Assessing scientific claims is hard enough when you stick to empirical evidence. When personal factors intrude, which they invariably do, such assessments get even trickier.

Personal factors smacked me in the face at the “Conclave on Political Polarization” I just attended at the Esalen Institute in Big Sur, California (featured, sort of, in the television show Mad Men, see Postscript). An eclectic bunch of social activists and scholars from the political left, right and center brainstormed on how to overcome the polarization entangling American politics--and science.

Participants represented groups such as, No Labels, Institute for Cultural Evolution, Breakthrough Institute, Third Way and We touched on lots of divisive issues—including fracking, gay marriage, regulation of industry, progressive taxation, campaign financing—but our primary focus was climate change and inequality.

The organizers asked me to kick off the climate-change discussion by stating which claims are “facts” and which are “opinions,” as I put it in a recent column. It is a fact, I noted, that human fossil-fuel consumption has increased atmospheric carbon dioxide, which in turn is driving up temperatures and sea levels; if such warming continues, it will probably cause more heat waves, droughts, storms, flooding and other disruptive events.

I tried to present this information in a non-polarizing manner. As a concession to climate-change doubters, I said it is a “fact” that scientific consensuses can be wrong, and it is an “opinion” that if humanity “does not take dramatic steps to curtail fossil-fuel consumption, civilization may collapse.”

I didn’t expect anyone to object to my basic facts, but the very next speaker did just that. Michael Zimmerman, a philosopher at the University of Colorado, expressed doubts about the scientific consensus on climate change. He handed out a “Background Paper” compiled in 2013 by anthropologist Benny Peiser, identified by Wikipedia as a “climate change skeptic.” The sheet asserted that “there has been no net increase in global temperatures for about 16 years.”

What made Zimmerman’s presentation doubly disturbing is that I’d already gotten to know him a little. He is smart, informed, funny. I liked him. He didn’t change my mind about global warming, but he reminded me that not all global-warming doubters are “ideologues or idiots,” as I put it in my recent post.

The same thing happened when the conclave turned to other divisive issues. Several participants criticized conventional liberal-left views—which I largely share--of inequality, labor unions and education. If Republican candidates for President voiced these criticisms, I’d swipe them aside. It wasn’t so easy to reject the arguments of my conservative conclave colleagues, because I’d gotten to know them a little, and I liked them.

Occasionally, personal factors nudge me into shifting my views. In 2010, I ranted about the perils of nuclear power in a chat with my old friend George Johnson, a science journalist whose work I admire. George questioned some of my statements, and so did the nuclear-energy advocates Rod Adams and Gwyneth Cravens, who contacted me after my talk to Johnson.

Adams and Cravens presented me with evidence of the benefits of nuclear energy in a respectful, friendly manner. Eventually I concluded that my fears of nuclear energy were excessive, and I became a “pro-nuke nut,” as I put it in one post.

Another old friend who has influenced me is Andrew Revkin, who for years was an environmental reporter for The New York Times and now writes its Dot Earth blog. In 2007, Andy recommended that I read Break Through: From the Death of Environmentalism to the Politics of Possibility.

I liked the book so much that I invited its authors, Ted Nordhaus (who was at the Esalen conclave) and Michael Shellenberger, to Stevens Institute of Technology to give a talk in 2008. We hit it off. That’s one reason why I’m sympathetic to the iconoclastic approach of their think tank, the Breakthrough Institute.

Personal relationships obviously play a huge role in politics. That was a major theme of the Esalen conclave. The key to overcoming polarization, some speakers said, is getting people on opposite sides of an issue to meet, so they have a harder time demonizing each other.

Some activists recalled changing their minds after getting to know political opponents. Others recalled changing opponents’ minds. In other words, astute activists exploit personal factors to advance their goals—just as astute polemicists appeal to readers’ emotions as well as reason.

Personal relationships matter; they nudge me into reconsidering my views. But what happens when personal relationships push you in opposite directions? Example: Nordhaus and Shellenberger criticize some environmentalists for being “alarmists,” whose warnings about the adverse effects of climate change are excessive and counterproductive.

One researcher often accused of alarmism is NASA atmospheric scientist James Hansen, who has been warning about global warming since the 1980s. "Our planet, with its remarkable array of life, is in imminent danger of crashing," Hansen wrote in his scary 2009 book Storms of my Grandchildren.

I liked the book, and I liked Hansen, when I brought him to Stevens to give a talk in 2010. He is a modest, self-effacing man, driven toward activism by his research. As I said at the Esalen conclave, I am an optimist by nature, and hope, I believe, is a better motivator than fear. But I am haunted by the possibility that Hansen’s frightening prophecies might turn out to be right.

At this point, many readers are surely thinking: Only facts matter! Personal relationships should not affect your assessments! Indeed. If I were an emotionless machine, making up my mind based entirely on “facts,” I would be a much better journalist.

Postscript: The finale of the television show Mad Men takes place at an Esalen-type resort. According to an Esalen veteran at the conclave, those scenes were actually filmed not at Esalen itself—which declined the show’s request to film on site--but at a nearby location.