Ada Gjermundsen

• Smith, Chris; Ramme, Lennart; Wells, Christopher D.; Gjermundsen, Ada; Li, Hongmei & Ilyina, Tatiana [Vis alle 12 forfattere av denne artikkelen] (2026). Overshoot and (ir)reversibility to 2300 in two CO2-emissions driven Earth System models. Earth System Dynamics (ESD). ISSN 2190-4979. 17(3), s. 893–911. doi: 10.5194/esd-17-893-2026. Fulltekst i vitenarkiv Vis sammendrag

  Future climate scenario projections are usually run with prescribed atmospheric CO2 concentrations. However, by not allowing the carbon cycle to interactively respond to emissions in Earth System models, the role of carbon cycle feedbacks on contributions to differences in climate model projections may be undersampled. Here, we present the main findings of two Earth System Models (MPI-ESM1.2-LR and NorESM2-LM) run with CO2 emissions to 2300 for three scenarios, two of which are climate overshoot scenarios, that were part of the Coupled Model Intercomparison Project Phase 6 (CMIP6). These experiments serve three important purposes: (i) an increasing focus on emissions driven runs, supplementing scenarios produced for the Coupled Climate-Carbon Cycle (C4MIP) and Carbon Dioxide Removal (CDRMIP) contributions to CMIP6; (ii) a focus on overshoot scenarios; and (iii) an extension of results beyond 2100, the timescales at which some of the most significant differences play out. Of the two models, NorESM2-LM shows more asymmetry in its climate response at the same global mean temperature levels before and after peak warming, particularly in terms of its regional pattern of warming and Atlantic Meridional Overturning Circulation (AMOC) response, with a substantially weakened AMOC persisting for decades after peak warming that takes more than a century to recover. In contrast, MPI-ESM1.2-LR shows reversibility with AMOC strength and regional warming more closely following surface temperature, but with some climate signals such as sea-level rise and ocean deoxygenation essentially irreversible. This diversity in model responses highlights the need for further research with a larger model ensemble that focuses on long-term emissions-driven model runs, particularly for overshoot scenarios, for CMIP7.

• Steensen, Birthe Marie Rødssæteren; Myhre, Gunnar; Byrom, Rachael; Gjermundsen, Ada; Jouan, Caroline & Stjern, Camilla Weum (2026). European summer precipitation. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 26(3), s. 2041–2054. doi: 10.5194/acp-26-2041-2026. Fulltekst i vitenarkiv Vis sammendrag

  Observations indicate that parts of Europe have experienced summer drying over recent decades. There is, however, substantial uncertainty in terms of precipitation changes projected by global climate models, underscoring the need for improved understanding to guide adaptation. Here, we analyse changes in European summer precipitation with global warming in 35 CMIP6 Earth system Models using a regional atmospheric energy budget framework. Over the historical period we compare these models to two reanalysis datasets, ERA5 and MERRA-2, as well as the E-OBS daily gridded observational dataset. Although ERA5 and MERRA-2 compare well to observed precipitation, they diverge substantially from each other and exhibit large discrepancies with the CMIP6 models when evaluating other terms in the atmospheric energy budget. In future projections, variability across models increases relative to the historical period for the changes in precipitation, sensible heat and the dry static energy flux divergence, highlighting the uncertainties in the magnitude of these terms. Nevertheless, the models show consistent agreement on the projection of summer drying over continental Europe with anthropogenic forcing over time.

• Wells, Christopher D.; Ramme, Lennart; Smith, Chris; Breier, Jannes; Adakudlu, Muralidhar & Li, Chao [Vis alle 10 forfattere av denne artikkelen] (2026). FRIDA-Clim v1.0.1: a simple climate model with process-based carbon cycle used in the integrated assessment model FRIDAv2.1. Geoscientific Model Development. ISSN 1991-959X. 19(4), s. 1429–1453. doi: 10.5194/gmd-19-1429-2026. Fulltekst i vitenarkiv Vis sammendrag

