Too much can be made about mistakes in US surface-temperature data from the Goddard Institute for Space Studies (GISS). Too little can be made about them, too.Conservative commentators overreacted to revelations that GISS had erred in ways that stoked alarm about global warming. GISS is run by James Hansen, one of the first scientists to issue warnings about human contributions to observed warming and a longstanding ally of Al Gore in the former vice-president’s crusade for aggressive response. When a Canadian mathematician pressed for and won a downward correction to GISS temperature data, bloggers and radio talk-show hosts pounced. One of them, Rush Limbaugh, called the correction...