Climate of The Past Discussions最新文献

{"title":"The middle-to-late Eocene greenhouse climate, modelled using the CESM 1.0.5","authors":"M. Baatsen, A. S. von der Heydt, M. Huber, M. Kliphuis, P. Bijl, A. Sluijs, H. Dijkstra","doi":"10.5194/cp-2020-29","DOIUrl":"https://doi.org/10.5194/cp-2020-29","url":null,"abstract":"Abstract. While the early Eocene has been considered in many modelling studies, detailed simulations of the middle and late Eocene climate are currently scarce. To get a better understanding of both Antarctic glaciation at the Eocene-Oligocene transition (~34 Ma) and late middle Eocene warmth, it is vital to have an adequate reconstruction of the middle-to-late Eocene climate. Results of higher (CMIP5-like) resolution coupled climate simulations are represented here using the Community Earth System Model (CESM) version 1. Two middle-to-late Eocene cases are considered with the same general boundary conditions but a different radiative forcing, using a new detailed 38 Ma geography reconstruction. Under 4× pre-industrial concentrations (PIC) of both CO2 (i.e. 1120 ppm) and CH4 (~2700 ppb), equilibrium sea surface temperatures correspond well to the available late middle Eocene (42–38 Ma; ~Bartonian) proxies. Being generally cooler, the simulated climate under 2× PIC forcing is a good analog for that of the late Eocene (38–34 Ma; ~Priabonian). Terrestrial temperature proxies, although their geographical coverage is sparse, also indicate that the results presented here are realistic. The reconstructed 38 Ma climate has a reduced equator-to-pole temperature gradient and a more symmetric meridional heat distribution compared to the pre-industrial reference. The collective effects of geography, vegetation and ice accounts for a global mean 5–7 °C difference between pre-industrial and 38 Ma Eocene boundary conditions, with important contributions from cloud and water vapour feedbacks. These simulations effectively show that a realistic middle-to-late Eocene climate can be reconstructed without the need for greenhouse gas concentrations much higher than proxy estimates (i.e. ~500–1200 ppm CO2). Equilibrium climate sensitivity is reduced (0.62 °C/W m2; 3.2 °C warming between 38 Ma 2× PIC and 4× PIC) compared to that of the present-day climate (0.79 °C/W m2; 3.1 °C per CO2 doubling). Despite very limited sea ice and snow cover in both 38Ma cases, the model still shows a factor ~2 polar amplification in response to a further increase of atmospheric greenhouse gas concentrations. High latitudes in the modelled Eocene climate are mainly kept warm by an altered radiative balance in combination with global changes in geography and the absence of polar ice sheets compared to the pre-industrial reference.","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-03-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130820479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"ENSO and internal sea surface temperature variability in the tropical Indian Ocean since the Maunder Minimum","authors":"M. Leupold, M. Pfeiffer, Takaaki K. Watanabe, L. Reuning, D. Garbe‐Schönberg, Chuan‐Chou Shen, G. A. Brummer","doi":"10.5194/cp-2020-22","DOIUrl":"https://doi.org/10.5194/cp-2020-22","url":null,"abstract":"Abstract. The dominant modes of climate variability on interannual timescales in the tropical Indian Ocean are the El Nino Southern Oscillation (ENSO) and the Indian Ocean Dipole. El Nino events have occurred more frequently during recent decades and it has been suggested that an asymmetric ENSO teleconnection (warming during El Nino events is stronger than cooling during La Nina events) caused the pronounced warming of the western Indian Ocean. In this study, we test this hypothesis using coral Sr / Ca records from the central Indian Ocean (Chagos Archipelago) to reconstruct past sea surface temperatures (SST) in time windows from the Maunder Minimum to the present. Three sub-fossil massive Porites corals were dated to the 17–18th century (one sample) and 19–20th century (two samples), and were compared with a published, modern coral Sr / Ca record from the same site. All corals were sub-sampled at a monthly resolution for Sr / Ca measurements, which were measured using a simultaneous ICP-OES. All four coral records show typical ENSO periodicities, suggesting that the ENSO-SST teleconnection in the central Indian Ocean was stationary since the 17th century. To determine the symmetry of ENSO events, we compiled composite records of positive and negative ENSO-driven SST anomaly events. We find similar magnitudes of warm and cold anomalies indicating a symmetric ENSO response in the tropical Indian Ocean. This suggests that ENSO is not the main driver of central Indian Ocean warming.","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131069865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Revised Mid-Pliocene Composite Section for ODP Site 846","authors":"T. Herbert, R. Caballero‐Gill, Joseph