Trond Iversen

• Guo, Jianing; Xie, Xiaoning; Myhre, Gunnar; Shindell, Drew; Kirkevåg, Alf & Iversen, Trond [Vis alle 14 forfattere av denne artikkelen] (2026). Distinct drivers of recent seasonal precipitation increase over Central Asia: roles of anthropogenic aerosols and greenhouse gases. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 26(7), s. 5169–5184. doi: 10.5194/acp-26-5169-2026. Fulltekst i vitenarkiv Vis sammendrag

  Observational evidence reveals a pronounced wetting trend over Central Asia in recent decades, with the most substantial increases occurring during winter and summer. Yet the extent to which the drivers of these changes differ seasonally remains unknown. Here, we use single-forcing experiments from the Precipitation Driver and Response Model Intercomparison Project (PDRMIP) to examine the effects of various external forcings on winter and summer precipitation across Central Asia and to explore the physical mechanisms underlying seasonal precipitation changes. We find that greenhouse gas (GHG) forcing mainly increases winter precipitation by enhancing atmospheric moisture content through warming. In contrast, in summer, Asian sulfate aerosols enhance precipitation by modulating the westerly jet, which strengthens atmospheric moisture transport into the region. Asian black carbon exerts an opposing influence that partially offsets the sulfate-induced effect. Further attribution analysis based on CMIP6 simulations reinforces these sensitivity results and shows that GHG forcing is the primary driver of winter precipitation increases whereas anthropogenic aerosols dominate summer trends. Future CMIP6 projections suggest that under moderate- to high-emission scenarios, winter precipitation will continue to rise due to increasing GHG concentrations, while summer precipitation may decline across much of Central Asia as a result of reduced aerosol emissions following Asian clean air policies. These findings highlight a distinct seasonality in the drivers of recent precipitation increase and suggest a plausible divergence in future winter and summer precipitation trends.

• Myhre, Gunnar; Samset, Bjørn Hallvard; Stjern, Camilla Weum; Hodnebrog, Øivind; Kramer, Ryan & Smith, Chris [Vis alle 16 forfattere av denne artikkelen] (2025). The warming effect of black carbon must be reassessed in light of observational constraints. Cell Reports Sustainability. 2(9), s. 1–11. doi: 10.1016/j.crsus.2025.100428. Fulltekst i vitenarkiv Vis sammendrag

  Anthropogenic emissions of black carbon (BC) aerosols are generally thought to warm the climate. However, the magnitude of this warming remains highly uncertain due to limited knowledge of BC sources; optical properties; and atmospheric processes such as transport, removal, and cloud interactions. Here, we assess and constrain estimates of the historical warming influence of BC using recent observations and emission inventories. Based on simulations from four climate models, we show that the current global mean surface temperature change from anthropogenic BC due to aerosol-radiation interaction spans a factor of three— from +0.02 ± 0.02 K to +0.06 ± 0.05 K. Rapid atmospheric adjustments reduce the instantaneous radiative forcing by nearly 50% (multi-model mean), substantially lowering the net warming. Yet, recent satellite constraints suggest a stronger effect, highlighting the need for a more comprehensive reassessment of BC’s climate influence.

• Guo, Jianing; Xie, Xiaoning; Myhre, Gunnar; Shindell, Drew; Kirkevåg, Alf & Iversen, Trond [Vis alle 12 forfattere av denne artikkelen] (2024). Increased Asian Sulfate Aerosol Emissions Remarkably Enhance Sahel Summer Precipitation. Earth's Future. 12(11), s. 1–15. doi: 10.1029/2024EF004745. Fulltekst i vitenarkiv Vis sammendrag

  Observational evidence shows that Sahel summer precipitation has experienced a considerable increase since the 1980s, coinciding with significant diverging trends of increased sulfate emissions in Asia and decreased emissions in Europe (dipole pattern of aerosols between Asia and Europe). The decrease in European sulfate aerosols has substantial effects on the Sahel summer precipitation increase, but the corresponding effect of increased Asian sulfate is unknown. Multi-model simulations in the Precipitation Driver and Response Model Intercomparison Project (PDRMIP) show, compared to decreased European aerosols, that increased Asian aerosols similarly enhance the Sahel summer precipitation but with different large-scale atmospheric circulation changes. Further analysis of the Sixth Coupled Model Intercomparison Project (CMIP6) simulations under historical attribution and various emission scenarios reinforces the results about the climate impacts of anthropogenic aerosols and suggests that in future scenarios with strong international cooperation and rapid climate mitigations (SSP2-45), the Sahel drought will be intensified likely due to the decline in Asian aerosol emissions. Our results suggest that Asian anthropogenic aerosols are likely a non-negligible driver of the recent recovery in Sahel precipitation amounts.

• Iversen, Emilie Claussen; Hodnebrog, Øivind; Graff, Lise Seland; Nygaard, Bjørn Egil Kringlebotn & Iversen, Trond (2023). Future Winter Precipitation Decreases Associated With the North Atlantic Warming Hole and Reduced Convection. Journal of Geophysical Research (JGR): Atmospheres. ISSN 2169-897X. 128(12). doi: 10.1029/2022JD038374. Fulltekst i vitenarkiv Vis sammendrag

  Climate projections in the North Atlantic region suffer from great uncertainties, and projections of precipitation are given with a large spread. Some of this uncertainty is related to projections of the North Atlantic warming hole (NAWH). The Community Earth System Model version 2 (CESM2) projects a relatively strong and extensive NAWH, with future sea surface cooling extending to Northern Scandinavia. This study investigates the relatively large winter precipitation decrease projected by CESM2 in the northeastern North Atlantic region, reinforced in a regional model. Three future scenarios from CESM2 are dynamically downscaled with the Weather Research and Forecast model. A methodology to separate convective and orographic from stratiform precipitation is applied to explore the physical mechanisms. Changes in stratiform precipitation closely relate to storm-track changes, which varies between the scenarios. Convective precipitation decreases by up to 50% over the Norwegian Sea at the end of the century, which is robust across the scenarios. This is explained by the underlying reduced sea surface temperatures of the NAWH, leading to reduced evaporation and reduced convective activity and intensity. The orographic precipitation maximum over the Scandinavian mountains is shifted upstream, likely affected by increased static stability and flow blocking, which also relates to the NAWH. This shift is possibly also explained by more frequent rain versus snow, as well as reduced cross-barrier wind speeds. This study contributes to highlight the importance of focusing future research efforts on the NAWH, in order to constrain future climate projections in this region.

• Myhre, Gunnar; Samset, Bjørn Hallvard; Forster, Piers M.; Hodnebrog, Øivind; Sandstad, Marit & Mohr, Christian Wilhelm [Vis alle 29 forfattere av denne artikkelen] (2022). Scientific data from precipitation driver response model intercomparison project. Scientific Data. 9. doi: 10.1038/s41597-022-01194-9. Fulltekst i vitenarkiv Vis sammendrag

  This data descriptor reports the main scientific values from General Circulation Models (GCMs) in the Precipitation Driver and Response Model Intercomparison Project (PDRMIP). The purpose of the GCM simulations has been to enhance the scientific understanding of how changes in greenhouse gases, aerosols, and incoming solar radiation perturb the Earth’s radiation balance and its climate response in terms of changes in temperature and precipitation. Here we provide global and annual mean results for a large set of coupled atmospheric-ocean GCM simulations and a description of how to easily extract files from the dataset. The simulations consist of single idealized perturbations to the climate system and have been shown to achieve important insight in complex climate simulations. We therefore expect this data set to be valuable and highly used to understand simulations from complex GCMs and Earth System Models for various phases of the Coupled Model Intercomparison Project.

• 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.

• Stjern, Camilla Weum; Samset, Bjørn Hallvard; Boucher, Olivier; Iversen, Trond; Lamarque, Jean-Francois & Myhre, Gunnar [Vis alle 8 forfattere av denne artikkelen] (2020). How aerosols and greenhouse gases influence the diurnal temperature range. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 20(21), s. 13467–13480. doi: 10.5194/acp-20-13467-2020. Fulltekst i vitenarkiv Vis sammendrag

  The diurnal temperature range (DTR) (or difference between the maximum and minimum temperature within a day) is one of many climate parameters that affects health, agriculture and society. Understanding how DTR evolves under global warming is therefore crucial. Physically different drivers of climate change, such as greenhouse gases and aerosols, have distinct influences on global and regional climate. Therefore, predicting the future evolution of DTR requires knowledge of the effects of individual climate forcers, as well as of the future emissions mix, in particular in high-emission regions. Using global climate model simulations from the Precipitation Driver and Response Model Intercomparison Project (PDRMIP), we investigate how idealized changes in the atmospheric levels of a greenhouse gas (CO2) and aerosols (black carbon and sulfate) influence DTR (globally and in selected regions). We find broad geographical patterns of annual mean change that are similar between climate drivers, pointing to a generalized response to global warming which is not defined by the individual forcing agents. Seasonal and regional differences, however, are substantial, which highlights the potential importance of local background conditions and feedbacks. While differences in DTR responses among drivers are minor in Europe and North America, there are distinctly different DTR responses to aerosols and greenhouse gas perturbations over India and China, where present aerosol emissions are particularly high. BC induces substantial reductions in DTR, which we attribute to strong modeled BC-induced cloud responses in these regions.

