The Global Analysis, Integration and Modelling Task Force (GAIM) was a component of the International Geosphere Biosphere Program (IGBP) of the International Council of Scientific Unions (ICSU, now ISC). The GAIM Task Force Office was located in the Institute for the Study of Earth, Oceans, and Space, University of New Hampshire.

The goal of GAIM was to advance the study of the coupled dynamics of the Earth system using as tools both data and models. GAIM emphasized activities designed to expand upon the development, testing, and analysis of integrative data sets and models of those aspects of the Earth system where IGBP has the scientific lead, and it committed to collaborate on aspects of the Earth system where WCRP and IHDP had the lead.

The role of GAIM was multi-fold. The Task Force had to analyze current models and data, assess the capability of current models and experimental programs to resolve key questions, and advance and synthesize our understanding of the global biogeochemical cycles and their links to the hydrologic cycle and to the physical-climate system as a whole. This was done both for natural systems and variability as well as in the context of anthropogenic perturbations. The challenge to GAIM was to initiate activities that would lead to the rapid development and application of a suite of Earth system models spanning a range of model complexity that integrated the roles and interactions of physical climate, ecological, and human systems.


The GAIM Task Force was a collection of scientists each conducting independent research which was coordinated and integrated through the GAIM office. The GAIM modelling effort was structured by Topic and Time Period. The Topics were CO2, Trace Gas, and Climate-Vegetation Interactions. The Time periods were Paleo (<20 kyrs), fossil fuel (<200 yrs), contemporary (<20 yrs), and future. In addition to modelling projects, GAIM was involved in collaborative activities with various IGBP core projects. These activities included thematic workshops and various cross-disciplinary and support activities.

I. Model Intercomparison Activities

One of the most significant contributions made by GAIM was the development of techniques and tools for model intercomparison. Whereas individual scientists or modelling groups can and do develop numerical models of various aspects of the Earth System, the value of the results of isolated models was greatly enhanced by comparison with other models. The discrepancies in model results between different approaches to the same problem provided critical insights into model shortcomings, and paved the way for model refinement and improvement. Below are GAIM’s major sub-system level model intercomparison projects. The tools developed through these activities were applied to the interpretation and assessment of the broader Earth System models (EMIC, C4MIP, CCMLP). As these major GAIM intercomparison activities came to fruition, we coupled the models loosely at first, and then more interactively between 2003 and 2006.


  • Analysis of MIPs
  • Ecosystem Model/Data Intercomparison (EMDI)
  • Ocean Carbon-Cycle Model Intercomparison Project (OCMIP)
  • Atmospheric Tracer Transport Model Intercomparison Project (TransCom)
  • Global Net Primary Productivity (NPP)

II. Integration of IGBP Science & Earth System Modelling

As Earth subsystem models developed to a more robust level, GAIM prepared to enter an integrative phase. This involved the establishment of techniques for coupling and integration of biogeochemical subsystem models in preparation for the construction of an integrated prognostic biogeochemical model. Such integration involved coordination with each of the IGBP Core Projects. The integration program was structured in three segments, each contributing to the overall objective of developing the modelling capacity which will ensure the achievement of GAIM’s goals. The first was at the subsystem level, where GAIM activities were designed to bring developing subsystem models into boundary compatibility. This was done through modelling workshops involving intercomparisons of like subsystem models, and intercomparisons involving coupling between adjacent subsystem models (which must match boundary conditions and fluxes). The second segment was at the system level, where simple Earth system models were compared to highlight differences in coupling techniques, inter-element fluxes, and sensitivity studies to reveal the differences between models of the relative importance of individual system parameters. The third segment was at the IGBP Core Project level, where GAIM worked with Core Project modelling teams to help facilitate inter-subsystem coordination.

Subsystem models

The subsystem integration plan involved four key linkages: Land atmosphere, ocean-atmosphere, atmospheric physics with atmospheric chemistry, and Land-ocean. These subsystems had different space and time scales (which themselves depend upon what is being tracked) and were often quite stiff as linked systems and therefore difficult in perturbation experiments. There were also greatly differing degrees of parameterization with little understanding as to effects.

Important linkage experiments were done: a) the ocean carbon model inter-comparison project has linked atmosphere GCM’s (mainly as drivers) with ocean GCM’s containing carbon chemistry and crude biology; b) similarly, the terrestrial carbon models (NPP Efforts) were being driven (partially) by GCM results; and c) we took the preliminary steps with the GCM Atmosphere transport codes studies for tackling the chemistry connection.

