For hundreds of years, Shinto priests living on the banks of Lake Suwa, in the Nagano Prefecture of Japan, watched the surface of the lake freeze solid each winter. Partway through the winter, the ice would crack and refreeze, creating a long, jagged ridge stretching from shore to shore: the footprints of a god walking across the lake to see his beloved, the story goes.

But since the Industrial Revolution, the inexorable impacts of warming have thinned out Lake Suwa’s ice, leaving the lake dark and unfrozen more years than not.

And Lake Suwa is far from alone, according to new research published Monday in Nature Climate Change: Around the world, lakes are already freezing less, and for shorter stretches of