The New York times has a piece today about low water levels in Lakes Huron and Michigan and the impact that this is having on shipping in the area as well as on communities. As is pointed out, this is another impact which it is difficult to tell if it completely atrributable to climate change or not. Lake levels do fluctuate over longer time frames as rain fall varies from year to year, evaporation changes and other variables change.
When thinking about risks from climate change, the risks to shipping due to decreased water levels in places like the Great Lakes needs to be considered. The dynamic between increases sea levels and decreased freshwater levels also needs to be considered. Maybe this means less of an impact on inland shipping than previously thought. On the other hand, sea water going further inland into freshwater ecosystems could impact the fisheries and other biological resources in these inland waters.