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Atmospheric Rivers transport high amounts of water from subtropical regions to Europe. They are an important driver of heavy precipitation and flooding. Their response to a warmer future climate has so far been assesed only by global climate models. In this study we apply for the first time a high resolution regional climate model that better resolves small scale land – atmosphere interactions.

The Pacific Ocean heat engine regulates global climate, linking the cooler eastern Central Pacific with the warmer western Pacific, moving heat east to west. The heat engine maintains constant climate conditions. From pre-industrial climate to the mid-20^th century, climate was in free mode, a more relaxed state. Later in the 20^th century, as heat accumulated in the climate system, it switched into forced mode. Energy imbalances cause regime shifts, producing a staircase in global temperature.

When the ocean and atmosphere are coupled in climate models, the Pacific Ocean heat engine and climate network emerge. Thermodynamic forcing of heat imbalance produces a staircase in warming which is normally interpreted as climate variability. This is limited by the energy constraints of equator-to-pole heat transport and external forcing. The result is a homeostatic, self-regulating complex system that occupies steady-state regimes, the most basic being the decadal climate regime.

To date, farmers perceptions of hydrological changes do not match analysis of meteorological data. In contrast, we find greening of vegetation, indicating water availability has increased in the past decades. The onset of the wet season however is highly variable, making farmers perceptions comprehensible. Hence, we show that El Niño Southern Oscillation has complex effects on vegetation seasonality but does not drive the greening we observe. Improved onset forecasts could help local farmers.

The ExtremeX experiment was designed to disentangle the contribution of processes leading to the occurrence recent weather and climate extremes. Global climate simulations are carried out with three climate models. The results show that temperature anomalies during heatwaves are well represented although climatological model biases remain. Further, a substantial contribution of both atmospheric circulation patterns and soil moisture conditions to heat extremes is identified.

Solar photovoltaics (PV) matters for the carbon neutrality goal. We use climate scenarios to quantify climate risk for PV in Europe and find higher PV potential. The seasonal cycle of PV generation changes in most places. We find an increase in the spatial correlations of daily PV production, implying that PV power balancing through redistribution will be more difficult in the future. Thus, changes in the spatio-temporal structure of PV generation should be included in power system design.

Atmospheric pCO₂ of the past shows large variability on different time scales. We focus on the effect of the strength of Atlantic Meridional Overturning Circulation (AMOC) on this variability and on the AMOC–pCO₂ relationship. We find that climatic boundary conditions, and the representation of biology in our model are most important for this relationship. Under certain conditions, we find internal oscillations, that can be relevant for atmospheric pCO₂ variability during glacial cycles.

A Large Ensemble of simulations with 100 members has been conducted with the state-of-the-art CESM2 Earth system model, using historical/SSP3-7.0 forcing. Our main finding is that there are significant changes in the variance of the Earth system in response to anthropogenic forcing, with these changes spanning a broad range of variables important to impacts for human populations and ecosystems.

We address the question of how large an initial condition ensemble of climate model simulations should be, if we are concerned with accurately projecting future changes in temperature and precipitation extremes. We find that for most cases (and both models considered) an ensemble of 20–25 members is sufficient for many extreme metrics, spatial scales and time horizons. This may leave computational resources to tackle other uncertainties in climate model simulations with our ensembles.

As part of the Baltic Earth Assessment Reports (BEAR), we present an inventory and discussion of different human-induced factors and processes affecting the environment of the Baltic Sea region, and their interrelations. Some are naturally occurring and modified by human activities, others are completely human-induced, and they are all interrelated to different degrees. The findings from this study can largely be transferred to other comparable marginal and coastal seas in the world.

The land surface can influence the occurrence of local rainfall through different feedback mechanisms. In Europe, this happens most frequently in summer. Here, we examine how differences the average atmospheric conditions change where and how often the land surface can influence rainfall. The results indicate that the differences barely change that the surface influence is strongest over Scandinavia and Eastern Europe, but they can change the frequency of feedback events.

Compound hazards occur when two different natural hazards impact the same time period and spatial area. This article presents a methodology for the Spatiotemporal Identification of Compound Hazards (SI–CH). The methodology is applied to compound precipitation and wind extremes in Great Britain for the period 1979–2019. The study finds that the SI–CH approach can accurately identify single and compound hazard events and represent their spatial and temporal properties.

