In the midst of the heated U.S. presidential race last summer, with hypercharged scrutiny of partisan propaganda on social media, Facebook Inc. Chief Executive Officer Mark Zuckerberg received a letter from a group of U.S. senators led by Massachusetts Democrat Elizabeth Warren that had nothing to do with elections. They were angry about a year-old piece of climate news.

A Washington Examiner article shared on Facebook in 2019 had denounced climate models, which are widely used by scientists around the world to measure and predict the impacts of warmer temperatures. Science Feedback, an outside organization Facebook works with on fact-checking, had labeled the story false. A review by five scientists found the story "highly misleading” because of "false factual assertions” and accused the authors of "cherry-picking datasets.” The conclusion meant Facebook posts linking to the story would now be saddled with a label saying it had been disputed.

But then Facebook said because the article was designated as an op-ed, it was exempt from fact checks under the company’s policies. The "false” label was removed. Warren’s letter called the op-ed policy a "massive loophole.” Facebook’s policies on climate lies "represents another unfortunate example of Facebook’s refusal to fully combat the deliberate spread of misinformation,” she added.