Methodology

This method, named IMPACT World+, is the update of the IMPACT 2002+, LUCAS, and EDIP methods. The IMPACT World+ method integrates developments in the following categories, all structured according to fate (or competition/scarcity), exposure, exposure response, and severity:

1. Complementary to the Global Warming Potential (GWP100), the IPCC Global Temperature Potential (GTP100) are used as a proxy for Climate Change, long-term impacts at midpoint. At damage level, shorter-term damages (over the first 100 years after emission) are also differentiated from long-term damages.
2. Marine acidification impact is based on the same fate model as climate change, combined with the H+ concentration affecting 50% of the exposed species.
3. For mineral resources depletion impact, the material competition scarcity index is applied as a midpoint indicator.
4. Terrestrial and freshwater acidification impact assessment combines, at a resolution of 2°x 2.5° (latitude x longitude), global atmospheric source-deposition relationships with soil and water ecosystems sensitivity.
5. Freshwater eutrophication impact is spatially assessed at a resolution grid of 0.5°x0.5°, based on a global hydrological dataset.
6. Freshwater ecotoxicity and human toxicity impacts are based on the parameterized version of USEtox on the continental scale.
7. We consider indoor emissions and differentiate the impacts of metals and persistent organic pollutants for the first 100 years from longer-term impacts.
8. Impacts on human health related to particulate matter formation are modeled using the USEtox regional archetypes to calculate intake fractions and epidemiologically derived exposure response factors.
9. Water consumption impacts are modeled using the consensus-based scarcity indicator AWARE as a proxy midpoint, whereas damages account for competition and adaptation capacity.
10. Impacts on ecosystem quality from land transformation and occupation are empirically characterized at the biome level.