Sustaining Earth's life support systems - the challenge for the next decade and beyond
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I G B P N E W S L E T T E R 4 1
May
No. 41 2000
The International Geosphere–Biosphere Programme (IGBP): A Study of Global Change
of the International Council for Science (ICSU)
Sustaining Earth’s life support systems – the challenge
for the next decade and beyond
by Berrien Moore III, Chair, IGBP
Integration, interdiscplinarity, and a sys- • A focus on three cross-cutting
tems approach mark the emerging ethos
in IGBP as the Programme evolves rap-
issues where advances in our
scientific understanding are Contents
idly into its second decade of international required to help human
global change research.
In late February in Cuernavaca,
societies develop in ways that Sustaining Earth’s Life
sustain the global life support Support Systems ........... 1
Mexico, the Scientific Committee of the
IGBP held a landmark meeting in which system.
it was decided that the strength and ma- The research will be undertaken in the con-
turity of the Programme would allow an text of an expanding and strengthening The Waikiki Principles ... 3
increased emphasis on the systemic chal- collaboration with the International Hu-
lenges of Global Environmental Change. man Dimensions Programme on Global
Environmental Change (IHDP) and the
Earth-System Models
The strength has been made particularly
apparent in the developing Core Project World Climate Research Programme of Intermediate
syntheses. (WCRP). The new challenge is to build, Complexity .................... 4
This strength and capability of the on our collective scientific foundation, an
IGBP at this point in time is extraordinar- international programme of Earth System
ily valuable since the SC-IGBP also rec- Science. This effort will be driven by a com- The Flying Leap ............ 7
ognised that the challenges of Global En- mon mission and common questions,
vironmental Change demand a treatment employing visionary and creative scien-
of the full Earth System. It is simply a re- tific approaches, and based on an ever- Understanding Earth’s
ality that a scientific understanding of the closer collaboration across disciplines, re- Metabolism ................... 9
Earth System is required to help human search themes, programmes, nations, and
societies develop in ways that sustain the regions.
global life support system. Driving the new structures and ap- Highlights of GAIM’s
The core of the IGBP Programme for proaches are two critical messages that First Phase ................... 11
the next decade will be built around three have become ever clearer through the past
interlocking and complementary struc- decade plus of global change research.
tures: First, the Earth functions as a system, The “Anthropocene” ...... 17
with properties and behaviour that are
• Core projects that focus on key characteristic of the system as a whole.
processes will continue to be These include critical thresholds, ‘switch’ Regional Data
the foundation for the IGBP; or ‘control’ points, strong nonlinearities, Bundles ........................ 18
teleconnections, and unresolvable uncer-
• A formal integrated study of tainties. Understanding components of the
the Earth System as a whole, in Earth System is critically important, but is
its full functional and insufficient on its own to understand the People and events ........ 19
geographical complexity over functioning of the Earth System as a
time, and whole.
1
I G B P N E W S L E T T E R 4 1
Second, humans are a significant force
in the Earth System, altering key process
rates and absorbing the impacts of glo-
bal environmental changes. In fact, the en-
vironmental significance of human activi-
ties is now so profound that the current
geological era can be called the
‘Anthropocene’ epoch (see article by Paul
Crutzen and Eugene Stoermer in this is-
sue of the NewsLetter).
Global biogeochemical cycling will
remain at the core of IGBP research, but
the Programme will evolve towards a
more systematic structure with major ac-
tivities located in the three compartments
– atmosphere, oceans, and land – and in
the three interfaces between them. These
six domains will more formally guide the
emerging Core Projects for the next dec-
ade. This theme is already apparent
within the IGBP. For instance, LOICZ is
positioned well at the Land-Ocean inter-
face, and the emerging Surface Ocean
Lower Atmosphere Study (SOLAS) is
clearly headed in this direction. We are
asking, in this formulation, hard and chal-
lenging questions. How can we join bet-
ter JGOFS science with GLOBEC science?
How can we bridge more strongly and
with less duplication the scientific agen-
das of BAHC and the Global Energy Wa-
ter Experiment (GEWEX) within the Figure 1.
WCRP? Similarly, how do we better link
in the future IGAC with SPARC
(Stratospheric Processes and their Role in
Climate)? What should be the nature of where gaps are identified. Strategic part- tatively scheduled for September.
the future GCTE, and how does it tie more nerships are being developed with other These initiatives will place great de-
closely with LUCC? research institutions outside the three mands on the IGBP. The strength of the
GAIM is being reoriented towards programmes and with policy and man- Programme will be tested and new struc-
integrating across this structure to focus agement institutions to ensure that the tures will be demanded. The recently ex-
on the Earth System as a whole (see John work is designed and implemented in panded role of the IGBP-DIS with its im-
Schellnhuber’s article in this issue of the ways that facilitate its application. portant work in both regional and global
NewsLetter). PAGES work provides an The Global Carbon Cycle joint project studies will add essential new capabili-
essential longer time context for the dy- is the most advanced, with a series of ac- ties, including support for our key re-
namics of the Earth System as well as for tivities planned for the rest of 2000. A gional studies (see the article on The Re-
parts of it. The accompanying figure small scoping meeting in April developed gional Data Bundle Concept by Wolfgang
shows the new structure. much of the human dimensions contri- Cramer in this NewsLetter).
It is hoped that at least three new joint butions to the effort, while additional This continuing evolution of the IGBP
projects will be launched with WCRP and meetings in May (Lisbon, Portugal) and in concert with the WCRP and the IHDP
IHDP on crosscutting issues of major October (Durham, New Hampshire, is important and merits the thoughts of
societal relevance. Three linked issues are USA) will complete the definition of a all. We continue to welcome and need
currently in the planning stages – the Glo- common international framework to help insights on directions, processes, objec-
bal Carbon Cycle, Water Resources, and guide research at national, regional and tives, and goals and the processes by
an initiative on Global Change and Food global scales, and will design a series of which they may be realised. These pages
and Fibre, with an emphasis on food vul- focused activities for 2001 and beyond. are genuinely open to your contributions.
nerability/security and opportunity For the Food and Fibre joint project, a The challenges of global environmental
analysis. Additional major issues, such as scoping meeting with IHDP and WCRP change are not going to vanish.
human health and ecosystem goods and was held in Paris in early March, which
services, are under consideration. began to defined the overall structure for
These joint projects, which are clearly the research. Further planning meetings Berrien Moore III
crosscutting in nature, will depend criti- are proposed for June/July (Reading, Institute for the Study of Earth,
cally upon the research in the Core UK), October (London), November/De- Oceans and Space (EOS),
Projects of the IGBP, IHDP and WCRP cember (Stockholm) and February 2001 University of New Hampshire,
that is already being undertaken or is (Washington) to complete the preparation 39 College Road, 305 Morse Hall,
planned. Considerable co-ordination is of a science plan and implementation Durham, NH 03824-3524, USA
needed, however, to bring these elements strategy. E-mail: b.moore@unh.edu
into a more integrated framework, and The initial co-ordination meeting for
some new work will need to be initiated the Water Resources joint project is ten-
2
I G B P N E W S L E T T E R 4 1
The Waikiki Principles: rules for a new GAIM
by John Schellnhuber Chair, GAIM
The first NewsLetter in the new millen- But integration is much more than a and problems dimensions
nium provides a convenient canvas for synthetic book-keeping exercise – re- primarily investigated by the
re-sketching the basic mission of GAIM, member that it took evolution almost 4 sister programmes WCRP and
that is, pioneering Earth System science billion years to compose the human brain IHDP.
