Tuesday, October 27, 2009

The Day After Tomorrow - could it ever happen?

As Professor Hirsch mentioned in class yesterday The Day After Tomorrow is a typical Hollywood exaggeration of the consequences of rising carbon dioxide levels and the effects of a climate shift that would result. For those of you who have yet to see it, the situation is this. Due to a gradual increase in global temperature, oceanic glaciers have continued to melt, allowing more freshwater to enter the ocean. As described yesterday in lecture, adding freshwater to the ocean disrupts natural currents and wind patterns that help maintain a somewhat "homeostasis" of the ocean and weather patterns (picture shown below). In The Day After Tommorow scientists first notice that the temperature in a few spots in the Atlantic ocean decrease rapidly. This temperature drop is the first indication the collapse of the Atlantic thermohaline circulation. In the movie, the collapse of the Atlantc thermohaline circulation launhces the globe into a new ice age, with ice covering nearly the entire Northern Hemisphere in less than a week. But are all aspects of the movie inaccurate?

First, the theory of an abrupt climate shift which occured in The Day After Tomorrow is somewhat accurate and has been proven to occur in the past. One of the most well known and most studied abrupt climate shifts started and ended the the Younger Dryas interval. The interval began with a rapid drop in temperature of about 10 degrees C that began about 12,800 years ago, and ended with a relatively rapid increase in temperature of about 8 degrees celsius which occured in less than a decade. The interval began about 12,800 years ago and ended abruptly about 11,600 years ago, representing a gradual climate shift that lasted nearly 1,200 years. So, the first and probably most obvious inaccuracy of The Day After Tomorrow is the speed of the global climate shift. Evidence shows that a global climate shift could not occur as fast as a week, rather it would occur gradually over thousands of years. But the overall aspect of a climate shift is accurate in that past abrupt climate changes have been especially common when the climate system itself was being rapidly altered.

Although it is not clearly known what exactly caused the abrupt climate shift of the Younger Dryas, a shutdown of the North Atlantic circulation is considered to be an unlikely cause. According to the National Academies, "A shutdown of the circulation would not induce a new glacial period, but it would cause major changes both in the ocean (major circulation regimes, upwelling and sinking regions, distribution of seasonal sea ice, ecological systems, and sea level)and in the atmosphere (land-sea temperature contrast, and the intensity, frequency, and paths of storms)." So the collapse of the North Atlantic circulation might not cause a new global ice age.

One aspect of The Day After Tomorrow is not inaccurate, but rather simply exaggerated. In the movie, the sea level rose about 50 feet in a matter of seconds, destroying New York City. What appeared to be a tsunami, was instead the outcome of rising sea levels. Again, the speed of this action was exaggerated. In the movie, the sea level rose in a matter of seconds, but in reality, it would take centuries. But, the rise in sea level due to global warming is not inaccurate. In fact, the sea level has been rising in many global areas, but at a speed that is not noticable. Increasing emissions and an overall rise in temperture would lead to a large rise in sea level. Shown below is a picture of the outcome of a rise in sea level of about 1 meter, which according to the Department of Geosciences, is believed to happen during this century.

So, although the movie was blown way out of proportion, the aspect of an induced abrupt climate shift resulting in a rise in global sea levels, is believed to be accurate. Although we are not likely to see any of these major changes in our lifetime, we should act as soon as possible to decrease our emissions.

1 comment:

  1. It may all just seem like a exaggeration but for some people it is very real there houses have been destroyed by hurricanes that were unexplainable, flashfloods that could have been prevented if only we knew the infomation we needed but it was to late, other people not just my self need to know more and we need to know it now.