Consequences of global warming in Switzerland

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The consequences of global warming in Switzerland are among the regional effects of global warming on society, health, nature and in technical matters, which become noticeable in the rise in average temperatures. The global warming is probably the main cause of climate change in the country in the last 50 to 100 years. At the UN climate summit in 2019 , the Swiss Federal President Ueli Maurer pointed out that Switzerland, as a country with high mountains, is particularly affected by global warming.

The effects of climate change can be positive or negative. For most regions, however, the negative effects clearly outweigh the positive effects - such as the reduced heating requirement in winter.

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Observed changes (National Center for Climate Services NCCS 2018)
Temperature observations Switzerland 1981-2010 summer
Mean annual temperatures in Switzerland from 1750 to August 2013 as a moving 12-month mean. The 10-year mean values ​​are shown in red.

Temperatures in Switzerland have been recorded reliably and regularly since 1864. It turns out that the measured temperature changes are more than twice as high as the global average. The air temperature near the ground has increased by around 2 degrees Celsius in the last 150 years, particularly rapidly since the 1980s. Due to its size, this increase cannot be explained solely by natural fluctuations. It affects all regions of Switzerland and is clear despite annual temperature fluctuations: nine of the ten warmest years since temperature measurements began fall in the 21st century.

Similar findings are also made in neighboring countries (e.g. in Germany or France). In a global comparison, however, Switzerland is affected more than average by the rise in temperature: while the global average warming was 0.9 degrees Celsius compared to the reference year 1864, the air temperature near the ground in Switzerland has increased by around 2 degrees Celsius in the last 150 years . The increase has been the fastest since the 1980s.

The observed increase in temperature also affects other areas of the environment. Therefore, both the documented changes in the water cycle (e.g. increase in the average temperature in Swiss watercourses) and the glacier melt have at least one anthropogenic component.

The warming to date is reflected in various ways in Switzerland. Heavy precipitation is more intense and more frequent than at the beginning of the 20th century. Heat waves became more frequent and longer. In contrast, days with snowfall have decreased. Since 1970 by around 50 percent at an altitude of 800 m and around 20 percent at 2000 m. As a result, around 60 percent of the glacier volume has melted since 1850. Rockslides, such as the Bondo landslide in 2017, have been linked to the decline in permafrost . As a result of rock falls, z. B. the Axenstrasse are already blocked several times. The vegetation is also changing. The growing season has lengthened by two to four weeks since 1960. Various plants, for example the summer linden , bloom earlier and earlier.

So far, no clear changes have been identified in Switzerland in terms of precipitation amounts in summer, dry periods, high fog and wind speeds.

Without strong climate protection measures, climate change in Switzerland could take on dramatic proportions this century. By the end of the century, the temperature increase could triple and dry spells could be five times more frequent.

Climate scenarios for the year 2060 and beyond without climate protection

In 2018, the Swiss Confederation created a series of climate scenarios for climate development in Switzerland with and without climate protection. Simulations (climate scenarios CH2018) with a total of 21 computer models were carried out by various European research institutions. This comprehensive analysis makes it possible to better estimate the given uncertainties of such climate scenarios.

The period from 1981 to 2010 counts as the current norm of the Swiss climate and thus as the starting point for the simulations made here. Information about future changes is therefore always compared with these 30 years, which counts as today's climate. With the knowledge that the climate has already changed.

In the climate scenarios, mean values ​​from the climatic conditions of three decades are compared, which are grouped as follows:

  • The year 2035 means “near future”: 2020–2049
  • Year 2060 means “middle of the century”: 2045–2074
  • Year 2085 means "end of the century": 2070–2099

Dry summers

Drought indicator SPI3 (a standardized precipitation index) for various future periods under the "No climate protection" scenario (RCP8.3 of the IPCC) in north-eastern Switzerland.
Expected change in the longest summer dry period until 2060 without climate protection measures.

While mean temperatures can be simulated quite reliably with the help of climate models, predictions for precipitation are more difficult. This is related to the great variety of mechanisms that determine the water balance in the atmosphere. Despite this uncertainty, the climate simulations show a clear long-term trend in the decrease in precipitation. In the summer months, a noticeable decrease in precipitation can be expected in the future. It is true that on an average rainy day in summer there will be a similar amount of precipitation as before, but there are more rain-free days. In addition, not only does rain fall less often, more moisture also evaporates due to the higher temperatures. So the soils become drier, even if the precipitation does not decrease. In general, areas in the west and south are more affected by the possible fall in precipitation than those in the east. The heat wave in Europe in 2003 and the drought and heat in Europe in 2018 give an impression of the possible effects of hot and dry summers. In addition to agriculture , energy production and water management are affected by the increasing summer drought . For example, the fields in the Furttal are expected to be irrigated with water from the Limmat from 2022 .

