This paper provides key insight into the methodology of Working Group III of the IPCC Sixth Assessment Report on climate mitigation. The paper will be essential reading for anyone wishing to understand the assessment of climate outcomes of mitigation pathways in the context of the Paris Agreement.

The rapid increase in global warming in 2023 has sparked fears that Earth has entered a new warm state. Possible explanations for a warming spike have included transient changes in radiative forcing or deficiencies in climate models. This study shows that the primary cause is a mode of natural climate variability – the El Niño/Southern Oscillation (ENSO). The authors show that, while the magnitude of global warming caused by ENSO was particularly large in 2023, it is not unprecedented in the historical record. The implication is that global warming is continuing at a steady average rate without dramatic acceleration.

In 2020, a new international law was imposed that placed strong restrictions on sulfur emissions from the international shipping industry. In addition to reducing air pollution, an anticipated side effect was reduction of the climate cooling effect that is often associated with "ship-tracks". Aerosol pollutant emissions from ships, when they rise into overlying clouds, lead to higher cloud droplet number concentrations, smaller cloud droplet sizes, and clouds that are more reflective to incoming sunlight, easily seen in satellite imagery as long bright lines downwind of ships. Past studies into whether the new law has led to darker clouds have been equivocal. For this study, the authors used sophisticated statistical techniques to compare cloud droplet size and reflectivity before and after the law was implemented focusing on a shipping corridor in the southeast Atlantic. They found strong evidence that droplet sizes have indeed increased, and that clouds have darkened with a significant local climate warming. Globally, the impact is much smaller, but may still represent an important consideration for assessments of the total summed effect of aerosols on climate.

Machine Learning is a rapidly expanding technique in the field of weather and climate modelling. This paper takes stock of the state of the field at the present time, and will be invaluable to participants across the field and beyond who wish to understand the impact of Machine Learning on the field, its limitations, and current scope.

Tornadoes are having impact on peoples live and are in a general interest.

The manuscript presents a reconstruction of global temperature spanning the Holocene, which extends the scope of previous exercises in palaeoclimate data assimilation. The resulting reconstruction presents new insights into changes in global temperature over this period. Most notably, it confirms the results of previous studies that have shown a global cooling trend over the past 6,000 years. It also shows that a cooling trend is found even after allowing for potential biases in the proxies. These results are likely to be of considerable interest to the broader geoscience community.

This study presents FLUXCOM-X, a new modelling framework for terrestrial biogenic fluxes that builds on the widely used FLUXCOM observation-based dataset. FLUXCOM-X provides higher resolution water and carbon flux estimates (0.05 degree and hourly estimates), as well as a flexible framework for exploring the impact of methodological choices on the flux estimates, including the impact of machine learning approaches and input data selection and processing steps.

This paper examines the warning deficits in conjunction with the major flooding event in Germany of summer 2021. The event caused many fatalities and enormous damage. The warning procedures proved to be insufficient, and after investigations it was decided to install a cell broadcast system in Germany, which is already in place today. The deeper investigations on the warning perceptions and the influencing factors is of major interest to readers beyond the scientific community.

This paper shows that current climate policies risk triggering tipping points like permafrost thaw and rainforest loss. While these changes add some extra warming, human emissions remain the biggest driver. Lower emissions reduce the risk, but reaching tipping points is still possible.

The NHESS paper “A climate-conditioned catastrophe risk model for UK flooding” by Bates and colleagues presents and validates a new flood model for the UK that simulates pluvial, fluvial and coastal flood risks at a resolution of 20 to 25 metres. The authors then use their scheme to estimate the probability-loss distribution for UK flooding under various future climate and policy scenarios. Their paper provides the most detailed and realistic analysis to date of current and future flood risk in the UK. The key findings of their work are: (1) Previous UK flood losses based on government data and used in national climate change risk assessments are overestimated by a factor of about 3. (2) Official UK estimates lie well outside the paper's modelled loss distribution, which is plausibly centred on the observations. (3) The UK 1% annual probability flood losses were only about 6% greater in the average climate conditions of 2020 than for the period of historical river flow and rainfall observations (centred approximately on 1995). (4) Increases in risk can be kept to around ~8% if all COP26 2030 carbon emission reduction pledges and ‘net zero’ commitments are implemented in full. (5) Implementing only the COP26 pledges increases UK 1% annual probability flood losses by ~23% above recent historical values, and potentially ~37% if climate sensitivity turns out to be higher than currently thought.

