The IPCC is an intergovernmental scientific body which every six years or so summarises the current state of knowledge on climate change and assesses it from a scientific point of view. The IPCC Assessment Report consists of three parts, published at intervals of several months. The first publication on The Physical Science Basis of Climate Change was released on August 9, 2021.
721 independent experts from 90 countries are involved in the preparation of the IPCC reports, of which 234 are authors for the first publication, including five experts from Switzerland: Gian-Kasper Plattner from the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Samuel Jaccard from the University of Lausanne, and Sonia Seneviratne, Erich Fischer and Martin Wild from ETH Zurich.
The latest report on The Physical Science Basis of Climate Change essentially confirms the findings of previous IPCC reports. It is unequivocal that anthropogenic greenhouse gas emissions have warmed the climate system and are already affecting many climate and weather extremes. Moreover, greenhouse gas emissions continue to increase: the current CO2 concentration in the atmosphere has never been higher for at least two million years.
Climate change is already affecting every region across the globe. The average global surface temperature has increased by about 1.1 °C since the beginning of industrialization, with larger increases over land (1.6 °C) than over the ocean (0.9 °C). The mean temperature of the earth’s surface will continue to increase over the course of this century. Only deep reductions in CO2 and other greenhouse gas emissions will keep global warming below 2 °C compared to pre-industrial levels. If greenhouse gas emissions continue to rise, much greater warming can be expected. And the temperature increase will not be the same everywhere: in Switzerland, for example, temperatures are projected to increase stronger than the global average. Already observed changes in the climate system include an increase in the frequency and intensity of heatwaves and heavy precipitation, and more frequent droughts in some parts of the world. With increasing global warming, many changes in the climate system will become larger.
The IPCC reporting is closely linked to the national climate reporting. Based on the IPCC’s Fifth Assessment Report (2013), the CH2018 Climate Change Scenarios show where and how climate change affects Switzerland. CH2018 is a priority theme of NCCS and offers applied products for the assessment of adaptation and mitigation measures. Moreover, CH2018 translates the international state of knowledge into explicitly Swiss terms. In the coming years, these scenarios will be systematically updated in accordance with the findings of the IPCC’s Sixth Assessment Report.