Historically, much of the world’s permafrost has remained solid and stable for far longer, allowing people to build whole towns atop it. But as the planet warms, a process that is happening more rapidly near the poles than at more temperate latitudes, permafrost is thawing and causing a host of infrastructural and environmental problems. These scientists’ permafrost predictions are already helping communities like Nunapitchuk make those tough calls. One of the top US intelligence agencies, the National Geospatial-Intelligence Agency (NGA), is also interested in understanding permafrost better. In addition to the infrastructural consequences for real towns like Nunapitchuk, thawing permafrost contains sequestered carbon—twice as much as currently inhabits the atmosphere.