The Swiss Climate Change Scenarios (CH2011) provide a new assessment of how climate may change over the 21st century in Switzerland. The following quarterly updated diagrams show the observed and expected changes of mean temperature and mean precipitation in the northeastern part, in the western part and in the southern part of Switzerland.
What do the diagrams show
Past and future changes in seasonal temperature and precipitation over northeastern Switzerland. The changes are relative to the reference period 1980-2009. The thin colored bars (in red and blue) display the year-to-year differences with respect to the average of observations over the reference period, the heavy black lines are the corresponding smoothed 30-year averages. The grey shading indicates the range of year-to-year differences as projected by climate models for the A1B scenario (specifically, the 5-95 percentile range for each year across the available model set). The thick colored bars show best estimates of the future projections, and the associated uncertainty ranges, for selected 30-year time-periods (2020-2049, 2045-2074, 2070-2099) and for three greenhouse gas emission scenarios.
What do the projections say
Compared to the past 30 years, and for all Swiss regions considered, the best estimates for the non-intervention scenarios project increases of seasonal mean temperature of 3.2-4.8°C by the end of the century for the A2 scenario and 2.7-4.1°C for the A1B scenario. Summer mean precipitation is projected to decrease by 21-28% for the A2 scenario and 18-24% for the A1B scenario. For the stabilization scenario, Swiss climate would still change over the next decades, but is projected to stabilize at an annual mean warming of 1.2-1.8°C and a summer drying of 8-10% by the end of the century. Uncertainties due to climate model imperfections and natural variability typically amount to about 1°C in temperature and 15% in precipitation.
The assessment indicates more frequent, intense and longer-lasting summer warm spells and heat waves, while the number of cold winter days and nights is expected to decrease. Projections of the frequency and intensity of precipitation events are more uncertain, but substantial changes cannot be ruled out. In addition a shift from solid (snow) to liquid (rain) precipitation is expected, which would increase flood risk primarily in the lowlands.