Figure 1.

(a) Basic atmospheric cell circulation diagram of beryllium-7 being transported to the surface through stratosphere–troposphere exchange in the mid-latitudes (HFIZ) and polar latitudes (PFCZ). (b) Global warming caused by increasing CO₂ concentrations trigger the following changes in the global circulation: (1) tropopause height increase, (2) poleward extension of the Hadley cell, and (3) weakening of the atmospheric circulation in the mid-latitudes due to the decreasing temperature difference between the equator and the mid-latitudes. Poleward extension and weakened circulation extend the area where cosmogenic radionuclides are detected and increase the period of radionuclide detection during summer months. In the mid-latitudes, weaker circulation and increased vertical temperature differences due to the rising of the tropopause have two effects: stationary weather system and increased convective energy, resulting in more frequent and stronger convective storms. (a,b) are simplified with respect to the STE (Stratosphere-Troposphere exchange), as we do not represent tropopause folding (or duplication) in spring (Northern Hemisphere) and its role in the STE⁴³. See Figure S7 for flowchart representing step-by-step the process shown in (a,b). (c) The beryllium-7 concentration profile from Delaygue et al.²⁶ shows the relationship between tropopause height (blue line) and beryllium-7 concentrations, indicated by isolines²⁶.