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fair-2.1.3, calibration 1.4, AR6-updated_no-contrails_aubry-volcanic_2lm

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@chrisroadmap chrisroadmap released this 19 Oct 08:55
· 3 commits to main since this release
v1.4.3
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Calibration v1.4.3

A 1.6 million member prior and 421 member posterior are implemented. This version uses a two-layer energy balance model rather than a three-layer model. ERFari distributions are changed to bring them closer in line with the intent of AR6 WG1 Ch6. ERFaci prior is made slightly wider and non-uniform. Contrails are excluded from the calibration since few IAM scenarios provide detailed enough information to assess their future forcing (some kind of aviation activity indicator or proxy such as emissions from the sector would be needed).

  • 1.6 million prior ensemble
  • Climate response calibrated on 49 abrupt-4xCO2 experiments from CMIP6 and sampled using correlated kernel density estimates
  • Methane lifetime calibrated on 4 AerChemMIP experiments for 1850 and 2014 (Thornhill et al. 2021a, 2021b). Unlike other variables which are sampled around some prior uncertainty, only the best estimate historical calibration is used. The base (1750) lifetime has been fixed and consistently used across projections
  • Carbon cycle uses the parameters from Leach et al. 2021 calibrated for FaIR 2.0.0 using 11 C4MIP models.
  • Aerosol cloud interactions depend on SO2, BC and OC, using new calibrations from 13 RFMIP and AerChemMIP models, with the APRP code fixed by Mark Zelinka (Zelinka et al. 2023). Prior is a trapezoidal distribution with vertices at (-2.2, -1.6, -0.4, +0.2) W/m2.
  • Aerosol radiation interactions use prior values from AR6 Ch6, with best estimates and uncertainties scaled to create a prior in the range of -0.6 to 0.0 W/m2.
  • Ozone uses the same methodology as AR6 (Smith et al. 2021b).
  • Effective radaitive forcing uncertainty follows the distributions in AR6, with asymmetric distributions switched to skew-normal.
  • Volcanic forcing time series updated to 2022 (from IGCC).
  • Contrails are excluded from the calibration

Constraint sets:

AR6-updated_no-contrails_aubry-volcanic_2lm (v1.4.3)

As v1.4.2 except:

  • Two layer energy balance model
  • A 421 member posterior is used, since the overall ensemble performance is poorer using a two layer model.

AR6-updated_no-contrails_aubry-volcanic (v1.4.2)

As v1.4.0 except:

  • A 1000 member posterior is used, not 841. This is to match up ensemble members with the Chim/Aubry stochastic volcanic futures.
  • The solar_trend is discontinued and solar forcing is now sampled with only solar_amplitude
  • Volcanic forcing efficacy is set to 1.0 rather than 0.6

all-2022 (v1.4.1)

As v1.4.0 except:

  • Emissions are from several observational and proxy datasets updated to 2022 (Global Carbon Project, PRIMAP-Hist, Global Fire Emissions Database, Community Emissions Data System), and harmonized to run scenarios post-2022.

AR6-updated_no-contrails (v1.4.0)

  • 841-member posterior (deliberately chosen).
  • Emissions and concentrations from RCMIP (i.e. based on CMIP6), but with NOx updated as above. ssp245 chosen for post-2014.
  • Temperature from IGCC (Forster et al. 2023) (1850-2022, mean of 4 datasets).
  • Warming 2003-2022 relative to 1850-1900 range from IGCC.
  • CO2 concentrations constrained to IGCC estimate for 2022.
  • Ocean heat content from IGCC (1971-2020), linear.
  • two step constraining procedure used: first RMSE of less than 0.17K (up from 0.16), then 8-variable distribution fitting.
  • Aerosol ERF, ERFari and ERFaci as in AR6 WG1
  • No future warming constraints

References

Assets 2
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