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Global warming is an increase in the earth's temperature due to the use of fossil fuels and other industrial processes leading to a build-up of "greenhouse gases" (carbon dioxide, methane, nitrous oxide) in the atmosphere. It has been known since 1896 that carbon dioxide helps stop the sun's infrared radiation from escaping into space and thus functions to maintain the Earth's relatively warm temperature (this is called the greenhouse effect). The question is whether the increasing levels of carbon dioxide in the atmosphere will lead to elevated global temperatures, which could result major climatic changes, and have serious problems for agricultural productivity.