In a recent News article on the "end-of-century" weather forecast, there may be far more certainty inferred in global climate models than can be supported by science. While the evidence of current global warming is quite convincing, projections that "this area will be 5 to 12 degrees warmer in the winter and 7 to 14 degrees warmer in the summer" by the end of the century are another matter entirely.
A recent study published by the National Academy of Sciences points to a scenario that can, ironically, be caused by global warming and have quite the opposite effect for the Great Lakes. There is a large body of evidence that rapid climate change in the past has occurred several times during periods of global warming.
The "Little Ice Age" that began 500 years ago and lasted nearly 300 years was likely brought on by a reduction in North Atlantic salinity due to meltwater from shrinking glaciers and ice sheets. The melting, of course, was caused by warming. However, the influx of fresh water from that melting caused a reduction in the sinking of dense, very salty water in the North Atlantic.
This water's sinking and spreading southward is part of a great oceanic conveyer current that is responsible for driving the Gulf Stream. Such a slowing or stopping of the Gulf Stream has happened in the past and can occur in a period of a decade or less. When this occurs, the modifying effects of the Gulf Stream can disappear, in which case, much of eastern North America and western Europe fall into patterns that can mimic or be even far worse than the immediate past winter. A succession of such winters would allow new glacial expansion, and send our part of the world into an icy tailspin that could last more than a century, while other parts of the world experienced continued warming and drought.
The bottom line: No one should be attaching an undeserved certainty to regional climate change based on global models that do not take into account adequately such an important variable as North Atlantic salinity and solid paleoclimatological data from known past events.
Chief Meteorologist, WIVB