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The global climate projections in the Climate Data Store (CDS) are a quality-controlled subset of the wider CMIP5 CMIP6 data. These data represent only a small subset of CMIP5 CMIP6 archive. A set of 50 51 core variables from the CMIP5 CMIP6 archive were identified for the CDS. These are the most used of the CMIP5 data. These variables are provided from seven 9 of the most popular CMIP5 CMIP6 experiments.
The CDS subset of CMIP5 CMIP6 data have been through a metadata quality control procedure which ensures a high standard of reliability dependability of the data. It may be for example that similar data can be found in the main CMIP5 CMIP6 archive however these data come with no very limited quality assurance and may have metadata errors or omissions. The quality-control process means that the CDS subset of CMIP5 data is further reduced to exclude data that have metadata errors or inconsistencies. It is important to note that passing of the quality control should not be confused with validity: for example, it will be possible for a file to have fully compliant metadata but contain gross errors in the data that have not been noted. In other words, it means that the quality control is purely technical and does not contain any scientific evaluation (for instance consistency check).
Experiments
The CDS-CMIP5 subset consists of the following CMIP5 experiments
- amip: An atmosphere-only configuration of the model as in the Atmospheric Model Intercomparison Project (AMIP, a pre-cursor to CMIP). Models impose sea surface temperatures (SSTs) & sea ice (from observations over 1979 to at least 2008), but with other conditions including CO2 concentrations and aerosols prescribed in the same way as the ‘historical’ experiment.
- historical: Models impose changing conditions (consistent with observations from 1850-2005), which may include: atmospheric composition due to both anthropogenic and volcanic influences, solar forcing, emissions or concentrations of short-lived species and natural and anthropogenic aerosols or their precursors, as well as land use.
- piControl (Pre-industrial Control): Models impose non-evolving, pre-industrial conditions, which may include prescribed atmospheric concentrations or non-evolving emissions of gases, aerosols or their precursors, as well as unperturbed land use.
- The piControl experiment is often run for a long number of years (500 or more) this allows for the models to reach an equilibrium state however this means that model data from this experiment only have a time element where the year is a modelling year not a representative year. Therefore to avoid confusion this experimental data is currently only available through the CDS API and will not be visible through the data download menu.
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Experiments
Shared Socioeconomic Pathway (SSP) Experiments
The SSP scenario experiments can be understood in terms of two pathways, a Shared Socioeconomic Pathway (SSP) and a Representative Concentration Pathway (RCP). The two pathways are represented by the three digits that make up the experiment’s name. The first digit represents the SSP storyline for the socio-economic mitigation and adaptation challenges that the experiment represents (Figure 1). The second and third digits represent the RCP climate forcing that the experiment follows. For example, experiment ssp245 follows SSP2, a storyline with intermediate mitigation and adaptation challenges, and RCP4.5 which leads to a radiative forcing of 4.5 Wm-2 by the year 2100.
Figure 1 - The socioeconomic “Challenge Space” to be spanned by the CMIP6 SSP experiments (O’Neil et al. 2014).
Experiments in the CDS
The CDS-CMIP6 subset consists of the following CMIP6 experiments:
Experiment name | Extended Description |
historical | The historical experiment is a simulation of the recent past from 1850 to 2014, it is performed with a coupled atmosphere-ocean general circulation model (AOGCM). In the historical simulations the model is forced with changing conditions (consistent with observations) which include atmospheric composition, land use and solar forcing. The initial conditions for the historical simulation are taken from the pre-industrial control simulation (piControl) at a point where the remaining length of the piControl is sufficient to extend beyond the period of the historical simulation to the end of any future "scenario" simulations run by the same model. The historical simulation is used to evaluate model performance against present climate and observed climate change. |
ssp585 | ssp585 is a scenario experiment extending into the near future from 2015 to 2100, it is performed with a coupled atmosphere-ocean general circulation model (AOGCM). The forcing for the CMIP6 SSP experiments is derived from shared socioeconomic pathways (SSPs), a set of emission scenarios driven by different socioeconomic assumptions, paired with representative concentration pathways (RCPs), global forcing pathways which lead to specific end of century radiative forcing targets. ssp585 is based on SSP5 in which climate change mitigation challenges dominate and RCP8.5, a future pathway with a radiative forcing of 8.5 W/m2 in the year 2100. The ssp585 scenario represents the high end of plausible future forcing pathways. ssp585 is comparable to the CMIP5 experiment RCP8.5. |
ssp370 | ssp370 is a scenario experiment extending into the near future from 2015 to 2100, it is performed with a coupled atmosphere-ocean general circulation model (AOGCM). The forcing for the CMIP6 SSP experiments is derived from shared socioeconomic pathways (SSPs), a set of emission scenarios driven by different socioeconomic assumptions, paired with representative concentration pathways (RCPs), global forcing pathways which lead to specific end of century radiative forcing targets. ssp370 is based on SSP3 in which climate change mitigation and adaptation challenges are high and RCP7.0, a future pathway with a radiative forcing of 7.0 W/m2 in the year 2100. The ssp370 scenario represents the medium to high end of plausible future forcing pathways. ssp370 fills a gap in the CMIP5 forcing pathways that is particularly important because it represents a forcing level common to several (unmitigated) SSP baseline pathways. |
