The future climate becomes concrete

13 November 2018

The OCCR played a key role in developing the Climate Scenarios CH2018. Based on these model calculations, climate researchers in Bern are developing new tools to better identify flood risks. To this end, they are now launching the “Research Initiative Flood Risk”.
 

Switzerland is becoming drier, hotter, and less snowy, and in future will have to contend with heavier precipitation; these are the main messages of the Climate Scenarios CH2018 commissioned by the Swiss government. Developed jointly by researchers from MeteoSwiss, ETH Zurich and the OCCR, the scenarios make a distinction between developments with and without climate protection. “There’s a long tradition of cooperation within the Swiss climate community,” explains Christoph Raible. The climate dynamics professor coordinated the Bernese contributions to CH2018. In order to predict the future state of the climate, different knowledge and specialisations within climate research are required. “Within the framework of CH2018, the Oeschger Centre has mainly dealt with past climate developments in Switzerland to put future changes into a longer context.”

After the 2007 and 2011 editions, the CH2018 climate scenarios are now the third view of Switzerland’s future climate. The current climate scenarios, which combine simulations of state-of-the-art climate models with observations of previous trends, allow the most accurate view of our country’s climate future to date. Thus they represent an important basis for the Federal Council’s strategy for adapting to climate change in Switzerland.

Extreme precipitation will get heavier

New scenarios for the future development of Switzerland’s climate are becoming increasingly necessary because knowledge about the extent of global change and its regional impacts is becoming ever broader. “Compared with the last report, we now have observation data for an additional seven years,” explains Christoph Raible. This makes it possible for trends in the measurement series to be recorded more accurately, plus, “in recent years, new global as well as regional climate simulations have emerged. Their spatial resolution is four times higher than in the 2011 report”.
The current climate scenarios confirm the trends known so far, according to which we have to prepare for more very hot days, drier summers, and winters with less snow, among other things. However, now the scenarios also provide concrete figures for developments known only qualitatively, such as extreme precipitation. So rainfall on the rainiest day of 2060 will amount to 10 percent more than today. A once-in-a-century summer storm will even bring about 20 percent more rainfall.

Flood risks are a concern for everyone

Almost half of all natural damage to buildings in Switzerland is caused by flooding. Four out of five Swiss municipalities have been victims of floods in the past 40 years. Around 300,000 buildings – or 13 percent of all buildings – are located in flood-prone areas. Against this background, the future management of the consequences of floods is one of the topics being researched at the Mobiliar Lab for Natural Risks at the University of Bern. The research institute affiliated with the OCCR has just launched a three-year “Research Initiative Flood Risk – from Understanding to Action” (hochwasserrisiko.ch). “We want to lay the foundation for better risk management,” says Rolf Weingartner, hydrology professor at the University of Bern, to outline the aim of the various research projects. The new climate scenarios play an important role for Switzerland.

“Up to now, research has primarily been aimed at a better understanding of the origin of floods,” stresses the co-director of the Mobiliar Lab. “Now these findings will be supplemented with knowledge of what damage could be caused by flooding.” The research initiative consists of four parts. They deal with the probability of floods, the vulnerability of buildings, the effects of floods on roads and rail networks, and the prediction of flood damage.

The results of the Mobiliar Lab should, among other things, lead to better decision-making in terms of flood risk management. The various tools will help the authorities – as well as the local populations – in municipalities and cantons to identify flood risks. Last but not least, the research initiative also aims to raise general public awareness of flood risks. Every seventh person in Switzerland lives in a building at risk, and the replacement value of all buildings in danger areas is around CHF 500 billion. “Flood risks,” summarises Rolf Weingartner, “concern us all.”