186 results on '"Myhre, G."'
Search Results
2. Understanding model diversity in future precipitation projections for South America
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Hodnebrog, Ø., Steensen, B. M., Marelle, L., Alterskjær, K., Dalsøren, S. B., and Myhre, G.
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- 2022
- Full Text
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3. The Southern Hemisphere Midlatitude Circulation Response to Rapid Adjustments and Sea Surface Temperature Driven Feedbacks
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Wood, T., Maycock, A. C., Forster, P. M., Richardson, T. B., Andrews, T., Boucher, O., Myhre, G., Samset, B. H., Kirkevåg, A., Lamarque, J.-F., Mülmenstädt, J., Olivié, D., Takemura, T., and Watson-Parris, D.
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- 2020
4. Multi-model simulations of aerosol and ozone radiative forcing due to anthropogenic emission changes during the period 1990–2015
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Myhre, G, Aas, W, Cherian, R, Collins, W, Faluvegi, G, Flanner, M, Forster, P, Hodnebrog, Ø, Klimont, Z, Lund, MT, Mülmenstädt, J, Lund Myhre, C, Olivié, D, Prather, M, Quaas, J, Samset, BH, Schnell, JL, Schulz, M, Shindell, D, Skeie, RB, Takemura, T, and Tsyro, S
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Meteorology & Atmospheric Sciences ,Atmospheric Sciences ,Astronomical and Space Sciences - Abstract
Over the past few decades, the geographical distribution of emissions of substances that alter the atmospheric energy balance has changed due to economic growth and air pollution regulations. Here, we show the resulting changes to aerosol and ozone abundances and their radiative forcing using recently updated emission data for the period 1990-2015, as simulated by seven global atmospheric composition models. The models broadly reproduce large-scale changes in surface aerosol and ozone based on observations (e.g.-1 to-3%yr-1 in aerosols over the USA and Europe). The global mean radiative forcing due to ozone and aerosol changes over the 1990-2015 period increased by +0.17±0.08Wm-2, with approximately one-third due to ozone. This increase is more strongly positive than that reported in IPCC AR5. The main reasons for the increased positive radiative forcing of aerosols over this period are the substantial reduction of global mean SO2 emissions, which is stronger in the new emission inventory compared to that used in the IPCC analysis, and higher black carbon emissions.
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- 2017
5. AerChemMIP: Quantifying the effects of chemistry and aerosols in CMIP6
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Collins, JW, Lamarque, JF, Schulz, M, Boucher, O, Eyring, V, Hegglin, IM, Maycock, A, Myhre, G, Prather, M, Shindell, D, and Smith, JS
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Earth Sciences - Abstract
The Aerosol Chemistry Model Intercomparison Project (AerChemMIP) is endorsed by the Coupled-Model Intercomparison Project 6 (CMIP6) and is designed to quantify the climate and air quality impacts of aerosols and chemically reactive gases. These are specifically near-term climate forcers (NTCFs: methane, tropospheric ozone and aerosols, and their precursors), nitrous oxide and ozone-depleting halocarbons. The aim of AerChemMIP is to answer four scientific questions. 1. How have anthropogenic emissions contributed to global radiative forcing and affected regional climate over the historical period? 2. How might future policies (on climate, air quality and land use) affect the abundances of NTCFs and their climate impacts? 3.How do uncertainties in historical NTCF emissions affect radiative forcing estimates? 4. How important are climate feedbacks to natural NTCF emissions, atmospheric composition, and radiative effects? These questions will be addressed through targeted simulations with CMIP6 climate models that include an interactive representation of tropospheric aerosols and atmospheric chemistry. These simulations build on the CMIP6 Diagnostic, Evaluation and Characterization of Klima (DECK) experiments, the CMIP6 historical simulations, and future projections performed elsewhere in CMIP6, allowing the contributions from aerosols and/or chemistry to be quantified. Specific diagnostics are requested as part of the CMIP6 data request to highlight the chemical composition of the atmosphere, to evaluate the performance of the models, and to understand differences in behaviour between them.
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- 2017
6. Comparison and Evaluation of Statistical Rainfall Disaggregation and High-Resolution Dynamical Downscaling over Complex Terrain
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Poschlod, B., Hodnebrog, Ø., Wood, R. R., Alterskjær, K., Ludwig, R., Myhre, G., and Sillmann, J.
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- 2018
7. Drivers of Precipitation Change : An Energetic Understanding
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Richardson, T. B., Forster, P. M., Andrews, T., Boucher, O., Faluvegi, G., Fläschner, D., Hodnebrog, Ø., Kasoar, M., Kirkevåg, A., Lamarque, J.-F., Myhre, G., Olivié, D., Samset, B. H., Shawki, D., Shindell, D., Takemura, T., and Voulgarakis, A.
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- 2018
8. A first-of-its-kind multi-model convection permitting ensemble for investigating convective phenomena over Europe and the Mediterranean
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Coppola, Erika, Sobolowski, Stefan, Pichelli, E., Raffaele, F., Ahrens, B., Anders, I., Ban, N., Bastin, S., Belda, M., Belusic, D., Caldas-Alvarez, A., Cardoso, R. M., Davolio, S., Dobler, A., Fernandez, J., Fita, L., Fumiere, Q., Giorgi, F., Goergen, K., Güttler, I., Halenka, T., Heinzeller, D., Hodnebrog, Ø., Jacob, D., Kartsios, S., Katragkou, E., Kendon, E., Khodayar, S., Kunstmann, H., Knist, S., Lavín-Gullón, A., Lind, P., Lorenz, T., Maraun, D., Marelle, L., van Meijgaard, E., Milovac, J., Myhre, G., Panitz, H.-J., Piazza, M., Raffa, M., Raub, T., Rockel, B., Schär, C., Sieck, K., Soares, P. M. M., Somot, S., Srnec, L., Stocchi, P., Tölle, M. H., Truhetz, H., Vautard, R., de Vries, H., and Warrach-Sagi, K.
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- 2020
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9. A PDRMIP Multimodel Study on the Impacts of Regional Aerosol Forcings on Global and Regional Precipitation
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Liu, L., Shawki, D., Voulgarakis, A., Kasoar, M., Samset, B. H., Myhre, G., Forster, P. M., Hodnebrog, Ø., Sillmann, J., Aalbergsjø, S. G., Boucher, O., Faluvegi, G., Iversen, T., KirkevåG, A., Lamarque, J.-F., Olivié, D., Richardson, T., Shindell, D., and Takemura, T.
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- 2018
10. Implications of differences between recent anthropogenic aerosol emission inventories for diagnosed AOD and radiative forcing from 1990 to 2019
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Lund, M.T., Myhre, G., Skeie, R.B., Samset, B.H., and Klimont, Z.
