The potential impact of climate change on Great Lakes international shipping

The higher temperatures of climate change may result in a fall in Great Lakes water levels. For vessels carrying imports into and exports out of the Great Lakes lower lake levels will lead to restrictions on vessel drafts and reductions in vessel cargos, increasing the number of trips and the cost of moving cargo. Estimates of these impacts are derived from simulations of a recent year's international cargo movements, comparing a base case with no climate change to various climate change scenarios. The impacts vary from a 5% increase in vessel variable operating costs for a climate change scenario representing the possible climate in 2030 to over 22% for a scenario representing a doubling of atmospheric carbon dioxide. Impacts vary by commodity and route. For years of naturally occurring low water the impacts are up to 13% higher for even the most moderate climate change scenario. Climate change may also result in a shorter time of ice cover leading to an extension of the navigation season. Climate change is also expected to increase the threat of damage from aquatic invasive species, possibly leading to further requirements for ships to undertake preventive measures.