The Earth is warming, and not just its atmosphere and oceans. The land itself is warming too, leading to more extreme ground temperatures across the planet—along with unclear but dire consequences for surface dwellers like us. According to a new study, we’ve underestimated the problem, focusing on rising air and water temperatures while failing to appreciate the threat of heat waves beneath our feet. Soil temperatures have generally received relatively little attention in studies of human climate change, scientists say. That’s partly because the complexity of the measurements makes it difficult to find reliable enough data on soil temperatures compared to air temperatures near the surface. But in the new study, a team of researchers from across Germany gathered soil temperature data from a wide range of sources, including weather monitoring stations, remote sensing satellites, the ERA5-Land reanalysis dataset, and Earth system simulations. (RUSSELL MCLENDON)