Novak","doi":"10.5194/cp-2019-133","DOIUrl":"https://doi.org/10.5194/cp-2019-133","url":null,"abstract":"Abstract. The composite section from ODP Site 846 has provided key data sets for Pliocene stable isotope and paleoclimatic time series. We document here errors in primary data sets for stable isotopes and alkenone-derived sea surface temperature estimates (SST) in the late Pliocene interval containing the M2 glaciation (ca. 3.250–3.3 Ma) by tying high resolution core measurements to a continuous downhole conductivity log. In addition, we provide new stable isotopic and alkenone measurements that correlate well to the revised splices of color reflectance and gamma ray attenuation porosity evaluator data. A new composite splice is proposed, along with composite isotope and alkenone time series that should be integrated into revised Pliocene paleoclimatic stacks.","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"95 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126145494","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PlioMIP2 simulations using the MIROC4m climate model","authors":"W. Chan, A. Abe‐Ouchi","doi":"10.5194/cp-2020-17","DOIUrl":"https://doi.org/10.5194/cp-2020-17","url":null,"abstract":"Abstract. The second phase of the Pliocene Model Intercomparison Project (PlioMIP2) has attracted many climate modelling groups in its continuing efforts to better understand the climate of the mid-Piacenzian warm period (mPWP) when atmospheric CO2 was last closest to present day levels. Like the first phase, PlioMIP1, it is an internationally coordinated initiative that allows for a systematic comparison of various models in a similar manner to PMIP. Model intercomparison and model-data comparison now focus specifically on the interglacial at marine isotope stage KM5c (3.205 Ma) and experimental design is not only based on new boundary conditions but includes various sensitivity experiments. In this study, we present results from long-term model integrations using the MIROC4m atmosphere-ocean coupled general circulation model, developed at the institutes CCSR/NIES/FRCGC in Japan. The core experiment, with CO2 levels set to 400 ppm, shows a warming of 3.1 °C compared to the Pre-Industrial, with two-thirds of the warming being contributed by the increase in CO2. Although this level of warming is less than that in the equivalent PlioMIP1 experiment, there is a slightly better agreement with proxy sea surface temperature (SST) data at PRISM3 locations, especially in the northern North Atlantic where there were large model-data discrepancies in PlioMIP1. Similar changes in precipitation and sea ice are seen and the Arctic remains ice-free in the summer. However, unlike PlioMIP1, the Atlantic Meridional Overturning Circulation (AMOC) is now stronger than that of the Pre-Industrial, even though increasing CO2 tends to weaken it. This stronger AMOC is a consequence of a closed Bering Strait in the PlioMIP2 paleogeography. Also, when present day boundary conditions are replaced by those of the Pliocene, the dependency of the AMOC strength on CO2 is significantly weakened. Sensitivity tests show that lower values of CO2 give a global SST which is overall more consistent with the PRISM3 SST field presented in PlioMIP1. Inclusion of dynamical vegetation and the effects of all realistic orbital configurations should be considered in future experiments using MIROC4m for the mPWP.","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121755468","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Estimating the timescale-dependent uncertainty of paleoclimate records – a spectral approach. Part II: Application and interpretation","authors":"A. Dolman, T. Kunz, J. Groeneveld, T. Laepple","doi":"10.5194/cp-2019-153","DOIUrl":"https://doi.org/10.5194/cp-2019-153","url":null,"abstract":"Abstract. Proxy climate records are an invaluable source of information about the earth’s climate prior to the instrumental record. The temporal- and spatial-coverage of records continues to increase, however, these records of past climate are associated with significant uncertainties due to non-climate processes that influence the recorded and measured proxy values. Generally, these uncertainties are timescale-dependent and correlated in time. Accounting for structure in the errors is essential to providing realistic error estimates for smoothed or stacked records, detection of anomalies and identifying trend, but this structure is seldom accounted for. In the first of these companion articles we outlined a theoretical framework for handling proxy uncertainties by deriving the power spectrum of proxy error components from which it is possible to obtain timescale-dependent error estimates. Here in part II, we demonstrate the practical application of this theoretical framework using the example of marine sediment cores. We consider how to obtain estimates for the required parameters and give examples of the application of this approach for typical marine sediment proxy records. Our new