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This study focuses on implications of differences between recent global emissions inventories for simulated trends in anthropogenic aerosol abundances and radiative forcing (RF) over the 1990–2019 period. We use the ECLIPSE version 6 (ECLv6) and CEDS year 2021 release (CEDS21) as input to the chemical transport model OsloCTM3 and compare the resulting aerosol evolution to corresponding results derived with the first CEDS release, as well as to observed trends in regional and global aerosol optical depth (AOD). Using CEDS21 and ECLv6 results in a 3 % and 6 % lower global mean AOD compared to CEDS in 2014, primarily driven by differences over China and India, where the area average AOD is up to 30 % lower. These differences are considerably larger than the satellite-derived interannual variability in AOD. A negative linear trend over 2005–2017 in global AOD following changes in anthropogenic emissions is found with all three inventories but is markedly stronger with CEDS21 and ECLv6. Furthermore, we confirm that the model better captures the sign and strength of the observed AOD trend over China with CEDS21 and ECLv6 compared to using CEDS, while the opposite is the case for South Asia. We estimate a net global mean aerosol-induced RF in 2014 relative to 1990 of 0.08 W m−2 for CEDS21 and 0.12 W m−2 for ECLv6, compared to 0.03 W m−2 with CEDS. Using CEDS21, we also estimate the RF in 2019 relative to 1990 to be 0.10 W m−2, reflecting the continuing decreasing trend in aerosol loads post-2014. Our results facilitate more rigorous comparison between existing and upcoming studies of climate and health effects of aerosols using different emission inventories.
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- 2023
11. PDRMIP : A Precipitation Driver and Response Model Intercomparison Project—Protocol and Preliminary Results
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Myhre, G., Forster, P. M., Samset, B. H., Hodnebrog, Ø., Sillmann, J., Aalbergsjø, S. G., Andrews, T., Boucher, O., Faluvegi, G., Fläschner, D., Iversen, T., Kasoar, M., Kharin, V., Kirkevåg, A., Lamarque, J.-F., Olivié, D., Richardson, T. B., Shindell, D., Shine, K. P., Stjern, C. W., Takemura, T., Voulgarakis, A., and Zwiers, F.
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- 2017
12. Frequency of extreme precipitation increases extensively with event rareness under global warming
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Myhre, G., Alterskjær, K., Stjern, C. W., Hodnebrog, Ø., Marelle, L., Samset, B. H., Sillmann, J., Schaller, N., Fischer, E., Schulz, M., and Stohl, A.
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- 2019
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13. Sensible Heat Has Significantly Affected the Global Hydrological Cycle Over the Historical Period
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Myhre, G, Samset, B. H, Hodnebrog, Ø, Andrews, T, Boucher, O, Faluvegi, G, Fläschner, D, Forster, P.M, Kasoar, M, Kharin, V, Kirkevåg, A, Lamarque, J.-F, Olivie, D, Richardson, T.B, Shawki, D, Shindell, D, Shine, K.P, Stjern, C.W, Takemura, T, and Voulgarakis, A
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Meteorology And Climatology - Abstract
Globally, latent heating associated with a change in precipitation is balanced by changes to atmospheric radiative cooling and sensible heat fluxes. Both components can be altered by climate forcing mechanisms and through climate feedbacks, but the impacts of climate forcing and feedbacks on sensible heat fluxes have received much less attention. Here we show, using a range of climate modelling results, that changes in sensible heat are the dominant contributor to the present global-mean precipitation change since preindustrial time, because the radiative impact of forcings and feedbacks approximately compensate. The model results show a dissimilar influence on sensible heat and precipitation from various drivers of climate change. Due to its strong atmospheric absorption, black carbon is found to influence the sensible heat very differently compared to other aerosols and greenhouse gases. Our results indicate that this is likely caused by differences in the impact on the lower tropospheric stability.
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- 2018
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14. Weak Hydrological Sensitivity to Temperature Change over Land, Independent of Climate Forcing
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Samset, B. H, Myhre, G, Forster, P. M, Hodnebrog, O, Andrews, T, Boucher, O, Faluvegi, G, Flaeschner, D, Kasoar, M, Kharin, V, Kirkevag, A, Lamarque, J.-F, Olivie, D, Richardson, T. B, Shindell, D, Takemura, T, and Voulgarakis, A
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Meteorology And Climatology - Abstract
We present the global and regional hydrological sensitivity (HS) to surface temperature changes, for perturbations to CO2, CH4, sulfate and black carbon concentrations, and solar irradiance. Based on results from ten climate models, we show how modeled global mean precipitation increases by 2-3% per kelvin of global mean surface warming, independent of driver, when the effects of rapid adjustments are removed. Previously reported differences in response between drivers are therefore mainly ascribable to rapid atmospheric adjustment processes. All models show a sharp contrast in behavior over land and over ocean, with a strong surface temperature-driven (slow) ocean HS of 3-5%/K, while the slow land HS is only 0-2%/K. Separating the response into convective and large-scale cloud processes, we find larger inter-model differences, in particular over land regions. Large-scale precipitation changes are most relevant at high latitudes, while the equatorial HS is dominated by convective precipitation changes. Black carbon stands out as the driver with the largest inter-model slow HS variability, and also the strongest contrast between a weak land and strong sea response. We identify a particular need for model investigations and observational constraints on convective precipitation in the Arctic, and large-scale precipitation around the Equator.
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- 2018
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15. Drivers of Precipitation Change: An Energetic Understanding
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Richardson, T. B, Forster, P. M, Andrews, B, Boucher, O, Faluvegi, G, Flashner, D, Hodnebrog, O, Kasoar, M, Kirkevag, A, Lamarque, J.-F, Myhre, G, Olivie, D, B. H. Samset, Shawki, D, Shindell, D, Takemure, T, and Voulgarakis, A
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Meteorology And Climatology - Abstract
The response of the hydrological cycle to climate forcings can be understood within the atmospheric energy budget framework. In this study precipitation and energy budget responses to five forcing agents are analyzed using 10 climate models from the Precipitation Driver Response Model Intercomparison Project (PDRMIP). Precipitation changes are split into a forcing-dependent fast response and a temperature-driven hydrological sensitivity. Globally, when normalized by top-of-atmosphere (TOA) forcing, fast precipitation changes are most sensitive to strongly absorbing drivers (CO2, black carbon). However, over land fast precipitation changes are most sensitive to weakly absorbing drivers (sulfate, solar) and are linked to rapid circulation changes. Despite this, land-mean fast responses to CO2 and black carbon exhibit more intermodel spread. Globally, the hydrological sensitivity is consistent across forcings, mainly associated with increased longwave cooling, which is highly correlated with intermodel spread. The land-mean hydrological sensitivity is weaker, consistent with limited moisture availability. The PDRMIP results are used to construct a simple model for land-mean and sea-mean precipitation change based on sea surface temperature change and TOA forcing. The model matches well with CMIP5 ensemble mean historical and future projections, and is used to understand the contributions of different drivers. During the twentieth century, temperature-driven intensification of land-mean precipitation has been masked by fast precipitation responses to anthropogenic sulfate and volcanic forcing, consistent with the small observed trend. However, as projected sulfate forcing decreases, and warming continues, land-mean precipitation is expected to increase more rapidly, and may become clearly observable by the mid-twenty-first century.
