ISI-MIP – The Inter-Sectoral Impact Model Intercomparison Project | Umweltbundesamt

Atmospheric CO2 concentrations were prescribed according to the four representative concentration pathways (RCPs) also used to drive the general circulation models(GCMs) within in the latest, fifth phase of the Climate Model Intercomparison Project (CMIP5). To provide the associated climate information for ISI-MIP, five of the CMIP5 GCMs were selected to span the space of global mean temperature change and relative precipitation changes as best as possible, albeit with the limited available data in the CMIP5 archive at the relevant stage of the project.

The ISI-MIP climate dataset covers the period from 1960 through to 2099 on a horizontal grid with 0.5° × 0.5° resolution; where necessary, climate model output was spatially interpolated. The data were bias-corrected to ensure long-term statistical agreement with the observation-based watch forcing data over the period 1960–1999. Projected absolute trends in temperature and relative trends in precipitation and all other variables were preserved by the bias-correction method, which was developed specifically for this project. Preservation of the temperature trends in each grid cell also implies that the global warming trend and thus, in particular, the climate sensitivities of the GCMs, are preserved.

Of the 20 combinations of four RCPs and five GCMs considered, three exhibit global mean temperature greater than 4°C above present day (1980–2010) for the highest concentration scenario RCP8.5 in 2099. Note that the 1980–2010 reference period was also chosen as a baseline for the quantification of future climate impacts. This baseline period is ∼0.7°C warmer than preindustrial conditions. A set of 16 GCM-RCP combinations surpasses a warming of 1.3°C above 1980–2010, which corresponds to the internationally accepted threshold of 2°C above preindustrial. To illustrate the projected evolution of land-averaged precipitation, relative changes compared with the historical period are quantified in terms of global mean temperature. Both variables are filtered by a 30-y ⁠moving average⁠.

all parameters of the climate models

30-y moving average

Global impact models from five different sectors were involved in the ISI-MIP fast track: water, agriculture, biomes, coastal infrastructure, and malaria as an example of health impacts. The agricultural component of ISI-MIP was coordinated under the umbrella of the agro-economic model intercomparison(AgMIP) and an ISI-MIP component was included in the AgMIP.

Each impact model was driven by a common daily, gridded climate dataset and delivered results in the form of a sector-specific set of common output variables at time resolutions ranging from subdaily to monthly. Harmonization across models was limited to the driving climate input data and, where applicable, socio-economic data (population and gross domestic product, GDP). Additional input data were selected according to the default settings of each model, to gain a representative picture of uncertainty across the models using native settings.

The scenario suite for the ISI-MIP fast track was designed to allow for quantification of the uncertainty in the impacts of climate change—both across climate models and across impact models—at different levels of global warming. The list of chosen scenarios represents a balance between ensuring harmonization across the sectors and exploring the sector-specific modeling uncertainties.