  The new global Feedback-based knowledge Repository for IntegrateD Assessments version 2.1 (FRIDAv2.1) Integrated Assessment Model (IAM) seeks to study the dynamics of the coupled human-Earth system. Connecting anthropogenic emissions to the resultant climate response is one part of the two-way feedback within this system, with the resultant climate impacts the other. This paper documents both the Climate Module within FRIDAv2.1, and the modified version separately simulated as a standalone simple climate model termed FRIDA-Clim version 1.0.1. This approach, based loosely on the existing FaIR simple climate model, simulates the key radiative forcings and the resultant temperature response, with process-based representations of the carbon cycle across the ocean, land, and atmosphere. When connected within the FRIDA IAM, it features deep connections to the other modules, being affected by processes such as water use for irrigation and land use change. In both uses, i.e. with the climate response interactively connected to the upstream human drivers and downstream climate impacts within the FRIDA IAM (coupled) and when ran separately as FRIDA-Clim driven by exogenous forcings (uncoupled), its climate drivers are simplified as compared to FaIR. This is to allow for this reduced set of key drivers to be interactively simulated within FRIDA, tightly coupling the evolution of the social and climate systems within the full model. Both the Climate Module and FRIDA-Clim are fully calibrated to accurately reproduce observations of key climate variables, with a systematic exploration of the uncertainty in the climate response. Together with the rest of the FRIDA model, this module is used to incorporate climate change systematically in the FRIDA System Dynamics IAM. As a standalone climate model, FRIDA-Clim comprises a simple climate model, enabling fast calculation of the global climate response to forcing; to explore this, the response of the model to both idealised CO2 emissions experiments and plausible future scenarios is also presented here. This setup will allow FRIDA-Clim to contribute to inter-model simple climate modelling initiatives, helping to explore the structural uncertainty in this modelling domain.

• Graff, Lise Seland; Tjiputra, Jerry; Gjermundsen, Ada; Born, Andreas; Debernard, Jens Boldingh & Goelzer, Heiko [Vis alle 20 forfattere av denne artikkelen] (2025). Sensitivity of winter Arctic amplification in NorESM2. Earth System Dynamics (ESD). ISSN 2190-4979. 16(5), s. 1671–1698. doi: 10.5194/esd-16-1671-2025. Fulltekst i vitenarkiv Vis sammendrag

  While Arctic amplification is a robust feature of both observed and projected climate change, projections of Arctic climate change are characterized by substantial uncertainty. To better understand the drivers of this uncertainty, we performed a coordinated set of fully coupled experiments with the second version of the Norwegian Earth System Model (NorESM2), in which selected processes of key importance for the Arctic climate have been modified. They include improved representation of (1) mixed-phase clouds, (2) eddy processes in the upper ocean, (3) Greenland ice sheet coupling, (4) snow on sea ice processes, and (5) ozone chemistry. For each modification, we carried out sensitivity experiments following the protocols for the historical simulation of the sixth phase of the Coupled Model Intercomparison Project (CMIP6) and a future high-emissions scenario (ssp585). This results in an ensemble of modified historical and ssp585 experiments. The sensitivity experiments all demonstrate enhanced future Arctic warming compared to the unmodified historical and ssp585 experiments. Moreover, the amplitude of the additional warming varies considerably, with the difference between the experiment with the strongest and weakest Arctic mean warming reaching ∼ 9 K during the winter season by the end of the 21st century. The warming signal is dominated by a relatively uniform Arctic warming, which, according to the CMIP6 ssp585 long-term extension, starts to equilibrate during the 22nd century. Surface temperature decomposition shows that winter warming is primarily driven by an enhanced greenhouse effect due to increased cloud cover, near-surface humidity, and the resulting increase in downwelling longwave radiation. The temperature response is most pronounced in the sea ice retreat regions, with the greatest variability between experiments occurring on the Atlantic side. We also identify an emergent constraint, linking changes in Arctic surface temperatures to changes in ocean heat fluxes and sea ice area. This highlights the importance of correctly representing (contemporary) Northern Hemisphere (NH) sea ice when assessing future projected Arctic warming.

