“The Day After Tomorrow” 2004/Fox Pictures/Roland Emmirch

You watched the movie, here is the real dope.

Yes, global warming is indeed a reality. The temperature of the earth went up by about half a degree Celsius in the last century. That might not seem much really, but it creates quite a domino effect, affecting the whole climatic system.

Basically the atmosphere is like an insulating blanket, which maintains a comfortable temperature on earth (28-33 deg Celsius, yes what we generally and approximately refer to as room temperature). With automobiles and other energy guzzlers, continually burning fossil fuels, a lot of carbon gases are being added to the atmosphere, this addition is further accentuated by rampant deforestation. Effectively the burning of energy sources from below the earth surface (coal for example) is increasing the energy above the earth’s surface. (Remember the Law of conservation of Energy).

The increased temperature makes the water in the oceans expand; this raises the ocean levels, creating bigger stronger waves. The increased energy in the oceans, leads to more frequent storms, and storm like activity – unpredictable, rough and extreme weather.

Ocean water is in continual motion, it doesn’t move in random patterns. In fact it flows very much like a river, i.e. bodies of water flow from one region to another, so as to maintain a balance in the system. Environmentally 'Currents' are the whole system of water flow in our Oceans, which maintain a critical climatic balance.

One branch of this Current system is the North Atlantic Current, which dissipates heat as it travels from the tropics to the Polar Regions. Now because the flowing water continually dissipates heat, it becomes cooler and its effective salinity/density increases.
Focusing on the salinity, the currents salinity increases as its temperature decreases, and by the time it has traveled from the tropics to the Polar Regions, it reaches its maximum Salinity or “Critical Salinity”. This attaining of Critical Salinity(Increased density) is of vital importance, as it causes the current to sink to the ocean floor and flow back to the tropics. During this return journey it absorbs heat, effectively moderating the temperatures at the tropics. So as is evident, the attainment of this “Critical Salinity”, actually maintains a temperature/climate balance between the tropics and Polar Regions. Ensuring that the Polar Regions don’t get TOO cold, and the Tropics TOO warm.

Now with Global warming, the glaciers in the Polar Regions will melt adding FRESH WATER (Non-saline water) to the Oceans. This extra fresh water will PREVENT the North Atlantic Current attain “Critical Salinity”. Hence the North Atlantic Current will NOT sink to the ocean floor and will NOT flow back and forth from the tropics. Hence the whole Current system will go awry. This ‘failure’ of the North Atlantic Current will actually drive down the temperature of the Polar Regions greatly, and yes hurtle the earth towards an Ice Age.

The North Atlantic Current has failed twice in recorded/studied history of the world, 8200 years and 12700 years ago. And yes these were our two Ice Ages.