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CMIP6

This repository contains time series of annual-mean globally-averaged variables from various CMIP6 experiments, together with analysis of climate sensitivities, forcing and feedbacks.

Global-mean anomaly time series

Anomalies are calculated by subtracting the trend in piControl calculated over the time period parallel to the perturbation experiment, as in Andrews et al. (2012) and Forster et al. (2013). The final column is the multimodel mean.

filename description
delta_tas_abrupt-4xCO2_cmip6.csv anomalies in surface air temperature [tas] relative to piControl in the abrupt-4xCO2 experiment
delta_net_abrupt-4xCO2_cmip6.csv anomalies in net top-of-atmosphere flux [rsdt - rsut - rlut], relative to piControl in the abrupt-4xCO2 experiment
delta_tas_1pctCO2_cmip6.csv anomalies in surface air temperature [tas] relative to piControl in the 1pctCO2 experiment
delta_variable_experimentid_cmip6.csv anomalies in variable relative to piControl in the experimentid experiment

Analysis

gregory_plot_cmip6.csv

Linear regression of anomaly in net top-of-atmosphere flux vs. anomaly in surface air temperature over the first 150 years of the abrupt-4xCO2 experiment, following Gregory et al. (2004). gregory_plot_cmip6.txt contains the same information in a plain text file.

gregory_plot_fast_cmip6.csv and gregory_plot_slow_cmip6.csv

As for the standard Gregory plot but using years 1-20 (fast) and years 21-150 (slow) of the abrupt-4xCO2 experiment respectively, following Andrews et al. (2015)

parameter description units
Model CMIP6 Source ID
F4x 4xCO2 forcing (intercept) W m-2
lambda climate feedback (slope) W m-2 K-1
ECS effective climate sensitivity K
FSW, FLW shortwave and longwave components of F4x W m-2
lambdaSW, lambdaLW shortwave and longwave components of lambda W m-2 K-1

tcr_cmip6.csv

The transient climate response (TCR), derived from the 1pctCO2 experiment.

parameter description units
TCR tas anomaly averaged over years 61-80 K
T140 tas anomaly averaged over years 131-150 K
ratio T140 / TCR unitless

ohue_cmip6.csv

Linear regression of anomaly in net top-of-atmosphere flux vs. anomaly in surface air temperature in the 1pctCO2 experiment, following Gregory and Mitchell (1997). The slope of the regression line is the ocean heat uptake efficiency (OHUE, kappa).

parameter description units
kappa_01_70 OHUE calculated over years 1-70 W m-2 K-1
kappa_71_140 OHUE calculated over years 71-140 W m-2 K-1

two_layer_cmip6.csv

Fit to the two-layer model of the surface air temperature anomalies in the abrupt-4xCO2 experiment using the method described in Geoffroy et al. (2013).

parameter description units
tau_f fast (mixed layer) timescale years
tau_s slow (deep ocean) timescale years
gamma transfer co-efficient W m-2 K-1
C mixed-layer heat capacity W m-2 K-1 yrs
C_O deep-ocean heat capacity W m-2 K-1 yrs
a_f contribution to delta_tas from the fast mode unitless
a_s contribution to delta_tas from the slow mode, 1 - a_f unitless

Plots

ecs_cmip6_cmip5.png and tcr_cmip6_cmip5.png

Standard box plots (median, interquartile range, max, min) with ensemble mean shown as dashed line and individual models shown as open circles. The IPCC AR5 likely (17 - 83%) range is shown for reference.

Acknowledgement

I acknowledge the World Climate Research Programme, which, through its Working Group on Coupled Modelling, coordinated and promoted CMIP6. I thank the climate modeling groups for producing and making available their model output, the Earth System Grid Federation (ESGF) for archiving the data and providing access, and the multiple funding agencies who support CMIP6 and ESGF.

License

This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

CC BY-SA 4.0