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- 2017
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16. Understanding model diversity in future precipitation projections for South America
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Hodnebrog, Ø., primary, Steensen, B. M., additional, Marelle, L., additional, Alterskjær, K., additional, Dalsøren, S. B., additional, and Myhre, G., additional
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- 2021
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17. Fast and Slow Precipitation Responses to Individual Climate Forcers: A PDRMIP Multimodel Study
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Samset, B. H, Myhre, G, Forster, P.M, Hodnebrog, O, Andrews, T, Faluvegi, G, Flaschner, D, Kasoar, M, Kharin, V, Kirkevag, A, Shindell, D, and Voulgarakis, A
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Meteorology And Climatology - Abstract
Precipitation is expected to respond differently to various drivers of anthropogenic climate change. We present the first results from the Precipitation Driver and Response Model Intercomparison Project (PDRMIP), where nine global climate models have perturbed CO2, CH4, black carbon, sulfate, and solar insolation. We divide the resulting changes to global mean and regional precipitation into fast responses that scale with changes in atmospheric absorption and slow responses scaling with surface temperature change. While the overall features are broadly similar between models, we find significant regional intermodel variability, especially over land. Black carbon stands out as a component that may cause significant model diversity in predicted precipitation change. Processes linked to atmospheric absorption are less consistently modeled than those linked to top-of-atmosphere radiative forcing. We identify a number of land regions where the model ensemble consistently predicts that fast precipitation responses to climate perturbations dominate over the slow, temperature-driven responses.
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- 2016
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18. Energy Budget Constraints on the Time History of Aerosol Forcing and Climate Sensitivity
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Smith, C. J., primary, Harris, G. R., additional, Palmer, M. D., additional, Bellouin, N., additional, Collins, W., additional, Myhre, G., additional, Schulz, M., additional, Golaz, J.‐C., additional, Ringer, M., additional, Storelvmo, T., additional, and Forster, P. M., additional
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- 2021
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19. Heterogeneous ice nucleation in the WRF-Chem 3.9.1.1 model and its influence on cloudresponse to volcanic aerosols
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Marelle, Louis, Myhre, G., Raut, Jean-Christophe, Keita, Seitigi Aboubacar, and Cardon, Catherine
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[PHYS.PHYS.PHYS-AO-PH] Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph] - Abstract
Heterogeneous ice formation on aerosols is the main primary cloud ice formation process above temperatures of -38°C, and asa consequence it plays a major role in the formation of mixed-phase and ice clouds. Improving our understanding of iceprocesses could help better constrain the radiative forcing of cloud aerosol interactions, which remains a major source ofuncertainty in climate projections. Despite their importance, most atmospheric models do not represent aerosol-cloud iceprocesses explicitly.We extend in the WRF-Chem 3.9.1 model a recent parameterization of deposition-mode ice nucleation to also includeimmersion-mode nucleation, based on the classical nucleation theory (CNT) description. We also couple this parameterizationwith the aerosol-liquid cloud parameterization of Abdul Razzak and Ghan already included in WRF-Chem 3.9.1. This allows us tomodel the effect of aerosols on mixed-phase and ice clouds. We use volcanic eruptions as case studies, especially focusing onthe 2014/2015 Holuhraun/Bárðarbunga eruption in Iceland. Specifically, we investigate how volcanic aerosols influencemodeled cloud microphysical properties with and without the explicit ice nucleation parameterization, comparing the modelagainst MODIS satellite observations. We also investigate the effect of these processes on the cloud response in terms ofoptical properties, radiative fluxes, and precipitation during the eruptions
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- 2021
20. Extratropical–Tropical Interaction Model Intercomparison Project (Etin-Mip): Protocol and Initial Results
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Kang, S., Hawcroft, M., Xiang, B., Hwang, Y., Kim, H., Cazes, G., Codron, F., Crueger, T., Deser, C., Hodnebrog, Ø., Kim, J., Kosaka, Y., Losada, T., Mechoso, C., Myhre, G., Seland, Ø., Stevens, B., https://orcid.org/0000-0003-3795-0475, Watanabe, M., Yu, S., Ulsan National Institute of Science and Technology (UNIST), University of Exeter, NOAA Geophysical Fluid Dynamics Laboratory (GFDL), National Oceanic and Atmospheric Administration (NOAA), National Taiwan University [Taiwan] (NTU), Océan et variabilité du climat (VARCLIM), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU), Max Planck Institute for Meteorology (MPI-M), Max-Planck-Gesellschaft, National Center for Atmospheric Research [Boulder] (NCAR), Center for International Climate and Environmental Research [Oslo] (CICERO), University of Oslo (UiO), Research Center for Advanced Science and Technology [Tokyo] (RCAST), The University of Tokyo (UTokyo), Departamento Fisica de la Tierra, Astronomía y Astrofísica [Madrid], Universidad Complutense de Madrid = Complutense University of Madrid [Madrid] (UCM), University of California [Los Angeles] (UCLA), University of California, Norwegian Meteorological Institute [Oslo] (MET), Max-Planck-Institut für Meteorologie (MPI-M), Atmosphere and Ocean Research Institute [Kashiwa-shi] (AORI), Yale University [New Haven], Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), and University of California (UC)
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[SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph] - Abstract
ETIN-MIP is a community-wide effort to improve dynamical understanding of the linkages between tropical precipitation and radiative biases in various regions, with implications for anthropogenic climate change and geoengineering.This article introduces the Extratropical-Tropical Interaction Model Intercomparison Project (ETIN-MIP), where a set of fully coupled model experiments are designed to examine the sources of longstanding tropical precipitation biases in climate models. In particular, we reduce insolation over three targeted latitudinal bands of persistent model biases: the southern extratropics, the southern tropics and the northern extratropics. To address the effect of regional energy bias corrections on the mean distribution of tropical precipitation, such as the double Intertropical Convergence Zone problem, we evaluate the quasi-equilibrium response of the climate system corresponding to a 50-year period after the 100 years of prescribed energy perturbation. Initial results show that, despite a large inter-model spread in each perturbation experiment due to differences in ocean heat uptake response and climate feedbacks across models, the southern tropics is most efficient at driving a meridional shift of tropical precipitation. In contrast, the extratropical energy perturbations are effectively damped by anomalous heat uptake over the subpolar oceans, thereby inducing a smaller meridional shift of tropical precipitation compared with the tropical energy perturbations. The ETIN-MIP experiments allow us to investigate the global implications of regional energy bias corrections, providing a route to guide the practice of model development, with implications for understanding dynamical responses to anthropogenic climate change and geoengineering.
