Critical climate change as an approach to assess climate change impacts in Europe: development and application

Abstract

The “critical climate change” approach is particularly suited for integrated assessments because of its long-term and large-scale perspective. This is an analogous approach to the “critical loads” concept used for assessing regional air pollution impacts in Europe. Critical climate change is defined as the “quantitative magnitude of climate change (expressed as changes in temperature and precipitation) above which unacceptable long-term effects on ecosystems may occur, according to current knowledge”. The approach consists of four main steps:

1. Selection of appropriate indicators of climate change impact. Here we select changes in net primary productivity of ecosystems.
2. Assigning to the selected indicator a level of “unacceptable impact” of climate change. Here we assume this level to be at least a 10% loss in the net primary productivity of natural ecosystems, after considering other thresholds and the historical variation in ecosystem productivity.
3. Determining the response of the indicator to one or more climate-related driving force. This includes identifying the combinations of driving forces that produce the assigned unacceptable impact.
4. Computing the area where critical climate changes exceeded under climate change scenarios. An analysis of climate scenarios show that critical climate changes may be exceeded on 9–13% of Europe’s area by 2100, depending on the scenario. The areas where critical climate changes are exceeded are located mostly in southern Europe, even under relatively low emission scenarios.