The 12th International Workshop on Long-Term Changes and Trends in the Atmosphere (TRENDS 2024) took place from 6 to 10 May 2024 in Ourense, Galicia, Spain. Greenhouse gases and other drivers cause long-term changes and trends in the middle and upper atmosphere that are often much stronger than tropospheric trends. Long-term change in the upper atmosphere is a major consideration with respect to the safety and regulation of future constellations of low-Earth-orbit satellites and the accumulation of orbital debris. The TRENDS 2024 workshop covered, among others, the following topics:

• long-term variations and trends in the middle atmosphere;
• long-term changes and trends in the ionosphere and thermosphere;
• dynamic, physical, chemical, solar, and radiative mechanisms of long-term variations and trends;
• changes in the middle and upper atmosphere and links to satellite navigation and debris.

The special issue includes papers based on the workshop presentations as well as other original research papers related to the topic.

Review process: all papers of this special issue underwent the regular interactive peer-review process of Annales Geophysicae handled by members of the editorial board as well as guest editors designated by the ANGEO editors-in-chief.