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Changes in levels may not be as extreme in the near-term as previously predicted

A major goal of the Study was to bring the best possible hydroclimatic science to bear on selecting a robust regulation plan. In working towards that objective, the Study included state-of-the-science climate projections from one of the largest ensembles of GCM runs ever assembled for a regional study, regional climate modelling from two separate national modelling centers, a variety of statistical modelling approaches and innovations in modelling of the lake system’s responses to climate. Climate research showed that changes in lake levels in the near-term future may not be as extreme as previous studies have predicted. For example, comparing the results of statistically down-scaled GCMs with results of dynamical down-scaled GCM projections, the Study found that predicted changes in net basin supplies (NBS) for the design period of year 2040 varied considerably, with both drier or wetter conditions predicted depending on the models used and their resolution. The Study’s hydroclimate findings represent major steps forward in improving understanding of the largest regulated freshwater system in the world. Yet despite best efforts, in terms of understanding the lakes system relative to lake levels, the unavoidable conclusion from the Study is that the Great Lakes are a complex system whose dynamics are only partially understood, and this current state of understanding has its limitations for deriving predictions of the future. Furthermore, at present there is no evidence that the statistics of the historical record are not valid. The current record of Great Lakes NBS appears continuingly stationary, marked by strong interannual and decadal variability, and showing no response that may be attributable to climate change. During the planning period (i.e., 30 years), “natural variability” is likely to mask any forcing due to greenhouse gas emissions. Lake levels are likely to continue to fluctuate, but still remain within a relatively narrow historical range. While lower levels are likely, the possibility of higher levels cannot be dismissed but rather must be considered in the development of a new regulation plan. The best approach, therefore, is to make decisions in such a way as there is not great reliance on assumptions of the future.
Related Projects
Analysis of Angel and Kunkel Future Lake Levels and NBS
Climate Data Downscaling using CRCM
Modelling of Climate Change Impacts Using CHARM
Stochastic Generation and Forecasting of NBS
Hydroclimate Synthesis and Summary
Risk Assessment & Decision Making under Uncertainty