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- 2019
21. Emerging Asian aerosol patterns
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Samset, B. H., Lund, M. T., Bollasina, M. A., Myhre, G., and Wilcox, Laura
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Anthropogenic aerosol emissions over Asia are changing rapidly, both in composition and spatial distribution1. The Shared Socioeconomic Pathways (SSPs), potential narratives of development used by the Intergovernmental Panel for Climate Change in future projections, span a range of influences of aerosols on climate over the next decades. Several of these narratives project the continuation of a trend manifested in observations since 2010, with a clear dipole between South and East Asia. \ud \ud The patterns of radiative forcing that result from these distributions of aerosols will differ from those of the late 20th century. They may instigate large-scale atmospheric responses that could have wide ranging impacts on climate and society well beyond the aerosol source regions. South and East Asia are particularly vulnerable to climate change because of strong seasonal variations in precipitation, high average temperature, and very high population density. Therefore, any aerosol impacts on the strength or seasonal variations in monsoon rainfall, freshwater availability, or climate extremes, will incur large societal costs. We urge the scientific community to make definite progress towards understanding and quantifying the impacts of Asian aerosols and to tackle the potentially large regional and hemispheric implications of these emerging trends.
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- 2019
22. Acquired peri‐articular ganglion cyst in the lateral femorotibial joint in an 18‐year‐old Percheron cross mare
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Alsherif, A. A., primary, Myhre, G. D., additional, and Vin, R., additional
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- 2020
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23. Updated Global Warming Potentials and Radiative Efficiencies of Halocarbons and Other Weak Atmospheric Absorbers
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Hodnebrog, Ø., primary, Aamaas, B., additional, Fuglestvedt, J. S., additional, Marston, G., additional, Myhre, G., additional, Nielsen, C. J., additional, Sandstad, M., additional, Shine, K. P., additional, and Wallington, T. J., additional
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- 2020
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24. Black Carbon and Precipitation: An Energetics Perspective
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Sand, M., primary, Samset, B. H., additional, Tsigaridis, K., additional, Bauer, S. E., additional, and Myhre, G., additional
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- 2020
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25. The Spectral Nature of Stratospheric Temperature Adjustment and its Application to Halocarbon Radiative Forcing
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Shine, K. P., primary and Myhre, G., additional
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- 2020
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26. Bounding Global Aerosol Radiative Forcing of Climate Change
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Bellouin, N., primary, Quaas, J., additional, Gryspeerdt, E., additional, Kinne, S., additional, Stier, P., additional, Watson‐Parris, D., additional, Boucher, O., additional, Carslaw, K. S., additional, Christensen, M., additional, Daniau, A.‐L., additional, Dufresne, J.‐L., additional, Feingold, G., additional, Fiedler, S., additional, Forster, P., additional, Gettelman, A., additional, Haywood, J. M., additional, Lohmann, U., additional, Malavelle, F., additional, Mauritsen, T., additional, McCoy, D. T., additional, Myhre, G., additional, Mülmenstädt, J., additional, Neubauer, D., additional, Possner, A., additional, Rugenstein, M., additional, Sato, Y., additional, Schulz, M., additional, Schwartz, S. E., additional, Sourdeval, O., additional, Storelvmo, T., additional, Toll, V., additional, Winker, D., additional, and Stevens, B., additional
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- 2020
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27. Efficacy of Climate Forcings in PDRMIP Models
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Richardson, T. B., primary, Forster, P. M., additional, Smith, C. J., additional, Maycock, A. C., additional, Wood, T., additional, Andrews, T., additional, Boucher, O., additional, Faluvegi, G., additional, Fläschner, D., additional, Hodnebrog, Ø., additional, Kasoar, M., additional, Kirkevåg, A., additional, Lamarque, J.‐F., additional, Mülmenstädt, J., additional, Myhre, G., additional, Olivié, D., additional, Portmann, R. W., additional, Samset, B. H., additional, Shawki, D., additional, Shindell, D., additional, Stier, P., additional, Takemura, T., additional, Voulgarakis, A., additional, and Watson‐Parris, D., additional
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- 2019
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28. Intensification of summer precipitation with shorter time-scales in Europe
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Hodnebrog, Ø, primary, Marelle, L, additional, Alterskjær, K, additional, Wood, R R, additional, Ludwig, R, additional, Fischer, E M, additional, Richardson, T B, additional, Forster, P M, additional, Sillmann, J, additional, and Myhre, G, additional
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- 2019
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29. Very strong atmospheric methane growth in the four years 2014 - 2017: Implications for the Paris Agreement
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Nisbet, EG, Manning, MR, Dlugokencky, EJ, Fisher, RE, Lowry, D, Michel, SE, Lund Myhre, C, Platt, SM, Allen, G, Bousquet, P, Brownlow, R, Cain, M, France, JL, Hermansen, O, Hossaini, R, Jones, Anna, Levin, I, Manning, AC, Myhre, G, Pyle, JA, Vaughn, B, Warwick, NJ, and White, JWC
- Abstract
Atmospheric methane grew very rapidly in 2014 (12.7±0.5 ppb/yr), 2015 (10.1±0.7 ppb/yr), 2016 (7.0± 0.7 ppb/yr) and 2017 (7.7±0.7 ppb/yr), at rates not observed since the 1980s. The increase in the methane burden began in 2007, with the mean global mole fraction in remote surface background air rising from about 1775 ppb in 2006 to 1850 ppb in 2017. Simultaneously the 13C/12C isotopic ratio (expressed as δ13CCH4) has shifted, in a new trend to more negative values that have been observed worldwide for over a decade. The causes of methane's recent mole fraction increase are therefore either a change in the relative proportions (and totals) of emissions from biogenic and thermogenic and pyrogenic sources, especially in the tropics and sub‐tropics, or a decline in the atmospheric sink of methane, or both. Unfortunately, with limited measurement data sets, it is not currently possible to be more definitive. The climate warming impact of the observed methane increase over the past decade, if continued at >5 ppb/yr in the coming decades, is sufficient to challenge the Paris Agreement, which requires sharp cuts in the atmospheric methane burden. However, anthropogenic methane emissions are relatively very large and thus offer attractive targets for rapid reduction, which are essential if the Paris Agreement aims are to be attained.