This article describes the effect of the recent (January 2022) Hunga Tonga-Hunga Ha’apai volcanic eruption on the stratosphere. The eruption was highly energetic and as a result erupted material reached altitudes of around 30km. Such eruptions, with the 1991 Pinatubo eruption being a noteworthy example, often have a significant effect on tropospheric weather and climate, through the radiative effects of the volcanic aerosol, which may remain in the stratosphere for 2 or 3 years or more. In the 30 years since the Pinatubo eruption observations of the stratosphere, primarily from satellites, have improved enormously and in this Letter the authors provide a detailed description of the evolution of volcanic aerosol and of other chemical species injected by the eruption over a 6-month period following the eruption. The authors show that one important effect of the eruption was to inject a large quantity of water vapour into the stratosphere and suggest that the largest impact of the eruption on tropospheric weather and climate will be via the radiative effect of this water vapour, rather than of the injected aerosol. The initial detailed picture of the impact of the Hunga Tonga-Hunga Ha’apai eruption on the stratosphere provided in this Letter will stimulate further study of this remarkable natural event, which provides a rare opportunity to test our scientific understanding.

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.

I agree with the handling editor and suggest considering it as a highlight paper.

The Coupled Model Intercomparison Project lies at the core of global climate prediction. This paper details the Coupled Model Intercomparison Project phase 7 (CMIP7) and its Fast Track initiative. By transitioning into a continuous climate modeling program with enhanced coordination and federated planning, CMIP7 aims to address key climate questions more effectively. The expansion of the Diagnostic, Evaluation, and Characterization of Klima (DECK) experiments—including the addition of historical simulations, effective radiative forcing assessments, and CO₂-emissions-driven experiments—strengthens the foundation for climate model evaluation and projection. Additionally, the AR7 Fast Track ensures timely delivery of critical climate simulation data to support the upcoming 7th Intergovernmental Panel on Climate Change Assessment Report. This paper highlights how these advancements in experimental protocols and infrastructure support not only scientific understanding but also inform policy-making and climate services, ultimately contributing to global efforts in climate adaptation and mitigation.

The paper provides the general overview on the upcoming EarthCARE mission, which carries a unique suite of active and passive instruments for aerosol, cloud and radiation observations. It is thought to be the introductory paper for the AMT Special Issue "EarthCARE Level 2 algorithms and data products".

This review is topical and of potential interest to a broad audience

The explosive Hunga Tonga eruption in 2022 had several characteristics that are unique in the recent observational record. Its effects on the atmosphere are of great scientific interest and have included rapidly propagating patterns of Lamb and gravity waves and long-lived anomalies in stratospheric water vapour. This modelling study demonstrates how, through a coupled sequence of chemical, radiative and dynamical mechanisms, the additional water vapour in the tropical upper stratosphere is likely to have had a significant effect on the wintertime circulation of the stratosphere and hence the troposphere in Northern Hemisphere mid- and high latitudes. These results on the fascinating Hunga Tonga event have wider relevance to perturbations of the climate system where the initial impact is stratospheric but important secondary effects are felt elsewhere, including at the surface.

This manuscript provides a novel and comprehensive assessment of uncertainty associated with sea level rise. The model description is thorough and it is applied to a number of possible scenarios. The conclusions are important for framing future discussions on sea level rise.

The core element of climate change is the sensitivity of the Earth's climate system to the balance between incoming solar radiation and outgoing terrestrial radiation at the top of the atmosphere. CO2 is one of the key atmospheric parameters controlling the outgoing longwave radiation. In this paper, hyper-spectral satellite data of the outgoing long wave radiation from a decade of observations are successfully used for the first time to disentangle the radiative effect of CO2 increase from those of other relevant parameters such as temperature and water vapour variations. The paper demonstrates convincingly that the observed radiative changes agree excellently with theoretical predictions of outgoing long wave radiation changes due to the observed CO2 increase. While solely based on observations from space, these results confirm a fundamental theoretical underpinning of the science of global warming.

