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These are the intended use-case/justification for one or multiple variable groups. Opportunities are linked to relevant experiment groups. Identifying opportunities helps to provide a structure to map variables against requirements. Each opportunity description will convey why this combination of variables and experiments is important and how they contribute to impact.
| Attribute | Value |
|---|---|
| description | Towards gaining a broader understanding of thresholds in the climate system and its sensitivity to past and future perturbations, the Paleoclimate Modelling Intercomparison Project (PMIP) proposes to explore various expressions of past, present and future climate in one concerted effort. To this end, modelling centers are asked to provide various variables that allow increased understanding of the Earth System under - partially fundamentally different - forcings, that relate to past, present and future climates. The requested variables are organized via 13 different groups. Beyond various standard diagnostics of global climate and of the state of its components, where a clear focus is on atmosphere, ocean, sea-ice and large scale circulation, we request additional variables that support a deeper understanding of climate system dynamics, including variables that are relevant for data assimilation, stable water isotope research, and to diagnose the state of the cryosphere. The additional variables should ensure that published model simulations are as versatile and impactful as possible for future research in Earth System sciences. We invite modelling centers to provide these variables over the full period of model run time for transient simulations, of after spin-up has reached if the focus of a simulation is on the equilibrium state. Below we will further outline aspects of the research that shall be enabled by means of requested variables. Research on ongoing climate change creates awareness that we may be heading for uncharted territory regarding future environmental conditions and that our expectation of future climate is subject to large uncertainties. We are aware that climate models, applied to create projections of future climate, might be employed outside their calibrated range, raising questions regarding the degree of uncertainty in our expectations for the future. The greater understanding of how Earth's climate has changed in the past provides valuable context for its current and future changes. It is therefore valuable to study the record of past climate states and to aim for a better understanding of the dynamics of the Earth System in the context of different past, present, and future background climates. Doing so may provide a better description of the envelope of potential future climates that we may head into, thereby creating a link between future and past (e.g., Burke et al., 2018). Paleoclimate research as proposed for CMIP7 will follow several routes. First, it involves a stock-take of conventional climate model output that samples the state of various components of the Earth System. Beyond providing quantification of large-scale patterns and variability, this route will support understanding the status of tipping elements and evaluating the possibility of abrupt climate change. Output generated by CMIP7 models will serve as forcing for modelling of specific components of the Earth System like permafrost and ice sheets. As a second route, we consider novel developments in paleoclimate modelling. Where modelling groups can do so, we invite employment of stable water and other isotope dynamics, enabling an extended perspective on the hydrological cycle and a more direct comparison of model output with proxy-archives. Furthermore, we acknowledge significant recent advances in paleodata assimilation. These allow us to systematically combine climate model output with paleoclimate proxy reconstructions to create probabilistic reanalyses of the past. Research using single models has provided large insights, for example in the Last Glacial Maximum (Osman et al, 2021), which are vital to underpin constraints on climate sensitivity. The next crucial step is to create similar work based on an ensemble of CMIP7 models. The combination of methods described above will provide us with a reflection on climate model performance against the glaciologic and geologic records. The approach will help us to better interpret any model-data discord. In combination with simulations from other MIPs (e.g. ScenarioMIP), the research will highlight where model sensitivity and model processes must be improved to better capture patterns and variability of climates significantly different from today. References: Burke, K. D., Williams, J. W., Chandler, M. A., Haywood, A. M., Lunt, D. J., and Otto-Bliesner, B. L.: Pliocene and Eocene provide best analogs for near-future climates, _P. Natl. Acad. Sci._ USA, 115, 13288–13293, https://doi.org/10.1073/pnas.1809600115, 2018. Osman, M.B., Tierney, J.E., Zhu, J. _et al._: Globally resolved surface temperatures since the Last Glacial Maximum, _Nature, 599, _ 239–244 (2021). https://doi.org/10.1038/s41586-021-03984-4 |
| desirable_ensemble_size | 1 |
| expected_impacts | This data request aims at enabling the community to link model performance and inferences on climate dynamics across time scales - from past, to present, to future. We foresee the following use cases: 1. Studying the state of the ocean, including various ocean circulation patterns, across time scales, from the Last Interglacial, and even earlier time slices in PMIP, to the future. 2. The meridional overturning circulation (MOC) was different in the past and may change in the future. Model dependency of MOC stability may be an issue and model parameterizations can lead to biases in projections. Having the upcoming CMIP7 models produce metrics relevant for sampling model dependency and model uncertainty in MOC, for as many simulations and experiments as possible, would allow us to make the most of the information contained in the past MOC reconstructions. 3. Understanding the performance of sea ice models in climate states that are significantly different from today is key to the quantification of various climate feedbacks. We request several sea ice metrics beyond those traditionally considered in paleoclimate research. These will help to understand why sea ice models may show a different response to similar forcings. While our clear focus is on the PMIP-sponsored abrupt-127k simulation, we also aim to compare the results to DECK, historical and future scenarios. 