**GFDL's Earth System Model Development Plans**

ESMDT Leadership, 03/14/06

This document provides a summary of the anticipated Earth System Model
Development Team's plans in support of GFDL's ESM3 effort as outlined in
the recent Valentine Report by Delworth et al., and based on subsequent
ESMDT discussions (attached). These plans are organized into three
categories: model development with existing codes (ESM2.1), code and
model development towards a base case ESM3 (ESM3-basecase), and an
aggressive track towards an enhanced, more sophisticated ESM that
includes the complete suite of additional features possible under
development at GFDL (ESM3-enhanced). In interpreting the timeline below,
it is important to recognize that the carbon-climate model development
timescale is something akin to a probability distribution with a
potentially VERY long tail due to the research issues at hand.

![](media/image1.png){width="6.0in" height="1.6194444444444445in"}

**ESM2.1:**

**Goal:** To utilize currently-available codes to develop a working
carbon-climate ESM with physics similar to CM2.1 in order to test
fidelity of the carbon cycle. This effort will both allow us to both
gain experience in carbon-climate model development, sensitivity and
diagnostics development as well as allow the groups to begin doing
meaningful science and writing up Earth System components in scientific
papers.

**Background:** A slab model (SM2.1) has been coupled to LM3v (LM2
hydrology but dynamic vegetation). Experiments with this configuration
produce a climate similar to SM2.1 with LM2. The ocean
biogeochemistry-climate feedback has been studied separately and
demonstrated to be small. There are currently five ways that atmospheric
CO~2~ interacts in ESM2.1: canopy CO~2~ affects photosynthesis, canopy
CO~2~ and atm. CO~2~ affect the CO~2~ flux between the land and atm.,
surface ocean CO~2~ and atm. CO~2~ affect the CO~2~ flux between the
ocean and atm., atm. CO~2~ affects radiation model computations, and
atm. transport affects atm. CO~2~. River and sediment carbon fluxes are
ignored, though alkalinity fluxes may be included.

**Strategy:** This model development will begin from the code base in
the Memphis release. A run will be configured to include a limited
number of interactions with atmospheric CO~2~ fixed at a preindustrial
level (286 ppm) except in the photosynthesis model where it will be
fixed at the 1990 level (350 ppm). This experiment will be run for a
long time (500-1000 years) to attempt a stable biosphere with long-term
air-sea and air-land CO~2~ fluxes less than 0.1 PgC yr^-1^, or about 5
ppm per century. If we are successful, this will provide the initial
condition to begin including other CO~2~ interactions and test model
sensitivity. Once a fully stable model is achieved, we will perform
perturbation studies with idealized, historical and future CO~2~
emission scenarios.

**ESM3-basecase:**

**Goal:** To assure interactive CO~2~ cycling in CM3.

**Configuration:**

> Atmosphere: Interactive CO~2~ in AM3. Atmospheric chemistry and
> aerosols may be interactive. See GAMDT document for details.
>
> Land: Land carbon in LM3 including air-land CO~2~ fluxes, fire,
> agricultural harvest and carbon leaching. See LMDT document for
> details.
>
> Rivers: Rivers will transport carbon leached from land model to river
> mouths to be received by the ocean model. See LMDT document for
> details.
>
> Ocean: Three phytoplankton groups with cycling of C, N, P, Si, O~2~,
> Fe and alkalinity in the ocean component of CM3. See OMDT document for
> physics details.

**Strategy:** This is the minimum set of required code base for model
components necessary for delivery to CMDT by January, 2008 in order for
them to begin CM3 climate model development. Meanwhile, ESMDT will
continue carbon model development and science applications in ESM2.1 and
code development for ESM3-enhanced. Carbon model development of ESM3 may
wait until CM3 development is complete. Experience developing ESM2.1
will guide model development of ESM3, as will the evolving scenarios for
AR5.

**ESM3-enhanced:**

**Goal:** To implement the frontiers in Earth System Model Development
at GFDL into ESM3 - a rough tally of **what could be possible** with
focused effort.

