Sports like ice skating and ice fishing may be harder to do in the future.
Scientists who studied long-kept records have found that winters are getting warmer and some lakes are having ice-free years more often.
One of the lakes they studied, Lake Suwa in Japan, has records of when the lake freezes dating back to the 1400s. Since 1990, Lake Champlain and Grand Traverse Bay in Lake Michigan have both gone three years in a row without freezing, the scientists found.
When a lake doesn’t freeze, the water doesn’t get as cold as usual. This means the water can warm up faster in the summer. Warmer water in the summer can be harmful to fish, plants and bugs. It can also lead to blooms of deadly algae, those tiny green plants you see floating in a lake or pond. Toxic algae can kill fish as well as animals that drink the water.
"This isn't just happening in one lake in the northern United States," said Alessandro Filazzola, a community ecologist at York University and the University of Alberta in Canada. "It's happening in thousands of lakes around the world."
Lake Suwa, which once froze regularly, now freezes an average of two out of every 10 years, according to the study.
"There's already an obvious pattern that's occurring and it's showing that we're already experiencing a response from warming, which will likely get worse," Filazzola said.
The reason lakes aren’t freezing as often is global warming. Earth is slowly getting hotter because humans burn things like coal, gas, oil and wood for electricity, to power our cars and for heat to warm our homes. These create a gas called carbon dioxide, which traps heat.
— Brett French, email@example.com