150-year study confirms climate change
Copyright © 2000 Ananova Ltd
September 7, 2000
The longest ever study of climate change, which uses records going back 150 years, has revealed some of the strongest evidence yet that the world is getting warmer.
Scientists have used newspaper archives, shipping records and even religious documents to compare past dates when rivers and lakes annually froze over with the dates they freeze over now.
Libraries in Canada, Finland, Russia and Japan let a project team at the University of Wisconsin-Madison look at their records.
Data from Japan's Lake Suwa was taken from documents dating back to 1443 which were kept by a holy people who believed the ice layer there let two gods cross over and meet each other.
The team focussed on the northern hemisphere where they showed that lakes and rivers now freeze over almost nine days later than they used to and thaw 10 day earlier.
John Magnuson, one of the report's authors, said: "We think it is a very robust observation: It is clearly getting warmer in the northern hemisphere."
However he admitted that the results rely on how well the original observations were made - there is also no proof that greenhouse gases are responsible.