Simulation of the mid-Pliocene Warm Period using HadGEM3: Experimental design and results from model-model and model-data comparison

Abstract. Here we present the experimental design and results from a new mid-Pliocene simulation using the latest version of the UK’s physical climate model, HadGEM3-GC31-LL, conducted under the auspices of CMIP6/PMIP4/PlioMIP2. Although two other paleoclimate simulations have been recently run using this model, they both focused on more recent periods within the Quaternary and therefore this is the first time this version of the UK model has been run this far back in time. The mid-Pliocene Warm Period, ~3 Ma, is of particular interest because it represents a time period when the Earth was in equilibrium with CO2 concentrations roughly equivalent to those of today, providing a possible analogue for current and future climate change. The implementation of the Pliocene boundary conditions is firstly described in detail, based on the PRISM4 dataset, including CO2, ozone, orography, ice mask, lakes, vegetation fractions and vegetation functional types. These were incrementally added into the model, to change from a preindustrial setup to Pliocene conditions. The results of the simulation are then presented, which are firstly compared with the model’s pre-industrial simulation, secondly with previous versions of the same model and with available proxy data, and thirdly with all other models included in PlioMIP2. Firstly, the comparison with preindustrial suggests that the Pliocene simulation is consistent with current understanding and existing work, showing warmer and wetter conditions, and with the greatest warming occurring over high latitude and polar regions. The global mean surface air temperature anomaly at the end of the Pliocene simulation is 5.1 °C, which is the 2nd highest of all models included in PlioMIP2 and is consistent with the fact that HadGEM3-GC31-LL has one of the highest Effective Climate Sensitivities of all CMIP6 models. Secondly, the comparison with previous generation models and with proxy data suggests a clear increase in global sea surface temperatures as the model has undergone development. Up to a certain level of warming, this results in a better agreement with available proxy data, and the “sweet spot” appears to be the previous CMIP5 generation of the model, HadGEM2-AO. The most recent simulation presented here, however, appears to show poorer agreement with the proxy data compared with HadGEM2, and may be overly sensitive to the Pliocene boundary conditions resulting in a climate that is too warm. Thirdly, the comparison with other models from PlioMIP2 further supports this conclusion, with HadGEM3-GC31-LL being one of the warmest and wettest models in all of PlioMIP2 and, if all the models are ordered according to agreement with proxy data, HadGEM3-GC31-LL ranks approximately halfway among them.

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Simulation of the mid-Pliocene Warm Period using HadGEM3: experimental design and results from model–model and model–data comparison

Climate of the Past ◽

10.5194/cp-17-2139-2021 ◽

2021 ◽

Vol 17 (5) ◽

pp. 2139-2163

Author(s):

Charles J. R. Williams ◽

Alistair A. Sellar ◽

Xin Ren ◽

Alan M. Haywood ◽

Peter Hopcroft ◽

...

Keyword(s):

