Researchers say 30 percent to 50 percent of the ice loss is due to natural variation in temperature and humidity, while human-caused warming is responsible for the rest.
The spring eagle migration usually coincides with the ice-out of Minnesota's lakes and rivers. But mild weather in February meant the ice broke up earlier than usual and also melted much of the snow dotting the ground.
NASA is studying snow with the same technology it uses to study ice on Mars. What they've found so far: The climate is changing -- and so is our relationship with snow.
This year's mild winter has meant another record low year for ice cover on Lake Superior. The climate shift is easy to see from the bow of a Madeline Island ferry.
Every night in February, Michelle Courtright is hosting vegetarian dinner parties to share the message that animals raised for food in Minnesota put more greenhouse gas emissions into the atmosphere than passenger cars.