For decades, the United Nations’ Intergovernmental Panel on Climate Change (IPCC) has offered a snapshot of the planet’s changing climate – but University of Toronto researchers have found that some of the underlying data underrepresents a key driver of Arctic warming. The IPCC reports rely on a wealth of climate data, including observations from the U.S.’s National Oceanic and Atmospheric Administration (NOAA) of autumn snow cover – the extent to which the land is covered by snow – in the Northern Hemisphere. The observations have been made annually since the 1960s.