4. Beyond the strong interest to gain an understanding of changes in the hydrological cycle under the impact of different climate forcings from past to future, simulated stable water isotope output may support the interpretation of proxy records of past climates, which are often linked to isotope compositions. For recent climate, simulated isotopes can be compared to observational networks, providing an opportunity to quantify the skill of isotope-enabled climate models to reproduce the observed hydrological cycle. 5. Studying radiative and energetic balance of the Earth System across time scales will put ongoing anthropogenic climate change into perspective. Via the requested additional albedo and fx quantities, and by means of a quantification of changes in ocean heat content, we hope to contribute to analyzing Earth's climate in the context of its long-term response to various forcings. 6. Proxy system models underpin paleodata assimilation, which take output from climate models and determine what a proxy record would look like if it had seen that simulated climate. Lodging the output required to run these models would not only provide an advance in data model comparisons, but would allow multi-model reanalyses to be made. 7. Improved understanding of the state of the land cryosphere and of its future are of key interest in a changing climate. How much carbon may become released from melting permafrost? What are the stabilizing and destabilizing mechanisms that control sea level in a warm climate? While CMIP7 models often will not be able to directly simulate the relevant processes, the data request shall ensure that CMIP7 model output can be used as a climate forcing to drive respective component models. |
| justification_of_resources | Most requested variables are part of the baseline data request and are assumed to be produced by modelling centers anyway. This is the case for most of the higher voluminous variables that go beyond the ocean surface and will help us to get a more detailed understanding of the ocean’s state and dynamics for climates significantly different from today. In some cases, we request variables that are beyond the baseline request. For some of them the definition process has been initiated specifically for this opportunity. We believe that our request will lead to a modest increase of resources consumption in comparison to the overall CMIP7 data request. Below we justify required resources by outlining how requested variable groups are key to realize our proposed scientific goals and impacts. Gaining improved understanding of the cryosphere (snow, land ice, sea ice), of its response to different climate drivers, and of its impact on the energy balance of the Earth System, necessitates detailed model output that relates to the state of these system components and to albedo. For the latter we request the respective radiative quantities rather than albedo itself. Note that this may involve computing radiative fluxes at sub-grid scale, for example over the sea-ice covered portion of the ocean only. At the interface between modern and orbital time scales we necessitate some variables at higher temporal resolution than commonly done in paleoclimate research. This involves both top-of-the-atmosphere radiative fluxes, and first order climate metrics, like surface temperature and precipitation fluxes, for performing calendar correction in simulations where the Earth's orbit differs from today. Understanding the state of the ocean, ocean dynamics, and related tipping points, necessitates availability not only of ocean state metrics (like heat, salt and volume transports and inventories), but also of the relevant boundary conditions at the surface, including continental runoff. There are parallels to other relevant CMIP7 opportunities, and variables requested by us will have a value beyond paleoclimate research. Towards enabling a more direct comparison of model output to proxies, fostering applications of CMIP model output in the framework of paleodata assimilation, and in appreciation of slow adjustment processes in the Earth System, we request variables that may be more specific than those typically requested for other CMIP7 opportunities. This involves extended information on various boundary conditions, but also refers to information on the state of the deep ocean. We note that there may be a benefit well beyond paleoclimate research. For example, simulated stable water isotopes may be compared to modern observational data sets and aid in understanding hydrological transport processes in climate models. Since we would like to compare model performance in the PMIP sponsored abrupt-127k simulation also to simulation of other climate states, it is necessary to provide the aforementioned types of model output also for other simulations than those typically linked to the keyword “paleo”. |
| lead_theme | Ocean & Sea-Ice |
| minimum_ensemble_size | 1 |
| name | Paleoclimate Research at the Interface between Past, Present, and Future |
| opportunity_id | 51 |
| technical_notes | For deck we are particularly interested in PI (plus historical), but we note that also for simulations that study the change of an abrupt or ramp CO2 forcing providing the requested additional variables will contribute to a better understanding of model dynamics in the framework of a rapidly changing climate. PMIP aims to improve our understanding of Earth's climate on longer time scales, including climates that are substantially warmer than today and that often are also more in equilibrium with the applied forcing. PMIP encourages modelling centers to provide data from scenario long-term extensions wherever doing so is feasible at an acceptable expense. |
| data_request_themes | Atmosphere, Land & Land-Ice, Ocean & Sea-Ice, Earth System |
| experiment_groups | pmip, picontrol, scenarios_extensions, scenarios, historical |
| mips | PMIP |
| time_subsets | 80ac3156-a698-11ef-914a-613c0433d878 |
| variable_groups | paleo_atmosphere, paleo_cryosphere_high_priority, paleo_cryosphere_low_priority, paleo_cryosphere_medium_priority, paleo_fx ... and 8 morepaleo_atmosphere, paleo_cryosphere_high_priority, paleo_cryosphere_low_priority, paleo_cryosphere_medium_priority, paleo_fx, paleo_land_atmosphere_surface, paleo_ocean, paleo_ocean_3D, paleo_ocean_transports, paleo_permafrost, paleo_radiation_fluxes, paleo_stable_isotopes, paleodata_assimilation |