Global warming is a phenomenon of the 20th and 21st centuries that deviates from Earth's normal global warming and cooling cycles brought about over millennium, not over centuries, that respond to amounts of CO2 and oxygen in the atmosphere; to variations in the Sun's energy cycles; and to subtle shifts in Earth's orbit.
Global warming is the rapid rise in temperatures across the entire globe that is a result of increased levels of greenhouse gases, primarily carbon dioxide (CO2) and methane (CH4), in Earth's nearest atmospheric layer, the Troposphere. These gases are produced from burning fossil fuels, such as coal burning in industry, and burning forests in deforestation, which has a compound effect of adding greenhouse gases through burning while reducing the greenhouse gas filters forest basins provide.
Global climate change is a result of global warming and is the present concern of greatest focus as events like the rapid breaking up of Arctic and Antarctic ice sheets adds fresh ice water to the ocean's warm salt water. Global mean surface temperature has risen from about -0.35 in 1880 to about +0.55 in 2010.