into a state of novel quality. This sounds from macro-molecules available already
rather preposterous yet turns into a solid in the early days of life. The virtual scien- III. GAIM is to implement Earth
ambition upon closer inspection of (i) the tific reconstruction of the planetary ma- System analysis by organizing
giant explorative strides taken by the big chinery (“Gaia”) is not much smaller a the construction, evaluation and
global research programmes (IGBP, task, although we expect it to be accom- maintenance of a hierarchy of
WCRP, IHDP, etc.) during the last years, plished in less than a couple of eons. What Earth System models. This
and (ii) the opportunities arising from the will be needed, at any rate, is a sophisti- means, in particular, to help
think-tank character of GAIM. Let me cated integration methodology as transpir- generate models of different
briefly elaborate on both aspects in the ing, e.g., from the modern theory of com-
degrees of complexity and to
following. plex non-linear dynamic systems, and it
In a recent essay for the Millennium will be necessary to account for all sorts employ the resulting
Supplement of Nature (Vol. 402, Supp. 2 of deterministic and stochastic uncertain- complementary ensemble for
Dec 1999, C19-C23) I argued that the “Sec- ties. conducting virtual planetary
ond Copernican Revolution” is just This is the point where the New experiments with respect to
around the corner. This revolution re- GAIM enters the scene: During the recent past, present, and future global
verses, in a way, the glorious first one by meeting of the Task Force in Waikiki, changes.
looking back on our planet from a (real Hawaii (31 January – 2 February 2000),
or virtual) distance, striving to under- the integration challenge was intensively As a consequence, the acronym GAIM
stand the so-perceived system as a whole discussed and identified as the central should from now on stand for “Global
and to develop concepts for global envi- research issue of the next decade of glo- Analysis, Integration and Modelling”.
ronmental management. The scientific bal change science. And the group, which Principle I is illustrated by the TRACES
trans-discipline thus emerging may be embraced the top representatives and (Trace Gas and Aerosol Cycles in the
called Earth Systems analysis; it is sup- executives of IGBP, concluded unani- Earth System) Initiative; principle II by
posed to yield a unified formalism for mously that GAIM shall become the cen- the intra-IGBP Carbon Project and the
describing the make-up and functioning tral driving force for Earth System analy- envisaged inter-programmatic cross-cut-
of the ecosphere machinery as well as its sis by fully utilizing the potential result- ting themes like water and food and fi-
susceptibility to erratic or judicious hu- ing from its cross-sectoral design. In or- bre; principle III by the EMIC (Earth Sys-
man interventions. Ultimately, Earth Sys- der to be specific, an explicit survey tem Models of Intermediate Complexity)
tem analysis will even be able to address among the participants was conducted Initiative and the “Flying Leap” towards
the challenge of sustainable development for revealing individual priorities and a fully coupled state-of-the-art ocean-at-
in a no-nonsense way by deducing the suggestions regarding the longer-term mosphere-biosphere model. There is no
macro-options for future ecosphere- targets to be met. A clear-cut picture doubt that GAIM will keep on providing
antroposphere co-evolution from first emerged which may be summarized in the IGBP community with sophisticated
cognitive and ethical principles. the following three “Waikiki Principles”. services like well-designed model and
In order to achieve all this, we clearly data intercomparisons, but its thrust will
still have a long way to go, but the signs I. GAIM is to explore and be focussed on research at the Earth-sys-
of hope accumulate at an ever increasing promote cognitive tem level.
pace. Take, for instance, the growing opportunities arising from the It has to be emphasized that the
stream of insights arising from the sepa- appropriate combination of Waikiki Rules for the New GAIM have
rate Core Projects of IGBP as highlighted Core Project results and tools. yet to be approved by the “legislative and
at the Second IGBP Congress held in Ja- This means, in particular, to executive bodies” of IGBP, but I am con-
pan last May (see Berrien Moore’s key- fident that they will gladly help to open
play the role of a trans-project
note in Global Change Newsletter 38, and up this avenue towards the scientific ho-
topics scout and a feasibility rizon.
Will Steffen’s reflections in Research assessor.
GAIM, Summer 1999). This breathtaking Here end my pre-Cuernavaca con-
progress was most impressively illus- II. GAIM is to advance the templations on the New GAIM. In the
trated by Hugh Ducklow’s lecture on the integration of wisdom inside meantime, the Scientific Committeee of
unravelling of the mysteries of the global IGBP held a meeting which undoubtedly
and outside IGBP. This means,
oceanic flux system. So it seems that “all” deserves the qualification as a “landmark
on the one hand, to make
that remains to be done is to take the sci- event” (see Berrien Moore’s article in this
available the best integrative issue of the NewsLetter). I have to con-
entific bits and pieces and to put them methodologies and, on the other
together. fess that I did not expect the SC to make
hand, to include the systems so far-reaching and far-sighted decisions
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I G B P N E W S L E T T E R 4 1
about the next decade of planetary re- citing opportunity to demonstrate perti- the most advanced methodologies avail-
search. As a matter of fact, the systems nent skills will be provided by the new able like the ones that have been devel-
approach was adopted as the guiding re- initiative on “Surprises and Nonlinearities oped by the complex dynamics commu-
search principle, and a strategic partner- in Global Change”, recently launched by nity. It is high time for joining forces with
ship with the international sister pro- GCTE. This is actually an issue of para- this cognitive community and similar
grammes was envisaged in order to cre- mount importance for Earth System sci- ones, yet this will become a rather chal-
ate a joint venture that may be called “In- ence as will be emphasized, i.a., by the lenging enterprise.
tegrated Earth Science”. All the crucial Third Assessment Report of the IPCC. The Compared with the opportunities
points of this historical resolution are suc- New GAIM has already started to think ahead, my caveats carry little weight
cinctly summarized in Berrien’s above- about establishing an international though. We are lucky to live in this era of
mentioned contribution. postdoc network for advancing research Global Scientific Change.
