Historical climate records help gauge future natural hazards

The online database “Euro-Climhist” supports research and public participation in the analysis of natural hazards. An expanded version of this unique database has just been launched. It has more than 155,000 historical records on weather, climate and natural hazards in Switzerland dating back as far as the year 1500.

How often does Switzerland experience flooding like that of August 2005, when floods and landslides caused approximately CHF 3 billion in damage? Information on the frequency and scope of natural disasters is of great practical value – not only for planning protective measures against rushing mountain streams, but also to assess the safety of nuclear power plants.

To estimate the frequency of extreme natural disasters, you need to look back in time. It’s only when you compare several centuries’ worth of data that you can gauge the probability of major flooding, mudslides or droughts – and whether their incidence has changed over time. Alongside risk specialists and climate researchers, insurance companies, for example, also rely on such information. They calculate their premiums based on so-called “once-in-a-hundred-years” events, so they’re interested in the longest possible comparison periods.

But until now, even specialists could hardly access data pre-dating the mid-19th century. It was only with the advent of measuring instruments that weather data were recorded systematically. Therefore, historical documents are of major value for research and practice. Dating back to the Middle Ages, they come from sources such as chronicles, personal weather diaries, and the accounting systems of early public buildings such as hospitals.

With the relaunch of the “Euro-Climhist” database – which was built up through many years of work by the Oeschger Centre’s group for climate and environmental history – such historical data are now publicly available on a large scale and for free. At www.euroclimhist.unibe.ch, both specialists and lay people can access a broad range of Swiss data – with the first new module covering the period from 1500 to the official launch of instrument-aided measurement in 1864. Another module covering European weather and climate data from the Middle Ages (1000-1500) is currently in preparation.

“Euro-Climhist” is co-financed by the Federal Office of Meteorology and Climatology MeteoSwiss as part of Switzerland’s Global Climate Observing System (GCOS).