Trond Iversen

• Boy, Michael; Thomson, Erik S.; Acosta Navarro, Juan-Camilo; Arnalds, Olafur; Batchvarova, Ekaterina; Bäck, Jaana; Berninger, Frank; Bilde, Merete; Brasseur, Zoé; Dagsson-Waldhauserova, Pavla; Castarède, Dimitri; Dalirian, Maryam; de Leeuw, Gerrit; Dragosics, Monika; Duplissy, Ella-Maria; Duplissy, Jonathan; Ekman, Annica; Fang, Keyan; Gallet, Jean-Charles; Glasius, Marianne; Gryning, Sven-Erik; Grythe, Henrik; Hansson, Hans-Christen; Hansson, Margareta; Isaksson, Elisabeth; Iversen, Trond; Jónsdóttir, Ingibjörg Svala; Kasurinen, Ville; Kirkevåg, Alf; Korhola, Atte; Krejci, Radovan; Kristjansson, Jon Egill; Lappalainen, Hanna K.; Lauri, Antti; Leppäranta, Matti; Lihavainen, Heikki; Makkonen, Risto; Massling, Andreas; Meinander, Outi; Nilsson, E. Douglas; Ólafsson, Haraldur; Pettersson, Jan B. C.; Prisle, Nønne L.; Riipinen, Ilona; Roldin, Pontus; Ruppel, Meri; Salter, Matthew E.; Sand, Maria; Seland, Øyvind; Seppä, Heikki; Skov, Henrik; Soares, Joana; Stohl, Andreas; Ström, Johan; Svensson, Jonas; Swietlicki, Erik; Tabakova, Ksenia; Thorsteinsson, Throstur; Virkkula, Aki; Weyhenmeyer, Gesa A.; Wu, Yusheng; Zieger, Paul & Kulmala, Markku (2019). Interactions between the atmosphere, cryosphere, and ecosystems at northern high latitudes. Atmospheric Chemistry and Physics.  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.

• Graff, Lise Seland; Iversen, Trond; Bethke, Ingo; Debernard, Jens Boldingh; Seland, Øyvind; Bentsen, Mats; Kirkevåg, Alf; Li, Camille & Oliviè, Dirk Jan Leo (2019). Arctic amplification under global warming of 1.5 and 2 °C in NorESM1-Happi. Earth System Dynamics.  ISSN 2190-4979.  10(3), s 569- 598 . doi: 10.5194/esd-10-569-2019 Fulltekst i vitenarkiv.
• 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
• 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 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.

• Stjern, Camilla Weum; Lund, Marianne Tronstad; Samset, Bjørn Hallvard; Myhre, Gunnar; Forster, Piers M.; Andrews, Timothy; Boucher, Olivier; Faluvegi, Gregory; Fläschner, Dagmar; Iversen, Trond; Kasoar, Matthew; Kharin, Viatcheslav; Kirkevåg, Alf; Lamarque, Jean-François; Oliviè, Dirk Jan Leo; Richardson, Thomas; Sand, Maria; Shawki, Dilshad; Shindell, Drew; Smith, Christopher J.; Takemura, Toshihiko & Voulgarakis, Apostolos (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 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.; Kasoar, Matthew; Andrews, T.; Boucher, O.; Forster, Piers M.; Hodnebrog, Øivind; Iversen, Trond; Kirkevåg, Alf; Lamarque, Jean-François; Richardson, T.; Samset, Bjørn Hallvard; Stjern, Camilla Weum; Takemura, Toshihiko & Smith, C. (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 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.

• Karset, Inger Helene H.; Berntsen, Terje Koren; Storelvmo, Trude; Alterskjær, Kari; Grini, Alf; Oliviè, Dirk Jan Leo; Kirkevåg, Alf; Seland, Øyvind; Iversen, Trond & Schulz, Michael (2018). Strong impacts on aerosol indirect effects from historical oxidant changes. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  18(10), s 7669- 7690 . doi: 10.5194/acp-18-7669-2018 Fulltekst i vitenarkiv.
• Kirkevåg, Alf; Grini, Alf; Oliviè, Dirk Jan Leo; Seland, Øyvind; Alterskjær, Kari; Hummel, Matthias; Karset, Inger Helene H.; Lewinschal, Anna; Liu, Xiaohong; Makkonen, Risto; Bethke, Ingo; Griesfeller, Jan; Schulz, Michael & Iversen, Trond (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.
• Li, Camille; Michel, Clio; Graff, Lise Seland; Bethke, Ingo; Zappa, Guiseppe; Bracegirdle, Thomas J.; Fischer, Erich; Harvey, Ben J.; Iversen, Trond; King, Martin Peter; Krishnan, Harinarayan; Lierhammer, Ludwig; Mitchell, Daniel; Scinocca, John; Shiogama, Hideo; Stone, Dáithí A. & Wettstein, Justin (2018). Midlatitude atmospheric circulation responses under 1.5°C and 2.0°C warming and implications for regional impacts. Earth System Dynamics.  ISSN 2190-4979.  9(2), s 359- 382 . doi: 10.5194/esd-9-359-2018 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.

