A Method for Reprojecting SSP–RCP-based Macroeconomic Damages under NGFS Scenario x IAM Trajectories

This document presents the methodological framework used to quantitatively translate the output from Schneider (2026), originally expressed under SSP–RCP pathways, into damages that are consistent with the NGFS scenario architecture and across Integrated Assessment Models (IAMs).

Author(s)

Nicolas Schneider

This document outlines the methodology used to translate sub-national physical risk-induced gross regional product (GRP) per capita damages, originally projected under SSP–RCP pathways in Schneider (2026), into outputs consistent with the NGFS scenario framework.

The approach involves:

constructing an aggregate damage function dynamically linking granular SSP-RCP based projected damages to trajectories of global mean temperature anomalies as emulated by the MAGICC module;
estimating >3,400 region-specific vectors of parameters collectively covering 191 economies, stable in sign and magnitude across scenario × IAM combinations; facilitating the smooth
re-projection of regional damage estimates distributed across seven original NGFS scenarios, specially extended with two extreme scenario realizations across the three IAMs. Moreover, we use scenario probabilities which, by giving unequal weights to all nine scenario outcomes, ultimately enable the calculation of an unconditional expected regional loss.

Resulting spatially disaggregated outputs may be aggregated to national and global levels using a population-density weighting method.