Climate Change
Climate change is a natural part of earth's history. However, the current rapid climate change is a unique consequence of human activity.
Each year, about 20 billion tons of carbon dioxide (CO2) and other greenhouse gases are released from energy production, cars and factories.
Only half of these CO2 emissions are absorbed naturally by the biosphere. The remaining CO2 stays in the atmosphere for about 100 years, warming the earth's surface.
As a result, there are four major categories of abrupt climate change currently under scientific consideration:
Ice Sheet Collapse | Ocean Acidification | Ocean Thermohaline Shutdown | Methane Release
Ice Sheet Collapse
Most of the world's fresh water is contained in the ice sheets of Greenland and Antarctica--the largest bodies of ice in the world. If the Greenland and West Antarctic ice sheets were to melt, sea level would rise by about 48 feet, flooding most of the world's coastal cities.
Once rapid melting begins, the meltwater lubricates the
ice, creating a likelihood of a "collapse". If the temperature
threshold that initiates a collapse is crossed, catastrophic sea level
rise will be extremely difficult to prevent.
Although the most extreme consequences might not be felt immediately, decisions we make today regarding greenhouse gas emissions will either increase or decrease the likelihood of a collapse.
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Ocean Acidification
The world's oceans absorb about half of the carbon dioxide emitted from the burning of fossil fuels. Because of this, over the past hundred years ocean water has become more acidic. Organisms most severely affected are those which make calcium carbonate shells, such as, corals, crustaceans, mollusks and certain types of plankton. Destabilizing these bottom-of-the-food-chain organisms will affect most marine species, including those we rely on for food.
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Ocean Thermohaline Shutdown
The ocean's thermohaline (thermo-heat, haline-salt, which together determine the density of sea water) circulation system acts as a conveyor belt, distributing warmth from equatorial regions to the north. The best-known example of this is the Gulf Stream. However, if the North Atlantic is flooded with fresh water from melting ice sheets, the Gulf Stream will become less dense, and its circulation might stop.
Without the Gulf Stream, climate would change drastically across much of the Northern Hemisphere.
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Large Scale Methane Release
Along with carbon dioxide, methane is a major greenhouse gas, contributing to climbing temperatures. Much of earth's methane is trapped either in permafrost or in the form of crystals called clathrates on the ocean's continental shelves.
Thus far, the methane is held in place by a combination of cold temperature and water pressure. But, with temperatures on the rise, large-scale methane release could exasperate the already-warming climate.
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