/oscar

The compact Earth system model used in teaching ENV367.

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OSCAR

A compact Earth system model.

How-to

Download a release. Read The Fine Manual.

OSCAR v3 is developed in Python 3.7 and run preferentially through IPython. It makes heavy use of the xarray package (v0.14.1), and netCDF4 for saving data (v1.4.2). It also relies on other common scientific packages: numpy (v1.16.5) and scipy (v1.3.1). Although the latest versions of the packages used to run OSCAR v3 are given, older versions are likely to work.

The source code is provided firstly for transparency, and only secondly for dissemination. This means that it is provided as is, and no support of any kind is guaranteed (but feel free to ask). Feedbacks and contributions are always welcome.

Changelog

v3.1
  • Improved: land carbon cycle, exactly as described by Gasser et al. (2020). This comes with a recalibration of the module's preindustrial steady-state on TRENDYv7 models.
  • Changed: the formulation of D_ewet (wetlands areal emissions), to account for the new flxible structure of the land carbon cycle. This reduces the speed at which CH4 emissions respond to a change in net primary productivity.
v3.0.1
  • Fixed: an error in the formula of the function describing the overlap of absorption bands between CH4 and N2O, causing significantly wrong RFs. This error appeared during the conversion from v2 to v3, however, and it did not affect the earlier versions of the model.
v3.0

The physical equations and parameter values of this version are exactly the same as in v2.4. A few notable changes are worth mentioning here.

  • Added: an option to choose the solving scheme of the differential system. The default solving scheme is now an Eulerian exponential integrator (that typically requires fewer sub-timesteps to be stable).
  • Removed: the possibility of recalibrating the model's parameters on-the-fly, and especially the regional aggregation of the land carbon cycle. For now, calibrated parameters are directly imported from OSCAR v2, but this feature will be progressively re-implemented has v3 is developed further and new calibrating data become available.
  • Changed: the global temperature 2-box model's formulation, to correspond to a more usual formulation found in climate science. This is purely esthetic; this does not change the projected global temperature.
  • Changed: the structure of the bookkeeping module for land-use emissions. Specifically, the initialisation is now coded like any other carbon cycle flux. This does not significantly alter the module's performance.

v3

This is a complete revamp of OSCAR, for which the code was rewritten from scratch and moved to Python 3. OSCAR v3 relies heavily on the xarray package (and therefore netCDF saving format), to better structure the input and output data, to more easily deal with the many dimensions of internal data, and to parallelize simulations so that the run time of a typical Monte Carlo ensemble has been significantly reduced. It also uses its own object classes (Model and Process) that make it easy to change, extend or tune the model's structure and/or equations. Because of this complete overhaul, manipulation of the model has to be learned from scratch, however.

v2.4

This version is the last update of OSCAR v2. It is meant to be as close to OSCAR v3.0 as possible.

  • Added: the mod_biomeV3 option to force biome aggregation to that of v3.0.
  • Added: the mod_EHWPspeed option that introduces further variations in the decay time of harvested wood products. In addition to the normal configuration, the fast one scales the value of tau_HWP so that 20% of the pool remains after 80% of the initial decay time (a rescale by ~0.5), and the slow one scales the value of tau_HWP so that 30% of the pool remains after 150% of the initial decay time (a rescale by ~1.25).
  • Removed: the mod_EHWPfct option, so that only exponential decay of harvested wood products is now possible. This slightly increases CO2 emissions from land-use change in a Monte Carlo run.
  • Removed: the dependency of p_wet on the mod_LSNKcover option. It is now the average of all possible configurations, which has very little effect on the simulated wetlands CH4 emissions.
v2.3.1
  • Added: a new parameter p_HWP1_BB quantifying how much of the harvested wood products in pool 1 are actually burnt in the open, and thus accounted for in non-CO2 anthropogenic biomass burning emissions. It is set to 0.5 to roughly match present-day estimates.
  • Added: a new configuration based on GISS-E2-R-TOMAS to the mod_O3Tradeff option.
  • Removed: the Laube-HL configuration of the mod_O3Sfracrel option, since it makes little physical sense to have parameters specific to high latitudes in a global model like OSCAR.
  • Removed: the Daniel2010-lin configuration of the mod_O3Snitrous option, since a non-saturating effect of N2O onto stratospheric O3 lacked physical ground.
  • Fixed: the discretization of r_HWP (the response function for harvested wood products). The previous discretization caused delayed and therefore too low emissions.
  • Fixed: the value of k_BC_adjust for the option mod_BCadjust == CSIRO. This has very little impact on a Monte Carlo run.
  • Fixed: the value of radeff_O3t for the option mod_O3Tradeff == mean_ACCMIP. This has no impact on a Monte Carlo run.
  • Fixed: the default values of the beta_npp0 and CO2_comp parameters when isolating the urban biome, to prevent NaN from appearing during the simulation.
  • Fixed: NaN values no longer appear in the alpha_BB parameters when isolating the urban biome.
v2.3
  • Added: permafrost carbon thaw and release, exactly as described by Gasser et al. (2018). This comes with a new CO2 atmospheric flux accounting for the oxidation of geologic CH4 released in the atmosphere.
v2.2.2
  • Fixed: an error in the pre-processing of the AeroChem_ACCMIP input data for the CSIRO-Mk360 configuration. This was causing biased atmospheric lifetimes for POA and BC aerosols under this configuration (and slightly biased ones under the average mean-ACCMIP configuration).
v2.2.1
  • Fixed: an error in the f_pCO2 functions, causing a too efficient ocean carbon sink under high warming and high atmospheric CO2.
  • Fixed: an error in the f_pH function, causing unrealistic surface ocean pH changes.
v2.2

Initial release on GitHub. Exact model used by Gasser et al. (2017).

References

v3.1 (partial) | : Gasser, T., L. Crepin, Y. Quilcaille, R. A. Houghton, P. Ciais & M. Obersteiner. "Historical CO2 emissions from land-use and land-cover change and their uncertainty." Biogeosciences Discuss., under review (2020). doi:10.5194/bg-2020-33

v2.3 (partial) | : Gasser, T., M. Kechiar, P. Ciais, E. J. Burke, T. Kleinen, D. Zhu, Y. Huang, A. Ekici & M. Obersteiner. "Path-dependent reductions in CO2 emission budgets caused by permafrost carbon release." Nature Geoscience 11: 830-835 (2018). doi:10.1038/s41561-018-0227-0

v2.2 (full) | Gasser, T., P. Ciais, O. Boucher, Y. Quilcaille, M. Tortora, L. Bopp & D. Hauglustaine. "The compact Earth system model OSCAR v2.2: description and first results." Geoscientific Model Development 10: 271-319 (2017). doi:10.5194/gmd-10-271-2017