The Amazon's role in the tropical and global carbon cycle is highly significant. Usually considered as the "lung of the planet", it is mandatory to monitor if this role is kept, or if the large rainforest even turns into a source of carbon dioxide. The study by Basso et al. finds that during the analysed years, from 2010 to 2018, the Amazon is a small net source of carbon to the atmosphere. They find that fire is the primary driver of the Amazonian source, while drought years intensify the carbon emissions. The study also examined the contributions of different regions to the Amazonian carbon budget and found that emissions in the eastern Amazon were greater than those in the western region, primarily due to fires. These findings are of high relevance - and concern - to the larger geosciences community and indicate how important it is to stop slash-and-burn in the large rainforests.

The role of chemical reactions within the atmospheric multiphase system, i.e. aerosol particles and cloud droplets surrounded by a gas phase, has been recognized for several decades to affect the atmospheric composition. In this article, significant advancements in measurement techniques during the past 20 years are briefly described that led to the identification of thousands of organic compounds and molecular-scale processes within the atmospheric multiphase system. Similarly, the complexity of multiphase chemistry models has been increasing to include in detail the underlying chemical processes and phase transfers between gas, aqueous, and organic phases. The authors propose how complementary techniques, such as machine learning and molecular dynamics, can be used to constrain the resulting model complexity. They also identify chemical parameters to be further constrained in lab and field studies. Overall, the article highlights the need and future directions of increasingly interdisciplinary efforts to characterize the atmospheric multiphase chemistry system and its impacts on climate-chemistry interactions, atmospheric oxidation capacity and human health.