The springs in Paris and the winters in the Alps have been more sensitive to outside climate influences such as volcanic eruptions and solar variations — as well as greenhouse gases — for much longer than scientists thought, a new study reports.
A detailed analysis going back 500 years employs everything from diary entrees of medieval monks to the world's most sophisticated computer modeling to develop a new look to the pattern and pace of change across the European Continent.
Earlier work left scientists thinking that seasonal variations in Europe before the 20th Century were largely the result of internal climate system forces. The new work detects the regional impact of intercontinental "radiative forcing" such as greenhouse gas buildup and stratospheric impacts of volcanic eruptions.
In the journal Nature Geosciences, an international team led by Gabrielle Hegerl of the University of Edinburgh reports that "external influences…have had a discernible influence on European temperatures throughout the past five centuries."
In particular, they write, external forcing "largely attributable to greenhouse-gas forcing" is responsible for "a best guess of 75 percent of the observed winter warming since the late 17th Century."
"Our results highlight the important role of radiative forcing even on regional scales, and indicate that present large radiative forcing will cause highly significant changes in European temperatures in the future."
IMAGE: Mt. Etna, Italy CREDIT: Gaeti