Before dawn, on the big river where he first found a taste for adventure, Will Steger wakes up tired and alone.

Another 18-hour day rushing around the Twin Cities awaits, more stops on a new quest unlike any other in his career.

The famed Minnesota explorer has forsaken his solitary home in the North Woods, his refuge for decades. Now he's navigating crowded freeways and blitzing churches, schools, Rotary clubs -- any group willing to listen to his pleas to take the growing threat of global warming seriously and rethink how we live.

Can one man going flat-out for a cause somehow change the world -- or at least his home state? Steger is upending his life to find out.

And so here he comes through the clanging gate outside his houseboat docked near downtown St. Paul, looking ragged but resolute, in faded jeans and muddy clogs, his wild heap of hair blowing in the wind as he lugs a backpack bulging with a banged-up laptop, old books, loose files and lord knows what else.

City lights twinkle over the Mississippi. "Let's go," he says.

He drives a rusting Toyota wagon with a missing hubcap and a radio he rarely uses, preferring silence.

He packs oatmeal into a 32-ounce water bottle for the road some days because he gets too busy to stop for meals.

He brought a kayak when he settled on the river a year ago, hoping to stay connected to the life he left. But he has only had time to put it in the water once.

Rugged and graying at 62, and with his historic expeditions to the North Pole and across Antarctica more than 15 years ago now distant memories, Steger is on a single-minded mission he has had to start from scratch.

"I've never worked in Minnesota like this before," he said. "I had no idea what to expect."

Michael Noble, executive director of Fresh Energy, an environmental group in St Paul, remembers the Sunday afternoon two years ago when his cell phone flashed with a call from someone in Ely: "He said, 'Hi, I'm Will Steger, and I've decided to dedicate the rest of my life to raising public awareness on global warming.' "

The two had never met. But their talk set in motion the roughly 200 events Steger has headlined around the metro and the state in the past year, appearances that often draw overflow crowds of hundreds of people.

He speaks to groups awed by his exploits and alarmed by his eyewitness accounts of what climate change in the Arctic portends -- how it could wipe out the polar bear, alter the rhythms of life in Minnesota and harm the American economy. He also stands before audiences that hardly know who he is and sound puzzled by or doubtful of what he says.

"Are we all going to die in 20 years from global warming?" a student at Lincoln High School in Lake City asked him after he concluded a recent talk there.

The school auditorium fell silent as Steger thought for a moment on stage.

"No," he gently told the teen. "Human beings will always adapt. But our lifestyles will be changed." Then he added, "This problem will dominate your life as long as you live."

Even where he gets a hero's welcome, Steger sees signs of the struggle ahead. When he spoke at Pax Christi Catholic Community in Eden Prairie last fall, a crowd of 1,000 people gathered inside the gleaming church gave him a standing ovation. Then some hopped into their gas-guzzling SUVs and drove away.