International environmental agreement to celebrate birthday

March 22 marks the 40th anniversary of the Vienna Convention for the protection of the ozone layer. This international agreement laid the foundation for the global protection of the stratospheric ozone layer in 1985 – and formed the basis for the Montreal Protocol, which was later adopted and regulates the gradual phase-out of ozone-depleting substances such as chlorofluorocarbons (CFCs). Thanks to continuous scientific monitoring and political measures, the ozone layer has since recovered.

Empa researchers have been measuring ozone-depleting substances and greenhouse gases on the Jungfraujoch for 25 years. However, a global measurement program had already been established back in 1978, even before the hole in the ozone layer was discovered. Today, the high alpine research station on the Jungfraujoch is part of the international Advanced Global Atmospheric Gases Experiment (AGAGE) network, which comprises more than ten measuring stations the world over. “In total, we detect and analyze around 50 different trace gases here – from ozone-depleting substances to pure greenhouse gases. Continuous measurements are crucial for tracking the development of these substances in the atmosphere and estimating the quantities released by human activities,” says Empa atmospheric scientist Stefan Reimann.

On the Jungfraujoch, Empa researchers are interested in two types of air masses: on the one hand, clean air that is hardly influenced by European emissions, for example from the Atlantic. It serves as a reference for the background pollution in the northern hemisphere and helps to detect global trends in halogenated hydrocarbons. On the other hand, the high alpine measuring station also captures polluted air from various "close-by" regions, which allows the identification of individual areas or countries emitting the pollutants in question. According to Empa researcher Martin Vollmer, a typical example of this is the strong southerly winds known in Switzerland as "Föhn". “In such weather conditions, air from the heavily industrialized and densely populated Po valley in northern Italy reaches the Jungfraujoch. These air masses often contain many pollutants, which we analyze in detail to better understand their sources and distribution.”

In addition to monitoring well-known substances, the Jungfraujoch station plays a key role in the discovery of new ozone-depleting and other halogenated compounds affecting the climate. For example, halogenated anesthetics and many new hydrofluorocarbons (HFCs), which are now regulated in an extension to the Montreal Protocol, were measured for the first time at the high alpine measuring station. Empa researchers were also able to detect new substitutes for the banned CFCs, known as hydrofluoroolefins (HFOs). They also succeeded in detecting the world's first substances that are released into the atmosphere exclusively as by-products of industrial manufacturing processes. “As some of these substances also affect the ozone layer, our measurements help to uncover possible gaps in the Montreal Protocol and ensure its effectiveness in the long term,” explains Reimann.

Continuous monitoring is essential for the discovery of new substances. As soon as Empa researchers classify a new compound as relevant, it is included in the AGAGE network and other measurement programs. “With new substances, pollution is often low at first. Only when they are regularly released into the atmosphere can larger emissions and their sources be identified,” says Alina Begley, a postdoctoral researcher at Empa who tracks down new ozone-depleting substances. “For example, when the hydrofluoroolefin HFO-1234yf was first recorded here in 2011, the concentration was still very low. Today, it is the most widely used refrigerant component in AC systems in cars worldwide.”

The high alpine research station on Jungfraujoch is located at 3,580 meters above sea level on a mountain saddle in the central Swiss Alps – and is the highest of its kind. Thanks to its unique location, year-round accessibility and excellent infrastructure, it offers ideal conditions for long-term measurements of trace gases in the free troposphere. Together with the Federal Office for the Environment (FOEN), Empa continuously records air pollutants, greenhouse gases and ozone-depleting substances in the National Air Quality Monitoring Network (NABEL) and in the global AGAGE network. This comprehensive analytical infrastructure also allows limit values to be checked and sources of pollutants in Europe to be identified.