Do graphic representations like these (and there are many) foster cooperation or foster polarization with little chance for real meaningful dialogue? Naysayers (left) and yeasayers (right).