• Madan, Gaurav; Gjermundsen, Ada; Iversen, Silje Christine & Lacasce, Joseph Henry (2023). The weakening AMOC under extreme climate change. Climate Dynamics. ISSN 0930-7575. 62, s. 1291–1309. doi: 10.1007/s00382-023-06957-7. Fulltekst i vitenarkiv Vis sammendrag

  Changes in the Atlantic Meridional Overturning Circulation (AMOC) in the quadrupled CO₂ experiments conducted under the sixth Coupled Model Intercomparison Project (CMIP6) are examined. Increased CO₂ triggers extensive Arctic warming, causing widespread melting of sea ice. The resulting freshwater spreads southward, frst from the Labrador Sea and then the Nordic Seas, and proceeds along the eastern coast of North America. The freshwater enters the subpolar gyre north of the separated Gulf Stream, the North Atlantic Current. This decreases the density gradient across the current and the current weakens in response, reducing the infow to the deepwater production regions. The AMOC cell weakens in tandem, frst near the North Atlantic Current and then spreading to higher and lower latitudes. This contrasts with the common perception that freshwater caps the convection regions, stifing deepwater production; rather, it is the infow to the subpolar gyre that is suppressed. Changes in surface temperature have a much weaker effect, and there are no consistent changes in local or remote wind forcing among the models. Thus an increase in freshwater discharge, primarily from the Labrador Sea, is the precursor to AMOC weakening in these simulations.

• Gjermundsen, Ada; Graff, Lise Seland; Bentsen, Mats; Breivik, Lars-Anders; Debernard, Jens Boldingh & Makkonen, Risto [Vis alle 10 forfattere av denne artikkelen] (2021). How representative is Svalbard for future Arctic climate evolution? An Earth system modelling perspective. SESS report. ISSN 2535-809X. 1(ISBN 978-82-691528-9-0), s. 38–79. doi: 10.5281/zenodo.4034104. Fulltekst i vitenarkiv
• Thornhill, Gillian; Collins, William J.; Oliviè, Dirk Jan Leo; Skeie, Ragnhild Bieltvedt; Archibald, Alexander T. & Bauer, Susanne E. [Vis alle 26 forfattere av denne artikkelen] (2021). Climate-driven chemistry and aerosol feedbacks in CMIP6 Earth system models. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 21(2), s. 1105–1126. doi: 10.5194/acp-21-1105-2021. Fulltekst i vitenarkiv Vis sammendrag

  Feedbacks play a fundamental role in determining the magnitude of the response of the climate system to external forcing, such as from anthropogenic emissions. The latest generation of Earth system models includes aerosol and chemistry components that interact with each other and with the biosphere. These interactions introduce a complex web of feedbacks that is important to understand and quantify. This paper addresses multiple pathways for aerosol and chemical feedbacks in Earth system models. These focus on changes in natural emissions (dust, sea salt, dimethyl sulfide, biogenic volatile organic compounds (BVOCs) and lightning) and changes in reaction rates for methane and ozone chemistry. The feedback terms are then given by the sensitivity of a pathway to climate change multiplied by the radiative effect of the change. We find that the overall climate feedback through chemistry and aerosols is negative in the sixth Coupled Model Intercomparison Project (CMIP6) Earth system models due to increased negative forcing from aerosols in a climate with warmer surface temperatures following a quadrupling of CO2 concentrations. This is principally due to increased emissions of sea salt and BVOCs which are sensitive to climate change and cause strong negative radiative forcings. Increased chemical loss of ozone and methane also contributes to a negative feedback. However, overall methane lifetime is expected to increase in a warmer climate due to increased BVOCs. Increased emissions of methane from wetlands would also offset some of the negative feedbacks. The CMIP6 experimental design did not allow the methane lifetime or methane emission changes to affect climate, so we found a robust negative contribution from interactive aerosols and chemistry to climate sensitivity in CMIP6 Earth system models.