For GAIM, this is an extremely encour- on the “irregular side of Global Change”.
aging development that puts the Waikiki Let me conclude with two caveats. John Schellnhuber
Principles on a solid basis and into the First, we should not be carried away now
right context. As a minor consequence, the by a frenzy of integrationist enthusiasm. Potsdam Inst for Climate Impact Re-
renaming of GAIM into “Global Analy- I firmly believe that the so-called search (PIK),
sis, Integration and Modelling” has been reductionist approach to Earth Science PO Box 60 12 03,
approved meanwhile. Much more impor- will still have to constitute the backbone D-14412 Potsdam,
tant, however, is the induced mandate for of our research body in the decades to GERMANY
GAIM to explore from now on all intrin- come: Yes, the whole is more than the sum E-mail: john@pik-potsdam.de
sic and extrinsic options for systems-ana- of its parts, but the sum of zeros is zero.
lytic progress, both from the topical and Second, systems science is by no means
the methodological point of view. An ex- an easy exercise. We will need to employ
Earth System Models of Intermediate Complexity
by Martin Claussen, Andrey Ganopolski, John Schellnhuber and Wolfgang
Cramer
Investigating the dynamic behavior of the Towards a Definition of anthroposphere, in particular the psycho-
Earth system remains a “grand challenge” social component. Hence development of
for the scientific community. It is moti- the Earth System and a model of the full Earth System has to be
vated by our limited knowledge about the undertaken in cooperation between IGBP
consequences of large-scale perturbations Earth System Models and IHDP. For the time being, it will be
of the Earth System by human activities, Within IGBP at least, the following defi- the task of IGBP to pursue models of the
such as fossil-fuel combus-tion or the frag- nition of the “Earth System”, which has natural Earth System in which anthropo-
mentation of terrestrial vegetation cover. been proposed by Schellnhuber (1998, genic activities are considered as exog-
Will the system be resilient with respect 1999) and Claussen (1998), for example, enous forces and fluxes. Hence in the fol-
to such disturbances, or could it be driven seems to be generally accepted: The Earth lowing, we consider only the natural
towards qualitatively new modes of plan- System encompasses the natural environ- Earth System. Earth System models need
etary operation? ment, i.e. the climate system according to to be globally comprehensive models,
This question cannot be answered, the definition by Peixoto and Oort (1992), because the fluxes within the system are
however, without prior analysis of how or sometimes referred to as the ecosphere, global (e.g. the hydrological cycle):
the unperturbed Earth System behaves and the anthroposphere. The climate sys- changes in one region may well be caused
and evolves in the absence of human in- tem consists of the abiotic world, the by changes in a distant region. A currently
fluence. Such an analysis should, for ex- geosphere, and the living world, the bio- open question is how much spatial (re-
ample, provide answers to questions con- sphere. Geosphere and biosphere are fur- gional) resolution is required to appropri-
cerning the amplification of Milankovich ther divided into components such as the ately capture processes with global signifi-
forcing to glaciation episodes or the atmosphere, hydrosphere, etc., which in- cance. Earth System models probably
mechanisms behind the Dansgaard- teract via fluxes of momentum, energy, need not capture all aspects of interaction
Oeschger oscillations. But also more gen- water, carbon, and other substances. The between the spheres at the regional scale
eral questions may be addressed: Does life anthroposphere can also be divided into -although it will be interesting to test
on Earth subsist due to an accidental and subcomponents such as socio- economy, whether certain regional processes nev-
fragile balance between the abiotic world values and attitudes, etc. ertheless affect global feedbacks.
(the geosphere) and a biosphere that has So far, only simplified, more concep-
emerged by chance? Or are there self-sta- tual Earth System models exist. While
bilizing feedback mechanisms at work as models of the natural Earth System can Models of Intermediate
proposed by the Gaia theory? And, if the be built upon the thermodynamic ap-
latter theory is valid, what is the role of proach, this does not seem to be feasible
Complexity
humanity in Gaia’s universe? for many components of the During the past decades marked progress
4
I G B P N E W S L E T T E R 4 1
has been achieved in modelling the sepa-
rate elements of the geosphere and the
biosphere, focusing on atmospheric and
ocean circulation, and on land vegetation
and ice-sheet dynamics. These develop-
ments have stimulated first attempts to
put all separate pieces together, first in
form of comprehensive coupled models
of atmospheric and oceanic circulation,
and eventually as so-called climate sys-
tem models which include also biologi-
cal and geochemical processes. One ma-
jor limitation in the application of such
comprehensive Earth System models
arises from their high computational cost.
On the other hand, simplified, more
or less conceptual models of the climate
system are used for a variety of applica-
tions, in particular paleoclimate studies
as well as climate change and climate im-
pact projections. These models are spa-
tially highly aggregated, for example,
they represent atmosphere and ocean as
two boxes, and they describe only a very
limited number of processes and vari-
Figure 1. Tentative definition of EMIC’s
ables. The applicability of this class of
model is limited not by computational
Figure 2. Structure of an EMIC
5I G B P N E W S L E T T E R 4 1
cost, but by the lack of many important ergy balance (e.g. Marchal et. al, 1998; extreme, three-dimensional comprehen-
processes and feedbacks operating in the Stocker et al., 1992), or with a statistical- sive models, e.g. coupling atmospheric
real world. Moreover, the sensitivity of dynamical atmospheric module (e.g. and oceanic circulation with explicit ge-
these models to external forcing is often Petoukhov et al., 1999) , and reduced- ography and high spatio-temporal reso-
prescribed rather than computed inde- form comprehensive models (e.g. lution, are under development in several
pendently (e.g. Houghton et al., 1997). Opsteegh et al., 1998). groups. During the IGBP Congress in
To bridge the gap, Earth System Mod- EMICs have been used for a number Shonan Village, Japan, May 1999, and the
els of Intermediate Complexity (EMICs) of palaeostudies, because they provide IGBP workshop on EMICs in Potsdam,
have been proposed which can be char- the unique opportunity for transient, Germany, June 1999, it became more
acterized in the following way. EMICs de- long-term ensemble simulations (e.g. widely recognized that models of in-
scribe most of the processes implicit in Claussen et al., 1999), in contrast to so termediate complexity could be very
comprehensive models, albeit in a more called time slice simulations in which the valuable in exploring the interactions be-
reduced, i.e. a more parameterized form. climate system is implicitly assumed to tween all components of the natural Earth
They explicitly simulate the interactions be in equilibrium with external forcings, System, and that the results could be
among several components of the climate which rarely is a realistic assumption. more realistic than those from conceptual
system including biogeochemical cycles. Also the climate system’s behaviour un- models. These meetings have pointed at
On the other hand, EMICs are simple der various scenarios of greenhouse gas the potential that EMICs might have even
enough to allow for long-term climate emissions has been investigated explor- for the policy guidance process, such as
simulations over several 10,000 years or ing the potential of abrupt changes in the the IPCC.
