Switzerland's climate is undergoing a process of change. The Swiss Climate Change Scenarios make it possible to evaluate the climatic evolution of the 21st century. They show expected changes in temperature and precipitation for various different assumptions on future global greenhouse gas emissions. Irrespective of the assumptions, temperatures are set to rise in all regions and seasons up until the end of this century.
Climate Change Scenarios
The current climate change scenarios have been developed by Swiss researchers for the "Swiss Climate Change Scenarios CH2011" initiative, led by the ETH Zurich and MeteoSwiss. The results, published in 2011, pull together the latest knowledge on climate change in Switzerland, as all relevant studies that were available at the time were fed into the model simulations. The changes that can be expected to occur in temperatures and precipitation were given for three Swiss regions: north eastern, western and southern Switzerland.
Evolution of spring temperatures in north-eastern Switzerland
The main focus of the Climate Change Scenarios are the changes in climatic conditions that can be expected in the future, based on the relevant average value during the reference period from 1980 to 2009. These changes are indicated for three different greenhouse gas emission scenarios and three time periods, with the coloured bars representing the uncertainty ranges. For the A2 scenario (significant rise in greenhouse gas emissions) for instance, an average increase in temperature of 2.2-4.3 °C can be expected for the period between 2070 and 2099 (lilac bars). The mean increase for this range, 3.2 °C, is represented by the small black line in the centre of the bar. In contrast, the average temperature in scenario RCP3PD (reduction in greenhouse gas emissions) is predicted to rise only by 0.7-1.7 °C in the same period (yellow bars).
The red and blue bars indicate the recorded annual temperature deviations from the reference value from the start of the measurement series up to the present day. The black line represents the average temperature over the course of 30 years. The grey shaded area represents the range of annual deviations as simulated by the climate model for emission scenario A1B. This example shows quite substantial deviations, both in the past as well as in the future. Positive as well as negative annual variations from the calculated 30-year average will continue to be a feature of our climate, as they have been in the past.
Towards the end of the 21st century, the climate of Switzerland will depend substantially on global greenhouse gas emissions. Emission scenarios are the plausible evolution paths of future greenhouse gas emissions. The way in which these emissions will develop depends on changes in social, economic and technological factors.
The Climate Change Scenarios CH2011 have been calculated for the following three global greenhouse gas emission scenarios. They do not give predictions as to the likelihood of any of these three emission scenarios.
- A2: sharp increase (continual rise in greenhouse gas emissions up until 2100)
- A1B: moderate increase (rise in greenhouse gas emissions until 2050, followed by a small decrease)
- RCP3PD: Reduction (fall in greenhouse gas emissions up until 2100 to the level in 1900)
The two scenarios A1B and A2 are based on the premise that no specific international efforts are made to reduce greenhouse gas emissions. In contrast, RCP3PD represents a scenario in which decisive and coordinated action is taken to reduce greenhouse gas emissions. In such a situation, global warming could be limited to a rise of only 2 °C over pre-industrial temperatures.
A view of the future
The climate of Switzerland over the course of the 21st century can be expected to be significantly different to our historic and present climate. Average temperatures will most probably rise by several degrees in all seasons. According to scenario A1B, by the end of the 21st century, all regions covered by the simulation are set to see a rise in temperature of between 2.7 and -4.1 °C above that of the 1980-2009 comparison period (black horizontal line on the chart), whilst the average summer precipitation is predicted to decrease by 18-24%. In scenario A2, an annual rise in temperature by 3.2-4.8 °C can be expected, with a 21-28 % decrease in precipitation in the summer months.
In the case of the stabilisation scenario of RCP3DP, the climate of Switzerland would experience less significant change over the coming decades. Up to the end of the 21st century, this scenario predicts an average annual rise in temperature by 1.2-1.8 °C, which is similar to the degree of warming which occurred between 1864 and 2010. An 8-10% reduction in summer precipitation can be expected.
Extreme climatic events
It can be assumed that there will be more frequent, more intense and longer-lasting periods of hot weather and heat waves in summer, whilst the number of cold winter days and nights looks set to decrease. Whilst projections of the frequency and intensity of precipitation events are hampered by greater levels of uncertainty, the possibility of substantial changes occurring cannot be ruled out. Moreover, we can expect a shift from snow to a greater amount rain, which would increase the risk of flooding, particularly in low-lying areas. At the moment, it is not possible to make sound predictions about changes in the occurrence of gales and highly complex weather events such as hail or tornadoes.
New projections for Swiss Climate Change Scenarios
New climate change scenarios have been generated for CH2018, based on the most recent simulations for climate across Europe, and drawing on the latest scientific knowledge. The new scenarios will be published in 2018 and replace the scenarios currently in use which were generated in 2011.