**Configuration:**

> Atmosphere: Interactive atmospheric chemistry and aerosols including
> dynamic generation of dust with vegetation and Fan iron solubilization
> as well as dynamic land-atmosphere gas fluxes including Hg.
>
> Land: Prognostic land-atmosphere gas fluxes of not only CO~2~ but also
> NO~X~, NH~3~, CH~4~, CO, and VOCs. Internally, includes not only C,
> but also N and P for nutrient limitation. It would provide not only
> leaching of C, but N land P from both natural and agricultural sources
> with redistribution of agricultural N and P to point sources of
> sewage.
>
> Rivers: Transport and river biogeochemistry of not only C but N, P,
> sediment and Hg before transit to the ocean model.
>
> Ocean: Includes atmospheric inputs of Fe, N, and Hg and river inputs
> of C and alkalinity for carbon cycling, N, P and Fe for
> eutrophication, sediment transport for water clarity, sediments for
> coastal processes, harmful algal blooms and Hg for human
> health/fisheries and krill for fisheries.

**Strategy:** This is the most optimistic/aggressive set of additional
model components that could be made available in the enhanced version of
ESM3 with focused effort. Serious questions exist about how to construct
climate change scenarios given the great number and uncertainty of model
forcing data sets relating to natural and anthropogenic sources,
redistribution and feedbacks as well of the necessary suite of
calibration studies and analysis schemes.

Notes from ESMDT meetings on 02/22/06 and 03/01/06

For background, I had asked the various people involved in the
development of the various model components to describe their
perspective and concerns relating to:\
\
1) development status\
2) configuration issues for historical and predictive runs\
3) expectations of what will definitely be accomplished for ESM3\
4) expectations of what additional features could be feasible with
focused effort\
5) assessment of resources necessary\
\
We were able to make progress on the first six agenda items on
Wednesday:\
\
1) General summary of CM3/ESM3 white paper as it relates to general
Earth\
System Modeling activities (Dunne) and 2)
fidelity/nomenclature/component integration schedule (Dunne/Stouffer)

We first need to clarify what we mean by CM3 versus ESM3. In actuality,
the terms CM3 and ESM3 define the bounds of a continuum of models from a
common code base ranging from a purely physical base case (CM3 - in
which biogeochemical, chemical and human-related interactions with
climate are absent and their effects only prescribed and/or diagnosed)
to the fully advanced case of a complete biosphere (ESM3 - in which
biogeochemical, chemical and human-related interactions with climate are
present and fully prognostic).

The scope of the CM3/ESM3 development effort is as GFDL's contribution
to the IPCC's fifth assessment report (AR5) as laid out by Delworth et
al. white paper:. The Stream 1 (base case) model development effort will
have mainly the same resolution as CM2.1 except for heightened vertical
resolution in the atmosphere. Potentially new atmospheric physics, the
capacity for interactive chemistry and aerosols, LM3 hydrology, and
potentially a new ocean model formulation will be tested. In addition,
it is fully expected that GFDL's model contribution will be capable of
simulating a prognostic CO~2~ cycle driven by CO~2~ emissions and land
and ocean biogeochemistry (rather than applied atmospheric CO~2~
concentrations as has been done previously.)

A central question to the development strategy is whether ESMDT expends
its limited resources on vetting the current ESM2.1 model (FV, MOM4,
LM3v, ocean biogeochemistry, CO~2~ exchange), or whether it focuses on
quickly adapting CM3-generation components and new ESM capabilities as
they become available. While there are many intermediate practical goals
associated with CCSP and the various demonstration projects underway,
these are intended to serve as strategic milestones to demonstrate
competency and technical capacity rather than scientific credibility. As
such, these intermediate goals do not pose EXTERNAL fidelity
restrictions that require full climate and carbon model vetting as
required for AR5, giving ESMDT the flexibility of focusing on
development rather than scientific application in the near term.
HOWEVER, in order to assure that GFDL is able to contribute
scientifically to the ESM community, it behooves us to pose the INTERNAL
goal of building the scientific groundwork with the models that already
exist.

After discussion, the consensus was to stress the importance of
continuing BOTH the climate vetting of the existing carbon ESM2.1 as
well as the push to keep ESM3 development close on the heels of CM3
development, but that, in the grand scheme of things, science
application with the carbon-ESM2.1 was an essential product given the
likelihood that ESM3 development will lag CM3 development and
potentially miss the AR5 timescale. Because of this, ESMDT must retain
simultaneous efforts on both [code development]{.underline} for ESM3 as
well as [model development and application]{.underline} of ESM2.1. This
will allow us to (1) run ESM2.1 in any new code base and (2) quickly
move to the ESM3 development if the opportunity presents itself.

3\) Model development in ESM2.1.

The goal of this effort is to utilize currently-available codes to
develop a working carbon-climate ESM with physics similar to CM2.1 in
order to test fidelity of the carbon cycle. This effort will both allow
us to both gain experience in carbon-climate model development and
sensitivity and begin writing up Earth System components in scientific
papers.