Experimental Design ◽

Boundary Conditions ◽

Climate Model ◽

Computational Cost ◽

Surface Air Temperature ◽

Warm Period ◽

Future Climate Change ◽

Polar Regions ◽

Proxy Data ◽

Global Mean

Abstract. Here we present the experimental design and results from a new mid-Pliocene simulation using the latest version of the UK's physical climate model, HadGEM3-GC31-LL, conducted under the auspices of CMIP6/PMIP4/PlioMIP2. Although two other palaeoclimate simulations have been recently run using this model, they both focused on more recent periods within the Quaternary, and therefore this is the first time this version of the UK model has been run this far back in time. The mid-Pliocene Warm Period, ∼3 Ma, is of particular interest because it represents a time period when the Earth was in equilibrium with CO2 concentrations roughly equivalent to those of today, providing a possible analogue for current and future climate change. The implementation of the Pliocene boundary conditions is firstly described in detail, based on the PRISM4 dataset, including CO2, ozone, orography, ice mask, lakes, vegetation fractions and vegetation functional types. These were incrementally added into the model, to change from a pre-industrial setup to a Pliocene setup. The results of the simulation are then presented, which are firstly compared with the model's pre-industrial simulation, secondly with previous versions of the same model and with available proxy data, and thirdly with all other models included in PlioMIP2. Firstly, the comparison with the pre-industrial simulation suggests that the Pliocene simulation is consistent with current understanding and existing work, showing warmer and wetter conditions, and with the greatest warming occurring over high-latitude and polar regions. The global mean surface air temperature anomaly at the end of the Pliocene simulation is 5.1 ∘C, which is the second highest of all models included in PlioMIP2 and is consistent with the fact that HadGEM3-GC31-LL has one of the highest Effective Climate Sensitivities of all CMIP6 models. Secondly, the comparison with previous generation models and with proxy data suggests a clear increase in global sea surface temperatures as the model has undergone development. Up to a certain level of warming, this results in a better agreement with available proxy data, and the “sweet spot” appears to be the previous CMIP5 generation of the model, HadGEM2-AO. The most recent simulation presented here, however, appears to show poorer agreement with the proxy data compared with HadGEM2 and may be overly sensitive to the Pliocene boundary conditions, resulting in a climate that is too warm. Thirdly, the comparison with other models from PlioMIP2 further supports this conclusion, with HadGEM3-GC31-LL being one of the warmest and wettest models in all of PlioMIP2, and if all the models are ordered according to agreement with proxy data, HadGEM3-GC31-LL ranks approximately halfway among them. A caveat to these results is the relatively short run length of the simulation, meaning the model is not in full equilibrium. Given the computational cost of the model it was not possible to run it for a longer period; a Gregory plot analysis indicates that had it been allowed to come to full equilibrium, the final global mean surface temperature could have been approximately 1.5 ∘C higher.

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Simulation of the mid-Pliocene Warm Period using HadGEM3-GC31-LL: Pliocene climate relative to the pre-industrial era, previous model versions, other climate models and proxy data

10.5194/egusphere-egu21-7707 ◽

2021 ◽

Author(s):

Charles Williams ◽

Daniel Lunt ◽

Alistair Sellar ◽

William Roberts ◽

Robin Smith ◽

...

Keyword(s):

Climate Change ◽

Climate Models ◽

Climate Model ◽

High Sensitivity ◽

Warm Period ◽

Future Climate ◽

Future Climate Change ◽

Last Interglacial ◽

Proxy Data ◽

Global Mean

To better understand the processes contributing to future climate change, palaeoclimate model simulations are an important tool because they allow testing of the models&#8217; ability to simulate very different climates than that of today.&#160; As part of CMIP6/PMIP4, the latest version of the UK&#8217;s physical climate model, HadGEM3-GC31-LL (hereafter, for brevity, HadGEM3), was recently used to simulate the mid-Holocene (~6 ka) and Last Interglacial (~127 ka) simulations and the results were compared to the preindustrial era, previous versions of the same model and proxy data (see Williams et al. 2020, Climate of the Past).&#160; Here, we use the same model to go further back in time, presenting the results from the mid-Pliocene Warm Period (~3.3 to 3 ma, hereafter the &#8220;Pliocene&#8221; for brevity).&#160; This period is of particular interest when it comes to projections of future climate change under various scenarios of CO2 emissions, because it is the most recent time in Earth&#8217;s history when CO2 levels were roughly equivalent to today.&#160; In response, albeit due to slower mechanisms than today&#8217;s anthropogenic fossil fuel driven-change, during the Pliocene global mean temperatures were 2-3&#176;C higher than today, more so at the poles.&#160;Here, we present results from the HadGEM3 Pliocene simulation.&#160; The model is responding to the Pliocene boundary conditions in a manner consistent with current understanding and existing literature.&#160; When compared to the preindustrial era, global mean temperatures are currently ~5&#176;C higher, with the majority of warming coming from high latitudes due to polar amplification from a lack of sea ice.&#160; Relative to other models within the Pliocene Modelling Intercomparison Project (PlioMIP), this is the 2nd warmest model, with the majority of others only showing up to a 4.5&#176;C increase and many a lot less.&#160; This is consistent with the relatively high sensitivity of HadGEM3, relative to other CMIP6-class models.&#160; When compared to a previous generation of the same UK model, HadCM3, similar patterns of both surface temperature and precipitation changes are shown (relative to preindustrial).&#160; Moreover, when the simulations are compared to proxy data, the results suggest that the HadGEM3 Pliocene simulation is closer to the reconstructions than its predecessor.