• Liu, L.; Shawki, Dilshad; Voulgarakis, Apostolos; Kasoar, Matthew; Samset, Bjørn Hallvard; Myhre, Gunnar; Forster, Piers M.; Hodnebrog, Øivind; Sillmann, Jana; Aalbergsjø, Siv Gundrosen; Boucher, Olivier; Faluvegi, Gregory S.; Iversen, Trond; Kirkevåg, Alf; Lamarque, Jean-François; Oliviè, Dirk Jan Leo; Richardson, Thomas Benjamin; Shindell, Drew & Takemura, Toshihiko (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
• Tang, Tao; Shindell, Drew; Samset, Bjørn Hallvard; Boucher, Olivier; Forster, Piers M.; Hodnebrog, Øivind; Myhre, Gunnar; Sillmann, Jana; Voulgarakis, Apostolos; Andrews, Timothy; Faluvegi, Gregory S.; Fläschner, Dagmar; Iversen, Trond; Kasoar, Matthew; Kharin, Viatcheslav; Kirkevåg, Alf; Lamarque, Jean-Francois; Oliviè, Dirk Jan Leo; Richardson, Thomas; Stjern, Camilla Weum & Takemura, Toshihiko (2018). Dynamical response of Mediterranean precipitation to greenhouse gases and aerosols. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  18(11), s 8439- 8452 . doi: 10.5194/acp-18-8439-2018 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

• Acosta Navarro, Juan-Camilo; Ekman, Annica; Pausata, Francesco S. Rocco; Lewinschal, Anna; Varma, Vidya; Seland, Øyvind; Gauss, Michael; Iversen, Trond; Kirkevåg, Alf; Riipinen, Ilona & Hansson, Hans Christen (2017). 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
• Mitchell, Daniel A.; AchutaRao, Krishna; Allen, Myles; Bethke, Ingo; Beyerle, Urs; Ciavarella, Andrew; Forster, Piers M.; Fuglestvedt, Jan S.; Gillett, Nathan; Haustein, Karsten; Ingram, William; Iversen, Trond; Kharin, Viatcheslav; Klingaman, Nicholas; Massey, Neil; Fischer, Erich; Schleussner, Carl-Friedrich; Scinocca, John; Seland, Øyvind; Shiogama, Hideo; Shuckburgh, Emily; Sparrow, Sarah; Stone, Dáithí A.; Uhe, Peter; Wallom, David; Wehner, Michael & Zaaboul, Rashyd (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 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.

• Myhre, Gunnar; Forster, Piers M.; Samset, Bjørn Hallvard; Hodnebrog, Øivind; Sillmann, Jana; Aalbergsjø, Siv Gundrosen; Andrews, Timothy; Boucher, Olivier; Faluvegi, G.; Fläschner, Dagmar; Iversen, Trond; Kasoar, Matthew; Kharin, V; Kirkevåg, Alf; Lamarque, Jean-Francois; Oliviè, Dirk Jan Leo; Richardson, Thomas; Shindell, Drew; Shine, Keith P.; Stjern, Camilla Weum; Takemura, Toshihiko; Voulgarakis, Apostolos & Zwiers, Francis W. (2017). 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 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.

• Sand, Maria; Samset, Bjørn Hallvard; Balkanski, Yves; Bauer, Susanne; Bellouin, Nicolas; Berntsen, Terje Koren; Bian, Huisheng; Chin, Mian; Diehl, Thomas; Easter, Richard; Ghan, Steve J.; Iversen, Trond; Kirkevåg, Alf; Lamarque, Jean-Francois; Lin, Guangxing; Liu, Xiaohong; Luo, Gan; Myhre, Gunnar; Van Noije, Twan P.C.; Penner, Joyce E.; Schulz, Michael; Seland, Øyvind; Skeie, Ragnhild Bieltvedt; Stier, Philip; Takemura, Toshihiko; Tsigaridis, Kostas; Yu, Fangqun; Zhang, Kai & Zhang, Hua (2017). Aerosols at the poles: an AeroCom Phase II multi-model evaluation. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  17(19), s 12197- 12218 . doi: 10.5194/acp-17-12197-2017 Fulltekst i vitenarkiv.
• Stjern, Camilla Weum; Samset, Bjørn Hallvard; Myhre, Gunnar; Forster, Piers M.; Hodnebrog, Øivind; Andrews, Timothy; Boucher, Olivier; Faluvegi, Gregory S.; Iversen, Trond; Kasoar, Matthew; Kharin, Viatcheslav V.; Kirkevåg, Alf; Lamarque, Jean-Francois; Oliviè, Dirk Jan Leo; Richardson, Thomas Benjamin; Shawki, Dilshad; Shindell, Drew; Smith, Christopher J.; Takemura, Toshihiko & Voulgarakis, Apostolos (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
• Acosta Navarro, Juan-Camilo; Varma, Vidya; Riipinen, Ilona; Seland, Øyvind; Kirkevåg, Alf; Struthers, Hamish; Iversen, Trond; Hansson, Hans-Christen & Ekman, Annica (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
• Cassiani, Massimo; Stohl, Andreas; Oliviè, Dirk Jan Leo; Seland, Øyvind; Bethke, Ingo; Pisso, Ignacio & Iversen, Trond (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.
• Jung, Thomas; Iversen, Trond; Gordon, Neil D.; Bauer, Peter; Bromwich, David H.; Chevallier, Mattheu; Day, Jonathan D.; Dawson, Jackie; Doblas-Reyes, Francisco Javier; Fairall, Christopher; Goessling, Helge F.; Holland, Marika M.; Inoue, Jun G.; Klebe, Stefanie; Lemke, Peter; Losch, Martin; Makshtas, Alexander P.; Mills, Brian; Nurmi, Pertti; Perovich, Donald; Reid, Philip C.; Renfrew, Ian A.; Smith, Gregory; Svensson, Gunilla; Tolstykh, Mikhail A. & Yang, Qinghua (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
• Kipling, Zak; Stier, Philip; Johnson, Colin E.; Mann, Graham W.; Bellouin, Nicolas; Bauer, Susanne E.; Bergman, Tommi; Chin, Mian; Diehl, Thomas; Ghan, Steven John; Iversen, Trond; Kirkevåg, Alf; Kokkola, Harri; Liu, Xiaohong; Luo, Gan; van Noije, Twan P.C.; Pringle, Kirsty J.; von Salzen, Knut; Schulz, Michael; Seland, Øyvind; Skeie, Ragnhild Bieltvedt; Takemura, Toshihiko; Tsigaridis, Kostas & Zhang, Kai (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.  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.