Heavy rainfall

Strongest one-day precipitation of the year for the city of Zurich.

Compared to 2018, the amount of precipitation from individual heavy precipitation in Switzerland has increased by 12 percent since 1901. Despite decreasing amounts of precipitation, individual events are becoming stronger. Since air can absorb around 6 to 7 percent more water per degree Celsius of warming, the intensification of precipitation can be explained physically. In the future, heavy precipitation will probably occur noticeably more frequently and intensely than we are experiencing today. This affects all seasons, but especially winter. With unchecked climate change, it is to be expected that the strongest one-day precipitation in winter will be around 10 percent more severe by the middle of this century. The expected increase is 20 percent by the end of the century.

Even very rare precipitation events, such as those that occur about once every 100 years, increase. The change is 10 to 20 percent in the middle of the century and around 20 percent towards the end of the century. Most models predict an intensification of the severe events in autumn for the Alps.

Trends in one-day precipitation in Switzerland.

The greater intensity of heavy precipitation can have significant cost implications. Heavy rainfall can cause landslides and floods, for example, and cause great damage, as was the case with the Alpine floods in 2005 . Therefore, infrastructures such as flood protection structures and sewer systems must be adequately dimensioned. The potential for damage from extreme precipitation will not be greater in the future solely because of the higher amounts of precipitation. The rise in the snow line increases the proportion of liquid precipitation, especially in winter, and thus accelerates runoff.

Extremes get stronger

The increasing summer drought known from the Mediterranean region will also increasingly affect Switzerland. At the same time, an increase in heavy and extreme precipitation from northern Europe will affect Switzerland.

An accumulation of extreme precipitation at a certain location is not easy to determine statistically. The highest measured one-day precipitation each year varies considerably and the highest peaks in precipitation are rare. In the Swiss-wide mean, however, the trend towards heavier precipitation events is clearly evident. 158 of 173 measuring stations show an increase and 53 of them show a significant increase. On the other hand, nowhere was a significant decrease in precipitation intensity recorded.

More hot days

Not only will the average temperatures rise, the hot days (≥ 30 ° C maximum daily temperature ) will also become more extreme and frequent. Four hot days are normal for a summer. With the heat waves in Europe in 2019 , Switzerland recorded 21 hot days. The regions that will be particularly hard hit are the populous cities in the lower elevations.

Hot days in Switzerland for the future period 2060 without climate protection measures.

The summers will be particularly affected by the rising temperatures. In 2060 it can get up to 4.5 degrees Celsius warmer in an average year, and even 5.5 degrees Celsius in an average summer. One reason for this increase in temperature is the lower soil moisture, which means that less water evaporates and the soil is less cooled.

The region around the Mediterranean Sea, and therefore also Switzerland, is the region around the world most affected by the extreme heat.

The number of very hot days doubles with every additional degree Celsius. Very hot days are defined as the 1 percent hottest summer days from 1981 to 2010. The number of very hot days is currently one, but this number could increase to 18 by the end of this century. Most additional hot days are expected in Valais, Geneva and southern Switzerland. Ticino in particular has to reckon with around 30 days of heat stress every summer until the middle of the century , as the Ticino climate is more strongly influenced by the Mediterranean Sea.

The combination of heat and high humidity is a major challenge for humans and many animal species, which means that cases of heat stress are becoming more common. Cities and their agglomerations will be particularly affected by the heat, as it heats up more during the day and cools down less at night (see urban climate ).

Winter with little snow

Zero degree winter Switzerland.png

The winters in Switzerland will be significantly warmer around 2060 than they are today. The additional precipitation will come down mainly as rain because of the higher temperatures , especially at lower altitudes: it snows less and less there. In fact, the number of snow days in areas below 800 meters has halved since 1970. The snowy areas of Switzerland are also declining sharply overall. Due to global warming , Switzerland has lost a lot of ice deposits. The Alpine glaciers have lost around 60 percent of their volume since 1850.

