The Day After Tomorrow

The Hollywood blockbuster The Day After Tomorrow recently hammered home the potential impact of global warming, public awareness of dramatic predictions has been raised again - but how do we know what's fact and what's fiction?

Abstract--by its spectacular special effects, the movie The Day after tomorrow shook the World and made people sensitive to Global Warming phenomenon. Despite the undeniable quality of the film, we have to figure out what is plausible and what is definitely not. To do so, I will first describe what kind of elements maintain our specific atmosphere, then I will present how scientists explain1 the Global Warming phenomenon, its causes and its forecasts. It will be followed by a comparison between accumulated scientific facts and catastrophic scenarios of the film. To finish, I will try to explore a possible hidden aim of the film.

Released on 27 May 2004, The Day After Tomorrow is a fictionalized account of the havoc wreaked by out-of-control climate as North America is beset by the chilling beginnings of a new Ice Age. The movie features numerous catastrophic weather events including hurricanes, tornadoes, floods, and tidal waves striking New York. New York City swings from sweltering to freezing in just one day.

The featured weather extremes, claimed to be the result of a run-away greenhouse effect, create gripping special effects. However, The Day After Tomorrow is fantasy.

The National Center for Atmospheric Research, a federal lab, looks at three of the movie's key scenarios.

Movie scenario:

Temperatures in New York City plummet from sweltering to freezing in hours.

Actual climate change:

Temperatures in parts of the world could drop, but not nearly as rapidly or dramatically as portrayed in the movie. In a warmer world, additional rain at middle and high latitudes, plus melt from glaciers, will add more fresh water to the oceans. This could affect currents, such as the Gulf Stream, that transport heat north from the tropics and might result in parts of North America and Europe becoming relatively cooler. Even if this were to occur, it would take many years or decades because oceans move heat and cold much more slowly than the atmosphere. (Some ocean changes, however, such as the periodic warming of Pacific Ocean waters known as El Niсo, may affect regional weather patterns within weeks.)

Movie scenario:

A massive snowstorm batters New Delhi as an ice age advances south.

Actual climate change:

Although human-related emissions of carbon dioxide and other greenhouse gases might cool some parts of Earth by affecting ocean currents, they cannot trigger a widespread ice age. That is because increased levels of greenhouse gases will increase temperatures across much of the planet. In addition, Earth's orbit is in a different phase than during the peak of the last major ice age 20,000 years ago, and the Northern Hemisphere is receiving more solar energy in the summer than would be associated with another ice age.

Movie scenario:

Tornadoes strike Los Angeles and grapefruit-sized hail falls on Tokyo.

Actual climate change:

Research has shown that climate change might lead to more intense hurricanes and certain other types of storms. In a hotter world, evaporation will happen more quickly, providing the atmosphere with more fuel for storms. In fact, scientists have found this is already happening with rain and snowfall in the United States. But even when scientists run scenarios on the world's most powerful supercomputers, they cannot pinpoint how climate will change in specific places or predict whether Los Angeles or other cities will face violent weather (internet 17),(internet 18),(internet 19),(internet 20),(internet 21).

How likely are the climatic changes portrayed in the movie?

Extremely unlikely, Global warming may cause climate to change abruptly in the future, but the likelihood of this occurring in the next few decades is very low. Abrupt changes in climate have occurred in the geological past, but over decades not days as portrayed in the film. The film also dramatically exaggerates the impacts of the changes. It is not possible for an Ice Age to occur in a few days.

What is abrupt climate change?

Abrupt climate change is a sudden, dramatic departure from the prevailing conditions.

The technical definition is "when the climate system is forced to cross some threshold, triggering a transition to a new state at a rate determined by the climate system itself and faster than the cause". Thus even slow forcing can trigger an abrupt change.

we can think of this as like gently applying pressure to a light switch. Nothing happens until you push with enough force. Then the switch clicks and the light comes on.

What drives abrupt change in climate?

Abrupt climate change can be driven by changes in ocean currents. Europe's climate is warmer than other countries at the same latitude because an ocean current pattern called the overturning circulation, or ocean conveyor, carries heat from low to high latitudes. (The Gulf Stream is part of this global oceanic conveyor belt.) Large floods of fresh water released from melting ice sheets could disrupt the ocean conveyor, decrease ocean heat transport, and cause cooling in Europe and Northern America (internet 1).

Another possible cause of abrupt climate change might be significant release of underground methane as the Siberian permafrost thaws. Methane is a more powerful and faster-acting greenhouse gas than carbon dioxide (internet 2).

Have abrupt climatic changes happened in the past?

Yes. During the last Ice Age (20,000 to 100,000 years ago), temperatures in the northern

Atlantic repeatedly changed by up to 10oC in 10 years.

Less extreme events occurred 8200 years ago, causing cold conditions and widespread drought, and during the so-called Little Ice Age (1300-1850 AD), which caused significant agricultural, economic and political impacts in Europe.

Is abrupt cooling the same as an Ice Age?

Abrupt cooling does not mean the start of another Ice Age. The present orbit of the Earth

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