even glacial cycles. Similar to those of system (e.g. Stocker and Schmittner, 1997; Finally, it should be emphasized that
comprehensive models, but in contrast to Rahmstorf and Ganopolski, 1999). To il- EMICs are considered to be one part of
conceptual models, the degrees of free- lustrate the complexity of EMICs we the above mentioned hierarchy of simu-
dom of an EMIC exceed the number of present - see Figure 2 - the structure of lation models. EMICs are not likely to
adjustable parameters by several orders CLIMBER 2.3, an EMIC developed in replace comprehensive nor conceptual
of magnitude. Tentatively, we may define Potsdam by Petoukhov et al. (1999). models, but they offer a unique possibil-
an EMIC in terms of a three-dimensional ity to investigate interactions and
vector: Integration, i.e. number of com- feedbacks at the large scale while largely
ponents of the Earth System explicitly Perspective maintaining the geographic integrity of
described in the model, number of proc- Earth System analysis generally relies on the Earth System.
esses explicitly described, and detail of a hierarchy of simulation models. De- Martin Claussen
description of processes (See Figure 1). pending on the nature of questions asked
Currently, there are several EMICs in and the pertinent time scales, there are, Potsdam-Institut für
operation such as 2-dimensional, zonally on the one extreme, zero-dimensional Klimafolgenforschung e. V. (PIK),
averaged models (e.g. Gallée et al., 1991), tutorial or conceptual models like those Telegrafenberg C 4,
2.5-dimensional models with a simple en- in the “Daisyworld” family. At the other 14473 Potsdam,
GERMANY.
E-mail: claussen@pik-potsdam.de
References
Claussen, M., 1998: Von der Klimamodellierung zur Erdsystemmodellierung: Konzepte und erste
Versuche. An-nalen der Meteorologie (NF) 36, 119-130. Andrey Ganopolski
Claussen, M., Brovkin, V., Ganopolski, A., Kubatzki, C., Petoukov, V., Rahmstorf, S., 1999: A new model
for cli-mate system analysis. Env. Mod.Assmt., im Druck. Potsdam Institute for Climate Impact
Research,
Claussen, M., Kubatzki, C., Brovkin, V., Ganopolski, A., Hoelzmann, P., Pachur, H.J., 1999: Simulation
of an abrupt change in Saharan vegetation at the end of the mid-Holocene. Geophys. Res. Letters, Telegrafenberg,
24 (No. 14), 2037- 2040. PO Box 60 12 03,
Gallée, H., J.-P. van Ypersele, T. Fichefet, C. Tricot, and A. Berger, 1991: Simulation of the last glacial D-144 12 Potsdam,
cycle by a coupled, sectorially averaged climate–ice sheet model. I. The climate model, J. Geophys GERMANY
Res., 96, 13,139– 13,161. E-mail: Andrey.Ganopolski@pik-
Houghton, J.T., Meira, Filho, L.G., Griggs, D.J., Maskell, K., 1997: An introduction to simple climate potsdam.de
models used in the IPCC second assessment report. IPCC Technical Paper II 47 pp.
Marchal, O., T.F. Stocker, F. Joos, 1998: A latitude-depth, circulation-biogeochemical ocean model for Wolfgang Cramer
paleocli-mate studies: model development and sensitivities. Tellus 50B, 290-316.
Opsteegh, J. D., R. J. Haarsma, F. M. Selten, and A. Kattenberg, 1998: ECBILT: A dynamic alternative Potsdam Inst for Climate Impact
to mixed boundary conditions in ocean models, Tellus, 50A, 348–367. Research (PIK),
Peixoto, J.P., Oort, A.H., 1992: Physics of Climate. American Institute of Physics, New York PO Box 60 12 03,
Petoukhov, V., Ganopolski, A., Brovkin, V., Claussen, M., Eliseev, A., Kubatzki, C., and Rahmstorf, S.,
D-14412 Potsdam,
2000: CLIMBER-2: a climate system model of intermediate complexity. Part I: Model description and GERMANY
performance for present climate. Climate Dyn. 16 (No.1), 1-17. E-mail: wolfgang.cramer@
Rahmstorf, S., Ganopolski, A., 1999: Long-term global warming scenarios computed with an efficient pik-potsdam.de
coupled cli-mate model. Climatic Change, 43, 353-367.
Schellnhuber, H.J., 1998: Discourse: Earth System Analysis - The Scope of the Challenge. in: John Schellnhuber
Schellnhuber, H.-J., Wenzel, V. (eds.) Earth System Analysis - Integrating science for sustainability.
Springer, Heidelberg. 5-195. Potsdam Inst for Climate Impact
Schellnhuber, H.J., 1999: ’Earth system’ analysis and the second Copernican revolution. Nature, 402, Research (PIK),
C19 - C PO Box 60 12 03,
Stocker T.F., Schmittner, A., 1997: Influence of CO 2 emission rates on the stability of the thermohaline D-14412 Potsdam,
circulation. Nature, 388, 862-865. GERMANY
Stocker,T.F., Wright, D.G., Mysak, L.A., 1992: A zonally averaged, coupled ocean-atmosphere model for E-mail: john@pik-potsdam.de
paleo-climate studies. J Climate, 5, 773-797
6I G B P N E W S L E T T E R 4 1
Full-Form Earth System Models:
Coupled Carbon-Climate Interaction Experiment
(the “Flying Leap”)
by Inez Fung, Peter Rayner, and Pierre Friedlingstein; Edited by Dork Sahagian
Investigating the dynamic behaviour actions and feedbacks between processes tatively approved. The project would in-
and complexities of the Earth System re- that operate primarily within subsystems troduce terrestrial and oceanic carbon
mains a “grand challenge” for the scien- such as the terrestrial ecosystem, atmos- cycle modules into coupled atmosphere-
tific community. It is motivated by our phere, ocean, etc. ocean-land climate models, in essence to
limited knowledge about the conse- Each of these types of models can be introduce CO2 as a prognostic variable in
quences of large-scale perturbations of useful and full-form models are consid- the climate model, to investigate the co-
the Earth System by human activities ered to be one part of a hierarchy of simu- evolution of climate and CO2 given emis-
such as fossil-fuel combustion or the lation models. Information passes in both sion scenarios (rather than concentra-
fragmentation of terrestrial vegetation directions through this hierarchy. An ef- tions) of the greenhouse gas. The excite-
cover. During the past decades marked fect noted first in an EMIC should nor- ment lies in the identification and inves-
progress has been achieved in modelling mally be sought in a full-form model. tigation of interactions in a climate space
the separate elements of the geosphere Also, the candidate processes for a phe- beyond known experience. The project is
and the biosphere, focusing on atmos- nomenon noticed in a full-form model referred to as “The Flying Leap” to em-
pheric and ocean circulation, and on land should be included in an EMIC to test our phasize the uncertainties and excitement
vegetation and ice-sheet dynamics. understanding. of the endeavour.