• Boy, Michael; Thomson, Erik S.; Navarro, Juan-Camilo Acosta; Arnalds, Olafur; Batchvarova, Ekaterina & Bäck, Jaana [Vis alle 63 forfattere av denne artikkelen] (2019). Interactions between the atmosphere, cryosphere, and ecosystems at northern high latitudes. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 19, s. 2015–2061. doi: 10.5194/acp-19-2015-2019. Fulltekst i vitenarkiv Vis sammendrag

  The Nordic Centre of Excellence CRAICC (Cryosphere–Atmosphere Interactions in a Changing Arctic Climate), funded by NordForsk in the years 2011–2016, is the largest joint Nordic research and innovation initiative to date, aiming to strengthen research and innovation regarding climate change issues in the Nordic region. CRAICC gathered more than 100 scientists from all Nordic countries in a virtual centre with the objectives of identifying and quantifying the major processes controlling Arctic warming and related feedback mechanisms, outlining strategies to mitigate Arctic warming, and developing Nordic Earth system modelling with a focus on short-lived climate forcers (SLCFs), including natural and anthropogenic aerosols. The outcome of CRAICC is reflected in more than 150 peer-reviewed scientific publications, most of which are in the CRAICC special issue of the journal Atmospheric Chemistry and Physics. This paper presents an overview of the main scientific topics investigated in the centre and provides the reader with a state-of-the-art comprehensive summary of what has been achieved in CRAICC with links to the particular publications for further detail. Faced with a vast amount of scientific discovery, we do not claim to completely summarize the results from CRAICC within this paper, but rather concentrate here on the main results which are related to feedback loops in climate change–cryosphere interactions that affect Arctic amplification.

• Landgren, Oskar Andreas; Seierstad, Ivar A. & Iversen, Trond (2019). Projected future changes in Marine Cold-Air Outbreaks associated with Polar Lows in the Northern North-Atlantic Ocean. Climate Dynamics. ISSN 0930-7575. doi: 10.1007/s00382-019-04642-2. Fulltekst i vitenarkiv Vis sammendrag

  Marine Cold-Air Outbreaks (MCAO) can be used as a large-scale measure of the potential for development of Polar Lows in the Northern North Atlantic Ocean during NH winter. We applied an MCAO index to 30 members of the Community Earth System Model Large Ensemble to investigate model-projected future changes in the Nordic and Barents Seas in response to anthropogenic climate change. In agreement with previous studies we found an overall decrease in the MCAO index due to increased tropospheric static stability. We also found a changed seasonal profile, with a stronger decrease in December–January than in February–March, effectively leading to the peak occurring in February rather than January in the Nordic Seas. In the Barents Sea, the reductions were only statistically significant in the autumn and spring, with the winter reduction due to increased static stability was partly balanced by a retracting sea-ice edge. The contribution from circulation changes in mean sea-level pressure was assessed by a cluster analysis in lower-dimensional phase-space, spanned by the projections onto the four leading Empirical Orthogonal Functions. While there was a small but statistically significant increase of the Atlantic Ridge-like pattern, the overall changes in MCAO were dominated by changes in temperature at the sea surface and aloft.

• Landgren, Oskar Andreas; Batrak, Yurii; Haugen, Jan Erik; Støylen, Eivind & Iversen, Trond (2019). Polar low variability and future projections for the Nordic and Barents Seas. Quarterly Journal of the Royal Meteorological Society. ISSN 0035-9009. 145, s. 3116–3128. doi: 10.1002/qj.3608. Fulltekst i vitenarkiv Vis sammendrag

  Polar lows are intense mesoscale cyclones occurring during winter over open sea areas in certain polar sub‐regions. Due to their small size, they are not explicitly represented in present global climate models or Earth system models. In this study 18 members of the CESM Large Ensemble were dynamically downscaled to ∼12 km horizontal mesh width using the quasi‐hydrostatic ALARO model within the HARMONIE script system in climate mode (HCLIM‐ALARO). The domain covers the Nordic and Barents Seas. One historical and two future time‐periods were selected. For validation, the ERA‐Interim reanalysis was also downscaled. A cyclone‐tracking algorithm was used to identify tracks of individual polar lows. Their frequency of occurrence, lifetime, and maximum relative vorticity were estimated. Relative to ERA‐Interim, the historical frequency of occurrence of polar lows was slightly overestimated in the Nordic Seas and underestimated in the Barents Sea, which is likely due to positive biases in sea‐surface temperature and sea‐ice concentration. For future climate projections, the regions of polar low genesis are diagnosed to move northwards in accordance with the sea‐ice retreat. In the Nordic Seas, the number of polar lows decreases at the beginning of the season, while there is an increase in March. In the Barents Sea, a February–April increase in the occurrence of polar lows is seen.

• Stjern, Camilla Weum; Lund, Marianne Tronstad; Samset, Bjørn Hallvard; Myhre, Gunnar; Forster, Piers M. & Andrews, Timothy [Vis alle 22 forfattere av denne artikkelen] (2019). Arctic Amplification Response to Individual Climate Drivers. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 124(13), s. 6698–6717. doi: 10.1029/2018JD029726. Fulltekst i vitenarkiv Vis sammendrag

  The Arctic is experiencing rapid climate change in response to changes in greenhouse gases, aerosols, and other climate drivers. Emission changes in general, as well as geographical shifts in emissions and transport pathways of short‐lived climate forcers, make it necessary to understand the influence of each climate driver on the Arctic. In the Precipitation Driver Response Model Intercomparison Project, 10 global climate models perturbed five different climate drivers separately (CO2, CH4, the solar constant, black carbon, and SO4). We show that the annual mean Arctic amplification (defined as the ratio between Arctic and the global mean temperature change) at the surface is similar between climate drivers, ranging from 1.9 (± an intermodel standard deviation of 0.4) for the solar to 2.3 (±0.6) for the SO4 perturbations, with minimum amplification in the summer for all drivers. The vertical and seasonal temperature response patterns indicate that the Arctic is warmed through similar mechanisms for all climate drivers except black carbon. For all drivers, the precipitation change per degree global temperature change is positive in the Arctic, with a seasonality following that of the Arctic amplification. We find indications that SO4 perturbations produce a slightly stronger precipitation response than the other drivers, particularly compared to CO2.

• Tang, Tao; Shindell, D; Faluvegi, G.; Myhre, Gunnar; Oliviè, Dirk Jan Leo & Voulgarakis, A. [Vis alle 19 forfattere av denne artikkelen] (2019). Comparison of Effective Radiative Forcing Calculations Using Multiple Methods, Drivers, and Models. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 124(8), s. 4382–4394. doi: 10.1029/2018JD030188. Fulltekst i vitenarkiv Vis sammendrag

  We compare six methods of estimating effective radiative forcing (ERF) using a set of atmosphere‐ocean general circulation models. This is the first multiforcing agent, multimodel evaluation of ERF values calculated using different methods. We demonstrate that previously reported apparent consistency between the ERF values derived from fixed sea surface temperature simulations and linear regression holds for most climate forcings, excluding black carbon (BC). When land adjustment is accounted for, however, the fixed sea surface temperature ERF values are generally 10–30% larger than ERFs derived using linear regression across all forcing agents, with a much larger (~70–100%) discrepancy for BC. Except for BC, this difference can be largely reduced by either using radiative kernel techniques or by exponential regression. Responses of clouds and their effects on shortwave radiation show the strongest variability in all experiments, limiting the application of regression‐based ERF in small forcing simulations.

• Graff, Lise Seland; Iversen, Trond; Bethke, Ingo; Debernard, Jens Boldingh; Seland, Øyvind & Bentsen, Mats [Vis alle 9 forfattere av denne artikkelen] (2019). Arctic amplification under global warming of 1.5 and 2 °C in NorESM1-Happi. Earth System Dynamics (ESD). ISSN 2190-4979. 10(3), s. 569–598. doi: 10.5194/esd-10-569-2019. Fulltekst i vitenarkiv Vis sammendrag

  Differences between a 1.5 and 2.0 ∘C warmer climate than 1850 pre-industrial conditions are investigated using a suite of uncoupled (Atmospheric Model Intercomparison Project; AMIP), fully coupled, and slab-ocean experiments performed with Norwegian Earth System Model (NorESM1)-Happi, an upgraded version of NorESM1-M. The data from the AMIP-type runs with prescribed sea-surface temperatures (SSTs) and sea ice were provided to a model intercomparison project (HAPPI – Half a degree Additional warming, Prognosis and Projected Impacts; http://www.happimip.org/, last access date: 14 September 2019). This paper compares the AMIP results to those from the fully coupled version and the slab-ocean version of the model (NorESM1-HappiSO) in which SST and sea ice are allowed to respond to the warming, focusing on Arctic amplification of the global change signal. The fully coupled and the slab-ocean runs generally show stronger responses than the AMIP runs in the warmer worlds. The Arctic polar amplification factor is stronger in the fully coupled and slab-ocean runs than in the AMIP runs, both in the 1.5 ∘C warming run and with the additional 0.5 ∘C warming. The low-level Equator-to-pole temperature gradient consistently weakens more between the present-day climate and the 1.5 ∘C warmer climate in the experiments with an active ocean component. The magnitude of the upper-level Equator-to-pole temperature gradient increases in a warmer climate but is not systematically larger in the experiments with an active ocean component. Implications for storm tracks and blocking are investigated. We find considerable reductions in the Arctic sea-ice cover in the slab-ocean model runs; while ice-free summers are rare under 1.5 ∘C warming, they occur 18 % of the time in the 2.0 ∘C warming simulation. The fully coupled model does not, however, reach ice-free conditions as it is too cold and has too much ice in the present-day climate. Differences between the experiments with active ocean and sea-ice models and those with prescribed SSTs and sea ice can be partially due to ocean and sea-ice feedbacks that are neglected in the latter case but can also in part be due to differences in the experimental setup.