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- 2019
30. Carbon Dioxide Physiological Forcing Dominates Projected Eastern Amazonian Drying
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Richardson, TB, Forster, PM, Andrews, T, Boucher, O, Faluvegi, G, Fläschner, D, Kasoar, M, Kirkevåg, A, Lamarque, J-F, Myhre, G, Olivié, D, Samset, BH, Shawki, D, Shindell, D, Takemura, T, and Voulgarakis, A
- Subjects
Science & Technology ,CLIMATE-CHANGE ,PRECIPITATION CHANGE ,CIRCULATION ,food and beverages ,Geology ,DROUGHT SENSITIVITY ,UNCERTAINTY ,precipitation ,HYDROLOGICAL CYCLE ,Article ,stomatal response ,physiological forcing ,Physical Sciences ,MD Multidisciplinary ,fast response ,Meteorology & Atmospheric Sciences ,CO2 ,Geosciences, Multidisciplinary ,RAINFALL ,Amazon ,CO2 forcing ,SCALE ,RESPONSES - Abstract
Future projections of east Amazonian precipitation indicate drying, but they are uncertain and poorly understood. In this study we analyze the Amazonian precipitation response to individual atmospheric forcings using a number of global climate models. Black carbon is found to drive reduced precipitation over the Amazon due to temperature-driven circulation changes, but the magnitude is uncertain. CO2 drives reductions in precipitation concentrated in the east, mainly due to a robustly negative, but highly variable in magnitude, fast response. We find that the physiological effect of CO2 on plant stomata is the dominant driver of the fast response due to reduced latent heating and also contributes to the large model spread. Using a simple model, we show that CO2 physiological effects dominate future multimodel mean precipitation projections over the Amazon. However, in individual models temperature-driven changes can be large, but due to little agreement, they largely cancel out in the model mean. ©2018. The Authors.
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- 2018
31. Discrepancy between simulated and observed ethane and propane levels explained by underestimated fossil emissions /704/106/35/824 /704/172/169/824 /119 article
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Dalsøren, S.B., Myhre, G., Hodnebrog, O., Myhre, C.L., Stohl, A., Pisso, I., Schwietzke, S., Höglund-Isaksson, L., Helmig, D., Reimann, S., SAUVAGE, S., Schmidbauer, N., Read, K.A., Carpenter, L.J., Lewis, A.C., Punjabi, S., Wallasch, M., Ecole nationale supérieure Mines-Télécom Lille Douai (IMT Lille Douai), and Institut Mines-Télécom [Paris] (IMT)
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[SPI]Engineering Sciences [physics] - Abstract
Ethane and propane are the most abundant non-methane hydrocarbons in the atmosphere. However, their emissions, atmospheric distribution, and trends in their atmospheric concentrations are insufficiently understood. Atmospheric model simulations using standard community emission inventories do not reproduce available measurements in the Northern Hemisphere. Here, we show that observations of pre-industrial and present-day ethane and propane can be reproduced in simulations with a detailed atmospheric chemistry transport model, provided that natural geologic emissions are taken into account and anthropogenic fossil fuel emissions are assumed to be two to three times higher than is indicated in current inventories. Accounting for these enhanced ethane and propane emissions results in simulated surface ozone concentrations that are 5-13% higher than previously assumed in some polluted regions in Asia. The improved correspondence with observed ethane and propane in model simulations with greater emissions suggests that the level of fossil (geologic + fossil fuel) methane emissions in current inventories may need re-evaluation. © 2018 The Author(s).
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- 2018
32. Comparison of Effective Radiative Forcing Calculations Using Multiple Methods, Drivers, and Models
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Tang, T., primary, Shindell, D., additional, Faluvegi, G., additional, Myhre, G., additional, Olivié, D., additional, Voulgarakis, A., additional, Kasoar, M., additional, Andrews, T., additional, Boucher, O., additional, Forster, P.M., additional, Hodnebrog, Ø., additional, Iversen, T., additional, Kirkevåg, A., additional, Lamarque, J.‐F., additional, Richardson, T., additional, Samset, B.H., additional, Stjern, C.W., additional, Takemura, T., additional, and Smith, C., additional
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- 2019
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33. Very Strong Atmospheric Methane Growth in the 4 Years 2014–2017: Implications for the Paris Agreement
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Nisbet, E. G., primary, Manning, M. R., additional, Dlugokencky, E. J., additional, Fisher, R. E., additional, Lowry, D., additional, Michel, S. E., additional, Myhre, C. Lund, additional, Platt, S. M., additional, Allen, G., additional, Bousquet, P., additional, Brownlow, R., additional, Cain, M., additional, France, J. L., additional, Hermansen, O., additional, Hossaini, R., additional, Jones, A. E., additional, Levin, I., additional, Manning, A. C., additional, Myhre, G., additional, Pyle, J. A., additional, Vaughn, B. H., additional, Warwick, N. J., additional, and White, J. W. C., additional
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- 2019
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34. Radiative Forcing of Climate: The Historical Evolution of the Radiative Forcing Concept, the Forcing Agents and their Quantification, and Applications
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Ramaswamy, V., primary, Collins, W., primary, Haywood, J., primary, Lean, J., primary, Mahowald, N., primary, Myhre, G., primary, Naik, V., primary, Shine, K. P., primary, Soden, B., primary, Stenchikov, G., primary, and Storelvmo, T., primary
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- 2019
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35. Halfway to doubling of CO₂ radiative forcing
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Myhre, G, Myhre, CL, Forster, PM, and Shine, KP
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- 2017
36. Rapid Adjustments Cause Weak Surface Temperature Response to Increased Black Carbon Concentrations
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Stjern, CW, Samset, BH, Myhre, G, Forster, PM, Hodnebrog, O, Andrews, T, Boucher, O, Faluvegi, G, Iversen, T, Kasoar, M, Kharin, V, Kirkevåg, A, Lamarque, J-F, Olivié, D, Richardson, T, Shawki, D, Shindell, D, Smith, CJ, Takemura, T, and Voulgarakis, A
- Subjects
Article - Abstract
We investigate the climate response to increased concentrations of black carbon (BC), as part of the Precipitation Driver Response Model Intercomparison Project (PDRMIP). A tenfold increase in BC is simulated by 9 global coupled-climate models, producing a model-median effective radiative forcing (ERF) of 0.82 (ranging from 0.41 to 2.91) Wm(−2), and a warming of 0.67 (0.16 to 1.66) K globally and 1.24 (0.26 to 4.31) K in the Arctic. A strong positive instantaneous radiative forcing (median of 2.10 Wm(−2) based on five of the models) is countered by negative rapid adjustments (−0.64 Wm(−2) for the same five models), which dampen the total surface temperature signal. Unlike other drivers of climate change, the response of temperature and cloud profiles to the BC forcing is dominated by rapid adjustments. Low-level cloud amounts increase for all models, while higher-level clouds are diminished. The rapid temperature response is particularly strong above 400 hPa, where increased atmospheric stabilization and reduced cloud cover contrast the response pattern of the other drivers. In conclusion, we find that this substantial increase in BC concentrations does have considerable impacts on important aspects of the climate system. However, some of these effects tend to offset one another, leaving a relatively small global warming of 0.47 K per Wm(−2) – about 20 % lower than the response to a doubling of CO(2). Translating the tenfold increase in BC to the present-day impact of anthropogenic BC (given the emissions used in this work) would leave a warming of merely 0.07 K.