These developments have stimulated It would be unrealistic at present to The “Flying Leap” experiment will
preliminary attempts to put all separate expect to be able to develop full-form focus on CO2 emissions and concentra-
pieces together, first in form of compre- models that can be used as working tion and the response of the Earth Sys-
hensive coupled models of atmospheric simulations of the Earth System. How- tem to CO2 forcing, given a fixed scenario
and oceanic circulation, and eventually ever, for short time slices and under cer- for future emissions. This experiment
as so-called climate system models tain conditions, such comprehensive uses an emissions scenario that would
which also include biological and models can be practical, and only such give an increase in atmospheric CO2 con-
geochemical processes. It has been the models can answer certain key questions centration of 1%/yr without coupling or
rule rather than the exception that sur- about the Earth System and our under- feed backs.
prising behaviour has emerged when standing of the key processes that drive While this may be a modest increase
these components are coupled. responses of the system to anthropogenic relative to “business as usual” scenarios,
Major challenges lie at the boundaries perturbations. One such question is it provides a useful baseline for this ini-
between subsystems with regard to ef- “How robust must our understanding be tial development and application of a full-
forts to couple models and develop inte- of the internal processes of subsystems complexity model.
grated Earth System models. The devel- (e.g. terrestrial ecosystems, atmospheric The protocol for the experiment was
opment of a coupled model involves re- circulation, marine productivity) before discussed at the IGBP GAIM Task Force
laxation of prescribed boundary condi- coupling subsystem models reduces un- meeting in Honolulu, January 31-Febru-
tions so that modelled subsystems can certainty inherent in the coupled system ary 2, 2000. The goal of the experiment is
interact directly. As such models are run rather than increasing it?” to evaluate the sensitivity of the coupled
over time, one measure of their success is At the October 1998 meeting of carbon-climate system to anthropogenic
the stability with which they character- WCRP/WGCM (Working Group on perturbations. The procedure is to solve
ize the Earth System without the need for Coupled Modelling) in Melbourne (chair: simultaneously the coupled family of
“flux corrections” to adjust for model drift L. Bengtsson), a proposal from GAIM for equations for different specifications of
in an ad hoc manner. a collaborative IGBP/GAIM – WCRP/ external source/sinks of CO2 and other
In general, Earth System analysis re- WGCM project to investigate carbon-cli- greenhouse gases. See Figure 1.
lies on a hierarchy of simulation models. mate interactions was discussed and ten-
Depending on the nature of questions
asked and the pertinent time scales, there
are, on the one extreme, zero-dimensional
tutorial or conceptual models like those
in the “Daisyworld” family. At the inter-
mediate level, “Earth-system Models of
Intermediate Complexity” (EMICs) can
run for long model times, and capture
most of the critical interactions between
system components, but do not include
all processes within each part of the Earth
System. At the other extreme are three- Where Fba and Fab are the fluxes of carbon between the terrestrial biosphere and the
atmosphere and Foa and Fao are the equivalent fluxes between the ocean and the
dimensional full-form comprehensive atmosphere.
models, e.g. coupling atmospheric and
oceanic circulation with explicit geogra-
phy and high spatio-temporal resolution, Figure 1. Coupled equations describing climate -C02 interaction.
can be used to explore the detailed inter-
7I G B P N E W S L E T T E R 4 1
The experiments will involve a con- concentrations and climate viewed as one exploration of the
trol for the pre-industrial era with no ex- before coupling the subsystems. nonlinearities inherent in the Earth Sys-
ternal sources/sinks of CO2, and a for- The coupled system should be tem.
ward integration from the pre-industrial stable but slow drift has One should treat the “Flying Leap”
to beyond AD2000 for a specified emis- characterized many other such as a grand challenge to our understand-
sion scenario for CO2 and the other green- coupled systems and must not ing of the carbon cycle as well as of car-
house gases. No trace gas cycles will be be discounted. bon-climate interactions. It should be the
included for the other greenhouse gases. stimulus to take the models to another
Instead, they will be converted to CO2- 2) Historical period. With level. Glimpses of realism should be
equivalents and added to the radiatively prescribed emissions of CO2 hoped for, but their absence should not
active CO2 in the atmosphere. The CO2- and other gases, we run the be causes for despair. Much can be
equivalents will not be interactive with models from about 1800 until learned during the process of model de-
the terrestrial and oceanic carbon dynam- 2000. We can test the velopment, intercomparison, and refine-
ics. atmospheric concentration and ment.
To start, CO2 release from fossil fuel distribution of CO2 and its
combustion would be specified as a glo- Inez Fung
isotopes in such models against
bal value (PgC/yr) as a function of time ice core and direct atmospheric Center for Atmospheric Sciences,
based on a scenario that would have University of California, Berkeley,
data.
given a 1%/y increase in the absence of 301 McCone Hall #4767,
climate feedbacks on the carbon uptake. 3) Beyond 2000. We use projected Berkeley, CA 94720-4767,
The terrestrial and oceanic modules emissions with atmospheric USA
would be geographically resolving, to composition feedbacks turned E-mail: ifung@uclink4.berkely.edu
take account of the differential ecosys- on or off to investigate their
tem/circulation effects on the carbon ex- magnitude. Also we use Peter Rayner
change. The terrestrial and oceanic up- climates produced by the
take would be summed over area to yield feedback or no feedback cases CSIRO-DAR,
annual values (PgC/yr) of their uptakes. PMB #1,
to investigate the impact of such
Carbon uptake by the biosphere and Aspendale, Vic 3195
feedbacks on permissible
oceans would respond to the instantane- AUSTRALIA
ously simulated climate. In this way, car- emissions for stabilization. Off-
E-mail: pjr@
bon-climate interactions are included to line experiments will elucidate vortex.shm.monash.edu.au
determine the rate of CO2 increase and which processes contribute to
consequently the rate of climate warm- the feedbacks. It is important to
note here that the experiment Pierre Friedlingstein
ing.
The experimental protocol identifies will draw on previous Unite mixte CEA-CNRS,
the principal fully coupled carbon-cli- experience so that, for example, 91191 Gif sur Yvette,
mate calculations as well as several off- the different climate sensitivities FRANCE
line calculations that help to isolate the of the participating models can E-mail: pierre@lsce.saclay.cea.fr
importance of the processes. If atmos- be accounted for.
pheric composition feedbacks signifi- Dork Sahagian
cantly modify rates of climate change in In the contemporary carbon budget, the
the simulations, the mechanistic under- fossil fuel source is ~5% of the one-way Executive Director, IGBP/GAIM
standing will suggest regions and proc- gross terrestrial or oceanic flux. Small Climate Change Research Center and
esses to monitor in the real world. annual carbon flux imbalances or errors, Dept. of Earth Sciences
The experiment is in three general like air-sea heat and freshwater flux er- Institute for the Study of Earth, Oceans,
phases. rors, if sustained over a long-enough and Space
time, may lead to significant climatic mi- University of New Hampshire
1) Spin-up and stability. Here we grations. Other likely surprises may come Durham NH 03824
equilibrate the various carbon from nonlinearities in terrestrial and oce- USA
cycle components forced with anic carbon dynamics or in the climate Email: gaim@unh.edu
pre-industrial atmospheric system. Hence the experiments should
Global The Earth's environment and habitability are now,
as never before, affected by human activities. This
Change conference will present the latest scientific
Open understanding of natural and human-driven
changes on our planet. It will examine the effects Amsterdam
Science on our societies and lives, and explore what the
Amsterdam
10-13 July, 2001
2001
10-13 July,
Conference future may hold.
