Climate change in Switzerland – represented visually

The graph compares the climate of the period 1864-1990 with current data since 1991. Between these two periods, the average Swiss temperature in the summer months has risen by a good 1.6 degrees since pre-industrial times. «This is an enormous increase in temperature» says Christoph Schär, head of the Climate and Water Cycle Research Group at ETH Zurich. Even the coldest summer season since 1991, the summer of 1996, was warmer than the average between 1864 and 1990.

The analysis is based on long-term temperature series of MeteoSwiss in the Swiss Mittelland (Basel, Bern, Geneva and Zurich). For the examination and visualization, Schär used the same procedure as in a previous study from the year 2004.

Higher and more extreme temperatures to be expected

The shift of the climate to warm temperatures is obvious. The warming between the two periods is much stronger than would be expected due to natural fluctuations. It exceeds the year-to-year fluctuations (standard deviation) by more than a factor of two. What used to be considered warm in the past, is normal today. Extremely warm years are occurring more frequently. According to Schär, in the past, an extreme summer half-year, as in 2003, was statistically expected about every 1000 years. Due to climate change, the incidence has increased, with currently two events in the last 15 years. As climate change progresses, such extreme events become the norm. «For Switzerland, that would mean that summers such as 2003 and 2018 would occur regularly, and the extremes of the future would then be much hotter», says Schär.