Warming-level dependent adaptation requirements and consequent limits to adaptation

<p>The level of detail to understand the impacts associated with different levels of global temperature increase across space and time is increasing with and since the publication of the IPCC Special Report on Global Warming of 1.5°C (SR1.5). However, current adaptation assessments are limited in picking up this information to understand what the implications of different impact pathways are for adaptation. Yet, the intensity, frequency and timing of impacts are critical determinants of the feasibility of different adaptation options and their associated costs.</p><p>There is increasing awareness that limits to adaptation are likely to be approached or crossed with higher levels of warming, however differential analyses of adaptation needs as a consequence of different warming pathways are so far limited. While case study based assessment of warming- and scenario-depend adaptation responses are emerging, so far an aggregated regional to global assessment is lacking.</p><p>Adaptation is often seen as a process that can draw on existing approaches that have been successfully implemented elsewhere, assuming that a linear increase of impacts would allow impacted regions to scale existing approaches to deal with hazards. However, climate impacts are unlikely to increase in a linear fashion across space and time and we are likely to enter new regimes of impacts in terms of intensity and frequency, with implications on recovery times. As a consequence, existing approaches are unlikely to be able to respond to these fundamentally changed conditions and limits to adaptation as we know it are likely to be reached. Understanding adaptation needs and potentials at different levels of global warming is therefore an urgent need in order to understand the full scale of the challenge. Such information is also critical in understanding the full cost of different mitigation pathway choices.</p><p>This contribution presents a framework for the systematic assessment of warming-level dependent adaptation needs and potentials across sectors and presents first results of this approach in the context of adaptation in the water sector. Our results highlight the need for differentiated approaches to planning adaptation, drawing a strong link to available impacts and vulnerability science to avoid mal-adaptation and to understand the full scope of the challenge. Where transformational adaptation will be required and current warming trajectories, early action may reduce associated costs of such measures across different dimensions, including financial, social or cultural aspects.</p>