• Liu, L.; Shawki, Dilshad; Voulgarakis, Apostolos; Kasoar, Matthew; Samset, Bjørn Hallvard & Myhre, Gunnar [Vis alle 19 forfattere av denne artikkelen] (2018). A PDRMIP Multimodel study on the impacts of regional aerosol forcings on global and regional precipitation. Journal of Climate. ISSN 0894-8755. 31(11), s. 4429–4447. doi: 10.1175/JCLI-D-17-0439.1. Fulltekst i vitenarkiv
• Kirkevåg, Alf; Grini, Alf; Oliviè, Dirk Jan Leo; Seland, Øyvind; Alterskjær, Kari & Hummel, Matthias [Vis alle 14 forfattere av denne artikkelen] (2018). A production-tagged aerosol module for earth system models, OsloAero5.3-extensions and updates for CAM5.3-Oslo. Geoscientific Model Development. ISSN 1991-959X. 11(10), s. 3945–3982. doi: 10.5194/gmd-11-3945-2018. Fulltekst i vitenarkiv Vis sammendrag

  We document model updates and present and discuss modeling and validation results from a further developed production-tagged aerosol module, OsloAero5.3, for use in Earth system models. The aerosol module has in this study been implemented and applied in CAM5.3-Oslo. This model is based on CAM5.3–CESM1.2 and its own predecessor model version CAM4-Oslo. OsloAero5.3 has improved treatment of emissions, aerosol chemistry, particle life cycle, and aerosol–cloud interactions compared to its predecessor OsloAero4.0 in CAM4-Oslo. The main new features consist of improved aerosol sources; the module now explicitly accounts for aerosol particle nucleation and secondary organic aerosol production, with new emissions schemes also for sea salt, dimethyl sulfide (DMS), and marine primary organics. Mineral dust emissions are updated as well, adopting the formulation of CESM1.2. The improved model representation of aerosol–cloud interactions now resolves heterogeneous ice nucleation based on black carbon (BC) and mineral dust calculated by the model and treats the activation of cloud condensation nuclei (CCN) as in CAM5.3. Compared to OsloAero4.0 in CAM4-Oslo, the black carbon (BC) mass concentrations are less excessive aloft, with a better fit to observations. Near-surface mass concentrations of BC and sea salt aerosols are also less biased, while sulfate and mineral dust are slightly more biased. Although appearing quite similar for CAM5.3-Oslo and CAM4-Oslo, the validation results for organic matter (OM) are inconclusive, since both of the respective versions of OsloAero are equipped with a limited number of OM tracers for the sake of computational efficiency. Any information about the assumed mass ratios of OM to organic carbon (OC) for different types of OM sources is lost in the transport module. Assuming that observed OC concentrations scaled by 1.4 are representative for the modeled OM concentrations, CAM5.3-Oslo with OsloAero5.3 is slightly inferior for the very sparsely available observation data. Comparing clear-sky column-integrated optical properties with data from ground-based remote sensing, we find a negative bias in optical depth globally; however, it is not as strong as in CAM4-Oslo, but has positive biases in some areas typically dominated by mineral dust emissions. Aerosol absorption has a larger negative bias than the optical depth globally. This is reflected in a lower positive bias in areas where mineral dust is the main contributor to absorption. Globally, the low bias in absorption is smaller than in CAM4-Oslo. The Ångström parameter exhibits small biases both globally and regionally, suggesting that the aerosol particle sizes are reasonably well represented. Cloud-top droplet number concentrations over oceans are generally underestimated compared to satellite retrievals, but seem to be overestimated downwind of major emissions of dust and biomass burning sources. Finally, we find small changes in direct radiative forcing at the top of the atmosphere, while the cloud radiative forcing due to anthropogenic aerosols is now more negative than in CAM4-Oslo, being on the strong side compared to the multi-model estimate in IPCC AR5. Although not all validation results in this study show improvement for the present CAM5.3-Oslo version, the extended and updated aerosol module OsloAero5.3 is more advanced and applicable than its predecessor OsloAero4.0, as it includes new parameterizations that more readily facilitate sensitivity and process studies and use in climate and Earth system model studies in general.

• Karset, Inger Helene H.; Berntsen, Terje Koren; Storelvmo, Trude; Alterskjær, Kari; Grini, Alf & Oliviè, Dirk Jan Leo [Vis alle 10 forfattere av denne artikkelen] (2018). Strong impacts on aerosol indirect effects from historical oxidant changes. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 18(10), s. 7669–7690. doi: 10.5194/acp-18-7669-2018. Fulltekst i vitenarkiv Vis sammendrag

  Uncertainties in effective radiative forcings through aerosol–cloud interactions (ERFaci, also called aerosol indirect effects) contribute strongly to the uncertainty in the total preindustrial-to-present-day anthropogenic forcing. Some forcing estimates of the total aerosol indirect effect are so negative that they even offset the greenhouse gas forcing. This study highlights the role of oxidants in modeling of preindustrial-to-present-day aerosol indirect effects. We argue that the aerosol precursor gases should be exposed to oxidants of its era to get a more correct representation of secondary aerosol formation. Our model simulations show that the total aerosol indirect effect changes from −1.32 to −1.07 W m−2 when the precursor gases in the preindustrial simulation are exposed to preindustrial instead of present-day oxidants. This happens because of a brightening of the clouds in the preindustrial simulation, mainly due to large changes in the nitrate radical (NO3). The weaker oxidative power of the preindustrial atmosphere extends the lifetime of the precursor gases, enabling them to be transported higher up in the atmosphere and towards more remote areas where the susceptibility of the cloud albedo to aerosol changes is high. The oxidation changes also shift the importance of different chemical reactions and produce more condensate, thus increasing the size of the aerosols and making it easier for them to activate as cloud condensation nuclei.

• Tang, Tao; Shindell, Drew; Samset, Bjørn Hallvard; Boucher, Olivier; Forster, Piers M. & Hodnebrog, Øivind [Vis alle 21 forfattere av denne artikkelen] (2018). Dynamical response of Mediterranean precipitation to greenhouse gases and aerosols. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 18(11), s. 8439–8452. doi: 10.5194/acp-18-8439-2018. Fulltekst i vitenarkiv Vis sammendrag

  Atmospheric aerosols and greenhouse gases affect cloud properties, radiative balance and, thus, the hydrological cycle. Observations show that precipitation has decreased in the Mediterranean since the beginning of the 20th century, and many studies have investigated possible mechanisms. So far, however, the effects of aerosol forcing on Mediterranean precipitation remain largely unknown. Here we compare the modeled dynamical response of Mediterranean precipitation to individual forcing agents in a set of global climate models (GCMs). Our analyses show that both greenhouse gases and aerosols can cause drying in the Mediterranean and that precipitation is more sensitive to black carbon (BC) forcing than to well-mixed greenhouse gases (WMGHGs) or sulfate aerosol. In addition to local heating, BC appears to reduce precipitation by causing an enhanced positive sea level pressure (SLP) pattern similar to the North Atlantic Oscillation–Arctic Oscillation, characterized by higher SLP at midlatitudes and lower SLP at high latitudes. WMGHGs cause a similar SLP change, and both are associated with a northward diversion of the jet stream and storm tracks, reducing precipitation in the Mediterranean while increasing precipitation in northern Europe. Though the applied forcings were much larger, if forcings are scaled to those of the historical period of 1901–2010, roughly one-third (31±17 %) of the precipitation decrease would be attributable to global BC forcing with the remainder largely attributable to WMGHGs, whereas global scattering sulfate aerosols would have negligible impacts. Aerosol–cloud interactions appear to have minimal impacts on Mediterranean precipitation in these models, at least in part because many simulations did not fully include such processes; these merit further study. The findings from this study suggest that future BC and WMGHG emissions may significantly affect regional water resources, agricultural practices, ecosystems and the economy in the Mediterranean region

• Li, Camille; Michel, Clio; Graff, Lise Seland; Bethke, Ingo; Zappa, Guiseppe & Bracegirdle, Thomas J. [Vis alle 17 forfattere av denne artikkelen] (2018). Midlatitude atmospheric circulation responses under 1.5°C and 2.0°C warming and implications for regional impacts. Earth System Dynamics (ESD). ISSN 2190-4979. 9(2), s. 359–382. doi: 10.5194/esd-9-359-2018. Fulltekst i vitenarkiv Vis sammendrag

  This study investigates the global response of the midlatitude atmospheric circulation to 1.5 and 2.0C of warming using the HAPPI (Half a degree Additional warming, Prognosis and Projected Impacts) ensemble, with a focus on the winter season. Characterising and understanding this response is critical for accu- rately assessing the near-term regional impacts of climate change and the benefits of limiting warming to 1.5C above pre-industrial levels, as advocated by the Paris Agreement of the United Nations Framework Convention on Climate Change (UNFCCC). The HAPPI experimental design allows an assessment of uncertainty in the cir- culation response due to model dependence and internal variability. Internal variability is found to dominate the multi-model mean response of the jet streams, storm tracks, and stationary waves across most of the midlatitudes; larger signals in these features are mostly consistent with those seen in more strongly forced warming scenarios. Signals that emerge in the 1.5 ◦C experiment are a weakening of storm activity over North America, an inland shift of the North American stationary ridge, an equatorward shift of the North Pacific jet exit, and an equator- ward intensification of the South Pacific jet. Signals that emerge under an additional 0.5 ◦C of warming include a poleward shift of the North Atlantic jet exit, an eastward extension of the North Atlantic storm track, and an intensification on the flanks of the Southern Hemisphere storm track. Case studies explore the implications of these circulation responses for precipitation impacts in the Mediterranean, in western Europe, and on the North American west coast, paying particular attention to possible outcomes at the tails of the response distributions. For example, the projected weakening of the Mediterranean storm track emerges in the 2 ◦C warmer world, with exceptionally dry decades becoming 5 times more likely.