Sea level rise represents one of the most compelling aspects of anthropogenic climate change. The potential social and economic impacts are enormous, with little that can be done to mitigate them. It is therefore of critical importance that we are able to correctly anticipate these impacts in advance. This study presents a new, open-source platform that integrates numerical modelling with socioeconomic and physical datasets, whilst also allowing for the uncertainty in climate change projections. This tool therefore allows for new and improved estimates of the global costs of future sea level rise and is likely to be of widespread interest.

This article describes the design of the next version of emission scenarios that will be used for the 7th phase of the Coupled Model Intercomparison Project, which in turn will be used for the 7th Assessment Report of the Intergovernmental Panel on Climate Change. It provides the story lines for the creation of the emission scenarios and therefore it envisions future trajectories of policies and energy use. Models in CMIP 7 will use these scenarios to run simulations of future climate change using the scenarios as the main forcing. The authors carefully considered all community comments and maintained an open approach to develop these scenarios.

Emissions from conventional aircraft contribute to climate change by forming contrails and by increasing atmospheric CO2 concentrations. To fly faster and reduce the climate impact, super- or hypersonic aircraft fuelled by liquid hydrogen or natural gas are being considered. Hypersonic aircraft would fly at more than Mach 4 in the stratosphere, up to 35 km altitude, where the peak of the ozone layer resides. The paper by Pletzer et al. presents a thorough study of the chemical and radiative impacts of such high-speed aircraft using two chemistry-climate models. The study shows that hypersonic aircraft fuelled by liquid hydrogen and cruising at such altitudes would contribute to a significant global warming although they do not emit CO2. The main radiative effect comes from additional water vapour, with only a small effect from depletion of the ozone layer. Importantly, the authors discovered that although water vapour is destroyed in the stratosphere, perturbation of local photochemistry also creates water vapour. The authors estimate that the mean surface temperature change caused by a hypersonic transport fleet would be roughly 8-20 times larger than for a subsonic reference aircraft with the same transport volume. This comprehensive study provides convincing calculations for a large climatic effect of any future hydrogen-fuelled hypersonic aircraft fleet.

Strong reduction of sulfur emission from shipping since 2020 provides a rare opportunity to examine the response of climate system to anthropogenic forcing. Using a global climate model, this study estimates a global aerosol effective radiative forcing of 0.13 W m-2 from ship emission reduction. This emission reduction leads to a global mean warming of 0.04 K in 2020-2049 with larger warming at regional scales. The warming may not be evident at present day because of the climate variability, but can represent a significant fraction (17%) of the remaining warming to 1.5 K target.

The paper gives a comprehensive overview on the current state of the societally important field of Earth system tipping point early warning signals across different fields. Relevant conclusions are drawn on promising avenues for further advancing the research field.

This paper represents a community effort at identifying the critical needs of Earth system modeling. This is essential for the upcoming AR7 and UNFCCC second stocktake.

This work highlights the importance of data collected through citizen science for studying extreme geomagnetic storms. The Gannon storm was an unprecedented opportunity to test the limitations of citizen science data collection and to offer solutions to enable similar studies in the future. This study has great potential to be of interest to the wider public.

The paper deals with a topic that is current and of great importance to society. It reveals and illustrates the complexity of coupled human-hydrological-ecological systems and identifies starting points for improved management of droughts and associated risks.

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.

I think the paper contains some important messages for the management of soil water that have widespread implications

This paper reports the alarming increase in wildfires in the Amazon rainforest during the severe 2023/2024 drought leading to an increase in large-scale forest degradation. It is highly relevant as the fire-driven forest degradation impacted also intact forests and released large amounts of carbon dioxide to the atmosphere pushing the Amazon rainforest closer to a potential tipping point.