GFDL-ESM2M overshoot data

General Description

Data for stabilization and overshoot simulations performed with the model GFDL-ESM2M (Dunne et al., 2012) coupled to AERA (Terhaar et al., 2022). The data are organized under following simulations: 

AERA3_T15_TYPE2_ENS1_zen  : Coupled GFDL-ESM2M to AERA simulation for stabilization at 1.5 °C of global warming

AERA3_T20OS15SL_TYPE2_ENS1_zen : Coupled GFDL-ESM2M to AERA simulation for overshoot to 2.0 °C of global warming and return to 1.5 °C.

AERA3_T25OS15SL_TYPE2_ENS1: Coupled GFDL-ESM2M to AERA simulation for overshoot to 2.5 °C of global warming and return to 1.5 °C.

AERA3_T30OS15SL_TYPE2_ENS1: Coupled GFDL-ESM2M to AERA simulation for overshoot to 3.0 °C of global warming and return to 1.5 °C.

First the tar files need to be decompressed: tar –xvzf Overshoot_stabilization.tar.gz

Methods Description

The GFDL-ESM2M-AREA data was produced by running the Earth System Model GFDL ESM2M (Dunne et al., 2012; 2013) in emissions-driven configuration, coupled to the Adaptive Emission Reduction Approach (AERA; Terhaar et al. 2022).

GFDL-ESM2M

GFDL ESM2M consists of atmospheric, terrestrial, oceanic and sea ice components. The atmospheric component simulates processes at a dynamical 30-min time step and 3-h radiation time step on a 2 × 2.5° latitude-longitude grid using finite-volume advection. The land model LM3.0 represents hydrological, energy and carbon in vegetation, canopy and multi-layer snow and soil models. The ocean model consists of the Modular Ocean Model version 4p1, which simulates physical ocean processes at a horizontal resolution of 1° (mid-to-high latitudes) to 0.3° (tropics) resolution, with 50 vertical layers 

AERA

The adaptive emission reduction approach (AERA) aims to quantify CO2 forcing equivalent (CO2-fe) emission reductions every five years following the stocktake mechanism implemented in the Paris Agreement (Terhaar et al. 2022.). Every five years, the AERA estimates the necessary emission reductions for a chosen temperature target only based on simulations of the past annual global mean surface air temperature (GSAT), past CO2 emissions, and radiative forcing from non-CO2 forcing agents. The radiative forcing from non-CO2 forcing agents is used to calculate CO2-fe emissions, i.e., the amount of CO2 emissions over time that would lead to the simulated radiative forcing time series.

The AERA consists of three main steps: (1) determining the past anthropogenic warming and hence the remaining warming until a predefined temperature is reached, (2) estimating the remaining CO2-fe emission budget (REB), and (3) proposing a future CO2-fe curve.

First, the anthropogenic warming is calculated from simulated GSAT time-series using a simple 31-year running mean, in order to filter out internally-driven temperature changes. Second, the REB of CO2-fe emissions that can still be emitted before the target temperature will be reached is estimated using the transient climate response to cumulative emissions (TCRE) up to the current year, defined as the ratio of past warming and past cumulative CO2-fe emissions. The REB is estimated as the remaining warming until the temperature target is reached divided by TCRE. Here, we rely on the linear relationship between cumulative CO2-fe emissions and warming over the past and the near-future. When quantified, the REB of CO2-fe emissions is distributed over the future years in a third step using a cubic polynomial function.

Simulations

We performed simulations from 1861 to 2500 with GFDL-ESM2M-AERA to follow the temperature trajectories for the simulations given above.

The GFDL ESM2M was forced with historical fossil fuel carbon emissions, non-CO2 greenhouse gases, aerosols and land use change from 1861 to 2005. Afterwards, fossil fuel CO2 emissions follow observed emissions until 2020 (Friedlingstein et al. 2023) and projected emissions from the Nationally Determined Contributions (https://climateactiontracker.org/global/temperatures/; accessed December 2021) from 2021 to 2025. After 2025, the model was forced with fossil fuel CO2 emissions dictated by the Adaptative Emission Reduction Approach (AERA; Terhaar et al. 2022). , and Prescribed non-CO2 concentrations, aerosol and land use changes following followed the low emissions, high mitigation scenario RCP2.6 (van Vuuren et al., 2011) from 2006 to 2100, and are kept constant afterwards.

References:

Dunne et al. 2012: https://journals.ametsoc.org/view/journals/clim/25/19/jcli-d-11-00560.1.xml

Dunne et al. 2013: https://journals.ametsoc.org/view/journals/clim/25/19/jcli-d-11-00560.1.xml

Terhaar et al. 2022: https://www.nature.com/articles/s41558-022-01537-9

Friedlingstein et al .2023: https://essd.copernicus.org/articles/15/5301/2023/