www.sciconf.igbp.kva.se
8I G B P N E W S L E T T E R 4 1
An integrated approach to understanding Earth’s
metabolism
by Will Steffen
Ice core and other palaeo records provide Although the workshop participants strong correspondence to the cyclic vari-
a fascinating window on the metabolism discussed and debated many aspects of ations in the Earth’s orbit, although the
of Earth over hundreds of thousands of carbon-nutrient interactions, the remark- associated changes in incoming solar en-
years. No record is more intriguing than ably regular planetary metabolic pattern ergy are not enough to drive the glacial-
the rhythmic ‘breathing’ of the planet as embodied in the Vostok ice core record interglacial cycling on their own.
revealed in the Vostok ice core records of held a particular fascination. It is a clas- Many hypotheses have been put for-
temperature and CO2 and CH4 concen- sic example of ‘control theory’. It shows ward to explain the glacial-interglacial
trations (Petit et al., 1999, and Figure 1). cyclic variations of relatively long cold cycling, but most remain essentially dis-
The highly regular waxing and wan- (glacial) periods interrupted by shorter ciplinary, usually based on one aspect of
ing of Earth’s climate and atmospheric warm (interglacial) periods. The atmos- the Earth system such as ocean-atmos-
composition through the glacial-intergla- pheric CO2 concentration varied from phere dynamics. The aim of the IGBP
cial cycles provided the thematic context 180-200 ppmV during the glacial periods Carbon Working Group was not to de-
for a recent meeting of the IGBP Carbon to 265-280 during the interglacials. The velop yet another hypothesis or to pro-
Working Group. The workshop was the palaeo records show other interesting vide ‘the answer’ to the glacial-intergla-
first in a series of five workshops, co- details in the pattern: (i) during the gla- cial puzzle, but rather to show that when
sponsored by the IGBP, the Royal Swed- cial terminations, the increase in atmos- the Earth system behaves in such a highly
ish Academy of Sciences, Stockholm Uni- pheric CO2 is in phase with southern regular and reproducible fashion, a
versity, and the Swedish University of hemisphere warming; melting of the strongly integrated, interdisciplinary ap-
Agricultural Sciences, aimed at address- northern hemisphere ice caps lags by proach offers the best chance to advance
ing focused topics in the IGBP synthesis thousands of years; (ii) the strong cou- our understanding.
project. The objective of the October 1999 pling between temperature and atmos- The explanation developed at the Oc-
meeting was to synthesis our current un- pheric CO2 suggests that the latter is prob- tober workshop goes something like this:
derstanding of nutrient interactions with ably the primary amplifier of climate The precise nature of the upper and
the carbon cycle in terrestrial, marine and change during glacial terminations; and lower limits of atmospheric CO2 concen-
coastal systems. (iii) the periodicity of the cycles shows a tration are evidence of strong control
mechanisms – both terrestrial and oceanic
biological processes are critical el-
ements of the control loop.
Biogeochemical interactions be-
tween land and ocean transfer con-
trol from one to the other on a peri-
odic basis.
How do the control loops
work? The lower level of ca. 180
ppmV for atmospheric CO2 repre-
sents something of an ‘ecosystem/
biome compensation point’. Below
that level systems lose almost as
much carbon through respiration
as they can take up through pho-
tosynthesis in the cold, dry CO2-de-
pleted climate. As we see below,
this has implications for the trans-
fer of nutrients between land and
ocean. The upper limit (280 ppmV)
is the point at which the solubility-
driven flux of CO2 from the ocean
to the atmosphere is balanced by
the uptake of CO2 by the terrestrial
and oceanic biota.
How is control passed between
terrestrial and ocean systems?
There is strong evidence that the
glacial phase (terrestrial control) is
Figure 1. Glacial-interglacial dynamics of the Earth system as recorded in the terminated initially by an increase
Vostok ice core. Adated from Petit et al. 1999 in solar radiation due to a change
in the Earth’s orbit (Milankovich
9I G B P N E W S L E T T E R 4 1
Figure 2. Cartoon illustrating glacial-interglacial hypothesis on linked ocean -land biogeochemical cycling.
forcing); this could trigger a reorganisa-
tion of oceanic circulation and stimulate
the hydrological cycle. The initial warm-
ing would start to accumulate green-
house gases such as H2O, CO2 and CH4
in the atmosphere, due to, for example,
the reduced solubility of CO2 in warmer
water. Also, melting icecaps in the north-
ern hemisphere and the northwards ex-
pansion of forests would reduce the
Earth’s albedo, absorbing more incident
solar radiation and further warming the
planet, releasing even more oceanic CO2
in a positive feedback loop.
But as the climate warms and CO2
concentration increases, the increasing ac-
tivity of the terrestrial biosphere acceler-
ates the mobilisation of elements such as
P, Si and Fe from the geosphere through
enhanced root activity. These elements
eventually leak from the terrestrial bio-
sphere into rivers and to the coastal ocean. a set of feedbacks – initial cooling, increas-
Over thousands of years these nutrients at an atmospheric concentration of CO2 ing solubility of CO2, increasing sea ice
are entrained into the oceanic circulation of about 280 ppm. and further cooling – which drive the sys-
and, in areas of upwelling, stimulate oce- But the invigorated activity of the ter- tem towards the glaciated state. Although
anic net primary production and increase restrial biosphere is already sowing the the terrestrial biosphere is taking up less
the drawdown of CO2 from the atmos- seeds of its own “destruction”. The inter- CO2, it also releases P that was tied up in
phere. The increasing biotic uptake of CO2 glacial balance appears to be precarious,
in both oceans and land eventually and the vigour of terrestrial and marine This article continues on
matches the solubility-driven outgassing biological uptake overtakes the
of CO2 and the system reaches a balance outgassing from the oceans. This triggers page 16.
10I G B P N E W S L E T T E R 4 1
Highlights of GAIM’s first phase: building towards
Earth System Science
by Dork Sahagian
The ‘New GAIM’, as described in John past decade much work has been done data and models. The challenge to GAIM
Schellnhuber’s article in this issue, is ori- to lay a solid foundation on which to has been to initiate activities that will lead
ented strongly towards an integrative build an Earth System Science effort. to the rapid development and application
systems approach to studying the global The goal of GAIM has been to ad- of a suite of Global Prognostic
environment. This is not a completely vance the study of the coupled dynamics Biogeochemical Models. In GAIM’s first
novel task for GAIM, however; over the of the Earth System using as tools both several years, attention was focused on
Figure 1a. Annual net primary production (g C m-2 yr-1) estimated as the average of all model NPP estimates.