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Pliocene Model Intercomparison Project (PlioMIP): experimental design and boundary conditions (Experiment 2)

Geoscientific Model Development ◽

10.5194/gmd-4-571-2011 ◽

2011 ◽

Vol 4 (3) ◽

pp. 571-577 ◽

Cited By ~ 129

Author(s):

A. M. Haywood ◽

H. J. Dowsett ◽

M. M. Robinson ◽

D. K. Stoll ◽

A. M. Dolan ◽

...

Keyword(s):

Experimental Design ◽

Boundary Conditions ◽

Initial Phase ◽

Climate Models ◽

Model Development ◽

Warm Period ◽

Model Intercomparison ◽

Ocean Atmosphere ◽

Intercomparison Project ◽

Fully Coupled

Abstract. The Palaeoclimate Modelling Intercomparison Project has expanded to include a model intercomparison for the mid-Pliocene warm period (3.29 to 2.97 million yr ago). This project is referred to as PlioMIP (the Pliocene Model Intercomparison Project). Two experiments have been agreed upon and together compose the initial phase of PlioMIP. The first (Experiment 1) is being performed with atmosphere-only climate models. The second (Experiment 2) utilises fully coupled ocean-atmosphere climate models. Following on from the publication of the experimental design and boundary conditions for Experiment 1 in Geoscientific Model Development, this paper provides the necessary description of differences and/or additions to the experimental design for Experiment 2.

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CMIP6/PMIP4 simulations of the mid-Holocene and Last Interglacial using HadGEM3: comparison to the pre-industrial era, previous model versions and proxy data

Climate of the Past ◽

10.5194/cp-16-1429-2020 ◽

2020 ◽

Vol 16 (4) ◽

pp. 1429-1450 ◽

Cited By ~ 2

Author(s):

Charles J. R. Williams ◽

Maria-Vittoria Guarino ◽

Emilie Capron ◽

Irene Malmierca-Vallet ◽

Joy S. Singarayer ◽

...

Keyword(s):

Radiative Forcing ◽

Climate Model ◽

Geographical Location ◽

West African Monsoon ◽

Last Interglacial ◽

Atmospheric Concentration ◽

Industrial Control ◽

Proxy Data ◽

Orbital Configuration ◽

The Uk

Abstract. Palaeoclimate model simulations are an important tool to improve our understanding of the mechanisms of climate change. These simulations also provide tests of the ability of models to simulate climates very different to today. Here we present the results from two brand-new simulations using the latest version of the UK's physical climate model, HadGEM3-GC3.1; they are the mid-Holocene (∼6 ka) and Last Interglacial (∼127 ka) simulations, both conducted under the auspices of CMIP6/PMIP4. This is the first time this version of the UK model has been used to conduct palaeoclimate simulations. These periods are of particular interest to PMIP4 because they represent the two most recent warm periods in Earth history, where atmospheric concentration of greenhouse gases and continental configuration are similar to the pre-industrial period but where there were significant changes to the Earth's orbital configuration, resulting in a very different seasonal cycle of radiative forcing. Results for these simulations are assessed firstly against the same model's pre-industrial control simulation (a simulation comparison, to describe and understand the differences between the pre-industrial – PI – and the two palaeo simulations) and secondly against previous versions of the same model relative to newly available proxy data (a model–data comparison, to compare all available simulations from the same model with proxy data to assess any improvements due to model advances). The introduction of this newly available proxy data adds further novelty to this study. Globally, for metrics such as 1.5 m temperature and surface rainfall, whilst both the recent palaeoclimate simulations are mostly capturing the expected sign and, in some places, magnitude of change relative to the pre-industrial, this is geographically and seasonally dependent. Compared to newly available proxy data (including sea surface temperature – SST – and rainfall) and also incorporating data from previous versions of the model shows that the relative accuracy of the simulations appears to vary according to metric, proxy reconstruction used for comparison and geographical location. In some instances, such as mean rainfall in the mid-Holocene, there is a clear and linear improvement, relative to proxy data, from the oldest to the newest generation of the model. When zooming into northern Africa, a region known to be problematic for models in terms of rainfall enhancement, the behaviour of the West African monsoon in both recent palaeoclimate simulations is consistent with current understanding, suggesting a wetter monsoon during the mid-Holocene and (more so) the Last Interglacial, relative to the pre-industrial era. However, regarding the well-documented “Saharan greening” during the mid-Holocene, results here suggest that the most recent version of the UK's physical model is still unable to reproduce the increases suggested by proxy data, consistent with all other previous models to date.