• Gjermundsen, Ada; Nummelin, Aleksi; Oliviè, Dirk Jan Leo; Bentsen, Mats; Seland, Øyvind & Schulz, Michael (2021). Shutdown of Southern Ocean convection controls long-term greenhouse gas-induced warming. Nature Geoscience. ISSN 1752-0894. 14, s. 724–731. doi: 10.1038/s41561-021-00825-x. Fulltekst i vitenarkiv Vis sammendrag

  The effective climate sensitivity estimates the equilibrium response of near-surface temperature to doubling atmospheric carbon dioxide concentration and is a widely used metric to characterize potential global warming. Earth system models participating in phase 6 of the Coupled Model Intercomparison Project (CMIP6) exhibit considerable spread in effective climate sensitivity estimates. Cloud feedbacks are thought to be the cause of this, with marine boundary layer clouds over the Southern Ocean playing an important role. Here, we show that Southern Ocean deep convection is a major contributor to the CMIP6 intermodel spread in effective climate sensitivity. By comparing two Earth system models with very different sensitivities, we find that greater storage of heat at depth can delay the Southern Ocean surface warming and associated cloud response, thereby delaying global surface warming by centuries. The link between Southern Ocean convection and effective climate sensitivity is seen across 41 CMIP6 models, with low-sensitivity models exhibiting substantial deep ocean warming. Our results reveal the influence of Southern Ocean convection on potential long-term climate warming.

• Seland, Øyvind; Bentsen, Mats; Oliviè, Dirk Jan Leo; Toniazzo, Thomas; Gjermundsen, Ada & Graff, Lise Seland [Vis alle 30 forfattere av denne artikkelen] (2020). Overview of the Norwegian Earth System Model (NorESM2) and key climate response of CMIP6 DECK, historical, and scenario simulations. Geoscientific Model Development. ISSN 1991-959X. 13(12), s. 6165–6200. doi: 10.5194/gmd-13-6165-2020. Fulltekst i vitenarkiv Vis sammendrag

  The second version of the coupled Norwegian Earth System Model (NorESM2) is presented and evaluated. NorESM2 is based on the second version of the Community Earth System Model (CESM2) and shares with CESM2 the computer code infrastructure and many Earth system model components. However, NorESM2 employs entirely different ocean and ocean biogeochemistry models. The atmosphere component of NorESM2 (CAM-Nor) includes a different module for aerosol physics and chemistry, including interactions with cloud and radiation; additionally, CAM-Nor includes improvements in the formulation of local dry and moist energy conservation, in local and global angular momentum conservation, and in the computations for deep convection and air–sea fluxes. The surface components of NorESM2 have minor changes in the albedo calculations and to land and sea-ice models. We present results from simulations with NorESM2 that were carried out for the sixth phase of the Coupled Model Intercomparison Project (CMIP6). Two versions of the model are used: one with lower (∼ 2∘) atmosphere–land resolution and one with medium (∼ 1∘) atmosphere–land resolution. The stability of the pre-industrial climate and the sensitivity of the model to abrupt and gradual quadrupling of CO2 are assessed, along with the ability of the model to simulate the historical climate under the CMIP6 forcings. Compared to observations and reanalyses, NorESM2 represents an improvement over previous versions of NorESM in most aspects. NorESM2 appears less sensitive to greenhouse gas forcing than its predecessors, with an estimated equilibrium climate sensitivity of 2.5 K in both resolutions on a 150-year time frame; however, this estimate increases with the time window and the climate sensitivity at equilibration is much higher. We also consider the model response to future scenarios as defined by selected Shared Socioeconomic Pathways (SSPs) from the Scenario Model Intercomparison Project defined under CMIP6. Under the four scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5), the warming in the period 2090–2099 compared to 1850–1879 reaches 1.3, 2.2, 3.0, and 3.9 K in NorESM2-LM, and 1.3, 2.1, 3.1, and 3.9 K in NorESM-MM, robustly similar in both resolutions. NorESM2-LM shows a rather satisfactory evolution of recent sea-ice area. In NorESM2-LM, an ice-free Arctic Ocean is only avoided in the SSP1-2.6 scenario.

• Gjermundsen, Ada; Lacasce, Joseph Henry & Denstad, Liv (2018). The thermally-driven ocean circulation with realistic bathymetry. Journal of Physical Oceanography. ISSN 0022-3670. 48(3), s. 647–665. doi: 10.1175/JPO-D-17-0147.1. Fulltekst i vitenarkiv Vis sammendrag

