An anonymous reader writes: On Saturday, world leaders completed an ambitious international agreement to address climate change. But when the officials received the first copy of what was supposed to be the final draft, a one-word mistake threatened to derail their progress. Part of the agreement involved language that encouraged wealthy nations to provide monetary aid to poorer nations in order to help transition to more sustainable systems. But the draft used the word "shall," which would have made it a legally-binding requirement. U.S. Secretary of State John Kerry pushed back on the change, noting that previous versions of the document had used the word "should" instead. Officials tried to quickly figure out whether the swap had been made intentionally. Ultimately, they classified it as a typo, and hurriedly prepared a corrected version of the document, which was adopted without incident.