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Simulating the mid-Pliocene climate with the MIROC general circulation model: experimental design and initial results

Geoscientific Model Development ◽

10.5194/gmd-4-1035-2011 ◽

2011 ◽

Vol 4 (4) ◽

pp. 1035-1049 ◽

Cited By ~ 42

Author(s):

W.-L. Chan ◽

A. Abe-Ouchi ◽

R. Ohgaito

Keyword(s):

Experimental Design ◽

Boundary Conditions ◽

General Circulation Model ◽

General Circulation ◽

Climate Models ◽

Circulation Model ◽

Sea Surface ◽

Future Climate Change ◽

Model Intercomparison ◽

Initial Results

Abstract. Recently, PlioMIP (Pliocene Model Intercomparison Project) was established to assess the ability of various climate models to simulate the mid-Pliocene warm period (mPWP), 3.3–3.0 million years ago. We use MIROC4m, a fully coupled atmosphere-ocean general circulation model (AOGCM), and its atmospheric component alone to simulate the mPWP, utilizing up-to-date data sets designated in PlioMIP as boundary conditions and adhering to the protocols outlined. In this paper, a brief description of the model is given, followed by an explanation of the experimental design and implementation of the boundary conditions, such as topography and sea surface temperature. Initial results show increases of approximately 10°C in the zonal mean surface air temperature at high latitudes accompanied by a decrease in the equator-to-pole temperature gradient. Temperatures in the tropical regions increase more in the AOGCM. However, warming of the AOGCM sea surface in parts of the northern North Atlantic Ocean and Nordic Seas is less than that suggested by proxy data. An investigation of the model-data discrepancies and further model intercomparison studies can lead to a better understanding of the mid-Pliocene climate and of its role in assessing future climate change.

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Simulating the mid-Pliocene climate with the MIROC general circulation model: experimental design and initial results

Geoscientific Model Development Discussions ◽

10.5194/gmdd-4-2011-2011 ◽

2011 ◽

Vol 4 (3) ◽

pp. 2011-2046 ◽

Cited By ~ 1

Author(s):

W.-L. Chan ◽

A. Abe-Ouchi ◽

R. Ohgaito

Keyword(s):

Experimental Design ◽

Boundary Conditions ◽

General Circulation Model ◽

General Circulation ◽

Climate Models ◽

Circulation Model ◽

Sea Surface ◽

Future Climate Change ◽

Model Intercomparison ◽

Initial Results

Abstract. Recently, PlioMIP (Pliocene Model Intercomparison Project) was established to assess the ability of various climate models to simulate the mid-Pliocene warm period (MPWP), 3.29–2.97 million years ago. We use MIROC4m, a fully coupled atmosphere-ocean general circulation model (AOGCM), and its atmospheric component alone to simulate the MPWP, utilizing up-to-date data sets designated in PlioMIP as boundary conditions and adhering to the protocols outlined. In this paper, a brief description of the model is given, followed by an explanation of the experimental design and implementation of the boundary conditions, such as topography and sea surface temperature. Initial results show increases of approximately 10 °C in the zonal mean surface air temperature at high latitudes accompanied by a decrease in the equator-to-pole temperature gradient. Temperature in the tropical regions increase more in the AOGCM. However, warming of the AOGCM sea surface in parts of the northern North Atlantic Ocean and Nordic Seas is less than that suggested by proxy data. An investigation of the model-data discrepancies and further model intercomparison studies can lead to a better understanding of the mid-Pliocene climate and of its role in assessing future climate change.

