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Climate change

The climate is changing, both globally and in Switzerland. Many climate indices now provide stark and unequivocal proof of this. Temperatures are increasing, sea levels are rising, ice masses are melting, the hydrological cycle is changing, permafrost is thawing, and ecosystems are becoming disrupted. The observed climatic changes are almost exclusively due to greenhouse gas emissions resulting from human activity. The impacts will intensify as emissions further increase. Switzerland faces increasing risk from more extreme weather with more hot days, heavier precipitation, drier summers, and winters with little snow. The direst consequences can be avoided, however, if prompt action is taken globally.

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Climate change encompasses a great many aspects of climate, and raises numerous questions. Four key messages are used to explain climate change:

Climate change is real, and we know what is occurring.

It is an undisputed fact that the Earth has been getting considerably warmer since industrialisation, and that the climate has changed significantly, both globally and in Switzerland. Globally, the past decade was already 1.1°C warmer than the pre-industrial mean, and in Switzerland the increase was even higher at 2.4°C. The global mean temperature is higher today than it has ever been in the last 2,000 years, and most probably even in the last 125,000 years. Numerous other changes in the climate system can also be observed.

Observed global climate change

The decade of 2011–2020 was already 1.1°C warmer globally than the pre-industrial mean temperature for the period of 1850–1900. Breaking that figure down further, the temperature increase over land of around 1.6°C was much greater than the 0.9°C increase over the oceans. Furthermore, the warming is particularly pronounced in the high latitudes of the northern hemisphere. The temperature rise has accelerated considerably since the 1960s. The years 2015 to 2021 were the warmest since measurements began, with 2020, 2019 and 2016 being the current record holders. There are many other changes occurring that are connected to warming. These range from extreme weather events, changes in the hydrological cycle and melting ice masses, to rising sea levels, changes in ocean currents and ocean acidification.

Observed climate change in Switzerland

The climate has undergone substantial change in Switzerland, as can be seen from the developments in temperature, water balance and weather extremes.

Temperature

In Switzerland, the temperature was already 2.4°C warmer in the last decade (2012–2021) than the pre-industrial mean for 1871–1900. Since the 1960s, each decade has been warmer than the last. The six warmest years have all occurred since 2010. 2018 and 2020 were the two warmest years on record, with a deviation of 3.0°C relative to pre-industrial periods. The four coldest years in Switzerland all occurred before 1900. Warming in Switzerland is now more than double that of the global mean. This difference is readily explained (see “Why is Switzerland warming more strongly than the global mean?” below).

There are two main effects that readily explain the difference between the mean global warming and the warming over Switzerland. One of these is that the warming which has been taking place over land – 1.6°C compared to pre-industrial times – is much greater than it is over the oceans. Water masses absorb much of the extra heat and conduct it into the deeper ocean levels. Conversely, land masses do not store heat as effectively, which leaves more energy available for warming the air. In addition, since there is an unlimited amount of water available, much of the extra heat over the oceans is used in evaporation, which is not the case on land. The second effect is that warming increases towards the pole in the northern hemisphere. The decline in snow and ice cover, which leads to greater absorption of solar radiation, is likely to play an important role here, along with increased heat transport towards the pole. Since Switzerland is part of the land mass in the central northern latitudes, it is also subject to the second effect.

Glacial, snow and vegetation developments

The strong warming has an impact on many other climate indices in Switzerland. For instance, the zero degree line has climbed substantially, which has resulted in Alpine glaciers losing over 60 percent of their volume since 1850. It is likely that they will no longer be part of the Alpine landscape by the end of this century. The vegetation period now lasts several weeks longer in the lowlands than it did even in the 1960s. Due to warming, precipitation now falls more often as rain than snow. The number of snow days has reduced considerably, especially in low-lying areas. Winter precipitation, on the other hand, has increased in the last 150 years or more. The sunshine duration reduced between 1950 and 1980, but has been on the increase again since 1980.

Other weather extremes

Global climate change is also resulting in more extreme weather in Switzerland. Heat waves have significantly increased in frequency and intensity, while cold periods are occurring much less frequently. The number of frost days and ice days is declining, and frozen lakes are almost a thing of the past when it comes to the larger lakes. Heavy precipitation events are much more frequent and intense today than they were at the start of the 20th century. The principle underlying this has been well understood for over 150 years: Warm air is able to absorb a greater amount of moisture, which leads to heavier rainfall. Climate models have been predicting these changes for several decades already.

The influence of climate change is clear as far as many weather parameters are concerned. However, changes in localised processes and extremes such as fog, Foehn and other local winds, storm cells, tornadoes or hail are more difficult to explain. There is currently insufficient high-quality data for these indices, both in terms of observations and in modern climate models, to be able to draw robust conclusions about their respective changes. However, the observation datasets are constantly improving, and climate models are improving all the time and becoming more high-resolution. We therefore expect to be in a better position in the future to answer these outstanding questions.

Humans are causing almost all of the current changes

Nowadays, the mechanisms of the climate system are well understood. The greenhouse effect plays a central role. Due to human-induced emissions of greenhouse gases, the natural greenhouse effect is intensified and additional heat is directed towards the Earth’s surface. Almost all of the total observed warming since industrialisation began is attributable to human activity.

