• picture
  • picture
PRI's Environmental News Magazine

Lake Ice

Air Date: Week of October 13, 2000

Host Steve Curwood talks with John Magnuson of the University of Wisconsin about a new study revealing 150 years of observations about ice. Using the information researchers discovered less ice cover than previously thought in the Northern Hemisphere.


CURWOOD: Global climate change: a highly technical issue to be tracked by elite scientists using exotic technology, right? Not necessarily. A new study collected 150 years worth of observations made by average Joe's and Josephine's from across the Northern Hemisphere. Researchers found that for centuries people have been keeping track of when local lakes and rivers froze and melted. All the researchers had to do was pool the data, analyze it, and then see if the first freeze is coming later and the spring thaw earlier than in the past. John Magnuson, a limnologist at the University of Wisconsin and an author of the study, tells me the oldest records they found were religious-based.

MAGNUSON: One in Germany which is Lake Constance, or the Bodensee, goes back to the ninth century, and there they would carry a Madonna statue across the lake if it froze. It was a lake that didn't freeze very often. And then the next winter if the lake froze they would carry it across the other way between two churches. The other old record is from the Shinto religion in Japan. In Lake Sua there are two temples one on either side of the lake. And when the lake froze it had religious significance, the date that it froze. And they would keep this record year after year after year. They would keep the date the lake froze. And that record goes back to the fourteen hundreds. Those are the only two that we know, for sure, are religious -based. The others are probably started more in the area of practicality and commerce, in parts of the world where traveling over water or on ice or travelling up and down stream or across lakes in boats and canoes were important. I think that these kind of dates were as important to these people a hundred and fifty-or-so years ago as us knowing the plane schedules today.

CURWOOD: So, you looked at a total of thirty-nine records from around the Northern Hemisphere. What did you find in your analysis?

MAGNUSON: Of those thirty-nine, thirty-eight of them were all in the direction of reduced ice cover or warming. It's a remarkably consistent result around the entire Northern Hemisphere. Then, when we looked at individual lakes many of them also had a significant trend even as an individual. We also noted that it really didn't matter quite where this lake or river was, if it was up in the high arctic, or if it was down in southern Wisconsin, where I am, or if it were in Finland, or if it were in the Swiss Alps. The general pattern held around the entire Northern Hemisphere.

CURWOOD: So, what did you find in terms of freeze dates and ice break up?

MAGNUSON: Yeah, I think it's common sense that if it freezes later and breaks up earlier, that it Îs gotten warmer. If you look at the hundred and fifty year period, freeze dates change by about nine days in the hundred and fifty days on average, and the break up days about ten days. Almost three weeks difference in the duration of ice cover. And that's an important part of this observation as well because we do not have exact records of what criteria the people used to call the lake open or frozen. So, if we found only a small change a day or two, we would have very little confidence in this. But this is a large change over one hundred and fifty years. Much larger than the measurement error ever would have been under many different criteria.

CURWOOD: How do your findings correlate with other studies and other efforts to document what could be happening to the Earth's temperature?

MAGNUSON: Almost all the really long-term indicators are not direct observations by humans. For example, there's an excellent paleoclimate indicator from looking at tree ring growth, but it's not direct. People have to relate the growth of trees to a presumed past climate. I think the interesting thing is about the lake ice and freeze data is that these lakes and rivers are in many cases in people's back yards. And the kind of things that they themselves note, like when the first robin appears in the spring, or when a certain flower first blooms. Human beings have had this tendency to write this down in their diaries, their kitchen logs, their backyard garden logs, so that they are very much within the human experience. They're not a model output. They're not on the other side of the world. At least for people that live in a place that has a winter.

CURWOOD: So your study uses work by ordinary people and you also have all of your sources available. I guess one can go to the internet and get your basic data here. This sounds to me different from the way that many scientists operate. What's that like?

MAGNUSON: Well, I think it's exciting and I think it's also responsible. You know, the old adage of science is, you know, that you collect your data and you cluster it to your chest and it's private and some of the more important phenomena that are occurring around the world are not little private things that we can see and clutch to our chest. They're things that are the collected experience of people around the globe, whether they happen to be scientists, in many cases, or whether they happen to be lay people that are making observations. In the scientific arena of long-term ecological research we have argued that it's more important if we want to understand the ecological systems around us and the changes around us that we have to work in a network basis of science around us, and we gain more from the results if in fact they are shared. The fact that this depends on early religious records and early records perhaps of fur traders and shippers in Toronto harbor and things of that nature, I guess I'm just enough of a person who's interested in history that I think it adds, doesn't add much to the science, but it certainly adds to the flavor and joy with working with these data.

CURWOOD: John Magnuson is professor of limnology at the University of Wisconsin in Madison. His study was just published in Science Magazine . Thank you, Dr. Magnuson.

MAGNUSON: You're welcome.



Living on Earth wants to hear from you!

P.O. Box 990007
Prudential Station
Boston, MA, USA 02199
Telephone: 1-617-287-4121
E-mail: comments@loe.org

Donate to Living on Earth!
Living on Earth is an independent media program and relies entirely on contributions from listeners and institutions supporting public service. Please donate now to preserve an independent environmental voice.

Living on Earth offers a weekly delivery of the show's rundown to your mailbox. Sign up for our newsletter today!

Sailors For The Sea: Be the change you want to sea.

Creating positive outcomes for future generations.

Innovating to make the world a better, more sustainable place to live. Listen to the race to 9 billion

The Grantham Foundation for the Protection of the Environment: Committed to protecting and improving the health of the global environment.

Energy Foundation: Serving the public interest by helping to build a strong, clean energy economy.

Contribute to Living on Earth and receive, as our gift to you, an archival print of one of Mark Seth Lender's extraordinary hummingbird photographs. Follow the link to see Mark's current collection of photographs.