Mega-Storms and Movies

In a rather silly Harrison Ford movie that came out a few years ago, The Day After Tomorrow, the story begins with a huge hurricane forming over Scotland, then turning overnight into an icy freeze that transforms New York City into the arctic.  Ford, ever the scientist adventurer, has to rescue his daughter from a wolf pack, escaped from the zoo, before trekking off with a good part of the U.S. population, including the President, to Mexico, where they are welcomed as refugees.  As noted, the movie is quite silly, but not as silly as it might seem.  It merited a scientific analysis a few months later in Scientific American, which deals very seriously with science,  that found it contains the kernels of  some very serious science.  That science is known as tipping point theory, which describes a very controversial but possible outcome of global climate change.

The thing that made the story line of the movie just plausible enough for a movie plot, but also incredibly silly, was an overnight change in global climate which instantaneously converted NYC to the arctic.  Global climate just cannot change that quickly.  But, according to Scientific American, core drilling in the arctic ice cap reveals that temperatures have dropped by about 20 degrees, indicating the advent of an ice age, at least 4 times in our geologic history, suddenly, in a period of 20 to 40 years.  Scientists theorize a specific set of circumstances leading to such a “tipping point.”  The key is the performance of the Gulf Stream.  The Gulf Stream is a major part of the “ocean conveyer belt” which operates by convection to transfer heat between the tropics and the arctic.  Many people do not realize that Paris and London actually lie north of Quebec, Canada.  The reason there is no London or Paris Ice Festival is that the Gulf Stream keeps them, along with the rest of Western Europe and the northeastern U.S., warm enough to grow roses where in theory roses should not be.  The Gulf Stream is a heat pump which cools the tropics to warm Europe, then transfers back the cooled water to the tropics via the Polar Current. It relies on the salinity of cold water to keep it going. And that’s where the problem and the controversy arise.  Tipping point theory notes that global warming causes arctic ice masses, particularly the Greenland ice cap, to melt, diluting the salinity of the ocean at a key point with freshly melted glacier water.  That can cause the ocean conveyer to grind to a halt, putting all the burden of heat transfer onto atmospheric events like hurricanes, and leading to a period of sharp division between warming tropic areas and increasingly icy polar areas.  That period can last several hundred years, as seen in ice core samples from the arctic.  It can turn areas like New England or Western Europe into places more like Mongolia, while converting areas like the U.S. mid-Atlantic regions into atmospheric battle grounds between heat and cold that result in extreme weather events.  If it happens too fast, it can generate an ice age before a new level of stability is reached. 

Slowing of the Gulf Stream was first reported about 2004; then, in 2010 contradictory reports came out, claiming the slowing was a myth.  More recently, in 2012, the U.S. Geologic Survey published data indicating that not only was slowing of the Gulf Stream occurring, the pace of the slowing is actually speeding up.  As usual with the subject of climate change, the controversy rages on while no actions are taken.

Which brings me to hurricane Sandy, building up outside my window as I write.  Sandy is being described as a “mega-storm” involving a hurricane merging with a cold front from the west and wrapped around with an arctic front from the north.  It’s declared to be so large that it will cover the eastern U.S from Ohio to the Atlantic and from North Carolina to Michigan.  Meteorologists are describing it as a “once in 500 years event.”  I hope they are right.