For background, we currently have a slab model (SM2.1) that utilizes
LM3v (LM2 hydrology but dynamic vegetation with biophysical feedbacks)
that is able to reproduce a similar climate as the equivalent model with
LM2. The ocean biogeochemistry-climate feedback has been demonstrated to
be small. There are currently five roles of atmospheric CO~2~ in the
ESM: sensed by vegetation for growth, sensed by canopy for air-land
flux, sensed by ocean biogeochemistry for air-sea flux, transported in
atmosphere and sensed by atmospheric radiation model. River fluxes of
carbon will be ignored in this run.

The strategy will be to gather these codes and first attempt an
initialization run by fixing atmospheric CO~2~ at the preindustrial
level (286 ppm) for all types except that sensed by vegetation for
growth, which will be fixed at the 1990 level (350 ppm). This model will
then be allowed to run for a long period of time (500-1000 years) in the
attempt to get long-term air-sea and air-land CO~2~ fluxes to less than
0.1 PgC yr^-1^, or about 5 ppm per century. If we are successful, this
will provide the initial condition to begin to free each of the CO~2~
roles in turn to test model sensitivity. Once a fully stable model is
achieved, we will then perform perturbation studies with realistic and
idealized climate change scenarios.

4\) Initialization (Toggweiler/Dunne/Stouffer)

Initialization of the ocean carbon cycle, the long-term determining
factor of atmospheric CO~2~ in the current model, continues to be at
question, as the timescales are long (1000+ years) and the model is both
relatively slow and computationally expensive (\~10 years/day). The
default plan is to run out the model for 1000 years as we look to a net
air-sea CO~2~ flux within 0.1 PgC yr^-1^. A test case with CM2.1 and
active ocean biogeochemistry is currently underway.

Previously, Toggweiler had suggested that we develop a procedure to
accelerate equilibration of the ocean carbon cycle by separately
addressing biases in the solubility, organic and inorganic pumps on the
distributions of dissolved inorganic carbon and alkalinity. While some
research was done using the coarse resolution version of the ocean model
(OM1p5), this effort has been stalled for some time due to the convolved
questions of circulation biases, biological biases and non-steady state.

On Wednesday, Toggweiler presented a new idea for stabilizing the ocean
carbon cycle to be in equilibrium with a given atmospheric CO~2~
concentration via damping of the deep carbonate ion concentration at the
sediment interface. The damping would simulate dissolution and
precipitation of CaCO~3~ in sediments and act as a restoring force. The
full details of the concentration of carbonate ion (whether a
globally-fixed value, a geographically varying fixed value, or a
mechanistically-derived value based on z/T/S-dependent mineral
solubility and perhaps rain rate) and timescale for damping to use has
yet to be researched. Toggweiler plans to conduct feasibility studies in
the context of his 7-box ocean model:

5\) Summary of LMDT document as it relates to ESM (Milly/Shevliakova)

LMDT has already put together a description of their development
strategy for the LM3 land component of CM3/ESM3. The LM3 base
configuration includes a new code infrastructure, LM3W soil/snow physics
& rivers, LM3V vegetation dynamics, vegetation/soil carbon. The expected
delivery date of a version vetted in offline mode (forced by atmospheric
data) is March, 2007. This will enable timely tuning and vetting in a
suite of fidelity experiments in LMDT/GAMDT in order to meet AM3/LM3
deadline of December 2007. As carbon is strongly linked with water and
biophysics, LM3 will require evaluation and tuning with both atmospheric
and coupled models and with both climate and carbon data.

The key capabilities of this base version of LM3 include:

1)  Effects of the land-use (LU) change (1700- 2000)

2)  A vegetation parameterization of CO~2~ fertilization

3)  Vegetation distributions and functioning that respond dynamically to
    changes in climate

4)  An annual fire model parameterizes carbon loss from vegetation

5)  Soil and vegetation carbon initialization at an equilibrium state

6)  LM3 will have a model of the world river network, which will store
    and transport water (and carbon, and eventually other junk) to the
    oceans and to the bottoms of major areas of internal land drainage.

7)  Many-layer models of the snow pack and of the soilwater-groundwater
    continuum allowing for more realistic environmental conditions with
    which to modulate soil-atmosphere gas exchanges.