• Koffi, Brigitte; Schulz, Michael; Bréon, François-Marie; Dentener, Frank; Steensen, Birthe Marie Rødssæteren; Griesfeller, Jan; Winker, David; Balkanski, Yves; Bauer, Susanne E.; Bellouin, Nicolas; Berntsen, Terje Koren; Bian, Huisheng; Chin, Mian; Diehl, Thomas; Easter, Richard; Ghan, Steven; Hauglustaine, Didier A.; Iversen, Trond; Kirkevåg, Alf; Liu, Xiaohong; Lohmann, Ulrike; Myhre, Gunnar; Rasch, Phil; Seland, Øyvind; Skeie, Ragnhild Bieltvedt; Steenrod, Stephen D.; Stier, Philip; Tackett, Jason; Takemura, Toshihiko; Tsigaridis, Kostas; Vuolo, Maria Raffaella; Yoon, Jinho & Zhang, Kai (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 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.

• Ao, Chi O.; Jiang, Jonathan H.; Mannucci, Anthony J.; Su, Hui; Verkhoglyadova, Olga; Zhai, Chengxing; Cole, Jason; Donner, Leo; Iversen, Trond; Morcrette, Cyril; Rotstayn, Leon; Watanabe, Masahiro & Yukimoto, Seiji (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
• Sand, Maria; Iversen, Trond; Bohlinger, Patrik; Kirkevåg, Alf; Seierstad, Ivar Ambjørn; Seland, Øyvind & Sorteberg, Asgeir (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
• Samset, Bjørn Hallvard; Myhre, Gunnar; Herber, Andreas; Kondo, Yutaka; Li, Shao-Meng; Moteki, Nobuhiro; Koike, Makoto; Oshima, Naga; Schwarz, Joshua P.; Balkanski, Yves; Bauer, Susanne E.; Bellouin, Nicolas; Berntsen, Terje Koren; Bian, Huisheng; Chin, Mian; Diehl, Thomas; Easter, Richard C.; Ghan, Steven John; Iversen, Trond; Kirkevåg, Alf; Lamarque, Jean-François; Lin, Guangxing; Liu, Xiaohong; Penner, Joyce E.; Schulz, Michael; Seland, Øyvind; Skeie, Ragnhild Bieltvedt; Stier, Philip; Takemura, Toshihiko; Tsigaridis, Kostas & Zhang, Kai (2014). Modelled black carbon radiative forcing and atmospheric lifetime in AeroCom Phase II constrained by aircraft observations. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  14(22), s 12465- 12477 . doi: 10.5194/acp-14-12465-2014 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

• Tsigaridis, K; Daskalakis, N; Kanakidou, M; Adams, Peter J.; Artaxo, Paulo; Bahadur, R; Balkanski, Yves; Bauer, S. E.; Bellouin, Nicolas; Benedetti, Anna; Bergman, Tommi; Berntsen, Terje Koren; Beukes, J. P.; Bian, H; Carslaw, K; Chin, Mian; Curci, G; Diehl, Thomas; Easter, Richard C.; Ghan, Steven John; Gong, SL; Hodzic, A; Hoyle, CR; Iversen, Trond; Jathar, S; Jimenez, J. L.; Kaiser, Johannes W.; Kirkevåg, Alf; Koch, D; Kokkola, Harri; Lee, Y.H.; Lin, G; Liu, X; Luo, G; Ma, X; Mann, Graham W.; Mihalopoulos, N; Morcrette, J.J; Muller, JF; Myhre, Gunnar; Myriokefalitakis, S; Ng, NL; O'Donnell, D; Penner, J.E.; Pozzoli, L; Pringle, Kirsty J.; Russell, LM; Schulz, M; Sciare, J.; Seland, Øyvind; Shindell, Drew T.; Sillman, Sanford; Skeie, Ragnhild Bieltvedt; Spracklen, D; Stavrakou, T; Steenrod, S; Takemura, Toshihiko; Tiitta, P; Tilmes, S; Tost, Holger; Van Noije, T; van Zyl, P. G.; von Salzen, Knut; Yu, F.; Wang, Z; Wang, Z.; Zaveri, Rahul A.; Zhang, H; Zhang, K; Zhang, Q & Zhang, X (2014). The AeroCom evaluation and intercomparison of organic aerosol in global models. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  14(19), s 10845- 10895 . doi: 10.5194/acp-14-10845-2014 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; Maturilli, Marion; Seland, Øyvind; Stebel, Kerstin; Struthers, Hamish; Tesche, Matthias & Thomason, Larry (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.
• Jiao, C; Flanner, M; Balkanski, Y; Bauer, S.; Bellouin, N; Berntsen, Terje Koren; Bian, H; Carslaw, K; Chin, M; De Luca, N; Diehl, T; Ghan, S; Iversen, T; Kirkevag, A; Koch, D; Liu, X; Mann, G; Penner, J; Pitari, G; Schulz, M; Seland, O; Skeie, Ragnhild Bieltvedt; Steenrod, S; Stier, P; Takemura, T; Tsigaridis, K; Van Noije, T; Yun, Y & Zhang, K (2014). An aerocom assessment of black carbon in Arctic snow and sea ice. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  14(5), s 2399- 2417 . doi: 10.5194/acp-14-2399-2014 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.

