The mesosphere is a layer of the atmosphere in an altitude range of approximately 50-80km. Whilst the mass of the mesosphere is relatively very small, it is an important component of the climate system. Changes in the circulation and composition of the lower atmosphere may, for example, become evident through changes in the mesosphere. The recently launched MATS satellite will make valuable observations of mesospheric characteristics and this paper reports early observations of the oxygen airglow in particular. The global-scale structures in the airglow give valuable information on large-scale mesospheric dynamics.

Mixed phase clouds are difficult to model drivers of the climate system. This study presents novel, long-term observations of mixed-phase clouds in the Arctic using advanced remote sensing techniques, offering unprecedented insights into cloud microphysics and aerosol-cloud interactions. Leveraging the unique MOSAiC expedition measurements, for the first time, it provides height-resolved statistical analysis of mixed-phase cloud properties, with a particular focus on the characteristics of liquid phase clouds. The combination of novel lidar and radar retrieval techniques enables precise monitoring of phase transitions, ice formation via immersion freezing, and the influence of aerosol activation. Given the key role of mixed-phase cloud in regulating the Arctic energy balance and their significance in climate models, this study provides essential empirical data to help improve cloud representation and parameterizations. Based on these observations, the authors recommend to implement time-dependent parameterization schemes to properly account for the evolution of long-lasting mixed-phase cloud layers in models.

Feng et al. use a Bayesian inverse method to interpret global-scale atmospheric CO2 data from the NASA Orbiting Carbon Observatory. They find that the global annual mean atmospheric CO2 growth rate in 2023 was one of the highest since records began in 1958. Their analysis suggest that ongoing environmental degradation of the Amazon is now playing a substantial role in increasing the global atmospheric CO2 growth rate. This findings emphasize how important continues measurements and regularly reporting of regional CO2 fluxes are to better understand changes in the CO2 cycle and be able deliver frequent actionable information for policy makers.

Open access publishing is a milestone in the history of academic dissemination, and ACP has been at the forefront of this movement. This paper is co-authored by four scientists who played key roles in initiating ACP, and establishing and maintaining it as a leading journal in atmospheric science. It articulates the vision of 'open science' that motivated the establishment of ACP and provides a comprehensive overview of the publication process of ACP and other EGU journals and how open science is enabled and promoted within that process. Detailed statistics and commentary reveal how open science practices in publication in EGU journals have developed and evolved over the last 25 years, and how this may continue to develop into the future.