• Stjern, Camilla Weum; Samset, Bjørn Hallvard; Myhre, Gunnar; Forster, Piers M.; Hodnebrog, Øivind & Andrews, Timothy [Vis alle 20 forfattere av denne artikkelen] (2017). Rapid Adjustments Cause Weak Surface Temperature Response to Increased Black Carbon Concentrations. Journal of Geophysical Research (JGR): Atmospheres. ISSN 2169-897X. 122(21), s. 11,462–11,481. doi: 10.1002/2017JD027326. Fulltekst i vitenarkiv
• Sand, Maria; Samset, Bjørn Hallvard; Balkanski, Yves; Bauer, Susanne; Bellouin, Nicolas & Berntsen, Terje Koren [Vis alle 29 forfattere av denne artikkelen] (2017). Aerosols at the poles: an AeroCom Phase II multi-model evaluation. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 17(19), s. 12197–12218. doi: 10.5194/acp-17-12197-2017. Fulltekst i vitenarkiv Vis sammendrag

  Atmospheric aerosols from anthropogenic and natural sources reach the polar regions through long-range transport and affect the local radiation balance. Such transport is, however, poorly constrained in present-day global climate models, and few multi-model evaluations of polar anthropogenic aerosol radiative forcing exist. Here we compare the aerosol optical depth (AOD) at 550nm from simulations with 16 global aerosol models from the AeroCom Phase II model intercomparison project with available observations at both poles. We show that the annual mean multi-model median is representative of the observations in Arctic, but that the intermodel spread is large. We also document the geographical distribution and seasonal cycle of the AOD for the individual aerosol species: black carbon (BC) from fossil fuel and biomass burning, sulfate, organic aerosols (OAs), dust, and sea-salt. For a subset of models that represent nitrate and secondary organic aerosols (SOAs), we document the role of these aerosols at high latitudes. The seasonal dependence of natural and anthropogenic aerosols differs with natural aerosols peaking in winter (sea-salt) and spring (dust), whereas AOD from anthropogenic aerosols peaks in late spring and summer. The models produce a median annual mean AOD of 0.07 in the Arctic (defined here as north of 60°N). The models also predict a noteworthy aerosol transport to the Antarctic (south of 70°S) with a resulting AOD varying between 0.01 and 0.02. The models have estimated the shortwave anthropogenic radiative forcing contributions to the direct aerosol effect (DAE) associated with BC and OA from fossil fuel and biofuel (FF), sulfate, SOAs, nitrate, and biomass burning from BC and OA emissions combined. The Arctic modelled annual mean DAE is slightly negative (−0.12W m−2), dominated by a positive BC FF DAE in spring and a negative sulfate DAE in summer. The Antarctic DAE is governed by BC FF. We perform sensitivity experiments with one of the AeroCom models (GISS modelE) to investigate how regional emissions of BC and sulfate and the lifetime of BC influence the Arctic and Antarctic AOD. A doubling of emissions in eastern Asia results in a 33% increase in Arctic AOD of BC. A doubling of the BC lifetime results in a 39% increase in Arctic AOD of BC. However, these radical changes still fall within the AeroCom model range.

• Mitchell, Daniel A.; AchutaRao, Krishna; Allen, Myles; Bethke, Ingo; Beyerle, Urs & Ciavarella, Andrew [Vis alle 27 forfattere av denne artikkelen] (2017). Half a degree additional warming, prognosis and projected impacts (HAPPI): Background and experimental design. Geoscientific Model Development. ISSN 1991-959X. 10(2), s. 571–583. doi: 10.5194/gmd-10-571-2017. Fulltekst i vitenarkiv Vis sammendrag

  The Intergovernmental Panel on Climate Change (IPCC) has accepted the invitation from the UNFCCC to provide a special report on the impacts of global warming of 1.5 °C above pre-industrial levels and on related global greenhouse-gas emission pathways. Many current experiments in, for example, the Coupled Model Inter-comparison Project (CMIP), are not specifically designed for informing this report. Here, we document the design of the half a degree additional warming, projections, prognosis and impacts (HAPPI) experiment. HAPPI provides a framework for the generation of climate data describing how the climate, and in particular extreme weather, might differ from the present day in worlds that are 1.5 and 2.0 °C warmer than pre-industrial conditions. Output from participating climate models includes variables frequently used by a range of impact models. The key challenge is to separate the impact of an additional approximately half degree of warming from uncertainty in climate model responses and internal climate variability that dominate CMIP-style experiments under low-emission scenarios. Large ensembles of simulations (>  50 members) of atmosphere-only models for three time slices are proposed, each a decade in length: the first being the most recent observed 10-year period (2006–2015), the second two being estimates of a similar decade but under 1.5 and 2 °C conditions a century in the future. We use the representative concentration pathway 2.6 (RCP2.6) to provide the model boundary conditions for the 1.5 °C scenario, and a weighted combination of RCP2.6 and RCP4.5 for the 2 °C scenario.

• Koffi, Brigitte; Schulz, Michael; Bréon, François-Marie; Dentener, Frank; Steensen, Birthe Marie Rødssæteren & Griesfeller, Jan [Vis alle 33 forfattere av denne artikkelen] (2016). Evaluation of the aerosol vertical distribution in global aerosol models through comparison against CALIOP measurements: AeroCom phase II results. Journal of Geophysical Research (JGR): Atmospheres. ISSN 2169-897X. 121(12), s. 7254–7283. doi: 10.1002/2015JD024639. Fulltekst i vitenarkiv Vis sammendrag

  The ability of 11 models in simulating the aerosol vertical distribution from regional to global scales, as part of the second phase of the AeroCom model intercomparison initiative (AeroCom II), is assessed and compared to results of the first phase. The evaluation is performed using a global monthly gridded data set of aerosol extinction profiles built for this purpose from the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) Layer Product 3.01. Results over 12 subcontinental regions show that five models improved, whereas three degraded in reproducing the interregional variability in Zα0–6 km, the mean extinction height diagnostic, as computed from the CALIOP aerosol profiles over the 0–6 km altitude range for each studied region and season. While the models' performance remains highly variable, the simulation of the timing of the Zα0–6 km peak season has also improved for all but two models from AeroCom Phase I to Phase II. The biases in Zα0–6 km are smaller in all regions except Central Atlantic, East Asia, and North and South Africa. Most of the models now underestimate Zα0–6 km over land, notably in the dust and biomass burning regions in Asia and Africa. At global scale, the AeroCom II models better reproduce the Zα0–6 km latitudinal variability over ocean than over land. Hypotheses for the performance and evolution of the individual models and for the intermodel diversity are discussed. We also provide an analysis of the CALIOP limitations and uncertainties contributing to the differences between the simulations and observations.

• Kipling, Zak; Stier, Philip; Johnson, Colin E.; Mann, Graham W.; Bellouin, Nicolas & Bauer, Susanne E. [Vis alle 24 forfattere av denne artikkelen] (2016). What controls the vertical distribution of aerosol? Relationships between process sensitivity in HadGEM3-UKCA and inter-model variation from AeroCom Phase II. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 16(4), s. 2221–2241. doi: 10.5194/acp-16-2221-2016. Fulltekst i vitenarkiv Vis sammendrag

  he vertical profile of aerosol is important for its radiative effects, but weakly constrained by observations on the global scale, and highly variable among different models. To investigate the controlling factors in one particular model, we investigate the effects of individual processes in HadGEM3–UKCA and compare the resulting diversity of aerosol vertical profiles with the inter-model diversity from the AeroCom Phase II control experiment. In this way we show that (in this model at least) the vertical profile is controlled by a relatively small number of processes, although these vary among aerosol components and particle sizes. We also show that sufficiently coarse variations in these processes can produce a similar diversity to that among different models in terms of the global-mean profile and, to a lesser extent, the zonal-mean vertical position. However, there are features of certain models' profiles that cannot be reproduced, suggesting the influence of further structural differences between models. In HadGEM3–UKCA, convective transport is found to be very important in controlling the vertical profile of all aerosol components by mass. In-cloud scavenging is very important for all except mineral dust. Growth by condensation is important for sulfate and carbonaceous aerosol (along with aqueous oxidation for the former and ageing by soluble material for the latter). The vertical extent of biomass-burning emissions into the free troposphere is also important for the profile of carbonaceous aerosol. Boundary-layer mixing plays a dominant role for sea salt and mineral dust, which are emitted only from the surface. Dry deposition and below-cloud scavenging are important for the profile of mineral dust only. In this model, the microphysical processes of nucleation, condensation and coagulation dominate the vertical profile of the smallest particles by number (e.g. total CN  >  3 nm), while the profiles of larger particles (e.g. CN  >  100 nm) are controlled by the same processes as the component mass profiles, plus the size distribution of primary emissions. We also show that the processes that affect the AOD-normalised radiative forcing in the model are predominantly those that affect the vertical mass distribution, in particular convective transport, in-cloud scavenging, aqueous oxidation, ageing and the vertical extent of biomass-burning emissions.