• 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.  ISSN 1680-7316.  14(10), s 5127- 5152 . doi: 10.5194/acp-14-5127-2014
• Bentsen, Mats; Bethke, Ingo; Debernard, Jens B.; Iversen, Trond; Kirkevåg, Alf; Seland, Øyvind; Drange, Helge; Roelandt, Caroline; Seierstad, Ivar A.; Hoose, Corinna & Kristjansson, Jon Egill (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
• Iversen, Trond; Benestad, Rasmus & Kvamstø, Nils G (2013). Extremes of precipitation, In  Extreme weather events in Europe: Preparing for climate change adaptation.  Norwegian Meteorological Institute.  ISBN 978-82-7144-100-5.  Chapter 3.2.  s 36 - 46
• Kirkevåg, Alf; Iversen, Trond; Seland, Øyvind; Hoose, Corinna; Kristjansson, Jon Egill; Struthers, H.; Ekman, A.M.L.; Ghan, S; Griesfeller, J.; Nilsson, ED & Schulz, M. (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
• Myhre, Gunnar; Samset, Bjørn Hallvard; Schulz, M.; Balkanski, Y.; Bauer, S.; Berntsen, Terje Koren; Bian, H.; Bellouin, N; Chin, M; Diehl, T; Easter, R. C.; Feichter, J; Ghan, SJ; Hauglustaine, D; Iversen, Trond; Kinne, S; Kirkevåg, A; Lamarque, J. F.; Lin, G; Liu, X.; Lund, Marianne Tronstad; Luo, G; Ma, X; van Noije, T; Penner, JE; Rasch, P. J.; Ruiz, A.; Seland, Ø.; Skeie, Ragnhild Bieltvedt; Stier, P; Takemura, T.; Tsigaridis, K; Wang, P.; Wang, Z; Xu, L.; Yu, H; Yu, F.; Yoon, J.-H.; Zhang, K.; Zhang, H. & Zhou, C. (2013). Radiative forcing of the direct aerosol effect from AeroCom Phase II simulations. Atmospheric Chemistry and Physics.  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.

• Samset, Bjørn Hallvard; Myhre, Gunnar; Schulz, M.; Balkanski, Y.; Bauer, S.; Berntsen, Terje Koren; Bian, H.; Bellouin, N.; Diehl, T.; Easter, R.C.; Ghan, S.J.; Iversen, Trond; Kinne, S.; Kirkevåg, Alf; Lamarque, J.-F.; Lin, G.; Liu, X.; Penner, J.E.; Seland, Øyvind; Skeie, Ragnhild Bieltvedt; Stier, P.; Takemura, T.; Tsigaridis, K. & Zhang, K. (2013). Black carbon vertical profiles strongly affect its radiative forcing uncertainty. Atmospheric Chemistry and Physics.  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.

• Iversen, Trond; Bentsen, Mats; Bethke, Ingo; Debernard, JB; Kirkevåg, Alf; Seland, Øyvind; Drange, Helge; Kristjansson, Jon Egill; Medhaug, Iselin; Sand, Maria & Seierstad, Ivar A. (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
• Struthers, H.; Ekman, A.M.L.; Glantz, P.; Iversen, Trond; Kirkevåg, Alf; Seland, Øyvind; Mårtensson, E.M.; Noone, K. & Nilsson, ED (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
• Su, Hui; Jiang, Jonathan H.; Zhai, Chengxing; Perun, Vincent S.; Shen, Janice T.; Del Genio, Anthony; Nazarenko, Larissa S.; Donner, Leo J.; Horowitz, Larry W; Seman, Charles; Morcrette, Cyril; Petch, Jon; Ringer, Mark A.; Cole, Jason; von Salzen, Knut; Mesquita, Michel D Santos; Iversen, Trond; Kristjansson, Jon Egill; Gettelman, Andrew; Rotstayn, Leon; Jeffrey, Stephen; Dufresne, Jean-Louis; Watanabe, Masahiro; Kawai, Hideaki; Koshiro, Tsuyoshi; Wu, Tongwen; Volodin, Evgeny M.; L'Ecuyer, Tristan; Teixeira, João Paulo & Stephens, Graeme L. (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
• Jiang, Jonathan H.; Su, Hui; Zhai, Cheng Xiang; Perun, Vincent S.; Del Genio, Anthony; Nazarenko, Larissa S.; Donner, Leo J.; Horowitz, Larry W; Seman, Charles; Cole, Jason; Gettelman, Andrew; Ringer, Mark A.; Rotstayn, Leon; Jeffrey, Stephen; Wu, Tongwen; Brient, Florent; Dufresne, Jean-Louis; Kawai, Hideaki; Koshiro, Tsuyoshi; Watanabe, Masahiro; LEcuyer, Tristan S.; Volodin, Evgeny M.; Iversen, Trond; Drange, Helge; Mesquita, Michel D Santos; Read, William G.; Waters, Joe W.; Tian, Baijun; Teixeira, João Paulo & Stephens, Graeme L. (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
• Koffi, Brigitte; Schulz, Michael; Bréon, Francois-Marie; Griesfeller, Jan; Winker, David; Balkanski, Yves; Bauer, Susanne; Berntsen, Terje Koren; Chin, Mian; Collins, William D; Dentener, Frank; Diehl, Thomas; Easter, Richard; Ghan, Steven John; Ginoux, Paul; Gong, Sunling; Horowitz, Larry W; Iversen, Trond; Kirkevåg, Alf; Koch, Dorothy; Krol, Maarten; Myhre, Gunnar; Stier, Philip & Takemura, Toshihiko (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 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.