Subsystem models were developed with a variety of structures and emphases. While each model was taken to represent the processes within a biogeochemical subsystem, the analytical and numerical formulations were widely disparate, and often led to significant differences in model results. A fundamental issue was the development of subsystem models in such a way that the boundary conditions and fluxes for each were compatible with each of the others. This compatibility was defined in terms of the ability of each model to provide the necessary input to define the boundary conditions needed to most efficiently run the others. For example, the boundary between the terrestrial and marine biogeochemical systems involves physical and chemical conditions and fluxes which are so complex that no single subsystem model presently accounts for all. Thus, matching boundary fluxes at the boundary would be impossible unless carefully coordinated during the model development phase.

As each of the subsystems became better understood and models converged on realistic values of output parameters, it was timely to convene workshops to couple compatible models to form a more complete Earth system model. While it was not necessary to assume (and not possible to mandate) that all models of a particular subsystem would have identical input/output parameterizations, it was essential the each model be coupled only to other subsystem models with compatible parameterizations. Thus we envisioned the emergence of a suite of coupled models, each with consistent coupling and interactions between model components, but each based on a different style of formulation. The parallel development of coupled Earth system models had several advantages. The first was that because no single model (even an integrated Earth system model based on compatibly coupled subsystem models) accounts for all processes and interactions in the Earth system, each model would necessarily result in slight differences in inter-component fluxes and sensitivities. This set the stage for Earth system model intercomparison which highlighted the relative importance of the various processes, interactions, and feedbacks between subsystems modelled by each of the integrated models. This ultimately led to modified integrated models which correctly accounted for the interactions to which the Earth system was most sensitive, while becoming unburdened from those to which it is demonstrably insensitive.

System level

It was the ultimate mission of the GAIM Task Force to promote the development of integrated models of the Earth’s biogeochemical system for eventual linking to the physical climate system studied through WCRP as well as the societal systems studied through IHDP. Simple models of the Earth system already existed, but they were not sufficiently robust to incorporate the detailed subsystem models being developed throughout the IGBP. It was instructive to examine such simple holistic models because some features which emerged helped identify and thus forestall potential problems in developing more comprehensive models on the basis of subsystem model coupling. Important insights were gained from existing simple models of the Earth system, so we built on these simple models in two ways:

  1. an organized simple but total Earth System Model approach that raised difficult system dynamic issues (chaos, feedbacks, parameterization sensitivities, etc.), and
  2. an effort to collect and document existing models of key features of the Earth System (e.g. Carbon Cycle) that could run on a 486 class machine (or run over the www). The purpose of the former was to highlight key scientific issues that may be lost in the large model efforts; whereas, the purpose of the latter was more out-reach and educational.

In order to assess the validity of Earth system models, it was critical to understand the sensitivity of the system to each of the input data. Heuristic and mathematical models were becoming developed to a point where it was appropriate to consider model sensitivity. Consequently, we conducted model sensitivity analyses of dynamic vegetation models, ocean carbon cycle models, GCMs, and hydrologic models as well as for simple Earth system models with respect to the various input climate and ecological data. We plan to initiate this effort with a workshop in early 1988 with the goal of comparing the sensitivity of various models to a suite of input parameters.

IGBP Core Project Integration

Each of the IGBP Core Projects developed models of the appropriate biogeochemical subsystems. Once those were completed, it was GAIM’s task to promote the coupling of the various subsystem models and the development of an integrated Earth system model. Model coupling requires advance planning so that it will be possible to most effectively match boundary conditions and fluxes. Thus, input and output data sets needed to be assessed and standardized, model temporal and spatial resolutions had to be matched or scaled where necessary, and common numerical protocols needed to be defined so that the necessary parameters would flow through one subsystem model to the next. The development of Earth System Models is a complex problem, to which the extensive resources of various institutions were applied. The GAIM Task Force did not compete with these efforts, but rather, the Task Force was composed of key scientists from these leading institutions world-wide. The composition of the Task Force was determined by the scientific issue being addressed, and continued to evolve in response to the development of new Earth System Models. As such, GAIM provided a means for planning and coordination between these various institutional efforts.