• Jung, Thomas; Iversen, Trond; Gordon, Neil D.; Bauer, Peter; Bromwich, David H. & Chevallier, Mattheu [Vis alle 26 forfattere av denne artikkelen] (2016). ADVANCING POLAR PREDICTION CAPABILITIES ON DAILY TO SEASONAL TIME SCALES. Bulletin of The American Meteorological Society - (BAMS). ISSN 0003-0007. s. 1632–1647. doi: 10.1175/BAMS-D-14-00246.1. Fulltekst i vitenarkiv
• Navarro, Juan-Camilo Acosta; Ekman, Annica; Pausata, Francesco S. Rocco; Lewinschal, Anna; Varma, Vidya & Seland, Øyvind [Vis alle 11 forfattere av denne artikkelen] (2016). Future response of temperature and precipitation to reduced aerosol emissions as compared with increased greenhouse gas concentrations. Journal of Climate. ISSN 0894-8755. 30(3), s. 939–954. doi: 10.1175/JCLI-D-16-0466.1. Fulltekst i vitenarkiv
• Myhre, Gunnar; Forster, Piers M.; Samset, Bjørn Hallvard; Hodnebrog, Øivind; Sillmann, Jana & Aalbergsjø, Siv Gundrosen [Vis alle 23 forfattere av denne artikkelen] (2016). PDRMIP: A precipitation driver and response model intercomparison project-protocol and preliminary results. Bulletin of The American Meteorological Society - (BAMS). ISSN 0003-0007. 98(6), s. 1185–1198. doi: 10.1175/BAMS-D-16-0019.1. Fulltekst i vitenarkiv Vis sammendrag

  PDRMIP investigates the role of various drivers of climate change for mean and extreme precipitation changes, based on multiple climate model output and energy budget analyses. As the global temperature increases with changing climate, precipitation rates and patterns are affected through a wide range of physical mechanisms. The globally averaged intensity of extreme precipitation also changes more rapidly than the globally averaged precipitation rate. While some aspects of the regional variation in precipitation predicted by climate models appear robust, there is still a large degree of inter-model differences unaccounted for. Individual drivers of climate change initially alter the energy budget of the atmosphere leading to distinct rapid adjustments involving changes in precipitation. Differences in how these rapid adjustment processes manifest themselves within models are likely to explain a large fraction of the present model spread and needs better quantifications to improve precipitation predictions. Here, we introduce the Precipitation Driver and Response Model Intercomparison Project (PDRMIP), where a set of idealized experiments designed to understand the role of different climate forcing mechanisms were performed by a large set of climate models. PDRMIP focuses on understanding how precipitation changes relating to rapid adjustments and slower responses to climate forcings are represented across models. Initial results show that rapid adjustments account for large regional differences in hydrological sensitivity across multiple drivers. The PDRMIP results are expected to dramatically improve our understanding of the causes of the present diversity in future climate projections.

• Cassiani, Massimo; Stohl, Andreas; Oliviè, Dirk Jan Leo; Seland, Øyvind; Bethke, Ingo & Pisso, Ignacio [Vis alle 7 forfattere av denne artikkelen] (2016). The offline Lagrangian particle model FLEXPART-NorESM/CAM (v1): Model description and comparisons with the online NorESM transport scheme and with the reference FLEXPART model. Geoscientific Model Development. ISSN 1991-959X. 9(11), s. 4029–4048. doi: 10.5194/gmd-9-4029-2016. Fulltekst i vitenarkiv
• Navarro, Juan-Camilo Acosta; Varma, Vidya; Riipinen, Ilona; Seland, Øyvind; Kirkevåg, Alf & Struthers, Hamish [Vis alle 9 forfattere av denne artikkelen] (2016). Amplification of Arctic warming by past air pollution reductions in Europe. Nature Geoscience. ISSN 1752-0894. 9(4), s. 277–281. doi: 10.1038/ngeo2673. Fulltekst i vitenarkiv
• Ao, Chi O.; Jiang, Jonathan H.; Mannucci, Anthony J.; Su, Hui; Verkhoglyadova, Olga & Zhai, Chengxing [Vis alle 13 forfattere av denne artikkelen] (2015). Evaluation of CMIP5 upper troposphere and lower stratosphere geopotential height with GPS radio occultation observations. Journal of Geophysical Research (JGR): Biogeosciences. ISSN 2169-8953. 120(5), s. 1678–1689. doi: 10.1002/2014JD022239. Fulltekst i vitenarkiv
• Sand, Maria; Iversen, Trond; Bohlinger, Patrik; Kirkevåg, Alf; Seierstad, Ivar Ambjørn & Seland, Øyvind [Vis alle 7 forfattere av denne artikkelen] (2015). A standardised global climate model study showing unique properties for the climate response to black carbon aerosols. Journal of Climate. ISSN 0894-8755. 28(6), s. 2512–2526. doi: 10.1175/JCLI-D-14-00050.1. Fulltekst i vitenarkiv
• Jiao, C; Flanner, M; Balkanski, Y; Bauer, S.; Bellouin, N & Berntsen, Terje Koren [Vis alle 29 forfattere av denne artikkelen] (2014). An aerocom assessment of black carbon in Arctic snow and sea ice. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 14(5), s. 2399–2417. doi: 10.5194/acp-14-2399-2014. Fulltekst i vitenarkiv Vis sammendrag

  Though many global aerosols models prognose surface deposition, only a few models have been used to directly simulate the radiative effect from black carbon (BC) deposition to snow and sea ice. Here, we apply aerosol deposition fields from 25 models contributing to two phases of the Aerosol Comparisons between Observations and Models (AeroCom) project to simulate and evaluate within-snow BC concentrations and radiative effect in the Arctic. We accomplish this by driving the offline land and sea ice components of the Community Earth System Model with different deposition fields and meteorological conditions from 2004 to 2009, during which an extensive field campaign of BC measurements in Arctic snow occurred. We find that models generally underestimate BC concentrations in snow in northern Russia and Norway, while overestimating BC amounts elsewhere in the Arctic. Although simulated BC distributions in snow are poorly correlated with measurements, mean values are reasonable. The multi-model mean (range) bias in BC concentrations, sampled over the same grid cells, snow depths, and months of measurements, are −4.4 (−13.2 to +10.7) ng g−1 for an earlier phase of AeroCom models (phase I), and +4.1 (−13.0 to +21.4) ng g−1 for a more recent phase of AeroCom models (phase II), compared to the observational mean of 19.2 ng g−1. Factors determining model BC concentrations in Arctic snow include Arctic BC emissions, transport of extra-Arctic aerosols, precipitation, deposition efficiency of aerosols within the Arctic, and meltwater removal of particles in snow. Sensitivity studies show that the model–measurement evaluation is only weakly affected by meltwater scavenging efficiency because most measurements were conducted in non-melting snow. The Arctic (60–90° N) atmospheric residence time for BC in phase II models ranges from 3.7 to 23.2 days, implying large inter-model variation in local BC deposition efficiency. Combined with the fact that most Arctic BC deposition originates from extra-Arctic emissions, these results suggest that aerosol removal processes are a leading source of variation in model performance. The multi-model mean (full range) of Arctic radiative effect from BC in snow is 0.15 (0.07–0.25) W m−2 and 0.18 (0.06–0.28) W m−2 in phase I and phase II models, respectively. After correcting for model biases relative to observed BC concentrations in different regions of the Arctic, we obtain a multi-model mean Arctic radiative effect of 0.17 W m−2 for the combined AeroCom ensembles. Finally, there is a high correlation between modeled BC concentrations sampled over the observational sites and the Arctic as a whole, indicating that the field campaign provided a reasonable sample of the Arctic.

• Tsigaridis, K; Daskalakis, N; Kanakidou, M; Adams, Peter J.; Artaxo, Paulo & Bahadur, R [Vis alle 71 forfattere av denne artikkelen] (2014). The AeroCom evaluation and intercomparison of organic aerosol in global models. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 14(19), s. 10845–10895. doi: 10.5194/acp-14-10845-2014. Fulltekst i vitenarkiv Vis sammendrag

  This paper evaluates the current status of global modeling of the organic aerosol (OA) in the troposphere and analyzes the differences between models as well as between models and observations. Thirty-one global chemistry transport models (CTMs) and general circulation models (GCMs) have participated in this intercomparison, in the framework of AeroCom phase II. The simulation of OA varies greatly between models in terms of the magnitude of primary emissions, secondary OA (SOA) formation, the number of OA species used (2 to 62), the complexity of OA parameterizations (gas-particle partitioning, chemical aging, multiphase chemistry, aerosol microphysics), and the OA physical, chemical and optical properties. The diversity of the global OA simulation results has increased since earlier AeroCom experiments, mainly due to the increasing complexity of the SOA parameterization in models, and the implementation of new, highly uncertain, OA sources. Diversity of over one order of magnitude exists in the modeled vertical distribution of OA concentrations that deserves a dedicated future study. Furthermore, although the OA / OC ratio depends on OA sources and atmospheric processing, and is important for model evaluation against OA and OC observations, it is resolved only by a few global models

• Glantz, Paul; Bourassa, Adam; Herber, Andreas; Iversen, Trond; Karlsson, Johannes & Kirkevåg, Alf [Vis alle 12 forfattere av denne artikkelen] (2014). Remote sensing of aerosols in the Arctic for an evaluation of global climate model simulations. Journal of Geophysical Research (JGR): Atmospheres. ISSN 2169-897X. 119(13), s. 8169–8188. doi: 10.1002/2013JD021279. Fulltekst i vitenarkiv
• Makkonen, Risto; Seland, Øyvind; Kirkevåg, Alf; Iversen, Trond & Kristjansson, Jon Egill (2014). Evaluation of aerosol number concentrations in NorESM with improved nucleation parameterization. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 14(10), s. 5127–5152. doi: 10.5194/acp-14-5127-2014. Fulltekst i vitenarkiv
• Samset, Bjørn Hallvard; Myhre, Gunnar; Herber, Andreas; Kondo, Yutaka; Li, Shao-Meng & Moteki, Nobuhiro [Vis alle 31 forfattere av denne artikkelen] (2014). Modelled black carbon radiative forcing and atmospheric lifetime in AeroCom Phase II constrained by aircraft observations. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 14(22), s. 12465–12477. doi: 10.5194/acp-14-12465-2014. Fulltekst i vitenarkiv Vis sammendrag