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- 2017
37. A first-of-its-kind multi-model convection permitting ensemble for investigating convective phenomena over Europe and the Mediterranean
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Coppola, Erika, primary, Sobolowski, Stefan, additional, Pichelli, E., additional, Raffaele, F., additional, Ahrens, B., additional, Anders, I., additional, Ban, N., additional, Bastin, S., additional, Belda, M., additional, Belusic, D., additional, Caldas-Alvarez, A., additional, Cardoso, R. M., additional, Davolio, S., additional, Dobler, A., additional, Fernandez, J., additional, Fita, L., additional, Fumiere, Q., additional, Giorgi, F., additional, Goergen, K., additional, Güttler, I., additional, Halenka, T., additional, Heinzeller, D., additional, Hodnebrog, Ø., additional, Jacob, D., additional, Kartsios, S., additional, Katragkou, E., additional, Kendon, E., additional, Khodayar, S., additional, Kunstmann, H., additional, Knist, S., additional, Lavín-Gullón, A., additional, Lind, P., additional, Lorenz, T., additional, Maraun, D., additional, Marelle, L., additional, van Meijgaard, E., additional, Milovac, J., additional, Myhre, G., additional, Panitz, H.-J., additional, Piazza, M., additional, Raffa, M., additional, Raub, T., additional, Rockel, B., additional, Schär, C., additional, Sieck, K., additional, Soares, P. M. M., additional, Somot, S., additional, Srnec, L., additional, Stocchi, P., additional, Tölle, M. H., additional, Truhetz, H., additional, Vautard, R., additional, de Vries, H., additional, and Warrach-Sagi, K., additional
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- 2018
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38. Understanding Rapid Adjustments to Diverse Forcing Agents
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Smith, C. J., primary, Kramer, R. J., additional, Myhre, G., additional, Forster, P. M., additional, Soden, B. J., additional, Andrews, T., additional, Boucher, O., additional, Faluvegi, G., additional, Fläschner, D., additional, Hodnebrog, Ø., additional, Kasoar, M., additional, Kharin, V., additional, Kirkevåg, A., additional, Lamarque, J.‐F., additional, Mülmenstädt, J., additional, Olivié, D., additional, Richardson, T., additional, Samset, B. H., additional, Shindell, D., additional, Stier, P., additional, Takemura, T., additional, Voulgarakis, A., additional, and Watson‐Parris, D., additional
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- 2018
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39. Quantifying the Importance of Rapid Adjustments for Global Precipitation Changes
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Myhre, G., primary, Kramer, R. J., additional, Smith, C. J., additional, Hodnebrog, Ø., additional, Forster, P., additional, Soden, B. J., additional, Samset, B. H., additional, Stjern, C. W., additional, Andrews, T., additional, Boucher, O., additional, Faluvegi, G., additional, Fläschner, D., additional, Kasoar, M., additional, Kirkevåg, A., additional, Lamarque, J.‐F., additional, Olivié, D., additional, Richardson, T., additional, Shindell, D., additional, Stier, P., additional, Takemura, T., additional, Voulgarakis, A., additional, and Watson‐Parris, D., additional
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- 2018
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40. Strong constraints on aerosol–cloud interactions from volcanic eruptions
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Malavelle, FF, Haywood, JM, Jones, A, Gettelman, A, Clarisse, L, Bauduin, S, Allan, RP, Karset, IHH, Kristjánsson, JE, Oreopoulos, L, Cho, N, Lee, D, Bellouin, N, Boucher, O, Grosvenor, DP, Carslaw, KS, Dhomse, S, Mann, GW, Schmidt, A, Coe, H, Hartley, ME, Dalvi, M, Hill, AA, Johnson, BT, Johnson, CE, Knight, JR, O’Connor, FM, Partridge, DG, Stier, P, Myhre, G, Platnick, S, Stephens, GL, Takahashi, H, and Thordarson, T
- Abstract
Aerosols have a potentially large effect on climate, particularly through their interactions with clouds, but the magnitude of this effect is highly uncertain. Large volcanic eruptions produce sulfur dioxide, which in turn produces aerosols; these eruptions thus represent a natural experiment through which to quantify aerosol–cloud interactions. Here we show that the massive 2014–2015 fissure eruption in Holuhraun, Iceland, reduced the size of liquid cloud droplets—consistent with expectations—but had no discernible effect on other cloud properties. The reduction in droplet size led to cloud brightening and global-mean radiative forcing of around −0.2 watts per square metre for September to October 2014. Changes in cloud amount or cloud liquid water path, however, were undetectable, indicating that these indirect effects, and cloud systems in general, are well buffered against aerosol changes. This result will reduce uncertainties in future climate projections, because we are now able to reject results from climate models with an excessive liquid-water-path response.