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Consistently Estimating Internal Climate Variability from Climate Model Simulations

Journal of Climate ◽

10.1175/jcli-d-16-0428.1 ◽

2017 ◽

Vol 30 (23) ◽

pp. 9555-9573 ◽

Cited By ~ 24

Author(s):

Dirk Olonscheck ◽

Dirk Notz

Keyword(s):

Climate Variability ◽

Sea Ice ◽

Climate Model ◽

Surface Air Temperature ◽

Internal Variability ◽

Arctic Sea Ice ◽

New Method ◽

Polar Regions ◽

Internal Climate Variability ◽

Ensemble Simulations

This paper introduces and applies a new method to consistently estimate internal climate variability for all models within a multimodel ensemble. The method regresses each model’s estimate of internal variability from the preindustrial control simulation on the variability derived from a model’s ensemble simulations, thus providing practical evidence of the quasi-ergodic assumption. The method allows one to test in a multimodel consensus view how the internal variability of a variable changes for different forcing scenarios. Applying the method to the CMIP5 model ensemble shows that the internal variability of global-mean surface air temperature remains largely unchanged for historical simulations and might decrease for future simulations with a large CO2 forcing. Regionally, the projected changes reveal likely increases in temperature variability in the tropics, subtropics, and polar regions, and extremely likely decreases in midlatitudes. Applying the method to sea ice volume and area shows that their respective internal variability likely or extremely likely decreases proportionally to their mean state, except for Arctic sea ice area, which shows no consistent change across models. For the evaluation of CMIP5 simulations of Arctic and Antarctic sea ice, the method confirms that internal variability can explain most of the models’ deviation from observed trends but often not the models’ deviation from the observed mean states. The new method benefits from a large number of models and long preindustrial control simulations, but it requires only a small number of ensemble simulations. The method allows for consistent consideration of internal variability in multimodel studies and thus fosters understanding of the role of internal variability in a changing climate.

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The Pliocene Model Intercomparison Project (PlioMIP) Phase 2: scientific objectives and experimental design

Climate of the Past ◽

10.5194/cp-12-663-2016 ◽

2016 ◽

Vol 12 (3) ◽

pp. 663-675 ◽

Cited By ~ 67

Author(s):

Alan M. Haywood ◽

Harry J. Dowsett ◽

Aisling M. Dolan ◽

David Rowley ◽

Ayako Abe-Ouchi ◽

...

Keyword(s):

Climate Change ◽

Experimental Design ◽

Boundary Conditions ◽

Surface Topography ◽

Phase 1 ◽

Future Climate Change ◽

Phase 2 ◽

Model Intercomparison ◽

Ice Surface ◽

Intercomparison Project

Abstract. The Pliocene Model Intercomparison Project (PlioMIP) is a co-ordinated international climate modelling initiative to study and understand climate and environments of the Late Pliocene, as well as their potential relevance in the context of future climate change. PlioMIP examines the consistency of model predictions in simulating Pliocene climate and their ability to reproduce climate signals preserved by geological climate archives. Here we provide a description of the aim and objectives of the next phase of the model intercomparison project (PlioMIP Phase 2), and we present the experimental design and boundary conditions that will be utilized for climate model experiments in Phase 2. Following on from PlioMIP Phase 1, Phase 2 will continue to be a mechanism for sampling structural uncertainty within climate models. However, Phase 1 demonstrated the requirement to better understand boundary condition uncertainties as well as uncertainty in the methodologies used for data–model comparison. Therefore, our strategy for Phase 2 is to utilize state-of-the-art boundary conditions that have emerged over the last 5 years. These include a new palaeogeographic reconstruction, detailing ocean bathymetry and land–ice surface topography. The ice surface topography is built upon the lessons learned from offline ice sheet modelling studies. Land surface cover has been enhanced by recent additions of Pliocene soils and lakes. Atmospheric reconstructions of palaeo-CO2 are emerging on orbital timescales, and these are also incorporated into PlioMIP Phase 2. New records of surface and sea surface temperature change are being produced that will be more temporally consistent with the boundary conditions and forcings used within models. Finally we have designed a suite of prioritized experiments that tackle issues surrounding the basic understanding of the Pliocene and its relevance in the context of future climate change in a discrete way.

