CANADA – APRIL 20: Signs of the times: Citizens in the mid-’80s react to the worry posed by acid rain. (Photo by Jeff Goode/Toronto Star via Getty Images)

This story has been updated.

Long before our current politicized battles over the science of climate change, vaccines and evolution, there was an older generation of political science fights — over the health effects of smoking and the environmental costs of acid rain and the depletion of the Earth’s ozone layer, to name a few. And scientists working on these topics in the 1980s and earlier often had experiences not unlike those of scientists in contested fields today, including encountering concerted criticism of their work and a steady flow of politicized misinformation.

One of those scientists is Gene Likens, a celebrated ecologist who is president emeritus of the Cary Institute of Ecosystem Studies in Millbrook, N.Y., and who is widely regarded as one of the discoverers of acid rain. In the 1980s, as the science became increasingly clear that emissions of sulfur dioxide and nitrous oxide from fossil fuel burning were leading to acidic precipitation and deposition, a small science war began over the findings, with those opposed to regulatory action predictably raising doubts about the science. “I think it’s like global warming, climate change, in many ways,” Likens said.

Those days may seem long gone now. But as recent research by Likens in the open access journal PLOS One suggests, a vestige of them may still with us — preserved, of all places, in the record of edits made to the “acid rain” entry on Wikipedia.

In a new study that takes a close look at edits to this entry, and to two others where the subject is of far higher current political salience — “global warming” and “evolution” — Likens and University at Buffalo ecologist Adam Wilson find that “global warming” and “evolution” get way more edits than entries on other scientific issues. That’s presumably in part because on these contentious topics, science doubters are constantly trying to get their point of view through, even as other Wikipedia editors steadily push back.

But the research also showed that the “acid rain” entry got more edits, and had more words changed, than entries on scientific topics that either are not controversial at all, or haven’t been controversial in an extremely long time (in one case, hundreds of years): “heliocentrism,” “general relativity,” “continental drift,” and the “standard model” in physics.

The research project began because in 2011, Likens was reading the Wikipedia page for “acid rain” and noticed some curious edits. Phrases like “Acid rain is a popular term referring to the deposition of wet poo and cats” and “AciD Rain [sic] killed bugs bunny” were added to the entry (and, eventually, removed), their paper observes. The authors also noticed more substantive (but incorrect) changes to the entry — which led them to broaden their inquiry.

For seven Wikipedia entries — “acid rain,” “global warming,” “evolution,” “heliocentrism,” “general relativity,” “continental drift,” and the “standard model” in physics — Likens and Wilson downloaded the history of revisions over a nearly ten year period between mid-2003 and mid-2012. Then they crunched the data on how many edits there were per day, and how many average words were added, cut, or changed for each edit.

Sure enough, the “global warming” entry had the most average edits — almost two per day, and about 110 words changed — vastly more than the least edited entry, “standard model” (about .2 edits per day and less than 10 words changed). At one extreme, the “global warming” entry saw 239 edits in one day!

But “acid rain” was in the middle of the pack, clearly getting a lot more edit attention than the non-contested topics. This may suggest a lingering political concern over the topic, despite the fact that the political debate was resolved, through policymaking, in 1990 with the passage of the Clean Air Act amendments.

“There’s a lot of view out there that regulation is bad of any sort, and so regulation dealing with acid rain is still brought up frequently,” says Likens, who adds that he thinks acid rain is still a real problem, though it doesn’t get as much media attention any more.

The researchers conclude their study with a cautionary note about Wikipedia use. “Educators should ensure that students understand the limitations and appropriate uses of Wikipedia, especially for controversial scientific issues,” they write, although the study also praises the site on many other counts, such as the fact that “its scientific content increasingly references articles in established scientific journals and that the citation frequency of those journals is in general agreement with citation patterns in the scientific literature.”

In other words, Wilson and Likens are not not criticizing Wikipedia as a whole — they’re mostly worried about sudden changes to entries on contentious, politicized science topics. “I’m not trying to lambaste Wikipedia in any way, because I think that they are doing an amazing thing,” says Wilson. “I just wanted to call attention to this simple idea, really, that the content is so dynamic, so that at any point when you check it, it can be different from when you check it the next time.”

However, the Wikimedia Foundation, the non-profit that supports Wikipedia, had some criticisms of the work. “The authors of this study do not seem to have successfully correlated the frequency of edits to controversial articles with an increased likelihood of inaccuracy,” said Juliet Barbara, senior communications manager at the Wikimedia Foundation, in a statement. “Instead, the study simply seems to confirm that the articles chosen as controversial are, in fact, controversial. Although the authors reference anecdotal examples of inaccuracies, they note that it is, in fact, ‘difficult to assess causality.'”

Barbara continued:

Wikipedia has been widely found to be as accurate as traditional sources including Encyclopedia Britannica and the German-language encyclopedia Brockhaus. Automated accounts or “bots” detect and revert vandalism within seconds. Volunteer editors and administrators regularly ensure content meets the site’s policies and guidelines. Vandalism and inaccuracies occur, but thanks to Wikipedia’s open, collaborative model the vast majority of inaccurate content is removed within minutes.

Wikipedia has a longer statement about the study here.

The bigger lesson to be taken from the study, though, may be about the life-cycle of scientific controversies. While some appear to be perennials — evolution has been steadily controversial for over 150 years — many others, especially those that are controversial because of the present day political implications of a given body of science (like global warming or acid rain), seem to pass through stages.

These topics are argued about the most — with high emotion, and with large political and personal stakes — when the politics of the issue itself remains unresolved. That’s because in truth, people aren’t really fighting over science at all in these cases — they’re using science as a proxy for defending a broader worldview, and to oppose a political solution that is distasteful to them.

However, once a policy solution is achieved — in acid rain’s case, with the 1990 Clean Air Act amendments — the present day incentive for debating the science declines. A new status quo sets in, media coverage declines, and most people find something else to argue about. The issue appears “settled.”

But those who previously had a big stake in contesting the science behind a given issue — say, acid rain — don’t suddenly rewire their brains to erase all that intellectual investment. They are likely to linger in their beliefs that the science behind acid rain was bogus, even though there’s less public interest in what they have to say.

Now and again, though, they’ll bring up the same arguments — and, just maybe, try to edit Wikipedia to the same effect.

This matters, of course, because someday the world will truly take meaningful and concerted action on global warming. And when it does, scientific controversy will also subside substantially. But it could be a very long time before it is entirely gone. The arguments — and the emotions — may linger, in a kind of long twilight of science denial.