Figure 1b. Spatial distribution of the variability in NPP estimates among the models as represented by the standard deviation of
model NPP estimated in a grid cell.
11I G B P N E W S L E T T E R 4 1
Figure 2. Annual mean air-sea flux of anthropogenic CO2 in 1990.
developing the conceptual and proce- Earth System model development. Much therefore, the activities of GAIM intersect
dural tools necessary to meet this chal- of the progress to date in modelling spe- fundamentally with all the IGBP Core
lenge. This entailed scrutiny of each of the cific components within the global Projects.
three main subsystems on the Earth, and biogeochemical subsystems sets the con- During the last decade, there has been
the development and refinement of ter- text for modelling activities within the enormous progress in the development
restrial, marine, and atmospheric carbon various IGBP Core Projects. The GAIM of biogeochemical models for significant
models in preparation for integrated activity is by definition cross-cutting; components of the Earth System. Build-
Figure 3. Model simulation of the distribution of SF6 emissions for 1992.
12I G B P N E W S L E T T E R 4 1
ing upon process-based models for eco- GAIM’s techniques for assessing Since agricultural and forestry produc-
system metabolism in a variety of terres- model performance emerged from a set tion provide the principal food and fuel
trial systems, the scientific community of model intercomparison activities, be- resources for the world, monitoring and
began to extend these models to global ginning with the Net Primary Productiv- modelling of biospheric primary produc-
scales. Ocean carbon cycle models were ity (NPP) model intercomparison. Prior tion are important to support global eco-
developed, compared and evaluated by to the NPP Intercomparison project, sev- nomic and political policy making.
incorporating carbon chemistry and eral different terrestrial ecosystem mod- For estimates of the global carbon bal-
crude biological concepts in ocean gen- els existed nationally and internationally, ance, a large amount of uncertainty
eral circulation models; atmospheric but their results were vastly different. This centers on the role of terrestrial ecosys-
tracer transport models were developed was alarming, given that they were de- tems. Geographically referenced gross
and evaluated on the basis of compari- scribing the same system. Through the primary productivity (GPP), net primary
son of inversion results and observed at- model intercomparison process devel- productivity (NPP), and heterotrophic
mospheric tracer concentrations and oped by the GAIM Task Force, techniques respiration (Rh) and their corresponding
sources; and finally, the initial steps were were devised to both compare model re- seasonal variation are key components in
taken to begin to link these component sults in an objective manner, and to de- the terrestrial carbon cycle. At least two
models with atmospheric GCMs. This has termine the sources of model result dif- factors govern the level of terrestrial car-
set the stage for a more comprehensive ferences. This process made it possible for bon storage. First and most obvious is the
Earth System approach to global individual model developers to return to anthropogenic alteration of the Earth’s
biogeochemical cycling and the develop- their labs and refine or correct their mod- surface, such as through the conversion
ment of prognostic models at various lev- els on the basis of what was learned at of forest to agriculture, which can result
els of complexity. the intercomparison workshops. The in a net release of CO2 to the atmosphere.
As part of its “Analysis” program, same type of process was applied to Second, and more subtle, are the possi-
GAIM devoted considerable effort in ocean models in the Ocean Carbon-Cy- ble changes in net ecosystem production
identifying gaps in both conceptual un- cle Model Intercomparison Project resulting from changes in atmospheric
derstanding and data that would be nec- (OCMIP), and to the atmosphere in the CO2, other global biogeochemical cycles,
essary for modelling purposes. Working Atmospheric Tracer Transport Model and/or the physical climate system. The
toward filling those gaps, GAIM has con- Intercomparison Project (TransCom). significant influence of the terrestrial bio-
vened a number of targeted workshops GAIM’s three major sub-system level sphere on the global carbon balance and
on topics such as Wetland model intercomparison projects are de- hence on the problem of climate change
Biogeochemical Functioning (GAIM re- scribed below. Each of the three were has become more widely recognized dur-
port #2), Regional Interactions between highlighted as special sessions at the last ing the past two decades, and now the
Climate and Ecosystems (GAIM Report IUGG meeting (July 23, 1999 Birming- role of terrestrial ecosystems is recognized
#3), and Sea Level and Global Hydrol- ham, UK). The tools devised through to be an important factor influencing the
ogy (GAIM Report #8). In addition, these activities will be applied to the in- concentration of carbon dioxide in the at-
outreach programs such as the African terpretation and assessment of the mosphere.
GAIM Modelling Workshop (GAIM Re- broader Earth System models now being One of the early results that emerged
port #1), targeted at entraining more of developed (e.g. EMIC, Flying Leap. See from the first of a series of NPP model
the developing world into international other articles in this NewsLetter). intercomparison workshops, “Potsdam
global change research, have added to our ‘94”, was that a major reason for differ-
pool of expertise. All of these activities ences between outputs of the same vari-
are aimed toward placing the research Global Net Primary able between different models was that
community in a stronger position to de- the input data for the same variable were
velop the global prognostic Productivity: A model from different sources and carried differ-
biogeochemical models that are the ulti- intercomparison ent uncertainties (this was true for both
mate goal of GAIM. ground-based observations such as cli-
Among the most significant results Task Leaders: Wolfgang matic data and for remote sensing data
produced by GAIM to date is a set of tech- such as AVHRR-derived NDVI). Conse-
niques for comparing and assessing com- Cramer, Kathy Hibbard quently, many of these data were stand-
plex model performance. Without the Global primary production of ecosystems ardized for the second workshop,
ability to assess models developed by the on land and in the oceans is a crucial com- “Potsdam ’95.” The composite results of
global change research community, there ponent of biogeochemical model devel- the models are illustrated in Fig 1a, in
will be no basis for making reliable pro- opment within IGBP. As key components which the NPP values are averaged
jections regarding future system re- in the terrestrial carbon cycle, geographi- amongst the 17 participating models.
sponses to anthropogenic forcing, and no cally referenced net primary productiv- While the results appear reasonable, it
way for the community to properly con- ity (NPP) and gross primary productiv- should be stressed that there were large
tribute to the IPCC process beyond broad ity (GPP) and their corresponding sea- differences between models (Figure. 1b).
scenario-based projections. Whereas in- sonal variation are needed to enhance The NPP model intercomparison has
dividual scientists or modelling groups understanding of both the function of liv- made it clear that existing data must be
can and do develop numerical models of ing ecosystems and also their effects on chosen and used in a standardized way
various aspects of the Earth System, the the environment. Productivity is also a if like models are to be compared, and
value of the results of isolated models is key variable for the sustainability of hu- ultimately, if complementary models are
greatly enhanced by comparison with man use of the biosphere by, for exam- to coupled. It has also clarified data gaps
other models. The discrepancies in model ple, agriculture and forestry. Recently, it which can now be filled before models
results between different approaches to has become possible to investigate the can reliably simulate the role of terrestrial
the same problem provide critical insights magnitude and geographical distribution ecosystems in the global carbon cycle.
into model shortcomings, and pave the of these processes on a global scale by a However, it is not necessary for model
way for model refinement and improve- combination of ecosystem process mod- development to wait until all gaps in the
ment. elling and monitoring by remote sensing. global observing systems are closed.