  The global circulation driven solely by relaxation to an idealized surface temperature profile and to interior mixing is examined. Forcing by winds and evaporation/precipitation is excluded. The resulting circulation resembles the observed in many ways, and the overturning is of similar magnitude. The overturning is driven by large-scale upwelling in the interior (which is relatively large, because of the use of a constant mixing coefficient). The compensating downwelling occurs in the northern North Atlantic and in the Ross and Weddell Seas, with an additional, smaller contribution from the northern North Pacific. The latter is weaker because the Bering Strait limits the northward extent of the flow. The downwelling occurs in frictional layers near the boundaries and depends on the lateral shear in the horizontal flow. The shear, in turn, is linked to the imposed surface temperature gradient via thermal wind, and as such, the downwelling can be reduced or eliminated in selected regions by removing the surface gradient. Doing so in the northern North Atlantic causes the (thermally driven) Antarctic Circumpolar Current to intensify, increasing the sinking along Antarctica. Eliminating the surface gradient in the Southern Ocean increases the sinking in the North Atlantic and Pacific. As there is upwelling also in the western boundary currents, the flow must increase even more to accomplish the necessary downwelling. The implications of the results are then considered, particularly with respect to Arctic intensification of global warming, which will reduce the surface temperature gradient. This research was originally published in the Journal of Physical Oceanography. © 2018 American Meteorological Society

• Gjermundsen, Ada & Lacasce, Joseph Henry (2017). Comparing the linear and nonlinear buoyancy-driven circulation. Tellus A: Dynamic Meteorology and Oceanography. ISSN 0280-6495. 69(1). doi: 10.1080/16000870.2017.1299282. Fulltekst i vitenarkiv Vis sammendrag

  The buoyancy-driven circulation is studied in an idealized domain using two models, one based on the linearized planetary geostrophic equations and a fully nonlinear GCM. The surface buoyancy is specified (relaxed) to a chosen function of latitude in the linear (nonlinear) model. The models yield similar baroclinic flow in the interior, where the surface velocities are primarily zonal, and near the southern boundary, where a westward surface flow feeds the western boundary current (WBC). They differ however in the north. While the linear model has westward surface flow of limited vertical extent near the northern wall, the GCM has baroclinic flow which extends to the bottom with eastward surface velocities. The difference is due to convection, which weakens the stratification in the nonlinear model, amplifying the thermal wind transport associated with the surface buoyancy gradient. The WBC flow in the GCM feeds this, with northward surface flow over its entire length (as seen in nearly all previous similar studies). This in turn determines the meridional overturning circulation, since the WBC accounts for the largest meridional velocities. Roughly half the upwelling occurs in the WBC in the GCM and half in the interior, while the upwelling occurs in the interior and near the southern wall in the linear model. The study highlights the role of convection in modifying the response to the surface buoyancy gradient.

• Gjermundsen, Ada; Lacasce, Joseph Henry & Graff, Lise Seland (2014). The atmospheric response to surface heating under maximum entropy production. Journal of the Atmospheric Sciences. ISSN 0022-4928. 71(6), s. 2204–2220. doi: 10.1175/JAS-D-13-0181.1. Fulltekst i vitenarkiv Vis sammendrag

  In numerous studies, midlatitude storm tracks have been shown to shift poleward under global warming scenarios. Among the possible causes, changes in sea surface temperature (SST) have been shown to affect both the intensity and the position of the tracks. Increased SSTs can increase both the lateral heating occurring in the tropics and the midlatitude temperature gradients, both of which increase tropospheric baroclinicity. To better understand the response to altered SST, a simplified energy balance model (EBM) is used. This employs the principal of maximum entropy production (MEP) to determine the meridional heat fluxes in the atmosphere. The model is similar to one proposed by Paltridge (1975) but represents only the atmospheric response (the surface temperatures are fixed). The model is then compared with a full atmospheric general circulation model [Community Atmosphere Model, version 3 (CAM3)]. In response to perturbed surface temperatures, EBM exhibits similar changes in (vertically integrated) air temperature, convective heat fluxes, and meridional heat transport. However, the changes in CAM3 are often more localized, particularly at low latitudes. This, in turn, results in a shift of the storm tracks in CAM3, which is largely absent in EBM. EBM is more successful, however, at representing the response to changes in high-latitude heating or cooling. Therefore, MEP is evidently a plausible representation for heat transport in the midlatitudes, but not necessarily at low latitudes. This research was originally published in Journal of the Atmospheric Sciences. © 2014 American Meteorological Society