We interpret carbon dioxide emissions from fossil fuel burning and land use as a global stress-strain experiment to reflect the overall behaviour of the atmosphere–land/ocean system in response to increasing CO₂ emissions since 1850. We find that the system has been trapped progressively in terms of persistence, while its ability to build up memory has been reduced. We expect system failures globally well before 2050 if the current trend in emissions is not reversed immediately and sustainably.

This study sheds light on the changes of summer thermal environment in Chengdu Chongqing urban agglomeration due to urban expansion under complex terrain conditions in recent 40 years, using high-resolution simulations with the WRF model. We quantify the influence of single urban expansion factor and single complex terrain factor on urban thermal environment.Under the joint influence of complex terrain and urban expansion, the heat island effect caused by urbanization was enhanced.

Climate change over High Mountain Asia is investigated with CMIP6 climate models. A general cold bias is found in this area, often related to a snow cover overestimation in the models. Ensemble experiments generally encompass the past observed trends, suggesting that even biased models can reproduce the trends. Depending on the future scenario, a warming from 1.9 to 6.5 °C, associated with a snow cover decrease and precipitation increase is expected at the end of the XXIth century.

Leaching of dissolved organic carbon (DOC) from soils to the river network is an important component of the land carbon (C) budget but its spatio-temporal variation is not yet fully constrained. We use a land surface model to simulate at the European scale the present-day land C budget including leaching of DOC from the soil. We found an average leaching of 14.3 TgC/yr (0.6 % of the terrestrial net primary production) with seasonal variations. We determine runoff and temperature as main drivers.

Agriculture is sensitive to weather conditions and to climate change. We identify the weather conditions linked to soybean failures and explore changes related to climate change. Additionally, we build future versions of a historical extreme season under future climate scenarios. Results show that soybean failures are likely to increase with climate change. Future events with similar physical conditions to the extreme season are not expected to increase, but events with similar impacts are.

Soil organic carbon sequestration on cropland has been proposed as a climate change mitigation strategy. We here simulate different agricultural management practices under climate change scenarios, using a global biophysical model. We find that at the global aggregated level, agricultural management practices are not capable to enhance carbon storage in the soil, yet for some climate regions, we find that there is the potential to enhance the carbon content in cropland soils.

The oceans are typically darker than land surfaces. Expanding oceans through sea-level rise may thus lead to a darker planet Earth, reflecting less sun light. The additionally absorbed sun light may heat planet Earth, leading to further sea-level rise. Here, we provide a rough estimate of the strength of this feedback: it turns out to be very weak, but clearly positive, i.e., destabilizing the Earth system.

The variability in atmospheric CO₂ is largely controlled by terrestrial carbon fluxes. These land-atmosphere fluxes are predictable for around two years, but the mechanisms providing the predictability are not well understood. By decomposing the predictability of carbon fluxes into individual contributors we were able to explain the spatial and seasonal patterns, and the interannual variability of predictability.

In its content, the paper covers the aspects related to changes in carbon, nitrogen and phosphorus (C, N, P) external loads, their transformations in the coastal zone, changes in organic matter production (eutrophication) and remineralization (oxygen availability), and the role of sediments in burial and turnover of C, N and P. Furthermore, this paper focuses also on changes in the marine CO₂ system, structure of the microbial community and the role of contaminants for biogeochemical processes.

We study with the regionally-coupled climate model ROM the impact of climate change on the Tyrrhenian Sea circulation, as well as the possible mechanisms and consequences in the NW Mediterranean Sea. Our results show a shift towards the summer circulation pattern by the end of the century. Also, water flowing via the Corsica Channel is more stratified and smaller in volume. Both factors may contribute to the interruption of deep water formation in the Gulf of Lions in the future.

The salinity in the Baltic Sea is not only an important topic for physical oceanography as such, but it also integrates the complete water and energy cycle. It is a primary external driver controlling ecosystem dynamics of the Baltic Sea. The long-term dynamics is controlled by river runoff, net precipitation and the water mass exchange between North Sea and Baltic Sea. On shorter time scales, the ephemeral atmospheric conditions drive a very complex and highly variable salinity regime.