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- 2017
41. Aerosols at the poles: an AeroCom Phase II multi-model evaluation
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Sand, M., Samset, B. H., Balkanski, Y., Bauer, S., Bellouin, N., Berntsen, T. K., Bian, H., Chin, M., Diehl, T., Easter, R., Ghan, S. J., Iversen, T., Kirkevåg, A., Lamarque, J.-F., Lin, G., Liu, X., Luo, G., Myhre, G., Noije, T. V., Penner, J. E., Schulz, M., Seland, Ø., Skeie, R. B., Stier, P., Takemura, T., Tsigaridis, K., Yu, F., Zhang, K., Zhang, H., Center for International Climate and Environmental Research [Oslo] (CICERO), University of Oslo (UiO), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Modelling the Earth Response to Multiple Anthropogenic Interactions and Dynamics (MERMAID), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Department of Meteorology [Reading], University of Reading (UOR), Joint Center for Earth Systems Technology [Baltimore] (JCET), NASA Goddard Space Flight Center (GSFC)-University of Maryland [Baltimore County] (UMBC), University of Maryland System-University of Maryland System, NASA Goddard Space Flight Center (GSFC), JRC Institute for Environment and Sustainability (IES), European Commission - Joint Research Centre [Ispra] (JRC), Pacific Northwest National Laboratory (PNNL), Atmospheric Chemistry Observations and Modeling Laboratory (ACOML), National Center for Atmospheric Research [Boulder] (NCAR), Norwegian Meteorological Institute [Oslo] (MET), Department of Physics [Oxford], University of Oxford [Oxford], Kyushu University [Fukuoka], Center for Climate Systems Research [New York] (CCSR), Columbia University [New York], Atmospheric Sciences Research Center (ASRC), University at Albany [SUNY], State University of New York (SUNY)-State University of New York (SUNY), University of Maryland [Baltimore County] (UMBC), University of Maryland System-University of Maryland System-NASA Goddard Space Flight Center (GSFC), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), University of Oxford, and Kyushu University
- Subjects
Earth's energy budget ,Atmospheric Science ,010504 meteorology & atmospheric sciences ,010502 geochemistry & geophysics ,Atmospheric sciences ,7. Clean energy ,01 natural sciences ,Latitude ,lcsh:Chemistry ,chemistry.chemical_compound ,Sea ice ,Sulfate ,Optical depth ,0105 earth and related environmental sciences ,[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph] ,[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere ,geography ,geography.geographical_feature_category ,Radiative forcing ,lcsh:QC1-999 ,Aerosol ,lcsh:QD1-999 ,Arctic ,chemistry ,13. Climate action ,Climatology ,Environmental science ,lcsh:Physics - Abstract
International audience; 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 an-thropogenic aerosol radiative forcing exist. Here we compare the aerosol optical depth (AOD) at 550 nm 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 (de-fined 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 Published by Copernicus Publications on behalf of the European Geosciences Union. 12198 M. Sand et al.: Aerosols at the poles: an AeroCom Phase II multi-model evaluation models have estimated the shortwave anthropogenic radia-tive 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 (−0.12 W 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.
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- 2017
42. Radiative forcing of carbon dioxide, methane, and nitrous oxide: a significant revision of the methane radiative forcing
- Author
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Etminan, M., Myhre, G., Highwood, E. J., and Shine, K. P
- Abstract
New calculations of the radiative forcing (RF) are presented for the three main well‐mixed\ud greenhouse gases, methane, nitrous oxide, and carbon dioxide. Methane’s RF is particularly impacted\ud because of the inclusion of the shortwave forcing; the 1750–2011 RF is about 25% higher (increasing from\ud 0.48 W m−2 to 0.61 W m−2) compared to the value in the Intergovernmental Panel on Climate Change (IPCC)\ud 2013 assessment; the 100 year global warming potential is 14% higher than the IPCC value. We present new\ud simplified expressions to calculate RF. Unlike previous expressions used by IPCC, the new ones include the\ud overlap between CO2 and N2O; for N2O forcing, the CO2 overlap can be as important as the CH4 overlap. The\ud 1750–2011 CO2 RF is within 1% of IPCC’s value but is about 10% higher when CO2 amounts reach 2000 ppm, a\ud value projected to be possible under the extended RCP8.5 scenario.
- Published
- 2016
43. Fast and slow precipitation responses to individual climate forcers: a PDRMIP multi-model study
- Author
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Samset, B. H., Myhre, G., Forster, P. M., Hodnebrog, Ø., Andrews, T., Faluvegi, G., Fläschner, D., Kasoar, M., Kharin, V., Kirkevåg, A., Lamarque, J.-F., Olivié, D., Richardson, T., Shindell, D., Shine, Keith P., Takemura, T., and Voulgarakis, A.
- Subjects
sense organs - Abstract
Precipitation is expected to respond differently to various drivers of anthropogenic climate change. We present the first results from the Precipitation Driver and Response Model Intercomparison Project (PDRMIP), where nine global climate models have perturbed CO2, CH4, black carbon, sulfate, and solar insolation. We divide the resulting changes to global mean and regional precipitation into fast responses that scale with changes in atmospheric absorption and slow responses scaling with surface temperature change. While the overall features are broadly similar between models, we find significant regional intermodel variability, especially over land. Black carbon stands out as a component that may cause significant model diversity in predicted precipitation change. Processes linked to atmospheric absorption are less consistently modeled than those linked to top-of-atmosphere radiative forcing. We identify a number of land regions where the model ensemble consistently predicts that fast precipitation responses to climate perturbations dominate over the slow, temperature-driven responses.
- Published
- 2016
44. Recommendations for diagnosing effective radiative forcing from climate models for CMIP6
- Author
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Forster, P, Richardson, T, Maycock, AC, Smith, C, Samset, BH, Myhre, G, Andrews, T, Pincus, R, and Schulz, M
- Abstract
The usefulness of previous Coupled Model Intercomparison Project (CMIP) exercises has been hampered by a lack of radiative forcing information. This has made it difficult to understand reasons for differences between model responses. Effective radiative forcing (ERF) is easier to diagnose than traditional radiative forcing in global climate models (GCMs) and is more representative of the eventual temperature response. Here we examine the different methods of computing ERF in two GCMs. We find that ERF computed from a fixed sea-surface temperature (SST) method (ERF_fSST) has much more certainty than regression based methods. Thirty-year integrations are sufficient to reduce the 5-95% confidence interval in global ERF_fSST to 0.1 W m-2. For 2xCO2 ERF, 30 year integrations are needed to ensure that the signal is larger than the local confidence interval over more than 90% of the globe. Within the ERF_fSST method there are various options for prescribing SSTs and sea-ice. We explore these and find that ERF is only weakly dependent on the methodological choices. Prescribing the monthly-averaged seasonally varying model’s preindustrial climatology is recommended for its smaller random error and easier implementation. As part of CMIP6, the Radiative Forcing Model Intercomparison Project (RFMIP) asks models to conduct 30-year ERF_fSST experiments using the model’s own preindustrial climatology of SST and sea-ice. The Aerosol and Chemistry Model Intercomparison Project (AerChemMIP) will also mainly use this approach. We propose this as a standard method for diagnosing ERF and recommend that it be used across the climate modelling community to aid future comparisons.
- Published
- 2016
45. Manmade changes in Cirrus clouds from 1984 to 2007: A preliminary study
- Author
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Eleftheratos, K. Myhre, G. Minnis, P. Kapsomenakis, I. Zerefos, C.
- Abstract
We analyse cirrus cloud data over congested air traffic corridors during the period 1984–2007 and look into manmade changes in cirrus clouds due to air traffic. The analysis is based on the International Satellite Cloud Climatology Project (ISCCP) D2 data set for the period 1984–2007. Manmade changes in cirrus clouds were determined from the comparison of cirrus clouds over higher traffic regions and over lower traffic regions. These comparisons were done by calculating the differences between adjacent high and low air traffic areas over North America, Europe, North Atlantic and North Pacific. In all cases the differences show a positive trend which is consistent with the increasing trend of global air traffic in the past 20 years. Over North America, Europe, North Atlantic and North Pacific cirrus clouds increased by 0.9 % per decade over high air traffic regions relative to their low traffic counterparts. The result of manmade cirrus increase of 0.9 % over the western air traffic corridors is expected to have a measurable effect in radiative forcing. © 2016, Springer International Publishing Switzerland.
