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Causes of Global Warming

For decades, scientists have analyzed global warming by tracking events and natural cycles that influence climate but were unable to fully explain the observed patterns of global warming until the effect of greenhouse gases (GHGs) emitted by humans was discovered.

Several greenhouse gases emitted by humans in different ways are responsible for climate change. Most greenhouse gases are released into the atmosphere through the burning of fossil fuels like gas, oil or coal that power factories, cars and the production of electricity. When these fossil fuels are burned, they combine with oxygen in the atmosphere to create carbon dioxide, the gas that is responsible for most global warming. Other greenhouse gases include nitrous oxide emitted from fertilizers, biomass burning and soil cultivation; methane that stems from agriculture, manure management and landfills; and various gases used in industrial and refrigeration processes.These greenhouse gases act as a blanket for the Earth.

Sunlight passes through the atmosphere to warm the planet. Normally, the heat then radiates back toward space; however, the high levels of greenhouse gas molecules emitted by human activities now absorb most of the heat and transfer it in all directions. The result is increased temperatures in the lower atmosphere and on Earth.

The ability of greenhouse gases to trap heat varies. For instance, one molecule of methane has 20 times the heat-trapping ability of one molecule of carbon dioxide. One molecule of nitrous oxide is 300 times more dangerous than one molecule of carbon dioxide. Very powerful greenhouse gases like chlorofluorocarbons have been banned in many parts of the world because their heat-trapping ability is thousands of times greater than that of carbon dioxide. Although many greenhouses gases are more powerful than carbon dioxide, they are emitted in far smaller quantities and therefore do not contribute to global warming as much carbon dioxide.