# Presentation: 673354

## Recommendations of the Earth System Modeling Task Force 

**Challenge: How can we produce a decadal-centennial scale Earth System Model for GFDL?**

**Gross**

**Shevliakova**

**Dunne**

**Gnanadesikan**

**Levy**

**Stouffer**

## What is an Earth System Model?

- Simulate cycling between land, atmosphere, ice and ocean (also rivers, sediment, groundwater...) of:
- Heat
- Water (Salt)
- Carbon (first step)
- N (atm. chem., land/hydrology coupling, P, O2, Fe)
- ...dust, isotopes, CH4 (hydrates), S (DMS), etc.
- Formal test of Gaia Hypothesis (biosphere-climate feedbacks)
- Applications in biogeochemistry, anthropogenic impacts to fisheries, land use, air quality, water quality, etc.

**AKA Climate Model**

- }

## Modeler’s View of the Carbon Cycle

**Atmosphere**
**CO****2 ****= 280 ppmv (560 PgC) + FF**

**Ocean Circ.**
**+ BGC**

**Biophysics**
**+ BGC**

**37400 Pg C + FF**

**2000 Pg C **

***90******±***

***60******±***

**Turnover**
**Time of C**
**10****0****-10****3 ****yr**

**Turnover**
**time of C**
**10****0****-10****2 ****yr**

**Fossil Fuels**

**Turnover**
**Time of C**
**4**** ****yr**

**...****equilibrium takes 10****3****-10****4**** yrs**

## Central Questions

- What is the status of each component model?
- How should this effort be organized?
- How should the components be integrated?
- How should the carbon cycle be initialized?
- How should model fidelity be assessed?
- What can be accomplished in 6 months?
- What are the roles of collaborators?

## Status of Component Models

- Climate Model
- ESM2 (**1000 yrs in 500 days; 180pe; 130K cpu****.****hrs/mo**)
- Currently minimally acceptable for Dec-Cen
- Intensive efforts to improve both speed and realism
- ESM1p5 (**1000 yrs in 120 days; 40pe; 29K cpu****.****hrs/mo**)
- Unacceptable for Dec-Cen
- N**o support for development**
- Dynamic Land Biogeochemistry Model
- Preliminary LM3vp1-AM2p12 runs (code and FRE in 2 mo)
- Coupled Carbon code is in testing
- Continuing development on N45 grid
- Prognostic Ocean Biogeochemistry Model
- Prototype available in FRE
- Coupled version in a matter of weeks
- Continuing development on OM1p5 grid
- Atmospheric Transport Model – prototype available

## Proposed Organization

- Create an Earth System Model Development Team
- Goals:
- Integrate physical climate and biogeochemical cycling component models into an earth system model (minimally a coupled carbon model).
- Develop an evaluation strategy: identify performance criteria, compile datasets, implement a diagnostic set and design experiments to demonstrate fidelity.
- Provide GFDL and its collaborators with the modeling capabilities to address CCSP goals and to answer questions of the type posed in the IPCC process, and those of broader scientific community.
- Leadership:
- Dunne: Overall management, Code integration
- Toggweiler: Model fidelity
- Sarmiento: Goals, Design, Synthesis

## Component Integration Steps

- Code to pass CO2 between model components is ongoing
- Propose to develop individual components:
- Land dynamics and BGC at N45 resolution in stand-alone, AM2 and CM2 (within LMDT in collaboration with AMDT and CMDT)
- Ocean BGC in OMIP configurations
- Propose to develop ESM through:
- Including ESM components in Khartoum city release
- Developing prototype ESM1p5
- Incorporating ESM into Regression Test Suite as soon as components are ready for long spin-up
- Switching resolution to ESM2p1 if/when available

## Initialization of Carbon Cycle???

- Example: Ocean Carbon Model Inter-comparison Project
- “Steady state” has net air-sea CO2 flux < 0.01 Pg C/yr
**This requires model integrations of thousands of years!**
- Sensitivity of fully interactive system to initial conditions will be explored **BEFORE** ESM2p1 is run
- Coarse model is part of the pathway
- Some tricks will be explored
- Potential problems include
**Drift/ecological disaster/lack of fidelity**
**Runaway CO****2**
**Long-period  land-climate oscillations**

## Example Spin-up Strategy

**Ocean BGC spin-up with active ocean O(10****3****)y**

**Land BGC spin-up with atm clim. or active atm**
**O(10****2****)y **

**coupled phys.**
**Lnd/Ocn BGC adjustment**

**CO****2Tracer****=****prog**
**CO****2BGC****=280**
**CO****2Rad****=280**

**CO****2Tracer****=****prog**
**CO****2BGC****=****prog**
**CO****2Rad****=280**

**CO****2Tracer****=****prog**
**CO****2BGC****=****prog**
**CO****2Rad****=****prog**

**coupled phys.**
**Lnd/Ocn/Atm BGC adjustment**

**coupled phys.**
**fully coupled carbon-climate**

**~600 yr**

**100 yr**

**100 yr**

- CO2 roles: Atm. tracer, land/ocean BGC, radiative forcing
- Reminder:  Carbon inventory adjusts to climate
- Spin-up Goal:  find CO2 in equilibrium with climate
- Challenge:  fickle models and climate

- ...for a mimimum 1800 yr integration in ESM1p5 taking 4 months

## Establishing Fidelity of the ESM

- Define clear science goals for ESM simulations
- What do we need to achieve CCSP goals?
- What big science questions can this type of model address?
- Establish metrics/performance criteria
- Current climate
- Distribution of vegetation and terrestrial carbon in current climate
- Atmospheric pCO2 stability
- Seasonal-Interannual variability
- Oceanic pCO2, chl. and nutrients within X? of observations
- Compile observational datasets
- Implement standard set of diagnostics
- Design experiments and manage simulations
- Compare model to observations

## What can be accomplished in the next 6 months?

- Code incorporated into Khartoum release
- Definition of:
- Science goals
- Performance criteria and metrics
- Diagnostics
- Experimental design
- Compilation of observations for comparison
- Implementation of component models
- Exploration of carbon initialization in component models
- Integration of component models into prototype ESM
- Sensitivity tests in ESM1p5

- In 6 months:
- Will we be running fully-interactive ESM code?

**MOST PROBABLY**

**                                                    ****PROBABLY NOT**
**...****there are too many unknowns to say at this time.**

- Definite publication plans by 05/05 with:
- Land BGC with stand-alone, AM2, MLO, CM2 configurations
- Ocean BGC with OMIP configuration

- Will the results of this ESM be scientifically credible?

## Request for Resources

- Liaison to Modeling Services
- Computer time (Biospheric Processes Group?)
- Priority job tag

## Roles of collaborators

**Sarmiento Lab.** (AOS) - Contributed ocean tracer infrastructure, C system components, preliminary prognostic BGC code and plans to evaluate and apply ESM for C cycle studies.
**Pacala Lab.** (EEB) - Implemented LM3v and are evaluating biophysical feedbacks, vegetation dynamics and terrestrial carbon cycle
**UNH** - Contributed historical land use forcing and may contribute C and N river transport and water management models
**Hedin Lab.** (EEB; with Pacala Lab) - Plans to develop land N model
**USGS** - Plans to evaluate hydrology in ESM
**Wood Lab.** (CEE) - Plans to contribute to evaluation of LM3 hydrology