1978Report: Shorter lake and river ice seasons confirm global warming
- Jun 3, 2005Note date. So why did it take so long for people to believe it?
Report: Shorter lake and river ice seasons confirm global warming
Historic river and lake ice records were used to confirm that winter
seasons are indeed becoming shorter
September 7, 2000
MADISON, Wisconsin (CNN) -- Records from riverboat captains, Shinto
monks and others dating to the 15th century confirm a dramatic
warming trend in the Earth's recent history, scientists said
Studying climate observations from dozens of sites in the Northern
Hemisphere, an international team of researchers concluded that
temperatures have risen steadily for at least 150 years.
They compiled data on lake and river ice cover from newspaper
articles, business journals and individual diaries, some as far back
Piecing together a historic portrait, the researchers said the
Northern Hemisphere has experienced increasingly shorter winter
seasons since 1840.
"The thing that makes this catchy is that this is a very simple way
of looking at what happened over the last 150 years," said John
Magnuson, lead author of the report, to be published Friday in the
"These are direct observations of people. Some were religious people,
some were fur traders," said Magnuson, a freshwater expert at the
University of Wisconsin in Madison.
Holy men in Japan who kept precise records at Lake Suwa, where
deities were believed to have traveled on surface ice.
Clerics in Central Europe who walked a Madonna statue over Lake
Constance when it first froze each season.
Fur traders and riverboat skippers in Canada who measured river
The records, which also come from the United States, Russia and
Finland, indicate that lakes and rivers now freeze an average of 8.7
days later and ice cover begins disintegrating 9.8 days earlier than
150 years ago.
The findings are consistent with an increase in air temperatures
during the time of 1.8 degrees C (almost 4 degrees F). Climate
records confirm a rise of at least 1 degree C (2 degrees F) over the
The trend corresponds with the rise of the Industrial Revolution. Yet
significant warming takes place well before its peak, suggesting
other causes besides greenhouse gas emissions from human activities.
"These increases are generally consistent with scenarios for
greenhouse gas-forced climate warming, but they may be related to
other drivers, such as changes in solar activity," wrote Magnuson and
his colleagues in Science.