approach of estimating and providing timescale-dependent proxy errors overcomes the limitations of simplistic single value error estimates. We aim to provide the conceptual basis for a more quantitative use of paleo-records for applications such as model-data comparison, regional and global synthesis of past climate states and data assimilation.","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114209217","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reconstruction of multi-millennial summer climate variations in central Japan by integrating tree-ring cellulose oxygen and hydrogen isotope ratios","authors":"T. Nakatsuka, M. Sano, Zhen Li, Chenxi Xu, Akane Tsushima, Yuki Shigeoka, Kenjiro Sho, K. Ohnishi, M. Sakamoto, Hiromasa Ozaki, Noboru Higami, Nanae Nakao, Misao Yokoyama, T. Mitsutani","doi":"10.5194/cp-2020-6","DOIUrl":"https://doi.org/10.5194/cp-2020-6","url":null,"abstract":"Abstract. Oxygen isotope ratios (δ18O) of tree-ring cellulose are a novel proxy of summer hydroclimate in monsoonal Asia. In central Japan, we collected 67 conifer wood samples, mainly Chamaecyparis obtusa, with ages encompassing the past 2,600 yr. The samples were taken from living old trees, excavated archeological wood, old architectural wood, and naturally buried logs. We analyzed stable isotope ratios of oxygen (δ18O) and hydrogen (δ2H) in tree-ring cellulose in these samples without using a pooling method, and constructed a statistically reliable tree-ring cellulose δ18O time-series for the past 2,500 yr. However, there were distinct age trends and level offsets in the δ18O record, and cellulose δ18O values showed a gradual decrease as an individual tree matures. This suggested it is difficult to establish a cellulose δ18O chronology for low-frequency signals by simple averaging of all the δ18O time-series data. However, there were opposite age trends in the cellulose δ2H, and δ2H gradually increased with tree age. There were clear positive correlations in the short periodicity variations between δ18O and δ2H, probably indicating a common climate signal. A comparison of the δ18O and δ2H time-series in individual trees with tree-ring width suggested that the opposite age trends of δ18O and δ2H are caused by temporal changes in the degree of post-photosynthetic isotope exchange with xylem water, accompanied by changes in stem growth rate (growth effect) that are influenced by human activity in the forests of central Japan. Based on the assumptions that cellulose δ18O and δ2H vary positively and negatively with constant proportional coefficients due to climate variations and the growth effect, respectively, we solved simultaneous equations for the climatological and physiological components of variations in tree-ring cellulose δ18O and δ2H in order to remove the age trend (growth effect). This enabled us to evaluate the climatic record from cellulose δ18O variations. The extracted climatological component in the cellulose δ18O for the past 2,600 yr in central Japan was well correlated with numerous instrumental, historical, and paleoclimatological records of past summer climate at various spatial and temporal scales. This indicates that integration of tree-ring cellulose δ18O and δ2H data is a promising method to reconstruct past summer climate variations on annual to millennial time-scales, irrespective of the growth affect. However, analytical and statistical methods need to be improved for further development of this climate proxy.","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126481299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Estimating the timescale-dependent uncertainty of paleoclimate records – a spectral approach. Part I: Theoretical concept","authors":"T. Kunz, A. Dolman, T. Laepple","doi":"10.5194/cp-2019-150","DOIUrl":"https://doi.org/10.5194/cp-2019-150","url":null,"abstract":"Abstract. Proxy records represent an invaluable source of information for reconstructing past climatic variations, but they are associated with considerable uncertainties. For a systematic quantification of these reconstruction errors, however, knowledge is required not only of their individual sources but also of their auto-correlation structure, as this determines the timescale dependence of their magnitude, an issue that is often ignored until now. Here a spectral approach to uncertainty analysis is provided for paleoclimate reconstructions obtained from single sediment proxy records. The formulation in the spectral domain, rather than the time domain, allows for an explicit demonstration as well as quantification of the timescale dependence that is inherent in any proxy-based reconstruction uncertainty. This study is published in two parts. In this first part, the theoretical concept is presented and analytic expressions are derived for the power spectral density of the reconstruction error of sediment proxy records. The underlying model takes into account the spectral structure of the climate signal, seasonal and orbital