Humans impact the climate in various ways, and not only through carbon dioxide emissions. In addition to other greenhouse gases that persist for a long time in the atmosphere, such as methane and nitrous oxide (laughing gas), numerous climate-influencing substances are emitted as a result of industrial and domestic activities, and transportation. Humans thus alter the composition of the atmosphere which, as well as having a detrimental effect on air quality, also affects the climate. One of these substances is ozone. At altitudes close to the ground, ozone is a relatively short-lived greenhouse gas. At higher altitudes, it serves as a shield against dangerous ultraviolet radiation. In Switzerland, measurements of the ozone column have been taken continually since 1926.
Moreover, human activities emit particulate matter and other minute particles known as aerosols. The many and varied effects of these particles on the climate are currently not fully understood, and therefore contribute substantially to the uncertainties in climate projections. The long-series particle measurements taken on the Jungfraujoch over many years help us to gain a better understanding of the effects of aerosols on the climate.
Ozone is an irritant gas that can have a detrimental effect on health. As a greenhouse gas, it is also contributing to global warming. Due to its reactivity, however, it is shorter-lived than other greenhouse gases. At the same time, ozone is indispensable for life on Earth, as the ozone layer at an altitude of 10-40 km actually protects us from harmful solar UV radiation.
In the last century, emissions of hydrochlorofluorocarbons (HCFCs) used, for example, as propellants in spray cans, led to a concerning degradation of the ozone layer. HCFCs were banned with the entry into force of the Montreal Protocol in 1989, which resulted in the stabilisation of the ozone layer at low ozone concentrations.
Measuring ozone levels is an important task of MeteoSwiss. Long-term data series are fundamental to being able to recognise changes over longer time periods. Ozone measurements began in Switzerland back in 1926 in Arosa, moving to Davos in 2021, where they are now continuing. The Swiss ozone data series is the longest in the world, and is therefore extremely valuable when it comes to analysing long-term changes in the ozone layer. Between 1930 and 1970, the average annual ozone reading in Arosa fluctuated around 330 DU (Dobson units); 100 DU is equivalent to 1 mm of pure ozone at the normal pressure of 1,013 hPa and 0°C. Between 1970 and 1990, the value reduced to around 310 DU due to the use of ozone-depleting substances. Since then, ozone levels have stabilised, within the bounds of normal annual fluctuations.