Se alle arbeider i NVA

• Rosendahl, Andrea; Gjermundsen, Ada; Graff, Lise Seland & Schulz, Michael (2026). Nordic Precipitation Trends and North Atlantic Circulation Patterns in CMIP6 models. doi: 10.5194/egusphere-egu26-10875. Fulltekst i vitenarkiv Vis sammendrag

  Recent observed trends indicate increasing future precipitation in Northern Europe, yet CMIP6 models show substantial spread in sign and magnitude of both historical and future precipitation trends in the region. This large model spread highlights the difficulty in accurately modelling regional precipitation in global climate models, and the low confidence in future precipitation trends. In this study, we evaluate recent historical winter precipitation trends in selected models of the CMIP6 ensemble by validating the models against reanalysis and observations, and examining how the trends are influenced by sea surface temperatures (SSTs) and the large-scale atmospheric circulation, particularly the North Atlantic storm track. We consider data from CMIP6 historical and AMIP experiments, the latter using prescribed observed SST and sea ice concentration. Additionally, we include a complimentary set of AMIP-style experiments with the Norwegian Earth System Model (NorESM2) where we explore the effect of different time-evolving SST fields. Results show that models yield consistent precipitation patterns, which enables an assessment of the role of North Atlantic SST in shaping Nordic precipitation trends, when averaging over multiple ensemble members. Differences in Nordic precipitation trends are tied to differences in the North Atlantic SST pattern evolution, with consistent changes in latent heat flux, atmospheric baroclinicity and lower tropospheric zonal wind patterns. Particularly, differences in SST in the North Atlantic warming hole and along the eastern US coast and close to Svalbard, the latter related to rapid warming from Arctic sea ice loss, can influence the precipitation trends. Employing the relationship between North Atlantic SST and precipitation trends in the Nordic region, we can better understand the large precipitation spread among climate models, and thus increase confidence in both historical and future precipitation in the models. Furthermore, while the majority of CMIP6 models provide just a single ensemble member for the AMIP experiment, our results demonstrate that using multiple ensemble members for the AMIP experiments is essential to account for internal variability and to achieve robust results.

• Fuglestvedt, Herman Fæhn; Fjeldså, Johannes; Sandstad, Marit; Gjermundsen, Ada; Sanderson, Benjamin & Debernard, Jens Boldingh [Vis alle 11 forfattere av denne artikkelen] (2026). Informing tuning of coupled Earth system model NorESM3 with perturbed parameter ensembles. doi: https:/meetingorganizer.copernicus.org/EGU26/EGU26-17495.html. Fulltekst i vitenarkiv Vis sammendrag

  Quantifying parametric uncertainty is important for effective Earth system model development and calibration. Here, we present a 75-member perturbed parameter ensemble (PPE) with the coupled Earth system model NorESM3. As part of operational model calibration, we used the PPE to evaluate parameter sensitivities, identify bias‑reducing parameter choices and trade‑offs, and estimate parametric uncertainty within the model. The PPE was constructed by branching preindustrial (year 1850) simulations from a baseline run, perturbing parameters in the atmosphere, land, ocean, and sea ice modules within expert-informed ranges using Latin hypercube sampling. To study long-term behaviour, we continued a subset of members that met energy-balance criteria while preserving ensemble spread. We evaluated ensemble members against observational and reanalysis datasets to help distinguish biases responsive to parameter tuning from ones likely stemming from model structure.

• Nummelin, Aleksi Henrynpoika; Gjermundsen, Ada; Guo, Chuncheng; Jong, Marieke Femke de; Karpouzoglou, Theodoros & Labastida, René Gabriel Navarro [Vis alle 11 forfattere av denne artikkelen] (2026). Preparing for a potential crossing of an AMOC tipping point. PLOS Climate. 5(3 March). doi: 10.1371/journal.pclm.0000881. Fulltekst i vitenarkiv
• Lacasce, Joseph Henry; Li, Camille; Gjermundsen, Ada & Kappatou, Christina (2025). Investigating Bjerknes Compensation under the abrupt-x4CO2 CMIP6 experiment. doi: https:/meetingorganizer.copernicus.org/EGU25/EGU25-4868.html. Fulltekst i vitenarkiv Vis sammendrag