• Koch, D.; Balkanski, Y.; Bauer, S. E.; Easter, R. C.; Ferrachat, S.; Ghan, Steven John; Hoose, Corinna; Iversen, Trond; Kirkevåg, Alf; Kristjansson, Jon Egill; Liu, X.; Lohmann, Ulrike; Menon, Surabi; Quaas, Johannes; Schulz, M.; Seland, Øyvind; Takemura, T. & Yan, N. (2011). Soot microphysical effects on liquid clouds, a multi-model investigation. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  11(3), s 1051- 1064 . doi: 10.5194/acp-11-1051-2011
• 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. Series A, Dynamic meteorology and oceanography.  ISSN 0280-6495.  63(3), s 564- 584 . doi: 10.1111/j.1600-0870.2010.00502.x
• Frogner, Inger-Lise & Iversen, Trond (2011). EuroTEPS - a targeted version of ECMWF EPS for the European area. Tellus. Series A, Dynamic meteorology and oceanography.  ISSN 0280-6495.  63(3), s 415- 428 . doi: 10.1111/j.1600-0870.2010.00504.x
• Iversen, Trond; Deckmyn, Alex; Santos, Carlos; Sattler, Kai; Bremnes, John Bjørnar; Feddersen, Henrik & Frogner, Inger-Lise (2011). Evaluation of "GLAMEPS" - a proposed multi-model EPS for short range forecasting. Tellus. Series A, Dynamic meteorology and oceanography.  ISSN 0280-6495.  63, s 513- 530 . doi: 10.1111/j.1600-0870.2010.00507.x
• Kristiansen, Jørn; Sørland, Silje Lund; Iversen, Trond; Bjørge, Dag & Køltzow, Morten Andreas Ødegaard (2011). High-resolution ensemble prediction of a polar low development. Tellus. Series A, Dynamic meteorology and oceanography.  ISSN 0280-6495.  63(3), s 585- 604 . doi: 10.1111/j.1600-0870.2010.00498.x
• Kristjansson, Jon Egill; Barstad, Idar; Aspelien, Trygve; Føre, Ivan; Godøy, Øystein Arne; Hov, Øystein; Irvine, Emma; Iversen, Trond; Kolstad, Erik Wilhelm; Nordeng, Thor Erik; Mc Innes, Harold; Randriamampianina, Roger; Reuder, Joachim; Sætra, Øyvind; Shapiro, Melvyn A.; Spengler, Thomas & Ólafsson, Haraldur (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
• Kulmala, Markku; Asmi, Ari; Lappalainen, H. K.; Baltensperger, Urs; Brenguier, Jean-Louis; Facchini, Cristina; Hansson, H.-C.; Hov, Øystein; O'Dowd, Colin; Pöschl, U.; Wiedensohler, A.; Boers, Reinout; Boucher, Olivier; de Leeuw, G.; Denier van der Gon, H.A.C.; Feichter, Johann; Krejci, R.; Laj, P.; Lihavainen, H.; Lohmann, Ulrike; McFiggans, Gordon; Mentel, Thomas; Pilinis, C.; Riipinen, Ilona; Schulz, Michael; Stohl, Andreas; Swietlicki, Erik; Vignati, Elisabetta; Alves, C.; Amann, M.; Ammann, M.; Arabas, Sylvester; Artaxo, P.; Baars, H.; Beddows, D.C.S.; Bergström, R.; Beukes, J. P.; Bilde, Merete; Burkhart, John Faulkner; Canonaco, F.; Clegg, S. L.; Coe, H.; Crumeyrolle, S.; D'Anna, Barbara; Decesari, S.; Gilardoni, S.; Fischer, M.; Fjæraa, Ann-Mari; Fountoukis, C.; George, C.; Gomes, L.; Halloran, P.; Hamburger, T.; Harrison, R. M.; Herrmann, H.; Hoffmann, T.; Hoose, Corinna; Hu, M.; Hyvärinen, A.; Hõrrak, U.; Iinuma, Y.; Iversen, Trond; Josipovic, M.; Kanakidou, Maria; Kiendler-Scharr, A.; Kirkevåg, Alf; Kiss, G.; Klimont, Z.; Kolmonen, P.; Komppula, M.; Kristjansson, Jon Egill; Laakso, L.; Laaksonen, A.; Labonnote, L.; Lanz, V. A.; Lehtinen, K. E. J.; Rizzo, L. V.; Makkonen, R.; Manninen, H. E.; McMeeking, G.; Merikanto, J.; Minikin, A.; Mirme, S.; Morgan, W. T.; Nemitz, E.; O'Donnell, D.; Panwar, T. S.; Pawlowska, H.; Petzold, A.; Pienaar, J. J.; Pio, C.; Plass-Duelmer, C.; Prévôt, A. S. H.; Pryor, S.; Reddington, C. L.; Roberts, G.; Rosenfeld, Daniel; Schwarz, J.; Seland, Øyvind; Sellegri, K.; Shen, X. J.; Shiraiwa, M.; Siebert, H.; Sierau, Berko; Simpson, David; Sun, J. Y.; Topping, D.; Tunved, Peter; Vaattovaara, P.; Vakkari, V.; Veefkind, J. P.; Visschedijk, A.; Vuollekoski, H.; Vuolo, R.; Wehner, B.; Wildt, J.; Woodward, S.; Worsnop, D. R.; van Zadelhoff, G.-J.; Zardini, A. A.; Zhang, K.; van Zyl, P. G.; Kerminen, V.-M.; Carslaw, K. S. & Pandis, S. N. (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.  ISSN 1680-7316.  11(24), s 13061- 13143 . doi: 10.5194/acp-11-13061-2011 Fulltekst i vitenarkiv.
• Struthers, Hamish; Ekman, Annica; Glantz, Paul; Iversen, Trond; Kirkevåg, Alf; Mårtensson, E.M.; Seland, Øyvind & Nilsson, E. D. (2011). The effect of sea ice loss on sea salt aerosol concentrations and the radiative balance of the Arctic. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  11, s 3459- 3477 . doi: 10.5194/acp-11-3459-2011
• 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
• Koch, D.; Schulz, M; Kinne, S; McNaughton, C; Spackman, JR; Balkanski, Y; Bauer, S; Berntsen, Terje Koren; Bond, T. C.; Boucher, O; Chin, M; Clarke, A; De Luca, N; Dentener, F; Diehl, T; Dubovik, O; Easter, R; Fahey, DW; Feichter, J; Fillmore, D; Freitag, S; Ghan, S; Ginoux, P; Gong, S; Horowitz, L; Iversen, Trond; Kirkevåg, Alf; Klimont, Z; Kondo, Y; Krol, M; Liu, X; Miller, R; Montanaro, V; Moteki, N; Myhre, Gunnar; Penner, JE; Perlwitz, J; Pitari, G; Reddy, S; Sahu, L; Sakamoto, H; Schuster, G; Schwarz, JP; Seland, Øyvind; Stier, P; Takegawa, N; Takemura, T; Textor, C; van Aardenne, JA & Zhao, Y (2009). Evaluation of black carbon estimations in global aerosol models. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  9(22), s 9001- 9026