  Atmospheric black carbon (BC) absorbs solar radiation, and exacerbates global warming through exerting positive radiative forcing (RF). However, the contribution of BC to ongoing changes in global climate is under debate. Anthropogenic BC emissions, and the resulting distribution of BC concentration, are highly uncertain. In particular, long-range transport and processes affecting BC atmospheric lifetime are poorly understood. Here we discuss whether recent assessments may have overestimated present-day BC radiative forcing in remote regions. We compare vertical profiles of BC concentration from four recent aircraft measurement campaigns to simulations by 13 aerosol models participating in the AeroCom Phase II intercomparison. An atmospheric lifetime of BC of less than 5 days is shown to be essential for reproducing observations in remote ocean regions, in line with other recent studies. Adjusting model results to measurements in remote regions, and at high altitudes, leads to a 25% reduction in AeroCom Phase II median direct BC forcing, from fossil fuel and biofuel burning, over the industrial era. The sensitivity of modelled forcing to BC vertical profile and lifetime highlights an urgent need for further flight campaigns, close to sources and in remote regions, to provide improved quantification of BC effects for use in climate policy

• Samset, Bjørn Hallvard; Myhre, Gunnar; Schulz, M.; Balkanski, Y.; Bauer, S. & Berntsen, Terje Koren [Vis alle 24 forfattere av denne artikkelen] (2013). Black carbon vertical profiles strongly affect its radiative forcing uncertainty. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 13(5), s. 2423–2434. doi: 10.5194/acp-13-2423-2013. Fulltekst i vitenarkiv Vis sammendrag

  The impact of black carbon (BC) aerosols on the global radiation balance is not well constrained. Here twelve global aerosol models are used to show that at least 20% of the present uncertainty in modeled BC direct radiative forcing (RF) is due to diversity in the simulated vertical profile of BC mass. Results are from phases 1 and 2 of the global aerosol model intercomparison project (AeroCom). Additionally, a significant fraction of the variability is shown to come from high altitudes, as, globally, more than 40% of the total BC RF is exerted above 5 km. BC emission regions and areas with transported BC are found to have differing characteristics. These insights into the importance of the vertical profile of BC lead us to suggest that observational studies are needed to better characterize the global distribution of BC, including in the upper troposphere.

• Myhre, Gunnar; Samset, Bjørn Hallvard; Schulz, M.; Balkanski, Y.; Bauer, S. & Berntsen, Terje Koren [Vis alle 41 forfattere av denne artikkelen] (2013). Radiative forcing of the direct aerosol effect from AeroCom Phase II simulations. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 13(4), s. 1853–1877. doi: 10.5194/acp-13-1853-2013. Fulltekst i vitenarkiv Vis sammendrag

  We report on the AeroCom Phase II direct aerosol effect (DAE) experiment where 16 detailed global aerosol models have been used to simulate the changes in the aerosol distribution over the industrial era. All 16 models have estimated the radiative forcing (RF) of the anthropogenic DAE, and have taken into account anthropogenic sulphate, black carbon (BC) and organic aerosols (OA) from fossil fuel, biofuel, and biomass burning emissions. In addition several models have simulated the DAE of anthropogenic nitrate and anthropogenic influenced secondary organic aerosols (SOA). The model simulated all-sky RF of the DAE from total anthropogenic aerosols has a range from −0.58 to −0.02Wm−2, with a mean of −0.27Wm−2 for the 16 models. Several models did not include nitrate or SOA and modifying the estimate by accounting for this with information from the other AeroCom models reduces the range and slightly strengthens the mean. Modifying the model estimates for missing aerosol components and for the time period 1750 to 2010 results in a mean RF for the DAE of −0.35Wm−2. Compared to AeroCom Phase I (Schulz et al., 2006) we find very similar spreads in both total DAE and aerosol component RF. However, the RF of the total DAE is stronger negative and RF from BC from fossil fuel and biofuel emissions are stronger positive in the present study than in the previous AeroCom study.We find a tendency for models having a strong (positive) BC RF to also have strong (negative) sulphate or OA RF. This relationship leads to smaller uncertainty in the total RF of the DAE compared to the RF of the sum of the individual aerosol components. The spread in results for the individual aerosol components is substantial, and can be divided into diversities in burden, mass extinction coefficient (MEC), and normalized RF with respect to AOD. We find that these three factors give similar contributions to the spread in results.

• Kirkevåg, Alf; Iversen, Trond; Seland, Øyvind; Hoose, Corinna; Kristjansson, Jon Egill & Struthers, H. [Vis alle 11 forfattere av denne artikkelen] (2013). Aerosol-climate interactions in the Norwegian Earth System Model-NorESM1-M. Geoscientific Model Development. ISSN 1991-959X. 6(1), s. 207–244. doi: 10.5194/gmd-6-207-2013. Fulltekst i vitenarkiv
• Iversen, Trond; Bentsen, Mats; Bethke, Ingo; Debernard, JB; Kirkevåg, Alf & Seland, Øyvind [Vis alle 11 forfattere av denne artikkelen] (2013). The Norwegian Earth System Model, NorESM1-M - Part 2: Climate response and scenario projections. Geoscientific Model Development. ISSN 1991-959X. 6(2), s. 389–415. doi: 10.5194/gmd-6-389-2013. Fulltekst i vitenarkiv
• Bentsen, Mats; Bethke, Ingo; Debernard, Jens B.; Iversen, Trond; Kirkevåg, Alf & Seland, Øyvind [Vis alle 11 forfattere av denne artikkelen] (2013). The Norwegian Earth System Model, NorESM1-M - Part 1: Description and basic evaluation of the physical climate. Geoscientific Model Development. ISSN 1991-959X. 6(3), s. 687–720. doi: 10.5194/gmd-6-687-2013. Fulltekst i vitenarkiv
• Iversen, Trond; Benestad, Rasmus & Kvamstø, Nils G (2013). Extremes of precipitation, Extreme weather events in Europe: Preparing for climate change adaptation. Norwegian Meteorological Institute. ISSN 9788271441005. s. 36–46. Fulltekst i vitenarkiv
• Su, Hui; Jiang, Jonathan H.; Zhai, Chengxing; Perun, Vincent S.; Shen, Janice T. & Genio, Anthony Del [Vis alle 30 forfattere av denne artikkelen] (2013). Diagnosis of regime-dependent cloud simulation errors in CMIP5 models using "A-Train" satellite observations and reanalysis data. Journal of Geophysical Research (JGR): Atmospheres. ISSN 2169-897X. 118(7), s. 2762–2780. doi: 10.1029/2012JD018575. Fulltekst i vitenarkiv
• Struthers, H.; Ekman, A.M.L.; Glantz, P.; Iversen, Trond; Kirkevåg, Alf & Seland, Øyvind [Vis alle 9 forfattere av denne artikkelen] (2013). Climate-induced changes in sea salt aerosol number emissions: 1870 to 2100. Journal of Geophysical Research (JGR): Atmospheres. ISSN 2169-897X. 118(2), s. 670–682. doi: 10.1002/jgrd.50129. Fulltekst i vitenarkiv
• Koffi, Brigitte; Schulz, Michael; Bréon, Francois-Marie; Griesfeller, Jan; Winker, David & Balkanski, Yves [Vis alle 24 forfattere av denne artikkelen] (2012). Application of the CALIOP layer product to evaluate the vertical distribution of aerosols estimated by global models: AeroCom phase I results. Journal of Geophysical Research (JGR): Atmospheres. ISSN 2169-897X. 117. doi: 10.1029/2011JD016858. Fulltekst i vitenarkiv Vis sammendrag

  The CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) layer product is used for a multimodel evaluation of the vertical distribution of aerosols. Annual and seasonal aerosol extinction profiles are analyzed over 13 sub-continental regions representative of industrial, dust, and biomass burning pollution, from CALIOP 2007–2009 observations and from AeroCom (Aerosol Comparisons between Observations and Models) 2000 simulations. An extinction mean height diagnostic (Zα) is defined to quantitatively assess the models' performance. It is calculated over the 0–6 km and 0–10 km altitude ranges by weighting the altitude of each 100 m altitude layer by its aerosol extinction coefficient. The mean extinction profiles derived from CALIOP layer products provide consistent regional and seasonal specificities and a low inter-annual variability. While the outputs from most models are significantly correlated with the observed Zα climatologies, some do better than others, and 2 of the 12 models perform particularly well in all seasons. Over industrial and maritime regions, most models show higher Zα than observed by CALIOP, whereas over the African and Chinese dust source regions, Zα is underestimated during Northern Hemisphere Spring and Summer. The positive model bias in Zα is mainly due to an overestimate of the extinction above 6 km. Potential CALIOP and model limitations, and methodological factors that might contribute to the differences are discussed.

