Treated human waste has been used on farmland for decades, but the ick factor has not entirely faded. Some environmentalists think the treatment process may not get rid of all the harmful contaminants that could be in the waste.

Saturday is the opening of the walleye fishing season, and it's usually one of the busiest weekends for the state's resort communities. This year, many of the lakes in northern Minnesota are still iced over, putting a chill on the season.

Since 1958, researchers have been measuring the amount of carbon dioxide in the atmosphere at the Mauna Loa Observatory. The remote outpost has just reported a carbon dioxide level of 400 parts per million — the highest it has climbed in the modern age.

The amount of carbon dioxide in the atmosphere has crossed the "psychological threshold" of 400 parts per million. That number is one of the clearest measures of how humans are changing the planet by burning fossil fuels.

Taking a page from the playbook of decades past, college students are once again pressuring schools to pull investment funding from specific sectors. This time it's big oil and coal companies. But these campaigns have effects beyond the university — they're launching a new generation of activists.