Abstract: Why does climate change remain controversial despite an overwhelming scientific consensus? Across the 19th and 20th centuries, constantly changing, poorly standardized data practices created a need for substantial data detective work before questions about anthropogenic global warming could be answered. The practices of “climate data detectives,” who re-examine and re-analyze historical data, themselves became a focus of controversy in the 2000s. For example, the 2009 “Climategate” episode highlighted popular theories that scientists fudged or even faked historical data in order to promote belief in global warming. A second example: in the 2000s a crowd-sourced “audit” of US weather stations alleged a large warm bias in the US historical climate network due to poorly sited thermometers. Although this bias had already been removed from US climatologies by data models, climate change deniers continued to promote its existence to cast doubt on the reality of global warming. In conclusion Edwards will discuss the future of climate science in an age when blogs, independent “audits,” and social media are challenging traditional peer review systems.