13I G B P N E W S L E T T E R 4 1
Rather, IGBP can take the lead in coordi- Ocean Carbon-Cycle Model Almost all other forward models struggle
nating existing and future data sources Intercomparison Project (OCMIP) is to to get adequate CFC-11 vertical penetra-
in a way that will optimize their utility identify the principal differences between tion in the south. Only the models with a
throughout the global change research global-scale, three-dimensional, ocean coupled sea-ice model do a reasonable job.
community. carbon-cycle models, to accelerate their An interesting feature is the observed
The NPP intercomparison activity re- development, and to improve their pre- bump at around 40oS which is character-
vealed a strong need to not only compare dictive capacity. istic of formation of intermediate waters.
models to each other, but to some objec- OCMIP’s primary concern has been Models with explicit mixing along surfaces
tive measure of performance. This meas- to focus on the abilities of models to pre- of constant density (isopycnals) do a rea-
ure can only come from validation data dict ocean carbon distributions and air- sonable job of capturing this feature; other
that is difficult to obtain directly for NPP. sea fluxes of CO2. The first phase of models with only horizontal and vertical
However, indirect information is avail- OCMIP is complete (GAIM Report #7, mixing do a much poorer job.
able that bears on NPP, and this was com- 1998), and OCMIP-2 is now underway Studies during the first two phases of
piled in a “Gross Primary Productivity (http://www.ipsl.jussieu.fr/OCMIP/). OCMIP have relied on ocean models run
Data Initiative (GPPDI), which then led The OCMIP-1 strategy was to study (1) under present climatological conditions,
to the current effort to assess model per- natural CO2 fluxes, with simulations where circulation patterns do not evolve
formance using data from specific key which were allowed to reach equilibrium with time. Beyond OCMIP-2, future work
sites from around the world in a new Eco- with pre-industrial atmospheric CO2 (at will probably focus on the impact of
system Model-Data Intercomparison 278 ppm), and (2) anthropogenic CO2 changing climate on marine biogeochem-
(EMDI). fluxes, with simulations forced by ob- istry as well as the feedback of changes
The objective of EMDI is to compare served atmospheric CO2 from pre-indus- in marine biogeochemistry on climate. To
model estimates of terrestrial carbon trial time to present. In addition, to evalu- validate such simulations, it will be cru-
fluxes (NPP and net ecosystem produc- ate model behaviour, OCMIP-1 com- cial to focus on how well models are able
tion (NEP), where available) to estimates pared simulated vs. observed 14C distri- to reproduce observed interannual vari-
from ground-based measurements, and bution. A global network of 14C samples ability.
improve our understanding of environ- was taken during GEOSECS in the 1970s
mental controls of carbon allocation. The and more recent sections from WOCE are
primary questions to be addressed by this now available. Natural 14C offers a pow- Atmospheric Tracer
activity are to test simulated controls and erful test of an ocean model’s deep ocean
model formulation on the water, carbon, circulation; “bomb 14C” helps constrain Transport Model
and nutrient budgets with the observed the modelled circulation of surface and
NPP data providing the constraint for intermediate waters. Bomb 14C also ap-
Intercomparison Project
autotrophic fluxes and the integrity of pears to exhibit similar behaviour to an- (TRANSCOM)
scaled biophysical driving variables. The thropogenic CO2 under certain condi-
experimental design consists of a multi- tions. Exploiting the 14C- CO2 relationship, Task Leader: Scott Denning
tiered approach to make maximum use when appropriate, offers one way to cir-
of the available NPP and NEE measure- cumvent the difficulty of directly meas- The Atmospheric Tracer Transport Model
ments. These tiers include site model- uring the small anthropogenic change in Intercomparison Project (TransCom) is
data comparisons, grid-cell model-data dissolved inorganic carbon (DIC) in the part of a larger GAIM research program
comparisons, global model-data com- ocean, relative to the large DIC pool focused on the development of coupled
parisons, and flux data. The NPP data sets which is naturally present. ecosystem-atmosphere models that de-
emerging from GPPDI are derived from OCMIP Phase 1 demonstrated that scribe the time evolution of trace gases
both point and spatially explicit sampling predictions from ocean carbon-cycle mod- with changing climate and changes in
designs, thus enabling a valid compari- els differ regionally by a substantial anthropogenic forcing. Much of our cur-
son between point and area-based mod- amount, particularly in the Southern rent understanding about the global car-
els and data. Analyses and visualizations Ocean, where modelled air-sea fluxes of bon cycle has come from observing the
are being carried out within each tier to anthropogenic CO2 are also largest (Fig. changes in atmospheric CO2 concentra-
investigate the model controls on NPP 2). The recently launched OCMIP-2 in- tions over time. Time series (e.g., Mauna
and their underlying formulations. Initial volves 13 models and additional Loa record) provide insight into the sea-
results showed general agreement be- simulations. The focus remains on CO2, sonal cycle as well as global source/sink
tween models and data but with obvious but OCMIP-2 also includes emphasis on and interannual variations. Additionally,
differences that indicate areas for poten- new circulation tracers, such as CFC-11 existing flask networks (e.g. CMDL,
tial data and model improvement. and CFC-12, and new biogeochemical CSIRO, etc.) provide information about
tracers such as O2. OCMIP-2 also includes the distribution of atmospheric CO2. For
simulations with a common example, a disproportionate amount of
Ocean Carbon-Cycle biogeochemical model so that participants fossil fuel emissions occur in the north-
can better study effects due to differences ern hemisphere, and a large terrestrial
Model Intecomparison in modelled ocean circulation. OCMIP-2 CO2 sink is required to explain the weak
Project (OCMIP) also includes data specialists who are lead- observed north-south gradient. However,
ing the JGOFS and WOCE synthesis for an accurate quantitative interpretation of
CO2, 14C, and CFCs, thus strengthening the spatial structure requires realistic
Task Leaders: Jim Orr, Patrick models of trace gas transport.
Monfray, Ray Najjar model validation efforts.
Standard simulations for CFC-11 and Chemical tracer transport models
The ocean plays a critical role in the glo- CFC-12 have been completed by all 13 (CTMs) are used to study atmospheric
bal carbon budget because the solubility participating OCMIP-2 model groups. The CO2 and can be characterized by the
of CO2 in seawater provides an enormous AJAX section for CFC-11 reveals large dif- mechanisms they incorporate to transport
reservoir for sequestration (or release) of ferences between storage of that tracer in tracers horizontally and vertically across
atmospheric CO2. Thus, the goal of the the Southern Ocean, e.g., south of 50˚S. the globe. One class of CTMs transport
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