Getting used to slow climate and sea level changes: The danger of not recognizing and planning for thresholds

Abstract:

Slow changes in climate such as sea level rise and increased coastal flooding carry the danger that we get used to them without realizing all future consequences of these trends. Focus is often on the extreme events while thresholds that might be reached due to the slow changes receive less attention. For example, in Venice, the population and tourists get used to the frequent flooding and it becomes part of the daily life. But there is a threshold above which the frequency and magnitude of the tidal flooding will exceed coping capacity of businesses, population, and tourists alike. Sea level rise along the east coast of the U.S. has been greater than global sea level rise for at least the last century, and in most places, coastal urban settlements adapted to more than 30 cm of sea level rise in the last century without much efforts. Science is mostly occupied with describing and projecting the slow changes while governance is focused on land use planning that accommodates these changes. An often repeated questions from planners is "Which future trajectory should we pick and plan for?" The ability to adapt to slowly degrading situations often makes us blind for points where the trajectories could cross thresholds. As a result, the capabilities to identify these thresholds (the task of science) and prepare for them (the task of governance) is limited. Hampton Roads in Virginia, with a complex coupled socio-economic and environmental system and being a "hot spot" of sea level rise, is a natural laboratory to study the impacts of slow changes, and to integrate science into the development of governance responses. Increasingly large areas are barely above the present tidal range, and an accelerated sea level rise has the potential to increase hours of flooding per year and the number of flooding events per year in a non-linear way, with potentially damaging socio-economic consequences. At the same time, the slow process of sea level rise changes the risk associated with extreme weather events in a quantifiable way. Using the example of Hampton Roads, we will underline the importance of identifying and communicating thresholds where the slow trends lead to rapidly increasing damage and to address these thresholds in the development of policy for adaptation.