This activity tied in closely with the subsystem level problem described above. The IGBP Core Projects were organized in such a fashion to encourage interactions and collaborations between scientists specializing in each of the Earth’s biogeochemical subsystems. As such, the framework was in place for organization of collaborative and intercomparison activities which led most effectively toward meaningfully coupled models. We worked closely with each of the IGBP Core Project modelling teams to help direct the modelling efforts in a direction which would result in the most efficient coupling possible.


  • Earth System Models of Intermediate Complexity (EMIC)
  • Coupled Carbon Cycle Climate Model Intercomparison Project (C4MIP)
  • Coupled Carbon Model Linkage Project (CCMLP)


III. Earth System Atlas

The Earth’s climate, ecosystems and human activities are highly variable in both space and time. Past changes in climate, atmospheric composition and land use have affected the surface of the planet differently at each location, and all indications of future changes suggest that the pattern in every sphere will continue to be modified. Reconstructions of past environments and monitoring/mapping of the present have reached a major threshold, providing an understanding of the processes that drive the Earth System sufficiently to enable model simulations of future change to be made with unprecedented reliability.

Although great strides were made in global change and Earth system science, research results had been disseminated in a piecemeal fashion, with no standardized format that would allow comparison and assessment of the relations between the various factors that define and control the Earth system. Toward the end of rectifying this information dissemination gap, an Earth System Atlas was planned that presented and linked together the myriad global change research results.

The Earth System Atlas represented an initiative of the International Geosphere Biosphere Programme (IGBP) in conjunction with its Earth System Science Partners (ESSP), the World Climate Research Programme (WCRP), the International Human Dimensions Programme (IHDP), and the International Programme for Diversity Science (DIVERSITAS). As such, it was a product of the entire research community rather than that of a single center or institute. In this way, not only was a broad scope of Earth system-related data accessed, but the data was all displayed or downloaded in a common format viewed in a common map projection. As an effort by the entire community, there were much stronger quality controls than would have been possible within a single research entity.

The purpose of the Atlas was to provide a wide range of users with a series of Global Change related digital maps and time series, along with access to the underlying data from which they were constructed, and text explanation of data collection, analysis, and other pertinent information. The target audiences were:

  • the Global Change science community (both within and outside the ESSP)
  • the education community and non-governmental organizations (NGOs)
  • government organizations and policy makers
  • the general public

The overarching goal of the Atlas was to publicize as broadly as possible the results of recent global change research efforts.

Specific objectives included:

  • Establishing a well-known, single source of global change information
  • Presenting research results in an easily understandable format
  • Creating a format that can be updated as new results and refinements emerge
  • Enabling superposition of different aspects of global change for comparison, assessment, and interpretation
  • Linking maps and time series with original data
  • Enabling user-defined zoom, overlay, and snapshot/time interval
  • Identifying conceptual and data gaps that will help direct subsequent work within the research community

The Earth System Atlas contained pertinent information regarding changes in climate, atmosphere, land surface and ocean, as well as socio-economic factors. Maps were created from ground-based and satellite-derived data, conceptual and numerical models, census and additional relevant databases. The Earth System Atlas included, in addition to maps at global scale, products at a broad regional scale of particular interest (e.g. the Amazon or the Arctic Basin). Users of the Atlas were able to zoom in and out as needed. An important feature of the Earth System Atlas was that maps were developed in such a way that past conditions could be compared visually with the present, and also with future environmental conditions predicted on the basis of current models and forcing scenarios.

One of the primary unique features about the proposed Earth System Atlas was the fact that all data will be peer reviewed for quality. This involved two phases. The first was the evaluation of any data set for appropriateness and relevance. If the data was not deemed adequate to apply to the desired display, other alternatives were sought. Once a data set was selected for consider for the atlas, the second aspect of quality control involved peer review to scrutinize each data set for completeness, functionality, isolated errors, mismatches, etc. In addition, all accompanying text were reviewed for accuracy, writing style (for each intended audience), and appropriate context.

The Earth System Atlas was produced in electronic form with on-line access in order to provide the broadest possible availability to the general public. Underlying data was made available in electronic format. The free and open data exchange policy of the International Council of Scientific Unions (ICSU) applied to all aspects of the Atlas.

The scientific scope of the Atlas was organized in the following categories:

  • Background and Introduction
  • Physiography
  • Climate
  • Atmospheric Constituents
  • Physical/Chemical Ocean
  • Physical/Chemical Land
  • Hydrology
  • Biogeochemical Cycles
  • Ecosystems
  • Human Dimensions
  • Future Scenarios

Each data set included in the atlas was accompanied by explanatory text describing the data as well as the meaning of the selected display within the Earth system. The text had the form of extended “figure captions” and was written specifically for each of three target audiences for the atlas- Earth System Scientists; Lay public and Policy Community; School Children. The text was fully referenced including data source(s), published literature, and links to data-specific websites, as appropriate.

There were a number of excellent global change-related data compilations and directories already in existence at the time. The Earth System Atlas linked and incorporated these data archives to create on-line maps and time series in an atlas format as described above. Available data was categorized into two types, the first being “archived data” that existed in a variety of formats, but for which visualization tools had not been developed specifically, and the second being data from which maps and time series had already been made and were available online. The atlas was fundamentally different than any existing data visualization effort in that it had a broad Earth system focus, global coverage, a standardized data format and set of visualization projections, and perhaps most importantly, the atlas included a mechanism for reviewing and evaluating the relevance and quality of specific data sets. These attributed, and especially the latter set it quite apart from any previous effort, and led to the development of a unique resource for the research, policy, and educational communities as well as the lay public at large.

IV. IGBP Fast-Track Projects

At the 2003 SC-IGBP meeting in Punta Arenas, Chile, it was decided that GAIM should be charged with leading a number of relatively short-term projects (Fast Tracks) that would yield concrete results within a 2-4 year time frame. This fit into the “Analysis” role of GAIM, in that these topics were focused issues within the Earth system from which we could explore some of the key processes that control system behavior. A few initial Fast Tracks were identified and are described here.


  • Fire
  • Iron
  • Nitrogen

V. Understanding and Explaining Specific Observation of the Earth System 

The ‘Analysis’ part of the GAIM Acronym involved identification of specific problems and gaps in our understanding of critical aspects of the Earth System. This included finding explanations for the growing set of system-level observations being obtained through geological and instrumental techniques. The necessary conceptual understanding of the processes that controlled the behavior of the Earth System could only be gained by multidisciplinary approaches to unravel the complex set of interactions within the system that were not evident from disciplinary studies. Consequently, GAIM continued to identify specific observations at the system level, the explanations for which required a deeper understanding of the Earth System than existed at the time. 

  • Trace Gas & Aerosol Cycles in the Earth System (Traces)
  • Global Atmospheric Methan Synthesis (GAMS)
  • Global and Regional Sea-Level Changes and the Hydrological Cycle

VI. Outreach

In addition to exploring new aspects of model development and Earth System analysis, GAIM continued to work toward expanding its pool of expertise globally. Toward that end GAIM convened its first Open Science Conference in 1995. The second open conference was in conjunction with the overall IGBP Open Science Conference in 2001. Meanwhile, GAIM had been conducting more specific outreach activities. In 1997, GAIM convened the African-GAIM Modelling Workshop directed toward both training African ecosystem scientists and hydrologists in modelling methods, as well as entraining their own expertise in the international scientific programs of IGBP. In 2000, GAIM convened a similar workshop in Brazil for the specific purpose of enhancing the modelling capabilities of the LBA scientific community. A third training workshop was planned for 2003 in Asia. It was hoped that through enhanced training activities, GAIM would be able to increase the modelling capabilities of the international scientific community, and thus have a greater pool of expertise to contribute to its overall goal of Earth system analysis and prognostic biogeochemical model development.


VII. Participants


Colin Prentice

John Schellnhuber


Ayako Abe-Ouchi

Andre Berger

Richard Betts

Ken Caldeira

Martin Claussen

Bob Costanza

Wolfgang Cramer

Brad de Young

Jae Edmonds

Pierre Friedlingstein

Paul Falkowski

Inez Fung

Sylvie Joussaume

Pavel Kabat

Maria Kanakidou

Michio Kawamiya

Rik Leemans

Tim Lenton

Natalie Mahowald

Pam Matson

John Mitchell

Carlos Nobre

Wandera Ogana

Dominique Raynaud

Peter Rayner

Simon Shackley

Ferris Webster

Gary Yohe

VIII. Coordination

Executive Director: Dork Sahagian
Program Assistant: Jennifer Boles 

GAIM International Project Office was kindly hosted by University of New Hampshire, Durham, USA with generous financial support from NSF, NOAA, EPA and DOE.

IX. GAIM Newsletters