• Quaas, Johannes; Ming, Yin; Menon, Surabi; Takemura, T; Wang, M; Penner, Joyce; Gettelman, A; Lohmann, Ulrike; Bellouin, N; Boucher, Olivier; Sayer, AM; Thomas, GE; McComiskey, A; Feingold, Graham; Hoose, Corinna; Kristjansson, Jon Egill; Liu, Xiaohong; Iversen, Trond; Donner, LJ; Ginoux, PA; Stier, P; Grandey, B; Feichter, J; Sednev, I; Bauer, SE; Koch, D; Grainger, RG; Kirkevåg, Alf; Seland, Øyvind; Easter, R; Ghan, SJ; Rasch, PJ; Morrison, H; Lamarque, JF; Iacono, MJ; Kinne, S; Schulz, Michael & Balkanski, Y. (2009). Aerosol indirect effects - general circulation model intercomparison and evaluation with satellite data. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  9(22), s 8697- 8717
• 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. Series A, Dynamic meteorology and oceanography.  ISSN 0280-6495.  60 . doi: 10.1111/j.1600-0870.2008.00308.x
• 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. Series A, Dynamic meteorology and oceanography.  ISSN 0280-6495.  60 . doi: 10.1111/j.1600-0870.2008.00315.x
• Iversen, Trond; Kristiansen, J; Jung, T & Barkmeijer, J (2008). Optimal atmospheric forcing perturbations for the cold-ocean warm-land pattern. Tellus. Series A, Dynamic meteorology and oceanography.  ISSN 0280-6495.  60 . doi: 10.1111/j.1600-0870.2008.00310.x
• 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. Series A, Dynamic meteorology and oceanography.  ISSN 0280-6495.  60 . doi: 10.1111/j.1600-0870.2008.00313.x
• 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. Series A, Dynamic meteorology and oceanography.  ISSN 0280-6495.  60 . doi: 10.1111/j.1600-0870.2008.00309.x
• Seland, Øyvind; Iversen, Trond; Kirkevåg, Alf & Storelvmo, Trude (2008). Aerosol-climate interactions in the CAM-Oslo atmospheric GCM and investigation of associated shortcomings. Tellus. Series A, Dynamic meteorology and oceanography.  ISSN 0280-6495.  60A, s 459- 491 . doi: 10.1111/j.1600-0870.2008.00318.x
• 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.  ISSN 1748-9326.  3 . doi: 10.1088/1748-9326/3/4/O45001
• Textor, C; Schulz, M; Guibert, S; Kinne, S; Balkanski, Y; Bauer, S; Berntsen, Terje Koren; Berglen, Tore Flatlandsmo; Boucher, O; Chin, M; Dentener, F; Diehl, T; Feichter, J; Fillmore, D; Ginoux, P; Gong, S; Grini, Alf; Hendricks, J; Horowitz, L; Huang, P; Isaksen, Ivar S A; Iversen, Trond; Kloster, S; Koch, D; Kirkevåg, Alf; Kristjansson, Jon Egill; Krol, M; Lauer, A; Lamarque, JF; Liu, X; Montanaro, V; Myhre, Gunnar; Penner, JE; Pitari, G; Reddy, MS; Seland, O; Stier, P; Takemura, T & Tie, X (2007). The effect of harmonized emissions on aerosol properties in global models - an AeroCom experiment. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  7, s 1699- 1723
• Kinne, S; Schulz, M; Textor, C; Guibert, S; Balkanski, Y; Bauer, SE; Berntsen, Terje Koren; Berglen, Tore Flatlandsmo; Boucher, O; Chin, M; Collins, W; Dentener, F; Diehl, T; Easter, R; Feichter, J; Fillmore, D; Ghan, S; Ginoux, P; Gong, S; Grini, Alf; Hendricks, JE; Herzog, M; Horowitz, L; Isaksen, Ivar S A; Iversen, Trond; Kirkevåg, Alf; Kloster, S; Koch, D; Kristjansson, Jon Egill; Krol, M; Lauer, A; Lamarque, JF; Lesins, G; Liu, X; Lohmann, U; Montanaro, V; Myhre, Gunnar; Penner, JE; Pitari, G; Reddy, S; Seland, Øyvind; Stier, P; Takemura, T & Tie, X (2006). An AeroCom initial assessment - optical properties in aerosol component modules of global models. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  6, s 1815- 1834
• Schulz, M; Textor, C; Kinne, S; Balkanski, Y; Bauer, S; Berntsen, Terje Koren; Berglen, Tore Flatlandsmo; Boucher, O; Dentener, F; Guibert, S; Isaksen, Ivar S A; Iversen, Trond; Koch, D; Kirkevåg, Alf; Liu, X; Montanaro, V; Myhre, Gunnar; Penner, J; Pitari, G; Reddy, S; Seland, Øyvind; Stier, P & Takemura, T (2006). Radiative forcing by aerosols as derived from the AeroCom present-day and pre-industrial simulations. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  (6), s 5225- 5246
• Textor, C; Schulz, M; Guibert, S; Kinne, S; Balkanski, Y; Bauer, S; Berntsen, Terje Koren; Berglen, Tore Flatlandsmo; Boucher, O; Chin, M; Dentener, F; Diehl, T; Easter, R; Feichter, H; Fillmore, D; Ghan, S; Ginoux, P; Gong, S; Grini, Alf; Hendricks, J; Horowitz, L; Huang, P.; Isaksen, Ivar S A; Iversen, Trond; Kloster, S; Koch, D; Kirkevåg, Alf; Kristjansson, Jon Egill; Krol, M; Lauer, A; Lamarque, JF; Liu, X; Montanaro, V; Myhre, Gunnar; Penner, J; Pitari, G; Reddy, S; Seland, Øyvind; Stier, P; Takemura, T & Tie, X (2006). Analysis and quantification of the diversities of aerosol life cycles within AeroCom. Atmospheric Chemistry and Physics.  ISSN 1680-7316.  6, s 1777- 1813
• 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
• 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
• Iversen, T & Tropé, Claes Gøran (2005). Svulster i kvinnelige genitalia, I: Rolf Kåresen & Erik Wist (red.),  Kreftsykdommer - en basisbok for helsepersonell.  Gyldendal Akademisk.  ISBN 82-05-33494-3.  Chapter 2.9.  s 244 - 258
• 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
• Iversen, Trond (2004). Forandrer menneskene jordens klima?, I: Tilman Hartenstein & Elisabeth Skjervum Hole (red.),  P2-Akademiet. Bind XXXI.  Transit.  Del1.  s 9 - 18
• Barkmeijer, J.; Iversen, Trond & Palmer, T. N. (2003). Forcing singular vectors and other sensitive model structures. Quarterly Journal of the Royal Meteorological Society.  ISSN 0035-9009.  129, s 2401- 2423 . doi: 10.1256/qj.02.126

