Essay Instructions: Hollywood and Science: The Day After Tomorrow - deadline is BEFORE Midterm 2 (26th Feb)
Hollywood has always been keen on disaster films and certain features of earth system science that we will study in the class form the basis for disaster scenarios. However, the real science usually isn't exciting enough for Hollywood so they tend to make movies more dramatic by wildly exaggerating certain aspects or by simply making stuff up! With your new knowledge of earth system science take a new look at this movie and see how good a job you think the screenwriters and special effects team did.
To earn the full 5 extra credit points for each movie:
- read over my brief review of the 'good' and 'bad' science in the movie
- write one or two paragraphs (or more if you like) saying what you thought of the film, whether you think the film helped public understanding of science, whether knowing more about the science made you enjoy it more or has it spoiled it?
- answer the quick multiple choice questions (correctly!)
Hollywood and Science: The Good, The Bad and The Wildly Exaggerated
The Day After Tomorrow
This film is really a good example of ‘The Wildly Exaggerated’ category which is based on good science but takes considerable artistic license to make it more exciting for the audience!
Good science:
At the very beginning of the film we see some scientists taking ice cores on an ice-shelf on Antarctica. Ice-cores from Antarctica have given us huge amounts of vital information about past climate such as atmosphere composition and temperature although we don’t usually take cores from ice shelves!
Ice shelves do break apart and drift away although it does not happen instantly without any signs on the surface as seen in the film. Funnily enough, the break-up of this ice shelf (the Larsen B ice shelf on Antarctica) was written into the script of the film before it actually broke up in real life. The ice shelf, which was indeed the size of Rhode Island (3,250km2 and 220m thick), broke up over 3 weeks or so and disappeared over a season. It had been there for over 12,000 years. Collapses of these big ice shelves are expected with the warming of ocean and air temperatures at high latitudes due to climate change.
The fundamental concept behind the movie has a firm basis in fact. Abrupt climate change (over a decade or so) can occur due to abrupt slowing or shutdowns of the thermohaline circulation in the North Atlantic Ocean. In the North Atlanic, the Gulf Stream (an intensified western boundary current forming part of the North Atlantic gyre) brings warm salty water north where some of it subsequently cools, becomes more dense and sinks to form North Atlantic Deep Water (NADW). This formation of NADW, and so the flow of the Gulf Stream and thermohaline circulation, can be slowed or stopped by the input of large volumes of freshwater into the North Atlantic, for example by melting ice. The freshwater reduces the salinity and therefore the density of the water so that it cannot sink. This results in dramatic drops in temperature around the North Atlantic of up to 9oC. Evidence for such abrupt changes in thermohaline circulation in the past can be found in sediment records and ice cores. The most recent examples is the Younger Dryas (~11,000 years ago).
We do have buoys and other instruments throughout our oceans which record ocean temperatures and salinities and beam information back to scientists on land.
Wildly exaggerated
It is not possible for such changes in the thermohaline circulation to happen over a few days as seen in the movie. When we talk about ‘abrupt’ climate change, we really mean changes that occur over a decade or so. While the atmosphere warms and cools on the scale of hours (the morning is cooler than mid-day, for example) a change in ocean circulation that would trigger a climate effect would take place over much longer because of its immense volume and the heat capacity of water (which means that it gains and loses heat very slowly). Huge ice sheets and glaciers also cannot melt away or reform in a matter of weeks.
It is thought to be very unlikely that a complete shutdown of the thermohaline circulation could happen today as a result of increased melting of ice due to climate change. However, it is entirely possible that the circulation could slow or change over the next decades as a result of increased freshwater imputs in the North Atlantic.
Even if an abrupt shutdown in the thermohaline circulation were to occur, this would not cause a global ice age but rather just regional cooling. This is especially true today when our CO2 levels are much higher than during the last ice age causing higher global temperatures over most of the world. We would not see snow in India for example if the circulation were to stop!
Bad science
Unsurprisingly, most of the really bad science in the movie is related to the dramatic weather events which result from the unrealistic timescale of the change in ocean circulation.
Tornadoes Hit Los Angeles. California has never experienced a tornado higher than an F1 on the Fujita Scale nor has anyone ever died as a result of one.
