Constraining the entire Earth system projections for more reliable climate change adaptation planning.

The warming climate is creating increased levels of climate risk because of changes to the hazards to which human and natural systems are exposed. Projections of how those hazards will change are affected by uncertainties in the climate sensitivity of climate models, among other factors. While the level-of-global-warming approach can circumvent model climate sensitivity uncertainties in some applications, practitioners faced with specific adaptation responsibilities often find such projections difficult to use because they generally require time-oriented information. Earth system projections following specified emissions scenarios can, however, be constrained by applying the level-of-global-warming approach to observationally constrained warming projections to yield more reliable time-oriented projections for adaption planning and implementation. This approach also allows individual groups to produce consistent and comparable assessments of multifaceted climate impacts and causal mechanisms, thereby benefiting climate assessments at national and international levels that provide the science basis for adaptation action.