Last October, when Susan Hubbard and her team pulled sleds full of sensitive sensors across the snow near the northernmost point in Alaska, temperatures hovered in the single digits and low teens (e.g., 8–15 °F). Foremost in the researchers’ minds, aside from collecting data on the frozen ground beneath their feet, were two things: keep an eye out for polar bears and keep their equipment from freezing. Hubbard, an earth scientist at Lawrence Berkeley National Laboratory, had hired a polar bear guard to deal with the first problem and perfected the art of wrapping pieces of equipment up and periodically warming them …