Efforts are also underway in the areas of: land and river nitrogen
cycling, water management, dust generation, air pollution
parameterizations and effects (e.g. NO~X~, NH~4~, O~3~, BVOC), gradual
phenology (currently stepwise), soil erosion, and higher temporal and
mechanistic representations of fire. It is NOT expected, however, that
any of these capabilities will be sufficiently merged and vetted into
the main version LM3 by the AM3/LM3 deadline of December 2007 under the
current strategy. In particular, it is anticipated that the explicit
implementation of plant nitrogen cycling will require extensive retuning
of climate and carbon dynamics of LM3 from the carbon-only version in
both offline and coupled mode. As such, each of these capabilities
should be considered "advanced" or "extended" capabilities rather than
part of the "base" ESM.

The underlying scientific uncertainty of land use and CO~2~
fertilization effects suggests that an ensemble of ESM3 simulations with
different LM3 configurations will be needed to represent the range of
uncertainty of their implications. At the present time, it is of concern
that our computational capabilities may not permit an appropriately
broad ensemble. In addition, LM3 currently generates land use
transitions driven by an external data set for 1700-2000 -- How will
these scenarios need to be adjusted for the future (2000-2100)? How will
anthropogenic CO~2~ emissions scenarios be made consistent with land use
patterns?

6\) Land-atmosphere chemistry interactions (Horowitz/Fiore)

The tropospheric chemistry module is scientifically matured and has
already been merged into the pre-Memphis AM2 code base and has been run
in exploratory mode in AM2. It includes 69 chemical species and includes
a lightning parameterization. While not necessarily relevant for the
CO~2~/base EM case aside from wet and dry deposition to the ocean, the
atmospheric chemistry module will be important for ESM development in
the nitrogen cycle, CH~4~, O~3~, VOCs, biomass burning and other
applications. It currently runs at 2-3 times the base AM2 cost.
Improvements are ongoing. It is fully expected that this module will be
extended to include stratospheric chemistry and aerosol chemistry on the
CM3 timeline.

Results have been compared with surface, radiosonde and aircraft
concentration measurements and demonstrate qualitative agreement. The
major area of concern with respect to fidelity is wet deposition which
currently shows large discrepancies with observations and is an area of
current developmental research. A suite of model-data comparisons are
planned, but no large technical or fidelity hurdles are anticipated.

7\) Dust cycling (Ginoux/Shevliakova)

The scientifically mature atmospheric dust cycling module of Ginoux et
al (2001) calibrated using TOMS data has been ported into Memphis. This
model is currently forced by a temporally fixed but geographically
variable map of terrestrial dust-generation-potential (through aerial
desert fraction) that supplies dust based on the cube of wind speed. It
is anticipated that this version will be part of the "base" ESM3.

Current research is focusing on adapting LM3V to generate dust based on
leaf area index (LAI), and an understanding of the geographical
distribution of dry lake beds as well as an online scheme in AM2 for
restoring atmospheric aerosol concentrations to data. The current
calibration effort is focused on comparing model LAI with ISLSCP2 AVHRR
data. This effort hinges on limited land model development resources
(e.g. Lena). While there are serious developmental challenges to this
effort, it is hoped that this version can make it into "enhanced"
version of ESM3.

8\) Atmospheric Iron chemistry (Fan)

Fan has developed an algorithm for iron solubility of dust as it varies
with NO~3~- and SO~4~-based ageing (going from 1% to 60% solubility) and
has already calibrated the model using field data and submitted a
scientific paper on the results. This module can thus also be considered
to be scientifically mature. It is anticipated that only modest coding
effort will be requirted to implement this algorithm once Ginoux's dust
model is embedded within Horowitz's chemistry model, and as such, should
be available in the "base" version of ESM3.

9\) Land nitrogen cycling (Gerber)

A beta-version of nitrogen cycling within LM3v has been developed that
represents nitrogen limitation of land plant photosynthesis, organic
matter remineralization in soils, and leaching to groundwater. The
objective of the current work is to help constrain the CO~2~
fertilization effects on land plants. It is anticipated that this effort
will also required implementation of phosphorus limitation in tropical
areas. There is an extensive amount of code development required to
merge this capability into LM3. It is also anticipated that significant
re-tuning of LM3 climate will be required.

In order to include a complete nitrogen cycle, future work will need to
focus on representation of denitrification, N~2~-fixation, emissions of
organic species, NO~x~ and NH~3~, representation of fertilizer and
pastoral agriculture, and human redistribution to population centers.
Because of this suite of scientific and technical development
challenges, it is unlikely that a representation of the full nitrogen
cycle will available in even the "enhanced" version of ESM3 without
additional resources.