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The coupled atmosphere–chemistry–ocean model SOCOL-MPIOM

Geoscientific Model Development ◽

10.5194/gmd-7-2157-2014 ◽

2014 ◽

Vol 7 (5) ◽

pp. 2157-2179 ◽

Cited By ~ 22

Author(s):

S. Muthers ◽

J. G. Anet ◽

A. Stenke ◽

C. C. Raible ◽

E. Rozanov ◽

...

Keyword(s):

Climate Model ◽

Land Use Changes ◽

Surface Air Temperature ◽

Polar Vortex ◽

Ocean Model ◽

Boreal Winter ◽

Data Sets ◽

Polar Regions ◽

Stratospheric Temperature ◽

Climate Interactions

Abstract. The newly developed atmosphere–ocean–chemistry–climate model SOCOL-MPIOM is presented by demonstrating the influence of chemistry–climate interactions on the climate state and the variability. Therefore, we compare pre-industrial control simulations with (CHEM) and without (NOCHEM) interactive chemistry. In general, the influence of the chemistry on the mean state and the variability is small and mainly restricted to the stratosphere and mesosphere. The atmospheric dynamics mainly differ in polar regions, with slightly stronger polar vortices in the austral and boreal winter, respectively. The strengthening of the vortex is related to larger stratospheric temperature gradients, which are attributed to a parameterisation of the absorption of ozone and oxygen in different wavelength intervals, which is considered in the version with interactive chemistry only. A second reason for the temperature differences between CHEM and NOCHEM is related to diurnal variations in the ozone concentrations in the higher atmosphere, which are missing in NOCHEM. Furthermore, stratospheric water vapour concentrations substantially differ between the two experiments, but their effect on temperature is small. In both setups, the simulated intensity and variability of the northern polar vortex is inside the range of present-day observations. Additionally, the performance of SOCOL-MPIOM under changing external forcings is assessed for the period 1600–2000 using an ensemble of simulations. In the industrial period from 1850 onward SOCOL-MPIOM overestimates the global mean surface air temperature increase in comparison to observational data sets. Sensitivity simulations show that this overestimation can be attributed to a combination of factors: the solar forcing reconstruction, the simulated ozone changes, and incomplete aerosol effects and land use changes.

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A sea ice-free Arctic during the Last Interglacial supports fast future loss

10.5194/egusphere-egu2020-1399 ◽

2020 ◽

Author(s):

Maria Vittoria Guarino ◽

Louise Sime ◽

David Schroeder ◽

Irene Malmierca-Vallet ◽

Erica Rosenblum ◽

...

Keyword(s):

Sea Ice ◽

Elevated Temperatures ◽

Climate Model ◽

Arctic Sea Ice ◽

Future Climate Change ◽

Last Interglacial ◽

Ice Melt ◽

Arctic Sea ◽

Improved Model ◽

The Uk

The Last Interglacial (LIG) is a period of great importance as an analog for future climate change. Global sea level was 6-9 m higher than present. Stronger LIG summertime insolation at high northern latitudes drove Arctic land summer temperatures around 4-5 K higher than during the preindustrial era. Climate-model simulations have previously failed to capture these elevated temperatures. This may be because these models failed to correctly capture LIG sea ice changes.Here, we show that the latest version of the UK Hadley Center coupled ocean-atmosphere climate model (HadGEM3) simulates a much improved Arctic LIG climate, including the observed high temperatures. Improved model physics in HadGEM3, including a sophisticated sea ice melt-pond scheme, results in the first-ever simulation of the complete loss of Arctic sea ice in summer during the LIG.Our ice-free Arctic yields a compelling solution to the long-standing puzzle of what drove LIG Arctic warmth. The LIG simulation result is a new independent constraint on the strength of Arctic sea ice decline in climate-model projections, and provides support for a fast retreat of Arctic summer sea ice in the future.

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