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• Iversen, Trond & Lystad, Magne (ed.) (2005). RegClim Technical Report No. 8. Norwegian Meteorological Insitute.  120 s.

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• Michel, Clio; Li, Camille; Graff, Lise Seland; Zappa, Giuseppe; Bethke, Ingo; Iversen, Trond & Mitchell, Daniel (2018). Assessing the impacts of mid-latitude circulation changes under +1.5ºC and +2ºC warming.
• Michel, Clio; Li, Camille; Graff, Lise Seland; Zappa, Giuseppe; Bethke, Ingo; Iversen, Trond & Mitchell, Daniel (2017). Assessing the impacts of mid-latitude circulation changes under +1.5ºC and +2ºC warming.
• Fagerli, Hilde; Tsyro, Svetlana G.; Denby, Bruce; Oliviè, Dirk Jan Leo; Nyiri, Agnes; Gauss, Michael; Simpson, David; Wind, Peter; Benedictow, Anna Maria Katarina; Jonson, Jan Eiof; Schulz, Michael; Kirkevåg, Alf; Valdebenito Bustamante, Alvaro Moises; Iversen, Trond; Klein, Heiko; Mortier, Augustin; Seland, Øyvind; Aas, Wenche; Hjellbrekke, Anne-Gunn; Solberg, Sverre; Rud, Richard Olav; Tørseth, Kjetil; Yttri, Karl Espen; Mareckova, Katarina; Brendle, Christine; Pinterits, Marion; Schindlbacher, Sabine; Tista, Melanie; Ullrich, Bernhard; Wankmüller, Robert; Posch, Maximilian; Mona, Lucia; Acosta Navarro, Juan-Camilo; Ekman, Annica; Hansson, Hans-Christen; Riipinen, Ilona; Struthers, Hamish & Varma, Vidya (2016). Transboundary particulate matter, photo-oxidants, acidifying and eutrophying components. EMEP Status Report. 1.
• Iversen, Trond & Heinze, Christoph (2015). The Norwegian Earth System Model - NorESM, Status and Plans for CMIP6 and Crescendo.
• Hov, Øystein; Benestad, Rasmus; Cubasch, Ulrich; Fischer, Erich; Höppe, Peter; Iversen, Trond; Kvamstø, Nils G; Kundzewicz, Zbigniew W.; Rezacova, Daniela; Rios, David; Duarte Santos, Filipe; Schädler, Bruno; Veisz, Otto; Zerefos, Christos; Murlis, John; Donat, M; Leckebusch, Gregor C. & Ulbrich, Uwe (2013). Extreme weather events in Europe: Preparing for climate change adaptation.
• Schulz, Michael; Gauss, Michael; Benedictow, Anna Maria Katarina; Jonson, Jan Eiof; Tsyro, Svetlana G.; Nyiri, Agnes; Simpson, David; Steensen, Birthe Marie Rødssæteren; Klein, Heiko; Valdebenito Bustamante, Alvaro Moises; Wind, Peter; Kirkevåg, Alf; Griesfeller, Jan; Bartnicki, Jerzy; Oliviè, Dirk Jan Leo; Grini, Alf; Iversen, Trond; Seland, Øyvind; Valiyaveetil, Semeena; Fagerli, Hilde; Aas, Wenche; Hjellbrekke, Anne-Gunn; Mareckova, Katarina; Wankmüller, Robert; Schneider, Philipp; Solberg, Sverre; Svendby, Tove Marit; Liu, Li; Posch, Maximilian; Vieno, Massimo; Reis, Stefan; Kryza, Maciej; Werner, Malgorzata & Walaszek, Kinga (2013). Transboundary acidification, eutrophication and ground level ozone in Europe in 2011. EMEP status report 2013.. EMEP report. 1/2013.
• Gisler, Galen Ross; Celledoni, Elena; Helgaker, Trygve; Iversen, Trond; Jakobsen, Kjetill Sigurd; Jones, Colin N.; Lipniacka, Anna; Lundervold, Arvid; Olsen, Nils Reidar Bøe; De Smedt, Koenraad; Koster, Jacko & Høst, Gudmund (2010). The scientific case for eInfrastructure in Norway. Vis sammendrag

