The Rapid Impact Model Emulator (RIME) and its probabilistic extension, RIME-X (Rapid Impact Model Emulator Extended), are lightweight, open-source software tools developed at IIASA to bridge the gap between global emissions pathways and climate impacts and risk assessment. These emulators enable researchers to explore thousands of potential futures in seconds, facilitating a deeper integration between the climate impact (IPCC WGII) and mitigation (IPCC WGIII) communities. 

Model Overview 

While state-of-the-art earth system and impact models provide immense amounts of useful data, they require significant computational power and months of runtime, often limiting research to a handful of pre-defined scenarios. RIME builds on these data archives to calculate regional climate impact drivers (CIDs) and exposure metrics for new emissions scenarios. 

RIME-X extends this framework into the probabilistic domain. It unifies multiple sources of uncertainty, including Earth system parameter uncertainty from Simple Climate Models (SCMs), model uncertainty from weighted Model Intercomparison Projects (MIPs), and internal climate variability, to produce scenario-dependent distributions of regional impacts over time. 

Impact Indicators and Data 

The framework supports a large number of temperature-driven impact variables, drawing on high-quality datasets like ISIMIP3b. Example categories and indicators include: 

  • Heat and Cold: Air temperatures, heatwave events, tropical nights, and cooling degree days. 
  • Wet and Dry: Extreme precipitation, consecutive dry days, and precipitation variability. 
  • Hydrology: Drought intensity, runoff, discharge, and water stress indices. 
  • Land: Fire weather indices, crop yield changes. 
  • Economic damages: GDP losses, labour productivity. 
  • Applied Metrics: Population and land-area exposure, and maize yield changes. 

Applications and Vision 

RIME and RIME-X are designed for "closing the loop" between physical climate modelling, risk assessment and integrated assessment modelling. When used in conjunction with integrated assessment models, these emulators enable a more flexible assessment of climate impacts, such as changes in cooling demands or water resources, for new climate scenarios. 

To date, the framework has been central to high-profile initiatives such as: 

  • NGFS (Network for Greening the Financial System): A suite of updated  physical risk climate indicators for the NGFS transition scenarios and presented for all countries and regions on the Climate Impact Explorer. 
  • UN Environment Program Global Environment Outlook 7th edition: Providing an assessment of changes in population exposure to climate impacts drivers for Current Trends and Transformation scenarios. 

Technical Resources 

  • Publications: