ISIMIP diagram with arrow

Studies of climate-change mitigation pathways and strategies show that limiting global warming to 2° is much more ambitious and costly than a 3°.  However, little is known of the quantitative differences between impacts of different levels of global warming, not to mention how impacts in different sectors may interact and potentially amplify one another.

ISIMIP is a community-driven climate-impacts modelling initiative aimed at contributing to a quantitative and cross-sectoral synthesis of the differential impacts of climate change, including the associated uncertainties. ISIMIP offers a consistent framework for cross-sectoral, cross-scale modelling of the impacts of climate change. The key goal of ISIMIP is to contribute to the comprehensive (cross-sectoral) understanding of the impacts of politically and scientifically-relevant climate-change scenarios.

ISIMIP is organised into simulation rounds, which are guided by a focus topic.  For each round, a simulation protocol defines a set of common simulation scenarios based on the focus topic. Participating modelling groups are provided with a common set of climate input data, and other data (in some cases unique to one sector) necessary to ensure cross-sectorally consistent impacts simulations. Participation is open to all models capable of following the simulation protocol.

In the current simulation round, participating models cover impacts in the following sectors:

  • Global water
  • Regional water
  • Agriculture
  • Global biomes
  • Regional forests
  • Fisheries and marine ecosystems
  • Permafrost
  • Energy supply and demand
  • Biodiversity
  • Health - heat-related mortality
  • Tropical cyclones

Simulation rounds: ISIMIP2b

ISIMIP2b is designed to provide robust information about the impacts of 1.5°C global warming and related low-emission pathways, as required for the IPCC Special Report on this topic. In addition to those sectors already represented within ISIMIP, impacts on biodiversity, tropical cyclones, heat-related mortality, and energy supply and demand will be considered. The scientific rationale for the scenario design is described in detail in the paper by Frieler et al 'Assessing the impacts of 1.5  °C global warming – simulation protocol of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP2b)'.

Simulation rounds: ISIMIP2a

ISIMIP2a includes modelling intercomparison efforts in fisheries, permafrost, biodiversity, regional water, forests and energy, as well as those sectors already covered in the Fast Track. This will serve as a basis for model evaluation and improvement, allowing for improved estimates of the biophysical and socio-economic impacts of climate change at different levels of global warming. It also provides a unique opportunity for cross-sectoral integration.

A set of chosen focus regions was developed in conjunction with participants prior to and during the Side Event. In these focus regions global and regional models. All participants running regional (i.e. below global-scale) models are asked to set up and run their models for as large a part of each focus region as possible, in order to obtain maximal spatial overlap with other models.

The focus topic for ISIMIP2a is model validation, in particular with respect to the representation of impacts of extreme weather events and climate variability. During this phase we will provide a common global observational climate data set across all impact models and sectors. In addition, appropriate observational data sets of impacts for each sector have been identified, against which the models can be benchmarked. Access to all these data is provided through a central online ISIMIP archive.

In addition, models that have participated in the Fast Track are asked to run a number of new scenarios that focus on enhanced cross-sectoral integration. These new scenarios have been developed in close collaboration with the sectoral coordinators and in consultation with all participating modelling groups. For example, the water and biomes models will take as input the land-use change patterns obtained from the agro-economic models in the fast-track phase.

Please note that new models joining the second phase should run the ISIMIP fast-track climate data using the existing Fast-Track protocol in order to provide impact projections at different levels of global warming and to enable studies consistent with the existing content of the ISIMIP archive. For sectors that are new to ISIMIP, these simulations will have to await development of a sector-specific protocol.

In addition to climate data, sector-specific additional inputs are specified in the protocol and harmonized across the sectors where possible. There will be no further harmonisation of model settings. Modelling groups are asked to do the simulations based on their "default present-day parameter settings" (excluding adaptation as far as possible). As in the Fast Track, simulations allow for a quantification of “adaptive pressure” rather than impacts under various adaptation strategies.

Simulation rounds: ISIMIP Fast Track

This ISIMIP Fast Track provided outcomes for the IPCC’s Fifth Assessment Report (AR5). The Fast Track also initiated a longer-term coordinated impact assessment effort driven by the impacts modelling community.

Around 30 global climate impact modelling groups from the agriculture (including agro-economic models), water, ecosystems, infrastructure and health sectors participated in the Fast Track. Here you can find more information about downloading impact simulation data from the ISIMIP Fast Track.

Models were provided with pre-processed input data (climate data based on the Representative Concentration Pathways (RCPs) from the CMIP5 archive, and socio-economic data based on the SSPs).

A kick-off workshop in February 2012 and a results workshop in September 2012 provided opportunities to discuss comparison within sectors as well as appropriate synthesis metrics within and across sectors.

Results from the Fast Track appeared in a special issue of the PNAS, as well as other journals. See the publication list. Analysis was completed in time to be considered by the Working Group II of the IPCC for the fifth assessment report (AR5). Here is a list of references in the AR5 to papers based on ISIMIP simulation data.

The Impacts World 2013 conference was held in May 2013, where the state of the art in impact research was presented and plans for the next phase of ISIMIP were discussed and developed.

A short history

ISIMIP was initiated by the Potsdam Institute for Climate Impact Research (PIK) and the International Institute for Applied Systems Analysis (IIASA) and has since grown to involve over 100 modelling groups from around the world.

The first ISIMIP simulation round, the ISIMIP Fast Track, ran from early 2012 until mid 2013, with a focus on providing cross-sectorally consistent projections of the impacts of different levels of global warming in the 21st century. The common set of scenarios made use of climate projections from five Global Climate Models (GCMs) driven by the Recommended Concentration Pathways (RCPs), making ISIMIP a natural extension of the work done within the Coupled Climate Model Intercomparison Project (CMIP). 

Fast Track simulations were submitted by 35 impact-modelling teams, covering the agriculture, water, global biomes, coastal infrastructure and vector-borne diseases sectors all at the global scale. 

The results of the Fast Track were collected in two special issues: of the Proceedings of the National Academy of Sciences (PNAS, link to special issue), and in Earth Systems Dynamics (ESD, link to special issue). Many of these papers were cited in the Fifth Assessment Report of the IPCC (AR5).

In the current simulation round, ISIMIP2a, simulation scenarios were chosen to facilitate model evaluation, in particular the representation of the impacts of extreme events and variability. The corresponding climate-input data are observational data sets covering the last century. Around 90 modelling teams are actively participating in ISIMIP2a. In addition to the sectors covered by the Fast Track, simulations now also cover the regional forest, regional water, fisheries, permafrost and energy sectors.



Organisational structure

ISIMIP is organized in five groups, representatives of which form the strategy group, which is the main decision-making body within ISIMIP. The functions of these groups, and the associated workflow, are explained in detail in the ISIMIP Mission & Implementation Document (linked below).

The day-to-day coordination of ISIMIP is the task of the management group, comprising the project leader, Dr Katja Frieler, the project manager, and the data manager. 

The cross-sectoral science team performs analysis of the ISIMIP simulation data with a clear focus on cross-sectoral issues. This team is also responsible for input-data preparation, and the members act as sector-specific contact points.

Each sector has one or more sector coordinators responsible for overseeing simulations in their sector and working closely with the participating modeling teams. The sectoral coordinators play a key role in liaising with other sector-specific initiatives in order to minimize the overall burden on participating modelling groups.

Contact information for the management group and sector coordinators can be found here.

The Scientific Advisory Board (SAB) is a voluntary group of 5-10 internationally renowned scientists offering oversight and strategic advice to ISIMIP.
ISIMIP Organigram