10\) River biogeochemistry (Findell/Dunne)

It is anticipated that the "base" EM3 will include a representation of
dynamic/online leaching in LM3 and river transport of organic carbon,
but that other tracers will necessarily be handled as fixed/offline flux
inputs. Scientists in Vorosmarty's group at UNH are currently
collaborating with Findell to develop the necessary infrastructure to
track tracers in rivers. Enhanced/advanced versions of ESM3 may include
nitrogen (after the merge of LM3v-C and LM3v-N). UNH collaborators are
currently working on adding nitrogen biogeochemistry in rivers, a
critical component for seasonal/inter-annual ESM studies of coastal
eutrophication.

As an area of technical concern, initial attempts at driving the ocean
model with river nitrogen fluxes have demonstrated the need for modeling
services to address the possibility for river fluxes to be brought
directly to the exchange grid rather than be "diffused" onto the much
more coarse atmospheric grid before being mapped on the exchange grid
and then onto the ocean grid, or perhaps by having the land model pass
information as mass/time, lon, and lat, and having the ocean could
taking these fluxes as point sources at the closest coastal point.

11\) River mouth stoichiometry and sedimentology (Toggweiler and Dunne)

As river inputs are added to the ocean biogeochemical model, it is
important that these inputs not introduce long time scale drift to the
carbon system. Because of the large internal sources and sinks, we do
not anticipate that this will be a problem for Nitrogen, and, so long as
the fluxes are consistent between land and ocean, for Carbon as well.
However, we are very hesitant to add river inputs of SiO~4~ or PO~4~, as
these dissolved components all have very long residence times in the
ocean, much longer than the ocean circulation/overturning timescale.

12\) Ocean biogeochemistry/ecology (Dunne)

The current ocean biogeochemistry model considers three phytoplankton
groups, two forms of dissolved organic matter, a recently-added
heterotrophic biomass, and dissolved inorganic species for carbon,
nitrogen, phosphorus, silicon, iron, calcium carbonate-alkalinity and
oxygen cycling, including gas exchange, iron deposition and scavenging,
nitrogen fixation and denitrification. This model currently slows the
ocean model by a factor or 2.5. John needs to right up the present
version.

Current efforts are focused on adding functionality of river inputs and
atmospheric deposition of nitrogen, a more mechanistic formulation of
CaCO~3~ dissolution including simulation of sediment processes,
incorporation of a representation of lithogenic/aluminosilicate cycling
towards improving water clarity and particle sinking formulations, and a
representation of a harmful algal species through N:P
stoichiometry/limitation.

13\) Level of human activities prediction: scenarios for ESM3 and
identified directions for ESM4 and beyond (Shevliakova/Dunne)

One means of defining the scope of ESM development is through its level
of ESM prognosis - the degree to which Earth System Processes are
internally calculated rather than externally prescribed. For example,
CM3 has a minimum level of prognosticity as atmospheric greenhouse gas
concentrations are prescribed. ESM2.1 seeks the next level of prognosis
as CO~2~ concentrations are calculated rather than prescribed. In the
ultimate prognostic goal, nothing is prescribed as population and the
full scope of anthropogenic effects such as land cover changes, food
supply, lumber, green house gas and (air and water) pollutant emissions
and redistribution and each of their climate feedbacks are calculated
internally within the model. We are currently a long way from this, as
development of this model will involve whole groups of people who (1) do
not know us and (2) do not do predictive modeling and certainly will
require far-reaching advances in predictive economic modeling. The time
scale for this is AT LEAST ESM4 -- a decade - away.

With respect to scenarios for ESM3, Kassel and Henderson recently
suggested the current IPCC base case scenarios are entirely unrealistic.
This leads us to the question of what the AR5 scenarios will look like.
There is a whole suite of questions associated with this given the
degree to which the participating models will differ in configuration.
This uncertainty behooves the GFDL ESM3 effort to keep fully abreast of
-- and take an active role in - this decision-making process as
scenarios of future emissions, land use and population are considered.

In the meantime, ESM development should focus considerable effort on
optimizing our ability to reproduce observed changed - what has happened
in the past -- rather than rushing to use untested models to predict the
future. Towards that end, choices in development focus should be made
towards group-level interests in building models useful for increasing
our understanding of the various biogeochemical cycles and their impact
on climate and vice versa.