The influence aerosols have on climate has long been recognised, but our ability to observe and quantify them on global scales came of age with the use of new satellite-based instruments and data products in recent decades. As instrumentation technologies improve alongside our abilities to handle large quantities of data and process using the latest data science approaches, the data products available to atmospheric science will only improve in decades to come. This opinion article tries to anticipate what tools and insights the community can look forward to in the near future.

The Royal Society report on the Krakatoa eruption included some marvelous paintings of extraordinary and highly unusual green sunsets. This article provides a novel explanation employing a detailed physical model that emphasizes the necessity for large sizes and amounts of aerosols.

Equilibrium climate sensitivity (ECS), with a specific definition, has been used as a convenient measure, encapsulated in a single number, of the response of the climate to increases in long-lived greenhouse gases. The authors recall some of the history of how ECS has been estimated, by models and observations, including paleoclimate data and note recent progress in reducing uncertainty in the value of ECS. However they also note that there are important aspects of future potential climate change that are not captured by the ECS measure and therefore that there will be limited usefulness in too strong a focus on reducing uncertainty in ECS alone.

The paper provides an informative and up-to-date overview of the progress made in understanding the evolution of the stratospheric ozone layer since the introduction of the Montreal Protocol to a broad and interested readership. It discusses new evidence that, despite the success of the Montreal Protocol, the stratospheric ozone layer will not necessarily return in the long term to the state it was in before the start of the release of CFCs (before 1970). New challenges arise, due to man-made climate change or natural extreme events like volcanic eruptions that have been shown to impact the ozone layer. The authors' appeal is therefore to continue to closely monitor the state of the stratospheric ozone layer, which is important for life, in the future.