Zero degree limit.png
Number of new snow days.png

The mean temperatures in winter will continue to rise. Due to this trend, the zero degree limit could rise from 850 meters today to almost 1500 meters above sea level by around 2060 . The previous, significant increase in the zero degree limit will continue even more in the future. Therefore, the area in which it can snow is shrinking noticeably. Two opposing effects affect snowfall in winter . On the one hand, higher temperatures mean that more precipitation falls than rain, but on the other hand, more precipitation falls overall. Overall, a significant decline in both snowfall and snow cover can be expected for Switzerland, especially at low altitudes and in spring. In the future, snow-covered landscapes will largely disappear at low altitudes.

Climate scenarios Switzerland. Snow cover.png

The snow cover will therefore continue to decrease: below 1000 meters to around half by 2060, and probably by over 80 percent by the end of the century. Higher altitudes are also affected. In spring in particular, the vast majority of alpine towns have to expect less snow. In the Central Alps, around 30 days of new snow per year are expected until around 2060 than today. In addition, snow will fall significantly less often in the higher elevations, which have previously been rich in snow. This reduction in the amount of snow also affects the glaciers in the Alps . Their snow accumulation is reduced and their melting accelerates.

The predicted reductions in snowfall and snow cover have a major impact on winter tourism and the hydropower and transport sectors .

Climate scenarios for Switzerland with effective climate protection

The 2015 Paris Climate Protection Agreement aims to reduce the increase in the average temperature on the earth's surface to well below 2 degrees Celsius compared to the pre-industrial level. This global 2-degree target would probably still be achievable if the signatory states to the agreement were to immediately reduce the continuing increase in greenhouse gas emissions and stop them practically completely in the second half of this century.

Reducing global greenhouse gas emissions could effectively curb global warming. In Switzerland, around half of the possible climate changes could be avoided by the middle of the 21st century, and even two thirds by the end of the century.

Warming is therefore likely to increase in Switzerland even if climate protection measures are implemented, but significantly less than without these measures. For example, with climate protection in summer it would be an average of 1.5 degrees Celsius warmer than before, but without effective climate protection measures it would be 2.5 to 4.5 degrees Celsius.

Specifically, according to the NCCS report “ Climate scenarios for Switzerland” (2018), the following developments are expected in Switzerland by the middle of this century despite climate protection :

  • Summer temperature: +0.9 to +2.5 degrees Celsius;
  • Rainfall in summer: −16 to +7 percent;
  • Number of very hot days: 0 to +8 days;
  • Winter temperature: +0.5 to +2.5 degrees Celsius;
  • 100-year one-day precipitation event in winter: +5 percent.

The expected changes by the end of the century would remain in the range mentioned above: the climate protection measures can thus stabilize the climate in the long term.

Consequences for the infrastructure

The consequences of global warming can also be felt in the area of ​​infrastructure. This results in repair and adaptation costs and the reliability of the infrastructures decreases.

transport

With regard to the transport infrastructure, extreme weather events cause the greatest damage to roads and rails. Extreme temperatures require more heat-resistant road surfaces and lead to speed reductions on the railways. In addition, additional costs of CHF 13.4 million per year (2018 price level) from floods and CHF 4.11 million from storms are expected for 2060.

energy

Higher temperatures, more irregular rainfall and drier summers have a negative impact on the performance of hydropower and nuclear power plants. The demand for energy changes as the heating requirement decreases and the cooling requirement increases due to higher temperatures. The costs of these developments are difficult to estimate. Damage to the energy infrastructure caused by extreme events is easier to quantify. These are estimated at CHF 10-50 million annually for 2050. For hydropower plants, less available water, higher temperatures and more irregular rainfall could result in annual costs of CHF 50-100 million. In the case of nuclear power plants, the annual follow-up costs due to reduced performance are estimated at CHF 100-250 million.

Further infrastructure

Global warming is affecting water supplies, industrial infrastructures and tourism. The greatest damage is expected for the industrial infrastructure. These are caused by extreme events and could amount to more than CHF 250 million annually in 2050. A decline in winter tourism could result in annual costs of CHF 100-250 million for tourism.

Climate policy

Global warming can only be effectively limited through a globally coordinated climate policy . The question of what role Swiss climate policy should play has come more and more into the public eye in recent years and dominated the election campaign in the Swiss parliamentary elections in 2019 , where the Greens were able to record a historic election victory.

See also

Web links

Individual evidence

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  2. ^ Speeches by Federal President Maurer in New York. In: admin.ch. September 24, 2019, accessed on September 25, 2019 : “Les glaciers qui disparaissent, la neige qui ne tombe plus, les éboulements fréquents en montagne, c'est une part de notre identité, de notre tradition, qui s'éteint. Le changement climatique menace donc notre mode de vie. Nous devons le prendre au sérieux. "
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