Depending on what day you search, Wikipedia may say global warming is “a sham” or that there is “a consensus view that it is man-made.”

That kind of flux isn’t unusual: Wikipedia pages on hot-button issues such as global warming and evolution may change much more frequently than pages on less controversial subjects, according to a new study. The findings raise the question: Which science pages on Wikipedia can be trusted?

Wikipedia allows anyone to create pages or edit them — by tweaking, updating or deleting revisions, for example. A 2005 study in the journal Nature found that the information provided on Wikipedia is almost as reliable as that of the benchmark, Encyclopedia Britannica. A 2011 study found that Wiki articles were on a par with professionally edited databases for health-care professionals.

For the new study, which was published Aug. 14 in the journal PLOS One, Adam Wilson, a geographer at the University at Buffalo, and Gene Likens, a professor of ecosystem studies at the University of Connecticut, looked at Wikipedia entries on evolution, global warming and acid rain. The researchers compared them with entries on four topics that are less politically charged: continental drift, general relativity, the Standard Model and heliocentrism (the model in which the Earth and other planets revolve around the sun).

Global warming

The researchers found that the Wikipedia pages on the controversial topics were edited much more frequently than less contentious issues, with the explanation of global warming being revised two to three times a day. In some cases, users deleted huge chunks of text on the global-warming page, they discovered. By contrast, the Wikipedia page on the Standard Model, the reigning particle-physics model, has about 10 words changed every few weeks.

“The content in Wikipedia pages can be, for some pages, quite dynamic — meaning multiple times a day there are some significant changes where people will potentially delete an entire paragraph or add a paragraph,” Wilson said.

Some changes were anything but subtle, such as deleting an entire entry and replacing it with “global warming is a sham.”

“Anybody looking at that is going to see that that’s just ridiculous and it’s obviously just vandalism,” Wilson said. Many of the edits, he said, were biased, malicious or just wrong.

Still, more-dynamic pages are not necessarily less reliable, Wilson added. It could simply mean there are more people interested in and knowledgeable about the topic, as well as more people who care enough to tweak the content.

In fact, overall interest does seem to correspond with edit frequency: Many more people viewed the Wikipedia pages on climate change than clicked on the continental-drift page, Wilson said.

Freezing changes

Wikipedia has ways to stabilize pages, such as temporarily freezing changes and prohibiting anonymous editing, Wilson said.

In response to the study, Katherine Maher and Juliet Barbara, communications officers with the Wikimedia Foundation, which runs Wikipedia, released a statement arguing that the open-source encyclopedia’s editing process is part of what makes it so accurate.

They also took issue with some of the conclusions of the paper.

“It didn’t surprise us to learn that articles considered to be controversial are frequently edited. The nature of controversy, after all, is that it generates discussion and public attention. Unfortunately, the study also jumped to conclusions about what this means for Wikipedia’s reliability, overstating findings and inferring facts not in evidence.”

The study used only a few examples of inaccuracies and did not really show that the controversial articles that were edited more frequently were less accurate, they said. In fact, they continued, several past studies have found that the more an article is edited, the higher the quality.

Most science pages, however, suffer not from too much attention but from too little. Wikipedia pages on important scientific topics can be so small they are considered a “stub,” or alternatively, an overzealous grad student may decide to impart to the masses his or her knowledge on an arcane subject, meaning the entire page is written by just one person, said Amar Vutha, an atomic physicist at the University of Toronto.

“The problem is they’re used to writing for other scientists, and they write in the journal format and they put things in the abstract,” Vutha said. “They think, because it’s Wikipedia, we can just dump in a whole bunch of equations.”

Vutha, along with a few dozen other physicists, recently participated in a Wikipedia “edit-a-thon” at the American Physical Society meeting. The goal? To improve the quality of pages on atomic physics. The team spent three hours updating 51 of the most important topics in their field, including thespeed of light and quantum simulators. The scientists also created four new pages, including one on sub-Doppler cooling.

The experience may have changed the mind-sets of the many first-time Wikipedia editors who participated, Vutha said. “Now, you’ve set loose around 20 or 30 people who, hopefully, when they see something wrong on Wikipedia, won’t hesitate to fix it,” he said.

Frequent citations of references and the inclusion of links to other Wiki pages can be a sign that a page is carefully written or edited — or at least conforms to Wikipedia’s ideal style and is easier to check for accuracy, Wilson said.

But the best policy is to use Wikipedia as a jumping-off point, not the last word on any given topic, Wilson said.

Live Science

The Reality of Climate Change: 10 Myths Busted

Know Your Roots? Human Evolution Quiz

Fight, Fight, Fight: The History of Human Aggression