Transcripts

[SCREAMING] BOB KELLEHER: Another muggy August afternoon in Duluth. And once again, the Park Point City Beach is packed. Clara Gellner is one of the three lifeguards trying to keep an eye on the mob of teens and kids who are splashing away in water that's typically bone-chilling.

CLARA GELLNER: It's extremely warm. It's about 70 every day. Really big crowds, even on weekdays.

BOB KELLEHER: And it's not just little kids in the lake. There's a squad of teenage cheerleaders practicing lifts hip-deep in the water. This is Gellner's third year guarding the beach, and she knows warm water isn't the norm.

CLARA GELLNER: Normally, you have to wait until the wind is in the right direction for the warm water to be coming in. And you have to wait until August because it takes that long for the lake to warm up. But now it's been really warm even in July.

BOB KELLEHER: As Gellner is talking, the waters atop Lake Superior are reaching the highest temperature ever recorded. The lake-wide average surface temperature hit 68.3 degrees. The average for that date, August 10, is just 55 degrees.

The keeper of those records is Jay Austin with the University of Minnesota Duluth's large lakes observatory. And what he's observed is record warmth in both Lake Superior in Michigan, with Lakes Huron and Erie both quite warm as well. Is this year's record the result of global warming? Maybe, but not directly.

JAY AUSTIN: Really, what we think has gone on-- I think we're fairly confident about this-- is that 2009 was a very strong El Niño year. And that El Niño year led to a year, at least on Superior, where there was very little ice.

BOB KELLEHER: He says Superior's warm-up started last winter, which was largely ice free.

JAY AUSTIN: It allows the lake to warm up a lot more quickly, a lot more early than it would normally.

BOB KELLEHER: And the warm up may not be done. Austin says the Minnesota end of the lake will continue warming for the next week or two. It won't be clear whether the entire lake, top to bottom, has set a new temperature record until underwater sensors are pulled up for the season in September.

And should we expect more of the same? Climatologists think so. Tom Johnson is the Large Lakes Observatory's climate guy. Johnson avoids slapping blame for this year's heat on long-term global warming.

TOM JOHNSON: I don't look at this summer and say, aha, we have a hot summer. And therefore, it proves that global warming is happening.

BOB KELLEHER: At the same time, Johnson says, the long-term trend is clear. Warmer winters are affecting Lake Superior and are consistent with global trends.

TOM JOHNSON: I look at the last 30 years and say, man, we've had a lot of very warm years in the last 30 years.

BOB KELLEHER: Researchers say the trend for several decades now is clear. Ice is forming later on Superior, going out earlier, and like this year, allowing the lake to warm earlier and longer. So the warm water is great for swimming.

But what does it do to a lake's fish? Probably not much, at least not yet, according to Ted Halpern, the Minnesota DNR assistant area supervisor of Lake Superior fisheries. His office overlooks the big lake shoreline north of Duluth. Consider the lake's top predator, the lake trout. Halpern says lake trout don't like warm water. But he says there's still a lot of cold water out there.

TED HALPERN: Because there's so much deep water out there, it's really just a question of them moving half a mile or a mile or two offshore during the hottest weather. And they can still get to very cold water.

BOB KELLEHER: But there are several unknown should warm water become the norm, like how the heat affects the trouts' favorite foods, lake Herring, and smelt. Still, Halpern says, a warming climate would hit inland lakes sooner and harder than it will big, cold Lake Superior.

If the climate people are right and warm bouts will become more the norm, those chilly trips to Lake Superior in the coming years might become just another day at the beach. Bob Kelleher, Minnesota Public Radio News, Duluth.