- Published
- 2016
46. Comparison of aerosol optical properties above clouds between POLDER and AeroCom models over the South East Atlantic Ocean during the fire season
- Author
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Peers, F., Bellouin, Nicolas, Waquet, F., Ducos, F., Goloub, P., Mollard, J., Myhre, G., Skeie, R. B., Takemura, T., Tanré, D., Thieuleux, F., Zhang, K., Laboratoire d’Optique Atmosphérique - UMR 8518 (LOA), and Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)
- Subjects
above cloud ,aerosol ,[SDU]Sciences of the Universe [physics] ,POLDER ,absorption ,AeroCom - Abstract
Aerosol properties above clouds have been retrieved over the South East Atlantic Ocean during the fire season 2006 using satellite observations from POLDER (Polarization and Directionality of Earth Reflectances). From June to October, POLDER has observed a mean Above-Cloud Aerosol Optical Thickness (ACAOT) of 0.28 and a mean Above-Clouds Single Scattering Albedo (ACSSA) of 0.87 at 550nm. These results have been used to evaluate the simulation of aerosols above clouds in five Aerosol Comparisons between Observations and Models (Goddard Chemistry Aerosol Radiation and Transport (GOCART), Hadley Centre Global Environmental Model 3 (HadGEM3), European Centre Hamburg Model 5-Hamburg Aerosol Module 2 (ECHAM5-HAM2), Oslo-Chemical Transport Model 2 (OsloCTM2), and Spectral Radiation-Transport Model for Aerosol Species (SPRINTARS)). Most models do not reproduce the observed large aerosol load episodes. The comparison highlights the importance of the injection height and the vertical transport parameterizations to simulate the large ACAOT observed by POLDER. Furthermore, POLDER ACSSA is best reproduced by models with a high imaginary part of black carbon refractive index, in accordance with recent recommendations. ©2016. American Geophysical Union.
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- 2016
47. Climate responses to anthropogenic emissions of short-lived climate pollutants
- Author
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Baker, Laura, Collins, W J, Olivie, D. J. L., Cherian, R., Myhre, G., and Quaas, J.
- Abstract
Policies to control air quality focus on mitigating emissions of aerosols and their precursors, and other short-lived climate pollutants (SLCPs). On a local scale, these policies will have beneficial impacts on health and crop yields, by reducing particulate matter (PM) and surface ozone concentrations; however, the climate impacts of reducing emissions of SLCPs are less straightforward to predict. In this paper we consider a set of idealised, extreme mitigation strategies, in which the total anthropogenic emissions of individual SLCP emissions species are removed. This provides an upper bound on the potential climate impacts of such air quality strategies. \ud \ud We focus on evaluating the climate responses to changes in anthropogenic emissions of aerosol precursor species: black carbon (BC), organic carbon (OC) and sulphur dioxide (SO2). We perform climate integrations with four fully coupled atmosphere-ocean global climate models (AOGCMs), and examine the effects on global and regional climate of removing the total land-based anthropogenic emissions of each of the three aerosol precursor species. \ud \ud We find that the SO2 emissions reductions lead to the strongest response, with all three models showing an increase in surface temperature focussed in the northern hemisphere high latitudes, and a corresponding increase in global mean precipitation and run-off. Changes in precipitation and run-off patterns are driven mostly by a northward shift in the ITCZ, consistent with the hemispherically asymmetric warming pattern driven by the emissions changes. The BC and OC emissions reductions give a much weaker forcing signal, and there is some disagreement between models in the sign of the climate responses to these perturbations. These differences between models are due largely to natural variability in sea-ice extent, circulation patterns and cloud changes. This large natural variability component to the signal when the ocean circulation and sea-ice are free-running means that the BC and OC mitigation measures do not necessarily lead to a discernible climate response.
- Published
- 2015
48. An assessment of precipitation adjustment and feedback computation methods
- Author
-
Richardson, T. B., primary, Samset, B. H., additional, Andrews, T., additional, Myhre, G., additional, and Forster, P. M., additional
- Published
- 2016
- Full Text
- View/download PDF
49. Multi-model evaluation of short-lived pollutant distributions over east Asia during summer 2008
- Author
-
Quennehen, B., primary, Raut, J.-C., additional, Law, K. S., additional, Daskalakis, N., additional, Ancellet, G., additional, Clerbaux, C., additional, Kim, S.-W., additional, Lund, M. T., additional, Myhre, G., additional, Olivié, D. J. L., additional, Safieddine, S., additional, Skeie, R. B., additional, Thomas, J. L., additional, Tsyro, S., additional, Bazureau, A., additional, Bellouin, N., additional, Hu, M., additional, Kanakidou, M., additional, Klimont, Z., additional, Kupiainen, K., additional, Myriokefalitakis, S., additional, Quaas, J., additional, Rumbold, S. T., additional, Schulz, M., additional, Cherian, R., additional, Shimizu, A., additional, Wang, J., additional, Yoon, S.-C., additional, and Zhu, T., additional
- Published
- 2016
- Full Text
- View/download PDF
50. Declining uncertainty in transient climate response as CO2 forcing dominates future climate change
- Author
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Myhre, G, Boucher, O, Bréon, F-M, Forster, P, and Shindell, D
- Abstract
Carbon dioxide has exerted the largest portion of radiative forcing and surface temperature change over the industrial era, but other anthropogenic influences have also contributed. However, large uncertainties in total forcing make it difficult to derive climate sensitivity from historical observations. Anthropogenic forcing has increased between the Fourth and Fifth Assessment Reports of the Intergovernmental Panel of Climate Change (IPCC; refs,), although its relative uncertainty has decreased. Here we show, based on data from the two reports, that this evolution towards lower uncertainty can be expected to continue into the future. Because it is easier to reduce air pollution than carbon dioxide emissions and because of the long lifetime of carbon dioxide, the less uncertain carbon dioxide forcing is expected to become increasingly dominant. Using a statistical model, we estimate that the relative uncertainty in anthropogenic forcing of more than 40% quoted in the latest IPCC report for 2011 will be almost halved by 2030, even without better scientific understanding. Absolute forcing uncertainty will also decline for the first time, provided projected decreases in aerosols occur. Other factors being equal, this stronger constraint on forcing will bring a significant reduction in the uncertainty of observation-based estimates of the transient climate response, with a 50% reduction in its uncertainty range expected by 2030.
- Published
- 2015
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