The natural greenhouse effect

The Earth’s weather and climate are driven by incoming solar radiation. Around half the radiation is absorbed by the Earth’s surface, which then heats up. A further 20 percent is absorbed by the atmosphere, which also warms. Thirty percent is reflected back into space and is lost. It is essential for life on Earth that the heat radiated by the Earth’s surface does not immediately leave the atmosphere. Greenhouse gases such as water vapour, carbon dioxide, methane and nitrous oxide absorb the heat radiation and, in turn, radiate them back again. Thanks to this greenhouse effect (german) , the global mean temperature in the lower atmosphere increases by around 32°C, from -18 to +14°C. This is what makes the Earth inhabitable. We have known about these relationships for over 150 years and verified them through experiments and observations.

Humans are intensifying the greenhouse effect

Since the beginning of industrialisation in the 19th century, there have been substantial increases in atmospheric greenhouse gases as a result of human activity. The main culprits are the combustion of coal, oil and natural gas, intensive agriculture, the loss of large areas of forest and moorland, and changes in land use. For instance, in the last 150 years or so, the carbon dioxide content of the atmosphere has increased by almost 50 percent, from around 280 ppm (CO2 particles per million air molecules) to 415 ppm (as of December 2021). This is the highest CO2 content our atmosphere has seen in the last two million years.

Because human activity is intensifying the greenhouse effect, there is additional heat in the overall climate system. The majority of this heat is accumulating in the oceans and warming them. Only around one to two percent remains in and warms the atmosphere. Almost all of the total observed warming since industrialisation began is attributable to human activity. Solar and volcanic activity and internal fluctuations in the climate system play only a very minor role. These findings are partly based on simulations using climate models that have been adept at capturing the interactions between basic physical laws for several decades.

The climate has changed in many ways over the course of the Earth’s multimillion-year history. The main reasons for these changes are generally well understood by scientists. Throughout the Earth’s history, warm periods with high concentrations of greenhouse gases, and cold periods (ice ages) with low concentrations were caused primarily by changes in the Earth’s orbit around the sun or in the Earth’s axis of rotation, as well as by the shifting of continents. However, the changes caused by the above factors occurred much more slowly compared to the warming we are seeing today, and can therefore be ruled out as a cause of the rapid rate of warming over the last 150 years or so. Neither do changes in solar and volcanic activity explain today’s climate change.

Climate change predominantly poses risks, and Switzerland is strongly affected

Continued climate change will have more negative than positive consequences. Switzerland is threatened by more extreme weather with drier summers, heavier precipitation, greater numbers of hot days, and winters with little snow. Mountain regions are likely to be subject to additional risks such as rockfalls and debris flows, as well as loss of biodiversity.

Alongside global warming, climate change is having numerous other direct, global consequences, including changes in the hydrological cycle, more extreme weather, melting of ice masses, rising sea levels, changing ocean currents, and ocean acidification.

Swiss Climate Change Scenarios

MeteoSwiss works together with its research partners to produce national Climate Change Scenarios for Switzerland. These show the future climate evolution for our country, based on the current state of scientific knowledge. If greenhouse gas emissions continue to rise, this could result in temperatures being 2 to 3°C higher than they are today (1981–2010) by the middle of this century. Precipitation will also change without strong climate change mitigation efforts: In summer, we may see up to 25 percent less precipitation, while up to 20 percent increases are possible in the winter. The current Climate Change Scenarios (CH2018) show four main changes that at least partially reflect the observations made over the last 150 years: drier summers, heavier precipitation, more hot days, and winters with little snow.

Impacts of climate change in Switzerland

Climate change in Switzerland has major implications for the environment, society and the economy. The risks clearly outweigh the opportunities and affect almost every facet of life. Several risks, particularly heat, natural hazards and disease, affect the health of the population. Mountain regions are especially vulnerable, with the threat of additional risks from deteriorating slope stability, and increased landslides, debris flows and rockfalls. Biodiversity will also be affected by climate change, particularly at higher altitudes. Climate change does present certain opportunities for energy production in winter, reductions in snow damage, income from summer tourism, and also possibly from agriculture.

Worse consequences can be prevented by taking decisive action on a global scale

The impacts of climate change are already being experienced, calling for adaptation measures. The extent to which the Earth will warm and how severe the consequences will be depends primarily on the amount of greenhouse gases emitted globally. Rapid and concerted efforts to reduce these emissions can prevent the gravest consequences from becoming a reality.

Political consensus on restricting climate warming

At the Paris climate summit in 2015, the global community adopted an agreement committing all nations to reducing greenhouse gases. The goal of the Agreement is to limit global warming to well below 2°C, and preferably to 1.5°C, compared to pre-industrial levels. Switzerland has also ratified the Agreement, and is committed to a rapid and significant reduction in its greenhouse gas emissions. The aim is to reduce emissions by 50 percent compared to 1990 levels by 2030. This will require taking action in almost every sector, including transport, construction, industry, agriculture, services and waste management. A net zero target has been set for 2050, after which time no more greenhouse gases should enter the atmosphere than are removed via natural sinks and technological methods.

Climate change mitigation works, but adaptation measures will also be necessary

The Climate Change Scenarios CH2018 indicate that strong climate change mitigation efforts could effectively limit the consequences of climate change. The expected changes to Switzerland’s climate could be cut by around half by the middle of the 21st century, and by two thirds by the end of the century. However, adapting to climate change will also be necessary. Switzerland has been pursuing a strategy accordingly since 2012. The current action plan for 2020–2025 consists of 75 federal-level measures that apply to all sectors concerned.

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