variations, bioturbation, sampling of a finite number of signal carriers, uncorrelated measurement noise, and it includes the effects of spectral aliasing and leakage. The uncertainty estimation method, based upon this model, is illustrated by simple examples. In the second part of this study, published separately, the method is implemented in an application-oriented context, and more detailed examples are presented.","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"2018 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132900582","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The phase space of last glacial inception for the Northern Hemisphere from coupled ice and climate modelling","authors":"T. Bahadory, L. Tarasov, H. Andres","doi":"10.5194/cp-2020-1","DOIUrl":"https://doi.org/10.5194/cp-2020-1","url":null,"abstract":"Abstract. We present an ensemble of Last Glacial Inception (LGI) simulations for the Northern Hemisphere that largely captures inferred ice volume changes within proxy uncertainties. This ensemble was performed with LCice 1.0, a coupled ice sheet and climate model, varying parameters of both climate and ice sheet components, as well as the coupling between them. Certain characteristics of the spatio-temporal pattern of ice growth and subsequent retreat in both North America (NA) and Eurasia (EA) are sensitive to parameter changes, especially with respect to regional rates of ice growth and retreat. We find that the initial inception of ice over NA and EA is best characterized by the nucleation of ice at high latitude and high elevation sites. Subsequent spreading and merger along with large-scale conversion of snow fields dominate in different sectors. The latter plays an important role in the merging of eastern and western ice regions in NA. The inception peak ice volume in the ensemble occurs approximately at 111 ka and therefore lags the summer 60° N insolation minimum by more than 3 kyr. Ice volumes consistently peak earlier over EA than NA. The inception peak in North America is characterized by a merged Laurentide and Cordilleran ice sheet, with Davis Strait covered in ice in 80 % of simulations. Ice also bridges Greenland and Iceland in all runs by 114 ka and therefore blocks Denmark Strait. This latter feature would thereby divert the East Greenland Current and Denmark Strait overflow and thereby potentially have a significant impact on ocean circulation. The Eurasian ice sheet at its inception peak varies across ensemble runs between a continuous ice sheet to multiple smaller ice caps. In both continents, the colder high latitudes (Ellsmere and Svalbard) tend to grow ice through the entire simulation (to 102 ka), while lower latitudes lose ice after 110 ka. We find temperature decreases over the initial phases of the inception lead to the expansion of NA ice sheet area, and that subsequent precipitation increases contribute to its thickening. EA ice sheet area also expands with decreasing temperatures, but sea ice limits any increases in precipitation, leading to an earlier retreat away from the EA maximum ice sheet volume. We also examine the extent to which the capture of both LGI ice growth and retreat constrains the coupled ice/climate model sensitivity to changing atmospheric pCO2. For a standard transient climate response experiment (1 % increase in pCO2 until doubled), warming ranges between 0.6–2.0 °C for our initial set of 500 simulations without LGI constraint. The warming is reduced to 0.7–1.4 °C for the 55 member ensemble that captures both LGI ice growth and retreat. This therefore underlines the potential value of fully coupled ice/climate modelling of last glacial inception to constrain future climate change.","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"121 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122825553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The PMIP4-CMIP6 Last Glacial Maximum experiments: preliminary results and comparison with the PMIP3-CMIP5 simulations","authors":"M. Kageyama, S. Harrison, M. Kapsch, M. Löfverström, J. Lora, Uwe, Mikolajewicz, S. Sherriff-Tadano, T. Vadsaria, A. Abe‐Ouchi, N. Bouttes, Deepak, Chandan, A. Legrande, F. Lhardy, Gerrit Lohmann, P. Morozova, Rumi, Ohgaito, W. Peltier, A. Quiquet, D. Roche, Xiaoxu Shi, Andreas, Schmittner, J. Tierney, E. Volodin","doi":"10.5194/cp-2019-169","DOIUrl":"https://doi.org/10.5194/cp-2019-169","url":null,"abstract":"\u0000 <p>The Last Glacial Maximum (LGM, ~21,000 years ago) has been a major focus for evaluating how well state-of-the-art climate models simulate climate changes as large as those expected in the future using paleoclimate reconstructions. A new generation of climate models have been used to generate LGM simulations as part of the Palaeoclimate Modelling Intercomparison Project (PMIP) contributionto CMIP6. Here we provide a preliminary analysis and evaluation of the results of these LGM experiments and compare them with the previous generation of simulations (PMIP3-CMIP5). We show that the PMIP4-CMIP6 are globally less cold and less dry than the PMIP3-CMIP5 simulations, most probably because of the use of a more realistic specification of the northern hemisphere ice sheets in the latest simulations although changes in model configuration may also contribute to this. There are important differences in both atmospheric and ocean circulation between the two sets of experiments, with the northern and southern jet streams being more poleward and the changes in the Atlantic Meridional Overturning Circulation being less pronounced in the PMIP4-CMIP6 simulations than in the PMIP3-CMIP5 simulations. Changes in simulated precipitation patterns are influenced by both temperature and circulation changes. Differences in simulated climate between individual models remain large so, although there are differences in the average behaviour across the two ensembles, the new simulation results are not fundamentally different from the PMIP3-CMIP5 results. Evaluation of large-scale climate features, such as land-sea contrast and polar amplification, confirms that the models capture these well and within the uncertainty of the palaeoclimate reconstructions. Nevertheless, regional climate changes are less well simulated: the models underestimate extratropical cooling, particularly in winter, and precipitation changes. The spatial patterns of increased precipitation associated with changes in the jet streams are also poorly captured. However, changes in the tropics are more realistic, particularly the changes in tropical temperatures over the oceans. Although these results are preliminary in nature, because of the limited number of LGM simulations currently available, they nevertheless point to the utility of using paleoclimate simulations to understand the mechanisms of climate change and evaluate model performance.</p>\u0000","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128925769","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Large-scale features of Last Interglacial climate: Results from evaluating the lig127k simulations for CMIP6-PMIP4","authors":"B. Otto‐Bliesner, E. Brady, Anni Zhao, C. Brierley, Y. Axford, E. Capron, A. Govin, J. Hoffman, Elizabeth B. Isaacs, M. Kageyama, Paulo Scussolini, P. Tzedakis, C. Williams, E. Wolff, A. Abe‐Ouchi, P. Braconnot, S. Buarque, Jian Cao, A. Vernal, Maria Vittoria Guarino, Chuncheng Guo, A. Legrande, Gerrit Lohmann, K. Meissner, L. Menviel, K. Nisancioglu, Ryouta O’ishi, D. Mélia, Xioaoxu Shi, M. Sicard, L. Sime, R. Tomas, E. Volodin, Nicolas Yeung, Qiong Zhang, Zhonghi Zhang, Weipeng Zheng","doi":"10.5194/cp-2019-174-supplement","DOIUrl":"https://doi.org/10.5194/cp-2019-174-supplement","url":null,"abstract":"\u0000 <p>The modeling of paleoclimate, using physically based tools, is increasingly seen as a strong out-of-sample test of the models that are used for the projection of future climate changes. New to CMIP6 is the Tier 1 lig127k experiment, designed to address the climate responses to stronger orbital forcing than the midHolocene experiment, using the same state-of-the-art models and following a common experimental protocol. We present a multi-model ensemble of 17 climate models, all of which (except for two) have also completed the CMIP6 DECK experiments. The Equilibrium Climate Sensitivity (ECS) of these models varies from 2.1 to 5.3&#176;C. The seasonal character of the insolation anomalies results in strong warming over the Northern Hemisphere (NH) continents in the lig127k ensemble as compared to the piControl in June-July-August and a much-reduced minimum (August-September) summer sea ice extent in the Arctic. The multi-model results indicate enhanced summer monsoonal precipitation and areal extent in the Northern Hemisphere and reductions in the Southern Hemisphere. These responses are greater in the lig127k than midHolocene simulations as expected from the larger insolation anomalies at 127 ka than 6 ka.</p><p>New syntheses for surface temperature and precipitation, targeted for 127ka, have been developed for comparison to the multi-model ensemble. The lig127k model ensemble and data reconstructions are in good agreement for summer temperature anomalies over Canada, Scandinavia, and the North Atlantic and precipitation over the Northern Hemisphere continents. The model-data comparisons and mismatches point to further study of the sensitivity of the simulations to uncertainties in the specified boundary conditions and of the uncertainties and sparse coverage in current proxy reconstructions.</p><p>The CMIP6-PMIP4 lig127k simulations, in combination with the proxy record, have potential implications for confidence in future projections of monsoons, surface temperature, Arctic sea ice, and the stability of the Greenland ice sheet.</p>\u0000","PeriodicalId":263057,"journal":{"name":"Climate of The Past Discussions","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121059110","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}