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State-of-the-art Earth system models typically employ grid spacings of O(100 km), which is too coarse to explicitly resolve main drivers of the flow of energy and matter across the Earth system. In this paper, we present the new ICON-Sapphire model configuration, which targets a representation of the components of the Earth system and their interactions with a grid spacing of 10 km and finer. Through the use of selected simulation examples, we demonstrate that ICON-Sapphire can (i) be run coupled globally on seasonal timescales with a grid spacing of 5 km, on monthly timescales with a grid spacing of 2.5 km, and on daily timescales with a grid spacing of 1.25 km; (ii) resolve large eddies in the atmosphere using hectometer grid spacings on limited-area domains in atmosphere-only simulations; (iii) resolve submesoscale ocean eddies by using a global uniform grid of 1.25 km or a telescoping grid with the finest grid spacing at 530 m, the latter coupled to a uniform atmosphere; and (iv) simulate biogeochemistry in an ocean-only simulation integrated for 4 years at 10 km. Comparison of basic features of the climate system to observations reveals no obvious pitfalls, even though some observed aspects remain difficult to capture. The throughput of the coupled 5 km global simulation is 126 simulated days per day employing 21 % of the latest machine of the German Climate Computing Center. Extrapolating from these results, multi-decadal global simulations including interactive carbon are now possible, and short global simulations resolving large eddies in the atmosphere and submesoscale eddies in the ocean are within reach.

Simulations of Common Era climate evolution coordinated by PMIP\'s "Past2K" working group together with multi-proxy reconstructions from the PAGES 2k Network provide pivotal understanding for the evolution of the modern climate system and for expected changes in the near future.

East Asia has experienced strong warming since the 1960s accompanied by an increased frequency of heat waves and shrinking glaciers over the Tibetan Plateau and the Tien Shan. Here, we place the recent warmth in a long-term perspective by presenting a new spatially resolved warm-season (May-September) temperature reconstruction for the period 1â 2000 CE using 59 multiproxy records from a wide range of East Asian regions. Our Bayesian Hierarchical Model (BHM) based reconstructions generally agree with earlier shorter regional temperature reconstructions but are more stable due to additional temperature sensitive proxies. We find a rather warm period during the first two centuries CE, followed by a multi-century long cooling period and again a warm interval covering the 900-1200 CE period (Medieval Climate Anomaly, MCA). The interval from 1450 to 1850 CE (Little Ice Age, LIA) was characterized by cooler conditions and the last 150 years are characterized by a continuous warming until recent times. Our results also suggest that the 1990s were likely the warmest decade in at least 1200 years. The comparison between an ensemble of climate model simulations and our summer reconstructions since 850 CE shows good agreement and an important role of internal variability and external forcing on multi-decadal time-scales.

The spatial context is critical when assessing present-day climate anomalies, attributing them to potential forcings and making statements regarding their frequency and severity in a long-term perspective. Recent international initiatives have expanded the number of high-quality proxy-records and developed new statistical reconstruction methods. These advances allow more rigorous regional past temperature reconstructions and, in turn, the possibility of evaluating climate models on policy-relevant, spatio-temporal scales. Here we provide a new proxy-based, annually-resolved, spatial reconstruction of the European summer (June-August) temperature fields back to 755 CE based on Bayesian hierarchical modelling (BHM), together with estimates of the European mean temperature variation since 138 BCE based on BHM and composite-plus-scaling (CPS). Our reconstructions compare well with independent instrumental and proxy-based temperature estimates, but suggest a larger amplitude in summer temperature variability than previously reported. Both CPS and BHM reconstructions indicate that the mean 20th century European summer temperature was not significantly different from some earlier centuries, including the 1st, 2nd, 8th and 10th centuries CE. The 1st century (in BHM also the 10th century) may even have been slightly warmer than the 20th century, but the difference is not statistically significant. Comparing each 50 yr period with the 1951-2000 period reveals a similar pattern. Recent summers, however, have been unusually warm in the context of the last two millennia and there are no 30 yr periods in either reconstruction that exceed the mean average European summer temperature of the last 3 decades (1986-2015 CE). A comparison with an ensemble of climate model simulations suggests that the reconstructed European summer temperature variability over the period 850-2000 CE reflects changes in both internal variability and external forcing on multi-decadal time-scales. For pan-European temperatures we find slightly better agreement between the reconstruction and the model simulations with high-end estimates for total solar irradiance. Temperature differences between the medieval period, the recent period and the Little Ice Age are larger in the reconstructions than the simulations. This may indicate inflated variability of the reconstructions, a lack of sensitivity and processes to changes in external forcing on the simulated European climate and/or an underestimation of internal variability on centennial and longer time scales

This is the poster presented in the session "Decadal to millennial scale climate variability of the late Quaternary" at EGU2012 (poster ID EGU2012-11044). Please note, the email given in the poster is no longer valid. The initial abstract read: "Reconstructions and simulations of past climatic variability indicate three rather distinct periods between 1650 and 1850 CE consistent with estimates of past external drivers of the climate system. Rather cold conditions concurrent with negative radiative forcing anomalies persisted until the middle of the 18th century and throughout the first half of the 19th century. Interjacent, a warmer period occurred commensurate with positive radiative forcing anomalies. Previous work depicts these 200 years as the period in which large scale climate estimates by reconstruc- tions and simulations agree best. In addition, the number of available proxy indicators is comparably large in this time and their estimates less uncertain compared to earlier periods in the last millennium. By defining three climatologic periods (two cold and a warm episode), we are able to evaluate the perfor- mance of a number of climate simulations under relatively small uncertainty and under notably varying external forcing. We utilize simulations of the climate of the last millennium performed at the Max Planck Institute for Meteorology and the ensemble of “Last Millennium” simulations available in the CMIP5 database. Difference climatologies are calculated for temperature, precipitation and sea level pressure between the warmer period from 1741 to 1790 and the two colder episodes 1661 to 1710 and 1801 to 1850. While the so defined difference climatologies are generally similar within individual simulations, simulations strongly deviate from each other in estimates of temperature, hydrology and circulation. The difference climatologies are further compared to reconstructions focussing on the North Atlantic / European sector, and the probabilistic consistency is assessed."

