MILWAUKEE (WTAQ) - A report from the American Meteorological Society says the ice covering the Great Lakes has declined 71 percent over the last 40 years.

Researchers measure ice coverage by examining reports from the U.S. Coast Guard and satellite pictures taken between 1973 and 2010. They say only about 5 percent of the Great Lakes’ surface froze over this year.

The ice coverage was 79 percent less on Lake Superior and 88 percent less on Lake Ontario.

Scientists attribute the reduction to broad climate change and smaller climate cycles like El Nino and La Nina.