  In 1964 J. Bjerknes postulated that, when an anomaly occurs in ocean heat transport (OHT), the atmosphere heat transport (AHT) exhibits an anomaly of opposite sign so that the top of the atmosphere (TOA) transport is approximately preserved. This phenomenon is now known as Bjerknes Compensation (BJC) and has been the object of many studies in the context of steady state climate simulations, on decadal and centennial time scales. Here, we examine BJC under extreme climate forcing, specifically under the quadrupling of atmospheric CO2 in the Coupled Model Intercomparison Project Phase 6 (CMIP6). The models exhibit a pronounced decline in the Atlantic Meridional Overturning Circulation (AMOC), to varying degrees, in response to melting sea ice and increased freshwater runoff. The OHT is reduced accordingly, and this can trigger an increase in AHT, particularly in the Northern Hemisphere. We examine the degree of BJC, in the context of model climate sensitivity. We also examine how changes in overturning in the Southern Hemisphere impact AHT there. The issue is significant, as increased AHT partially compensates for the cooling implied by reduced OHT.

• Rosendahl, Andrea; Gjermundsen, Ada; Graff, Lise Seland; Oliviè, Dirk Jan Leo; Eckhardt, Sabine & Schulz, Michael (2025). Nordic precipitation trends and North Atlantic circulation patterns in NorESM2. Fulltekst i vitenarkiv
• Gjermundsen, Ada; Nummelin, Aleksi Henrynpoika; Oliviè, Dirk Jan Leo; Bentsen, Mats; Seland, Øyvind & Schulz, Michael (2023). Shutdown of Southern Ocean convection controls long-term greenhouse gas-induced warming. Fulltekst i vitenarkiv
• Gjermundsen, Ada; Bentsen, Mats; Oliviè, Dirk Jan Leo; Nummelin, Aleksi Henrynpoika; Seland, Øyvind & Schulz, Michael (2023). The Norwegian Earth System Model. Fulltekst i vitenarkiv
• Eckhardt, Sabine; Svendby, Tove Marit; Steensen, Birthe Marie Rødssæteren; Myhre, Gunnar; Gjermundsen, Ada & Oliviè, Dirk Jan Leo (2023). Moisture transport into the Arctic in a past and future climate. Fulltekst i vitenarkiv
• Gjermundsen, Ada; Nummelin, Aleksi Henrynpoika; Oliviè, Dirk Jan Leo; Bentsen, Mats; Seland, Øyvind & Schulz, Michael (2022). Assessing the oceanic control on ECS in CMIP6. Fulltekst i vitenarkiv
• Gjermundsen, Ada; Nummelin, Aleksi Henrynpoika; Oliviè, Dirk Jan Leo; Bentsen, Mats; Seland, Øyvind & Schulz, Michael (2022). NorESM2 and Climate Sensitivity. Fulltekst i vitenarkiv
• Gjermundsen, Ada; Nummelin, Aleksi Henrynpoika; Oliviè, Dirk Jan Leo; Bentsen, Mats; Seland, Øyvind & Schulz, Michael (2022). Shutdown of Southern Ocean convection controls long-term greenhouse gas-induced warming. Fulltekst i vitenarkiv
• Gjermundsen, Ada; Buraas, Marte Sofie; Oliviè, Dirk Jan Leo; Debernard, Jens Boldingh; Graff, Lise Seland & Nummelin, Aleksi Henrynpoika [Vis alle 9 forfattere av denne artikkelen] (2022). Assessing Arctic climate change with the Norwegian Earth System Model. Fulltekst i vitenarkiv
• Gjermundsen, Ada; Nummelin, Aleksi Henrynpoika; Oliviè, Dirk Jan Leo; Bentsen, Mats; Seland, Øyvind & Schulz, Michael (2022). Shutdown of Southern Ocean convection controls long-term greenhouse gas-induced warming. Fulltekst i vitenarkiv
• Oliviè, Dirk Jan Leo; Balkanski, Yves; Bergman, Tommi; Carslaw, Ken; Checa-Garcia, Ramiro & O'Connor, Fiona M [Vis alle 17 forfattere av denne artikkelen] (2022). Impact of natural aerosol uncertainty on anthropogenic aerosol forcing. Fulltekst i vitenarkiv
• Gjermundsen, Ada; Nummelin, Aleksi Henrynpoika; Oliviè, Dirk Jan Leo; Bentsen, Mats; Seland, Øyvind & Schulz, Michael (2021). Shutdown of Southern Ocean convection controls long-term greenhouse gas-induced warming. Fulltekst i vitenarkiv
• Gjermundsen, Ada; Nummelin, Aleksi Henrynpoika; Oliviè, Dirk Jan Leo; Bentsen, Mats; Seland, Øyvind & Schulz, Michael (2021). Shutdown of Southern Ocean convection controls long-term greenhouse gas-induced warming. Fulltekst i vitenarkiv
• Gjermundsen, Ada; Graff, Lise Seland; Bentsen, Mats; Breivik, Lars-Anders; Debernard, Jens Boldingh & Makkonen, Risto [Vis alle 10 forfattere av denne artikkelen] (2021). How representative is Svalbard for future Arctic climate evolution? An Earth system modelling perspective. Fulltekst i vitenarkiv
• He, Yanchun; Gupta, Alok Kumar; Bentsen, Mats; Schulz, Michael; Torsvik, Tomas & Gjermundsen, Ada [Vis alle 9 forfattere av denne artikkelen] (2021). The 3rd iNES NorESM User Workshop. Fulltekst i vitenarkiv Vis sammendrag

