Tipping Points, Unprecedented Events and Irreversibilities in the Climate System
High resolution paleoclimatic records, supported by Earth system modelling studies, have demonstrated that perturbations in the Earth system can lead to abrupt, non-linear, often irreversible changes and impacts at local, regional, and global scales. From a local point of view, even small changes in climate conditions may result in high impacts that threaten the livelihoods of people and the ecosystems they depend on. Such changes are referred to as surprises, tipping points, or high impact-low likelihood (HILL) events. They encompass regime changes across scales in atmospheric and ocean circulation, the hydrological cycle, extreme weather statistics, large-scale vegetation, monsoon systems, and ice masses in Greenland and Antarctica. Knowledge on impacts of future climate change is based on scenario simulations using the current generation of comprehensive models. However, two limitations are evident: (i) current models have difficulties simulating amplitudes and patterns of HILL events; and (ii) scenarios do not include surprises, nor out-of-scale extreme events. These limitations may be overcome by enhancing instruments capable on delivering insights into the consequences of HILL events. Improved model resolution, a more impact-oriented model analysis, and bolstered connections between the scientific and service sectors can ensure more efficient global to local adaptation initiatives and support National Meteorological and Hydrological Services (NMHSs) in protecting people, assets, and infrastructure.
Text from Annex to Decision 10 (EC-78)