The climate in the North Atlantic and its surrounding continents is expected to change considerably under global warming with specific regional characteristics. For example, the Atlantic Meridional Overturning Circulation is expected to slow down under global warming, which will leave an imprint in surface properties, such as sea-surface temperature patterns. Moreover, increasing greenhouses gas forcing may not only lead to changes in the mean state of the ocean but also to variations in the characteristics of internally-generated variability, to rapid transitions from one preferred state to another, and to modifications in tele-connections. Here we use a novel large ensemble of historical and scenario simulations carried out with the MPI-ESM to investigate how variability changes over time. The large number of ensemble members (100) allows us to better understand the role of internal variability by assessing the variance across the ensemble dimension. In addition, a large ensemble enables more robust estimates of spectral characteristics and boosts confidence in spectral peaks. We present an evaluation of variability changes in frequency space for different timescales and provide analyses of evolving relationships between the variability of climate indices (e.g. the North Atlantic Oscillation) and regional climate variability.

The climate in the North Atlantic and its surrounding continents is expected to change considerably under global warming with specific regional characteristics. For example, the Atlantic Meridional Overturning Circulation is expected to slow down under global warming, which will leave an imprint in surface properties, such as sea-surface temperature patterns. Moreover, increasing greenhouses gas forcing may not only lead to changes in the mean state of the ocean but also to variations in the characteristics of internally-generated variability, to rapid transitions from one preferred state to another, and to modifications in tele-connections. Here we use a novel large ensemble of historical and scenario simulations carried out with the MPI-ESM to investigate how variability changes over time. The large number of ensemble members (100) allows us to better understand the role of internal variability by assessing the variance across the ensemble dimension. In addition, a large ensemble enables more robust estimates of spectral characteristics and boosts confidence in spectral peaks. We present an evaluation of variability changes in frequency space for different timescales and provide analyses of evolving relationships between the variability of climate indices (e.g. the North Atlantic Oscillation) and regional climate variability.

The transient climate response (TCR) is 20% higher in the Alfred Wegener Institute Climate Model (AWI‐CM) compared to the Max Planck Institute Earth System Model (MPI‐ESM) whereas the equilibrium climate sensitivity (ECS) is by up to 10% higher in AWI‐CM. These results are largely independent of the two considered model resolutions for each model. The two coupled CMIP6 models share the same atmosphere‐land component ECHAM6.3 developed at the Max Planck Institute for Meteorology (MPI‐M). However, ECHAM6.3 is coupled to two different ocean models, namely the MPIOM sea ice‐ocean model developed at MPI‐M and the FESOM sea ice‐ocean model developed at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). A reason for the different TCR is related to ocean heat uptake in response to greenhouse gas forcing. Specifically, AWI‐CM simulations show stronger surface heating than MPI‐ESM simulations while the latter accumulate more heat in the deeper ocean. The vertically integrated ocean heat content is increasing slower in AWI‐CM model configurations compared to MPI‐ESM model configurations in the high latitudes. Weaker vertical mixing in AWI‐CM model configurations compared to MPI‐ESM model configurations seems to be key for these differences. The strongest difference in vertical ocean mixing occurs inside the Weddell and Ross Gyres and the northern North Atlantic. Over the North Atlantic, these differences materialize in a lack of a warming hole in AWI‐CM model configurations and the presence of a warming hole in MPI‐ESM model configurations. All these differences occur largely independent of the considered model resolutions., Plain Language Summary: The transient climate response (TCR) describes how strongly near‐surface temperatures warm in response to gradually increasing greenhouse‐gas levels. Here we investigate the role of the ocean which takes up heat and thereby delays the surface warming. Two models of the Coupled Model Intercomparison Project Phase 6 (CMIP6), the Alfred Wegener Institute Climate Model (AWI‐CM) and the Max Planck Institute Earth System Model (MPI‐ESM), which use the same atmosphere model but different ocean models are selected for this study. In AWI‐CM the upper ocean layers heat faster than in MPI‐ESM, while the opposite is true for the deep ocean. As a consequence, the TCR is 20% stronger in AWI‐CM compared to MPI‐ESM. We find that weaker vertical ocean mixing in AWI‐CM compared to MPI‐ESM, especially over the northern North Atlantic and the Weddell and Ross Gyres, is key for these differences. Our findings corroborate the importance of realistic ocean mixing in climate models when it comes to getting the strength and timing of climate change right., Key Points: The transient climate response in two coupled models with the same atmosphere but different ocean components differs by 20%. The upper (deeper) ocean heats faster (slower) in AWI‐CM compared to MPI‐ESM, independent of model resolution. Vertical mixing in the northern North Atlantic and the Weddell and Ross Gyres appears to be key for these differences., Bundesministerium für Bildung und Forschung (BMBF) http://dx.doi.org/10.13039/501100002347, German Climate Computing Centre (DKRZ), Federal Ministry of Education and Research of Germany, Helmholtz Association http://dx.doi.org/10.13039/501100009318, https://esgf-data.dkrz.de/projects/cmip6-dkrz/