  About 15 participants actively involved in the meeting, both physically and virtually on line. There are presentations and hands-on sessions for different topics. The agenda of the workshop is found at the workshop webpage: https://noresmhub.github.io/NorESM_Workshop_2021/

• Gjermundsen, Ada; Graff, Lise Seland; Bentsen, Mats; Breivik, Lars-Anders; Debernard, Jens Boldingh & Makkonen, Risto [Vis alle 10 forfattere av denne artikkelen] (2021). How representative is Svalbard for future Arctic climate evolution? An Earth system modelling perspective. Fulltekst i vitenarkiv
• Gjermundsen, Ada; Nummelin, Aleksi Henrynpoika; Oliviè, Dirk Jan Leo; Bentsen, Mats; Seland, Øyvind & Schulz, Michael (2021). Shutdown of Southern Ocean convection controls long-term greenhouse gas-induced warming. Fulltekst i vitenarkiv
• Oliviè, Dirk Jan Leo; Gjermundsen, Ada; Kirkevåg, Alf; Moseid, Kine Onsum; Schulz, Michael & Seland, Øyvind (2021). Comparing the climate impact of CMIP5 versus CMIP6 aerosol (precursor) emissions in NorESM2. Fulltekst i vitenarkiv
• Gjermundsen, Ada; Bentsen, Mats; Oliviè, Dirk Jan Leo; Seland, Øyvind & Schulz, Michael (2020). Earth System Models. Fulltekst i vitenarkiv
• He, Yanchun; Gupta, Alok Kumar; Bentsen, Mats; Schulz, Michael; Oliviè, Dirk Jan Leo & Torsvik, Tomas [Vis alle 9 forfattere av denne artikkelen] (2020). NorESM User Workshop 2020. Fulltekst i vitenarkiv
• Straume, Eivind Olavson; Gaina, Carmen; Gjermundsen, Ada; Lacasce, Joseph Henry; Klocker, Andreas & Nikurashin, Maxim (2018). Global Miocene paleobathymetry: implications for paleo-ocean circulation. Fulltekst i vitenarkiv
• Gjermundsen, Ada; Lacasce, Joseph Henry & Denstad, Liv (2017). On the thermally-driven ocean circulation with realistic topography. Fulltekst i vitenarkiv
• Nummelin, Aleksi; Broek, Daan van den; Leppänen, Leena; Leppänen, Saara; Merikanto, Joonas & Rantanen, Mika [Vis alle 44 forfattere av denne artikkelen] (2026). A Nordic Perspective on AMOC Tipping. Nordic Council of Ministers. ISSN 9789289384339. doi: 10.6027/temanord2026-504. Fulltekst i vitenarkiv

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