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1. The Pliocene Model Intercomparison Project Phase 2: large-scale climate features and climate sensitivity

   https://doi.org/10.5194/cp-16-2095-2020  

   Haywood, Alan M. ; Tindall, Julia C. ; Dowsett, Harry J. ; Dolan, Aisling M. ; Foley, Kevin M. ; Hunter, Stephen J. ; Hill, Daniel J. ; Chan, Wing-Le ; Abe-Ouchi, Ayako ; Stepanek, Christian ; et al ( January 2020 , Climate of the Past)

   null (Ed.)

   Abstract. The Pliocene epoch has great potential to improve ourunderstanding of the long-term climatic and environmental consequences of an atmospheric CO2 concentration near ∼400 parts permillion by volume. Here we present the large-scale features of Plioceneclimate as simulated by a new ensemble of climate models of varyingcomplexity and spatial resolution based on new reconstructions ofboundary conditions (the Pliocene Model Intercomparison Project Phase 2;PlioMIP2). As a global annual average, modelled surface air temperaturesincrease by between 1.7 and 5.2 ∘C relative to the pre-industrial erawith a multi-model mean value of 3.2 ∘C. Annual mean totalprecipitation rates increase by 7 % (range: 2 %–13 %). On average, surface air temperature (SAT) increases by 4.3 ∘C over land and 2.8 ∘C over the oceans. There is a clear pattern of polar amplification with warming polewards of 60∘ N and 60∘ S exceeding the global mean warming by a factor of 2.3. In the Atlantic and Pacific oceans, meridional temperature gradients are reduced, while tropical zonal gradients remain largely unchanged. There is a statistically significant relationship between a model's climate response associated with a doubling in CO2 (equilibrium climate sensitivity; ECS) and its simulated Pliocene surface temperature response. The mean ensemble Earth system response to a doubling of CO2 (including ice sheet feedbacks) is 67 % greater than ECS; this is larger than the increase of 47 % obtained from the PlioMIP1 ensemble. Proxy-derived estimates of Pliocene sea surface temperatures are used to assess model estimates of ECS and give an ECS range of 2.6–4.8 ∘C. This result is in general accord with the ECS range presented by previous Intergovernmental Panel on Climate Change (IPCC) Assessment Reports. 

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2. OSU-UVic Climate Model v2.9.10

   https://doi.org/10.5281/zenodo.11224826  

   Schmittner, Andreas ; Khatiwala, Samar ; Fillman, Nathaniel ; Somes, Christopher ; Kvale, Karin ( January 2024 , Zenodo)

   OSU-UVic Climate Model of Intermediate Complexity with Model of Ocean Biogeochemistry and Isotopes (MOBI2.2). New features in this release include Nathaniel Fillman's carbon and C13 decomposition code and Samar Khatiwala's Pa/Th code. 

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3. Iodine chemistry in the chemistry–climate model SOCOL-AERv2-I

   https://doi.org/10.5194/gmd-14-6623-2021  

   Karagodin-Doyennel, Arseniy ; Rozanov, Eugene ; Sukhodolov, Timofei ; Egorova, Tatiana ; Saiz-Lopez, Alfonso ; Cuevas, Carlos A. ; Fernandez, Rafael P. ; Sherwen, Tomás ; Volkamer, Rainer ; Koenig, Theodore K. ; et al ( January 2021 , Geoscientific Model Development)

   Abstract. In this paper, we present a new version of the chemistry–climate model SOCOL-AERv2 supplemented by an iodine chemistry module. We perform three 20-year ensemble experiments to assess the validity of the modeled iodine and to quantify the effects of iodine on ozone. The iodine distributions obtained with SOCOL-AERv2-I agree well with AMAX-DOAS observations and with CAM-chem model simulations. For the present-day atmosphere, the model suggests that the iodine-induced chemistry leads to a 3 %–4 % reduction in the ozone column, which is greatest at high latitudes. The model indicates the strongest influence of iodine in the lower stratosphere with 30 ppbv less ozone at low latitudes and up to 100 ppbv less at high latitudes. In the troposphere, the account of the iodine chemistry reduces the tropospheric ozone concentration by 5 %–10 % depending on geographical location. In the lower troposphere, 75 % of the modeled ozone reduction originates from inorganic sources of iodine, 25 % from organic sources of iodine. At 50 hPa, the results show that the impacts of iodine from both sources are comparable. Finally, we determine the sensitivity of ozone to iodine by applying a 2-fold increase in iodine emissions, as it might be representative for iodine by the end of this century. This reduces the ozone column globally by an additional 1.5 %–2.5 %. Our results demonstrate the sensitivity of atmospheric ozone to iodine chemistry for present and future conditions, but uncertainties remain high due to the paucity of observational data of iodine species. 

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4. Model-aided climate adaptation for future maize in the US

   https://doi.org/10.1088/2976-601X/ad3085  

   Hsiao, Jennifer ; Kim, Soo-Hyung ; Timlin, Dennis J. ; Mueller, Nathaniel D. ; Swann, Abigail L. S. ( April 2024 , Environmental Research: Food Systems)

   Over the next three decades rising population and changing dietary preferences are expected to increase food demand by 25%–75%. At the same time climate is also changing—with potentially drastic impacts on food production. Breeding new crop characteristics and adjusting management practices are critical avenues to mitigate yield loss and sustain yield stability under a changing climate. In this study, we use a mechanistic crop model (MAIZSIM) to identify high-performing trait and management combinations that maximize yield and yield stability for different agroclimate regions in the US under present and future climate conditions. We show that morphological traits such as total leaf area and phenological traits such as grain-filling start time and duration are key properties that impact yield and yield stability; different combinations of these properties can lead to multiple high-performing strategies under present-day climate conditions. We also demonstrate that high performance under present day climate does not guarantee high performance under future climate. Weakened trade-offs between canopy leaf area and reproductive start time under a warmer future climate led to shifts in high-performing strategies, allowing strategies with higher total leaf area and later grain-filling start time to better buffer yield loss and out-compete strategies with a smaller canopy leaf area and earlier reproduction. These results demonstrate that focused effort is needed to breed plant varieties to buffer yield loss under future climate conditions as these varieties may not currently exist, and showcase how information from process-based models can complement breeding efforts and targeted management to increase agriculture resilience.

    

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5. Characterizing unforced decadal climate variability in global climate model large ensembles

   https://doi.org/10.1007/s00382-021-05900-y  

   Yao, Bin ; Xu, Yangyang ; Dessler, Andrew E. ; Liu, Chao ( January 2022 , Climate Dynamics)