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• Kristjansson, Jon Egill; Hoose, Corinna; Alterskjær, Kari; Iversen, Trond; Kirkevåg, Alf; Seland, O; Chen, Jen-Ping & Hazra, Anupam (2009). Aerosol indirect effect of the 'wrong' sign. Geochimica et Cosmochimica Acta.  ISSN 0016-7037.  73(13), s A697- A697
• 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.
• Iversen, Trond; Kirkevåg, Alf; Seland, Øyvind; Debernard, Jens B.; Kristjansson, Jon Egill & Storelvmo, Trude (2008). Aerosoler og klimaeffekten. Klima.  ISSN 1504-8136.  (4), s 40- 43
• 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.
• Iversen, Trond (2008). Special issue with manuscripts from the RegClim (regional climate development under global warming) project - Preface. Tellus. Series A, Dynamic meteorology and oceanography.  ISSN 0280-6495.  60 . doi: 10.1111/j.1600-0870.2008.00319.x
• 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
• Kirkevåg, Alf; Iversen, Trond; Kristjansson, Jon Egill; Seland, Øyvind & Debernard, Jens (2005). Aerosolmodellering i CCM-Oslo.
• Kirkevåg, Alf; Iversen, Trond; Kristjansson, Jon Egill; Seland, Øyvind & Debernard, Jens (2005). Climate response to aerosols in two versions of CCM-Oslo.
• Kirkevåg, Alf; Iversen, Trond; Kristjansson, Jon Egill; Seland, Øyvind & Debernard, Jens (2005). On aerosol-climate feedbacks, and the effect of doubling CO2.
• Kirkevåg, Alf; Iversen, Trond; Seland, Øyvind & Kristjansson, Jon Egill (2005). Parameterized aerosol optics and cloud droplet properties in CCM-Oslo.
• Kirkevåg, Alf; Iversen, Trond; Seland, Øyvind & Kristjansson, Jon Egill (2005). Revised schemes for aerosol optical parameters and cloud condensation nuclei in CCM-Oslo. Institute report series (Universitetet i Oslo. Institutt for geofysikk. 128.
• Barkmeijer, Jan; Iversen, Trond; Palmer, Tim N. & Van Noorden, T. (2004). Time dependent forcing singular vetors and their applications.
• Iversen, Trond (2004). The Norwegian RegClim-Project: Uncertain Processes increases the Risks as Climate Change in Northern Europe.
• Iversen, Trond; Frogner, Inger-lise & Barkmeijer, Jan (2004). A comparison of singular vectors for forcing (FSV) and singular vectors for initial conditions (SV) in a full-scale AGCM under different phases of the North Atlantic oscillation.
• Iversen, Trond; Kristjansson, Jon Egill; Kirkevåg, Alf & Seland, Øyvind (2004). Calculated Feedback Effects of Climate Change caused by Anthropogenic Aerosols.
• Iversen, Trond; Kristjansson, Jon Egill; Kirkevåg, Alf & Seland, Øyvind (2004). Climate feedbacks of the indirect effect caused by anthropogenic aerosols.
• Iversen, Trond & Seland, Øyvind (2004). Coupling Cumulus parameterisation and contaminant transport in global models.
• 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.
• Kristjansson, Jon Egill; Iversen, Trond; Kirkevåg, Alf & Seland, Øyvind (2004). Response of the coupled climate system to indirect aerosol forcing.
• 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.
• Seland, Øyvind; Iversen, Trond; Kirkevåg, Alf & Kristjansson, Jon Egill (2004). Effects of alternative emission data on modelled properties of sulfur and carbonaceous aerosols ub CCM-Oslo.
• Iversen, T & Grønås, Sigbjørn (2004). Arne M. Bratseth, 1949-2004 - In memoriam. Tellus. Series A, Dynamic meteorology and oceanography.  ISSN 0280-6495.  56, s 271- 272
• Ekanger, R; Hagen, Berit; Himmelmann, Anna; Iversen, Ole-Erik; Iversen, T; Lyngstadaas, Anita; Nordal, Randi R; Norheim, Ole Frithjof; Onsrud, Mathias; Tretli, Steinar & Trope, Claes Gøran (2003). Primær behandling av ovarialcancer. Metodevurdering basert på egen litteraturgranskning. SMM-rapport. 5.
• Iversen, Trond (2003). Kombinasjon av to scenarier for 2030-2050: Ekstremene nedjusteres. Cicerone.  ISSN 0804-0508.  12(5), s 20- 24
• Iversen, Trond; Barkmeijer, J. & Palmer, T. N. (2003). Optimal Forcing Perturbations for the Atmosphere. RegClim General Technical Report. 7.
• Iversen, Trond & Lystad, Magne (ed.) (2003). RegClim General Technical Report No.7 Presentations from Spring Seminar 12-16 May 2003, Oslo, Norway. RegClim General Technical Report. 7.

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