The stratospheric ozone layer, which protects us from the sun’s ultraviolet radiation, has recovered considerably from past depletion since the implementation of the 1987 Montreal Protocol in 1987 and subsequent amendments, which phased out the production and consumption of major ozone-depleting substances (ODSs). But unexpected observed and potential emissions of long- and short-lived ODSs could delay the return of stratospheric ozone levels to 1980 levels by years to decades.

Recognizing the threat that unconstrained ODSs pose to the continued restoration of the ozone layer, this study provides an overview of these substances and the steps needed to control them in alignment with the Montreal Protocol. 

Changes in large-scale dynamics over West Africa—the strength and position of zonal jets—are a key interim step by which local and remote forcing is communicated into changes in rainfall. This study identifies a key mode of jet variability and demonstrates how it is strongly coupled with rainfall. The approach provides a quantitative framework to assess jet–rainfall coupling and a useful tool to investigate the concerning spread in CMIP5 rainfall projections over the West African Sahel. It is shown that many CMIP5 simulations fail to capture this coupling, indicating a fundamental limitation in their ability to predict future rainfall conditions. The results demonstrate that West African rainfall in the coming CMIP6 ensemble should be interpreted with caution; key atmospheric processes that deliver rainfall must be validated before conducting detailed analysis on rainfall.