Monks' diaries help experts make climate forecast

Ancient weather records, including details gleaned from monks' diaries, are helping scientists work out how and why climates have changed over the past 500 years.

Researchers found the historic data, from the likes of weather station archives and harvest records, closely matched modern computer simulations of European climate patterns over the last five centuries.

They say their findings will lead to more accurate predictions of climate change and suggest greenhouse gas emissions will shape the climate in future in a "significant and visible" way.

The study was carried out by the University of Edinburgh in collaboration with the Justus-Liebig University of Giessen in Germany, and the Universities of Bern and Madrid.

Professor Gabi Hegerl, of Edinburgh's School of GeoSciences, said the archives revealed a considerable amount of interesting information, particularly relating to the last 300 years.

She said: "Five hundred years ago, the records were quite sparse, but there is a lot of data going back to the 19th century and quite a lot of data from the 17th and 18th centuries.

"Around 1675 it gets quite sparse. Before that, we're working from monks' diaries and harvest records and all kinds of indirect evidence about whether they experienced warm or cold summers and winters.

"The records are much more accurate when you go past 1675 and the good thing is a lot of interesting things happened after that time.

"Around 1700 and the early 19th century, for example, there were very cold winters. That's been captured quite well in the records."

The computer simulations took account of influences on the weather, such as volcanic activity, variations in the sun's temperature and - more recently - an increase in greenhouse gases.

Scientists say the results, backed up by the historic records, suggest that present-day greenhouse gas emissions will play an important role in shaping future European climate.

Prof Hegerl, who led the study, said current human behaviour is "definitely going to shape the climate in a significant and visible way".

She said: "Our work shows that external influences on the weather are important, and that even small changes in factors outside the climate system have a significant effect.

"The climate models seem to be working quite well for the past, so we should expect that - at least when it comes to temperature - they will do well for the future. It indicates that the predictions might be on target."

Prof Hegerl said she next intends to look in detail at the causes of the cold winters in the late 16th and early 19th centuries, and at changes in rainfall, as well as looking at the climates of the tropics and southern hemisphere over the past 500 years.

The study, supported by the Natural Environment Research Council, the US National Science Foundation and the European Union, was published in the journal Nature Geoscience.