A 300-foot high storm surge whipped up by the intense winds of the superstorm smashes through Manhattan.
A storm surge does not arrive as a single, giant wave but typically as a rise in water over a period of a few hours. The wave seen in the movie is more like a tsunami that results from an earthquake or submarine landslide.
Storm surges along the coast are caused by the onshore winds pushing water against the land. A storm approaching from the north would have the wrong wind direction to create a surge in Manhattan. It would tend to move the surge out to sea, not landward. Also, the winds needed to create a storm surge of this magnitude are probably at least twice the speed of sound (1200 mph)! Hurricane Sandy caused a storm surge of about 13ft in Manhattan because it was moving from the south/east and unfortunately the sea wall designed to protect the city was just too low and so flooding resulted.
The force of the flow of water against buildings would immediately implode all submerged windows along with sections of wall leaving behind complete devastation with very little left standing, including the Statue of Liberty.
Super Cell hurricanes move down from the Arctic bringing freezing, sub-zero temperatures across massive continents killing everything in seconds.
Hurricanes gather strength from latent heat energy released when water vapor condenses into rain and so require moisture from warm, tropical ocean waters to form. They lose strength over land, and when the air or water temperature falls below tropical levels. Hurricanes cannot form in the Arctic. The superstorms are also shown in many scenes to be rotating clockwise, and in other scenes counter-clockwise. As you will remember from our lectures, due to the Coriolis force, all low-pressure systems (cyclones) in the northern hemisphere would rotate counter-clockwise.
The superstorm is an intense low pressure system so air flows into the low pressure zone at the ground and so air should move upwards (cooling and creating clouds). However, in the movie the superstorm supposedly sucks huge quantities of very cold air down from the troposphere to the surface, flash freezing anything caught outside. Even if this wasn’t the wrong way round, as you will remember from our lectures, air warms as it sinks and so air sinking from the troposphere would not be able to flash freeze anything. It does not matter how quickly it is descending ??" it is a fundamental law of physics that the air will warm up!
Please print or e-mail this page to me along with your review of the film.
Suggestions for your 2 paragraph review:
Do you think the writers improved public understanding of science or did damage to it?
Do you think that Hollywood should bother trying to get the science right?
Did you learn anything from the film?
How good a job do you think the special effects team did?
Does knowing more about the science mean that the film is spoiled for you now or do you still enjoy it?
Questions?1. The fundamental idea behind the movie is good science because:
North Atlantic Deep Water formation is sensitive to freshwater inputs and has been shown to slow or shut down in the past
Earth’s orbit means we should be expecting a new ice age
Antarctic Bottom Water can rise to the surface in the North Atlantic and would cause Europe and North America to get much colder
2. Circle/highlight all the factors below would cause density of North Atlantic surface waters to decrease ??" preventing deep water formation?
a) increase in temperature
b) increase in sea ice formation
c) decrease in temperature
d) increase in freshwater inputs from melting ice
3. The main flaw in this film is that the thermohaline circulation cannot change over only a few days as seen in the movie. This is because:
a) the oceans do not respond to changes in the amount of freshwater input
b) the atmosphere cannot change over the timescale of a few days
c) the volume of the oceans is huge and water has a high heat capacity
d) the volume of the oceans is huge and water has a low heat capacity
4. Which of the following statements is FALSE.
a) Hurricanes only form over the sea in tropical regions.
b) A 300 ft ‘wind-driven storm surge’ would require winds of over 1200 mph
c) The Gulf Stream current is responsible for moving warm, salty water from the North Atlantic back to the Equator
d) Only a large tsunami could result in the type of wave seen in the movie but the Atlantic Ocean is surrounded by passive continental margins so this is not likely.
5. A northern-hemisphere hurricane is a:
a) High pressure system where air circulates counter-clockwise due to Ekman transport
b) Low pressure system where air circulates clockwise due to Ekman transport
c) Low pressure system where air circulates counter-clockwise due to the Coriolis force
d) High pressure system where air circulates counter-clockwise due to the Coriolis force
6. If the thermohaline circulation were to shut down:
a) There would be strong regional cooling around the North Atlantic
b) There would be strong global warming
c) There would be global cooling
d) Large icesheets would reform rapidly all around the northern hemisphere over a decade or less
There are faxes for this order.