ssp245 | ssp245 is a scenario experiment extending into the near future from 2015 to 2100, it is performed with a coupled atmosphere-ocean general circulation model (AOGCM). The forcing for the CMIP6 SSP experiments is derived from shared socioeconomic pathways (SSPs), a set of emission scenarios driven by different socioeconomic assumptions, paired with representative concentration pathways (RCPs), global forcing pathways which lead to specific end of century radiative forcing targets. ssp245 is based on SSP2 with intermediate climate change mitigation and adaptation challenges and RCP4.5, a future pathway with a radiative forcing of 4.5 W/m2 in the year 2100. The ssp245 scenario represents the medium part of plausible future forcing pathways. ssp245 is comparable to the CMIP5 experiment RCP4.5. |
ssp126 | ssp126 is a scenario experiment extending into the near future from 2015 to 2100, it is performed with a coupled atmosphere-ocean general circulation model (AOGCM). The forcing for the CMIP6 SSP experiments is derived from shared socioeconomic pathways (SSPs), a set of emission scenarios driven by different socioeconomic assumptions, paired with representative concentration pathways (RCPs), global forcing pathways which lead to specific end of century radiative forcing targets. ssp126 is based on SSP1 with low climate change mitigation and adaptation challenges and RCP2.6, a future pathway with a radiative forcing of 2.6 W/m2 in the year 2100. The ssp126 scenario represents the low end of plausible future forcing pathways. ssp126 depicts a "best case" future from a sustainability perspective. |
ssp460 | ssp460 is a scenario experiment extending into the near future from 2015 to 2100, it is performed with a coupled atmosphere-ocean general circulation model (AOGCM). The forcing for the CMIP6 SSP experiments is derived from shared socioeconomic pathways (SSPs), a set of emission scenarios driven by different socioeconomic assumptions, paired with representative concentration pathways (RCPs), global forcing pathways which lead to specific end of century radiative forcing targets. ssp460 is based on SSP4 in which climate change adaptation challenges dominate and RCP6.0, a future pathway with a radiative forcing of 6.0 W/m2 in the year 2100. The ssp460 scenario fills in the range of medium plausible future forcing pathways. ssp370 defines the low end of the forcing range for unmitigated SSP baseline scenarios. |
ssp434 | ssp434 is a scenario experiment extending into the near future from 2015 to 2100, it is performed with a coupled atmosphere-ocean general circulation model (AOGCM). The forcing for the CMIP6 SSP experiments is derived from shared socioeconomic pathways (SSPs), a set of emission scenarios driven by different socioeconomic assumptions, paired with representative concentration pathways (RCPs), global forcing pathways which lead to specific end of century radiative forcing targets. ssp434 is based on SSP4 in which climate change adaptation challenges dominate and RCP3.4, a future pathway with a radiative forcing of 3.4 W/m2 in the year 2100. The ssp434 scenario fills a gap at the low end of the range of plausible future forcing pathways. ssp370 is of interest to mitigation policy since mitigation costs differ substantially between forcing levels of 4.5 W/m2 and 2.6 W/m2. |
ssp534-over | ssp534-over is a scenario experiment with simulations beginning in the mid-21st century running from 2040 to 2100, it is performed with a coupled atmosphere-ocean general circulation model (AOGCM). The forcing for the CMIP6 SSP experiments is derived from shared socioeconomic pathways (SSPs), a set of emission scenarios driven by different socioeconomic assumptions, paired with representative concentration pathways (RCPs), global forcing pathways which lead to specific end of century radiative forcing targets. ssp534-over is based on SSP5 in which climate change mitigation challenges dominate and RCP3.4-over, a future pathway with a peak and decline in forcing towards an eventual radiative forcing of 3.4 W/m2 in the year 2100. The ssp534-over scenario branches from ssp585 in the year 2040 whereupon it applies substantially negative net emissions. ssp534-over explores the climate science and policy implications of a peak and decline in forcing during the 21st century. ssp534 fills a gap in existing climate simulations by investigating the implications of a substantial overshoot in radiative forcing relative to a longer-term target. |
ssp119 | ssp119 is a scenario experiment extending into the near future from 2015 to 2100, it is performed with a coupled atmosphere-ocean general circulation model (AOGCM). The forcing for the CMIP6 SSP experiments is derived from shared socioeconomic pathways (SSPs), a set of emission scenarios driven by different socioeconomic assumptions, paired with representative concentration pathways (RCPs), global forcing pathways which lead to specific end of century radiative forcing targets. ssp119 is based on SSP1 with low climate change mitigation and adaptation challenges and RCP1.9, a future pathway with a radiative forcing of 1.9 W/m2 in the year 2100. The ssp119 scenario fills a gap at the very low end of the range of plausible future forcing pathways. ssp119 forcing will be substantially below ssp126 in 2100. There is policy interest in low-forcing scenarios that would inform a possible goal of limiting global mean warming to 1.5°C above pre-industrial levels based on the Paris COP21 agreement[1]. |
[1] The Paris Agreement https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement
Models, grids and pressure levels
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