• Jiang, Jonathan H.; Su, Hui; Zhai, Cheng Xiang; Perun, Vincent S.; Genio, Anthony Del & Nazarenko, Larissa S. [Vis alle 30 forfattere av denne artikkelen] (2012). Evaluation of cloud and water vapor simulations in CMIP5 climate models using NASA "A-Train" satellite observations. Journal of Geophysical Research (JGR): Atmospheres. ISSN 2169-897X. 117. doi: 10.1029/2011JD017237. Fulltekst i vitenarkiv
• Frogner, Inger-Lise & Iversen, Trond (2011). EuroTEPS - a targeted version of ECMWF EPS for the European area. Tellus A: Dynamic Meteorology and Oceanography. ISSN 0280-6495. 63(3), s. 415–428. doi: 10.1111/j.1600-0870.2010.00504.x. Fulltekst i vitenarkiv
• Kristiansen, Jørn; Sørland, Silje Lund; Iversen, Trond; Bjørge, Dag & Køltzow, Morten Andreas Ødegaard (2011). High-resolution ensemble prediction of a polar low development. Tellus A: Dynamic Meteorology and Oceanography. ISSN 0280-6495. 63(3), s. 585–604. doi: 10.1111/j.1600-0870.2010.00498.x. Fulltekst i vitenarkiv
• Kulmala, Markku; Asmi, Ari; Lappalainen, H. K.; Baltensperger, Urs; Brenguier, Jean-Louis & Facchini, Cristina [Vis alle 125 forfattere av denne artikkelen] (2011). General overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) - integrating aerosol research from nano to global scales. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 11(24), s. 13061–13143. doi: 10.5194/acp-11-13061-2011. Fulltekst i vitenarkiv Vis sammendrag

  In this paper we describe and summarize the main achievements of the European Aerosol Cloud Climate and Air Quality Interactions project (EUCAARI). EUCAARI started on 1 January 2007 and ended on 31 December 2010 leaving a rich legacy including: (a) a comprehensive database with a year of observations of the physical, chemical and optical properties of aerosol particles over Europe, (b) comprehensive aerosol measurements in four developing countries, (c) a database of airborne measurements of aerosols and clouds over Europe during May 2008, (d) comprehensive modeling tools to study aerosol processes fron nano to global scale and their effects on climate and air quality. In addition a new Pan-European aerosol emissions inventory was developed and evaluated, a new cluster spectrometer was built and tested in the field and several new aerosol parameterizations and computations modules for chemical transport and global climate models were developed and evaluated. These achievements and related studies have substantially improved our understanding and reduced the uncertainties of aerosol radiative forcing and air quality-climate interactions. The EUCAARI results can be utilized in European and global environmental policy to assess the aerosol impacts and the corresponding abatement strategies.

• Kristjansson, Jon Egill; Barstad, Idar; Aspelien, Trygve; Føre, Ivan; Godøy, Øystein Arne & Hov, Øystein [Vis alle 17 forfattere av denne artikkelen] (2011). The Norwegian IPY-THORPEX. Polar Lows and Arctic Fronts during the 2008 Andøya Campaign. Bulletin of The American Meteorological Society - (BAMS). ISSN 0003-0007. 92(11), s. 1443–1466. doi: 10.1175/2011BAMS2901.1. Fulltekst i vitenarkiv
• Aspelien, Trygve; Iversen, Trond; Bremnes, John Bjørnar & Frogner, Inger-Lise (2011). Short-range probabilistic forecasts from the Norwegian limited-area EPS: long-term validation and a polar low study. Tellus A: Dynamic Meteorology and Oceanography. ISSN 0280-6495. 63(3), s. 564–584. doi: 10.1111/j.1600-0870.2010.00502.x. Fulltekst i vitenarkiv
• Koch, D.; Balkanski, Y.; Bauer, S. E.; Easter, R. C.; Ferrachat, S. & Ghan, Steven John [Vis alle 18 forfattere av denne artikkelen] (2011). Soot microphysical effects on liquid clouds, a multi-model investigation. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 11(3), s. 1051–1064. doi: 10.5194/acp-11-1051-2011. Fulltekst i vitenarkiv
• Iversen, Trond; Deckmyn, Alex; Santos, Carlos; Sattler, Kai; Bremnes, John Bjørnar & Feddersen, Henrik [Vis alle 7 forfattere av denne artikkelen] (2011). Evaluation of "GLAMEPS" - a proposed multi-model EPS for short range forecasting. Tellus A: Dynamic Meteorology and Oceanography. ISSN 0280-6495. 63, s. 513–530. doi: 10.1111/j.1600-0870.2010.00507.x. Fulltekst i vitenarkiv
• Struthers, Hamish; Ekman, Annica; Glantz, Paul; Iversen, Trond; Kirkevåg, Alf & Mårtensson, E.M. [Vis alle 8 forfattere av denne artikkelen] (2011). The effect of sea ice loss on sea salt aerosol concentrations and the radiative balance of the Arctic. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 11, s. 3459–3477. doi: 10.5194/acp-11-3459-2011. Fulltekst i vitenarkiv
• Quaas, Johannes; Ming, Yin; Menon, Surabi; Takemura, T; Wang, M & Penner, Joyce [Vis alle 38 forfattere av denne artikkelen] (2009). Aerosol indirect effects - general circulation model intercomparison and evaluation with satellite data. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 9(22), s. 8697–8717. Fulltekst i vitenarkiv
• Hoose, Corinna; Kristjansson, Jon Egill; Iversen, T; Kirkevåg, A; Seland, Øyvind & Gettelman, A (2009). Constraining cloud droplet number concentration in GCMs suppresses the aerosol indirect effect. Geophysical Research Letters. ISSN 0094-8276. 36. doi: 10.1029/2009GL038568. Fulltekst i vitenarkiv
• Koch, D.; Schulz, M; Kinne, S; McNaughton, C; Spackman, JR & Balkanski, Y [Vis alle 50 forfattere av denne artikkelen] (2009). Evaluation of black carbon estimations in global aerosol models. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 9(22), s. 9001–9026. Fulltekst i vitenarkiv
• Storelvmo, Trude; Kristjansson, Jon Egill; Lohmann, Ulrike; Iversen, Trond; Kirkevåg, Alf & Seland, Øyvind (2008). Modeling of the Wegener-Bergeron-Findeisen process - implications for aerosol indirect effects. Environmental Research Letters. 3. doi: 10.1088/1748-9326/3/4/O45001. Fulltekst i vitenarkiv
• Koltzow, M; Iversen, Trond & Haugen, JE (2008). Extended Big-Brother experiments: the role of lateral boundary data quality and size of integration domain in regional climate modelling. Tellus A: Dynamic Meteorology and Oceanography. ISSN 0280-6495. 60. doi: 10.1111/j.1600-0870.2008.00309.x. Fulltekst i vitenarkiv
• Haugen, Jan Erik & Iversen, Trond (2008). Response in extremes of daily precipitation and wind from a downscaled multi-model ensemble of anthropogenic global climate change scenarios. Tellus A: Dynamic Meteorology and Oceanography. ISSN 0280-6495. 60. doi: 10.1111/j.1600-0870.2008.00315.x. Fulltekst i vitenarkiv
• Iversen, Trond; Kristiansen, J; Jung, T & Barkmeijer, J (2008). Optimal atmospheric forcing perturbations for the cold-ocean warm-land pattern. Tellus A: Dynamic Meteorology and Oceanography. ISSN 0280-6495. 60. doi: 10.1111/j.1600-0870.2008.00310.x. Fulltekst i vitenarkiv
• Kirkevåg, Alf; Iversen, Trond; Kristjansson, Jon Egill; Seland, Øyvind & Debernard, JB (2008). On the additivity of climate response to anthropogenic aerosols and CO2, and the enhancement of future global warming by carbonaceous aerosols. Tellus A: Dynamic Meteorology and Oceanography. ISSN 0280-6495. 60. doi: 10.1111/j.1600-0870.2008.00308.x. Fulltekst i vitenarkiv
• Seland, Øyvind; Iversen, Trond; Kirkevåg, Alf & Storelvmo, Trude (2008). Aerosol-climate interactions in the CAM-Oslo atmospheric GCM and investigation of associated shortcomings. Tellus A: Dynamic Meteorology and Oceanography. ISSN 0280-6495. 60A, s. 459–491. doi: 10.1111/j.1600-0870.2008.00318.x. Fulltekst i vitenarkiv
• Kirkevåg, Alf; Iversen, Trond; Seland, Øyvind; Debernard, J.; Storelvmo, Trude & Kristjansson, Jon Egill (2008). Aerosol-cloud-climate interactions in the climate model CAM-Oslo. Tellus A: Dynamic Meteorology and Oceanography. ISSN 0280-6495. 60. doi: 10.1111/j.1600-0870.2008.00313.x. Fulltekst i vitenarkiv
• Textor, C; Schulz, M; Guibert, S; Kinne, S; Balkanski, Y & Bauer, S [Vis alle 39 forfattere av denne artikkelen] (2007). The effect of harmonized emissions on aerosol properties in global models - an AeroCom experiment. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 7, s. 1699–1723. Fulltekst i vitenarkiv
• Storelvmo, Trude; Kristjansson, Jon Egill; Ghan, Steven John; Kirkevåg, Alf; Seland, Øyvind & Iversen, Trond (2006). Predicting cloud droplet number concentration in CAM-Oslo. Journal of Geophysical Research (JGR). ISSN 0148-0227. 111. doi: 10.1029/2005JD006300. Fulltekst i vitenarkiv
• Schulz, M; Textor, C; Kinne, S; Balkanski, Y; Bauer, S & Berntsen, Terje Koren [Vis alle 23 forfattere av denne artikkelen] (2006). Radiative forcing by aerosols as derived from the AeroCom present-day and pre-industrial simulations. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. s. 5225–5246. Fulltekst i vitenarkiv
• Textor, C; Schulz, M; Guibert, S; Kinne, S; Balkanski, Y & Bauer, S [Vis alle 41 forfattere av denne artikkelen] (2006). Analysis and quantification of the diversities of aerosol life cycles within AeroCom. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 6, s. 1777–1813. Fulltekst i vitenarkiv
• Kinne, S; Schulz, M; Textor, C; Guibert, S; Balkanski, Y & Bauer, SE [Vis alle 44 forfattere av denne artikkelen] (2006). An AeroCom initial assessment - optical properties in aerosol component modules of global models. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 6, s. 1815–1834. Fulltekst i vitenarkiv
• Storelvmo, Trude; Kristjansson, Jon Egill; Ghan, Steve J.; Kirkevåg, Alf; Seland, Øyvind & Iversen, Trond (2006). Predicting cloud droplet number concentration in Community Atmosphere Model (CAM)-Oslo. Journal of Geophysical Research (JGR). ISSN 0148-0227. 111(D24). doi: 10.1029/2005JD006300. Fulltekst i vitenarkiv
• Iversen, T & Tropé, Claes Gøran (2005). Svulster i kvinnelige genitalia. I Kåresen, Rolf & Wist, Erik (Red.), Kreftsykdommer - en basisbok for helsepersonell. Gyldendal Akademisk. ISSN 9788205334946. s. 244–258. Fulltekst i vitenarkiv
• Kristjansson, Jon Egill; Iversen, Trond; Kirkevåg, Alf; Seland, Øyvind & Debernard, Jens (2005). Response of the climate system to aerosol direct and indirect forcing: Role of cloud feedbacks. Journal of Geophysical Research (JGR). ISSN 0148-0227. 110(D 24). doi: 10.1029/2005JD006299. Fulltekst i vitenarkiv
• Iversen, Trond (2004). Forandrer menneskene jordens klima? I Hartenstein, Tilman & Hole, Elisabeth Skjervum (Red.), P2-Akademiet. Bind XXXI. Transit. s. 9–18. Fulltekst i vitenarkiv

