Meteorologist and climate scientist Guy Callendar first discovered the link between the rise in CO2 in the atmosphere and global warming in 1938. However, the published document received little attention at the time.
Compared to the pre-industrial average of 1850–1900, global temperature has already risen by more than 1.1 °C by 2020. How disproportionately the temperature has increased since the beginning of the new century can also be seen in the graph. In particular, temperatures from 2011 to 2020 exceed those of the most recent warm period several centuries ago (about 6500 years ago). In Switzerland, the increase is even more than twice as high at 2.5 °C.