Se alle arbeider i NVA

• Hov, Øystein; Andresen, Lars; Benestad, Rasmus; Eliassen, Anton; Førland, Eirik & Grasbakken, Ove [Vis alle 14 forfattere av denne artikkelen] (2023). Forskning til samfunnsnytte. Fagbokforlaget. ISBN 9788245045635. 459 s. Fulltekst i vitenarkiv
• Iversen, Trond & Lystad, Magne (2005). RegClim Technical Report No. 8. Norwegian Meteorological Insitute. 120 s. Fulltekst i vitenarkiv

Se alle arbeider i NVA

• Michel, Clio; Li, Camille; Graff, Lise Seland; Zappa, Giuseppe; Bethke, Ingo & Iversen, Trond [Vis alle 7 forfattere av denne artikkelen] (2018). Assessing the impacts of mid-latitude circulation changes under +1.5ºC and +2ºC warming. Fulltekst i vitenarkiv
• Michel, Clio; Li, Camille; Graff, Lise Seland; Zappa, Giuseppe; Bethke, Ingo & Iversen, Trond [Vis alle 7 forfattere av denne artikkelen] (2017). Assessing the impacts of mid-latitude circulation changes under +1.5ºC and +2ºC warming. Fulltekst i vitenarkiv
• Iversen, Trond & Heinze, Christoph (2015). The Norwegian Earth System Model - NorESM, Status and Plans for CMIP6 and Crescendo. Fulltekst i vitenarkiv
• Kristjansson, Jon Egill; Hoose, Corinna; Alterskjær, Kari; Iversen, Trond; Kirkevåg, Alf & Seland, O [Vis alle 8 forfattere av denne artikkelen] (2009). Aerosol indirect effect of the 'wrong' sign. Geochimica et Cosmochimica Acta. ISSN 0016-7037. 73(13), s. A697–A697. Fulltekst i vitenarkiv
• Hoose, Corinna; Kristjansson, Jon Egill; Iversen, Trond; Kirkevåg, Alf; Seland, Øyvind & Gettelman, A (2009). Constraining cloud droplet concentration in GCMs suppresses the aerosol indirect effect. Fulltekst i vitenarkiv
• Iversen, Trond (2008). Special issue with manuscripts from the RegClim (regional climate development under global warming) project - Preface. Tellus A: Dynamic Meteorology and Oceanography. ISSN 0280-6495. 60. doi: 10.1111/j.1600-0870.2008.00319.x. Fulltekst i vitenarkiv
• Hoose, Corinna; Kristjansson, Jon Egill; Kirkevåg, Alf; Iversen, Trond; Seland, Øyvind & Storelvmo, Trude (2008). Sensitivity of the cloud droplet concentration in a GCM to the representation of subgrid-scale vertical velocity. Fulltekst i vitenarkiv
• Iversen, Trond; Kirkevåg, Alf; Seland, Øyvind; Debernard, Jens B.; Kristjansson, Jon Egill & Storelvmo, Trude (2008). Aerosoler og klimaeffekten. Klima. ISSN 1504-8136. s. 40–43. Fulltekst i vitenarkiv
• Kirkevåg, Alf; Iversen, Trond; Kristjansson, Jon Egill; Seland, Øyvind & Debernard, Jens (2006). Partikkelforurensninger maskerer den globale oppvarmingen. Cicerone. ISSN 0804-0508. 15(2), s. 26–28. Fulltekst i vitenarkiv
• Iversen, Trond; Kristjansson, Jon Egill; Kirkevåg, Alf & Seland, Øyvind (2005). Calculated Feedback Effects of Climate Change caused by Anthropogenic Aerosols. Fulltekst i vitenarkiv
• Kirkevåg, Alf; Iversen, Trond; Kristjansson, Jon Egill; Seland, Øyvind & Debernard, Jens (2005). Climate response to aerosols in two versions of CCM-Oslo. Fulltekst i vitenarkiv
• Kirkevåg, Alf; Iversen, Trond; Kristjansson, Jon Egill; Seland, Øyvind & Debernard, Jens (2005). Aerosolmodellering i CCM-Oslo. Fulltekst i vitenarkiv
• Kirkevåg, Alf; Iversen, Trond; Seland, Øyvind & Kristjansson, Jon Egill (2005). Parameterized aerosol optics and cloud droplet properties in CCM-Oslo. Fulltekst i vitenarkiv
• Kirkevåg, Alf; Iversen, Trond; Kristjansson, Jon Egill; Seland, Øyvind & Debernard, Jens (2005). On aerosol-climate feedbacks, and the effect of doubling CO2. Fulltekst i vitenarkiv
• Iversen, Trond; Kristjansson, Jon Egill; Kirkevåg, Alf & Seland, Øyvind (2004). Climate feedbacks of the indirect effect caused by anthropogenic aerosols. Fulltekst i vitenarkiv
• Iversen, Trond & Seland, Øyvind (2004). Coupling Cumulus parameterisation and contaminant transport in global models. Fulltekst i vitenarkiv
• Kristjansson, Jon Egill; Iversen, Trond; Kirkevåg, Alf; Seland, Øyvind; Debernard, Jens & Røed, L. P. (2004). Feedbacks between chemistry and dynamics in simulations of climate response to aerosol indirect forcing. Fulltekst i vitenarkiv
• Barkmeijer, Jan; Iversen, Trond; Palmer, Tim N. & Noorden, T. Van (2004). Time dependent forcing singular vetors and their applications. Fulltekst i vitenarkiv
• Iversen, Trond; Seland, Øyvind; Kirkevåg, Alf & Kristjansson, Jon Egill (2004). Properties of aerosols as calculated by the atmospheric global climate model CCM-Oslo for AEROCOM phase B. Fulltekst i vitenarkiv
• Iversen, Trond & Seland, Øyvind (2004). The Role of Cumulus Parameterisation in Global and Regional Sulphur Transport. Fulltekst i vitenarkiv
• Kristjansson, Jon Egill; Iversen, Trond; Kirkevåg, Alf & Seland, Øyvind (2004). Response of the coupled climate system to indirect aerosol forcing. Fulltekst i vitenarkiv
• Fagerli, Hilde; Tsyro, Svetlana G.; Denby, Bruce; Oliviè, Dirk Jan Leo; Nyiri, Agnes & Gauss, Michael [Vis alle 38 forfattere av denne artikkelen] (2016). Transboundary particulate matter, photo-oxidants, acidifying and eutrophying components. Meteorologisk Institutt. Fulltekst i vitenarkiv
• Hov, Øystein; Benestad, Rasmus; Cubasch, Ulrich; Fischer, Erich; Höppe, Peter & Iversen, Trond [Vis alle 18 forfattere av denne artikkelen] (2013). Extreme weather events in Europe: Preparing for climate change adaptation. Norwegian Meteorological Institute. ISSN 9788271441005. Fulltekst i vitenarkiv
• Schulz, Michael; Gauss, Michael; Benedictow, Anna Maria Katarina; Jonson, Jan Eiof; Tsyro, Svetlana G. & Nyiri, Agnes [Vis alle 34 forfattere av denne artikkelen] (2013). Transboundary acidification, eutrophication and ground level ozone in Europe in 2011. EMEP status report 2013. Norwegian Meteorological Institute. Fulltekst i vitenarkiv
• Gisler, Galen Ross; Celledoni, Elena; Helgaker, Trygve; Iversen, Trond; Jakobsen, Kjetill Sigurd & Jones, Colin N. [Vis alle 12 forfattere av denne artikkelen] (2010). The scientific case for eInfrastructure in Norway. Norges forskningsråd. ISSN 9788212028319. Fulltekst i vitenarkiv Vis sammendrag

  Fulltekst: http://www.forskningsradet.no/servlet/Satellite?blobcol=urldata&blobheader=application%2Fpdf&blobheadername1=Content-Disposition%3A&blobheadervalue1=+attachment%3B+filename%3DeSOP-The-Scientific-Case-for-eInfrastructure-in-Norway-final%5B1%5D.pdf&blobkey=id&blobtable=MungoBlobs&blobwhere=1274464831935&ssbinary=true

• Kirkevåg, Alf; Iversen, Trond; Seland, Øyvind & Kristjansson, Jon Egill (2005). Revised schemes for aerosol optical parameters and cloud condensation nuclei in CCM-Oslo. Institutt for Geofag, Avdeling for Meteorologi og Oseanografi. ISSN 9788291885315. Fulltekst i vitenarkiv

Se alle arbeider i NVA