What Is Global Warming?

Greenland: A Laboratory For The Symptoms Of Global Warming
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The term "global warming" refers to the increase in the average temperature of global surface air and oceans since about 1950, and to continuing increases in those temperatures.

Another term for "global warming" is "climate change."

Per the Intergovernmental Panel on Climate Change, which shared the 2007 Nobel Peace with Al Gore for landmark work on climate change:

"The global surface temperature is an estimate of the global mean surface air temperature.

However, for changes over time, only anomalies... are used, most commonly based on the area-weighted global average of the sea surface temperature anomaly and land surface air temperature anomaly."

Per Wikipedia, "The Intergovernmental Panel on Climate Change (IPCC) concludes that... greenhouse gases are responsible for most of the observed temperature increase since the middle of the twentieth century, and that natural phenomena such as solar variation and volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect afterward.

"These basic conclusions have been endorsed by more than 40 scientific societies and academies of science, including all of the national academies of science of the major industrialized countries."

Greenhouse gases are defined by the IPCC as "gaseous constituents of the atmosphere, both natural and anthropogenic, that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared radiation emitted by the Earth’s surface, the atmosphere itself, and by clouds."

Also, ​read President Obama's Speech at U.N. Climate Change Conference in Copenhagen.

Why Do We Care About Greenhouse Gases?

The IPCC explains "... Greenhouse gases effectively absorb thermal infrared radiation, emitted by the Earth’s surface, by the atmosphere itself due to the same gases, and by clouds.

Atmospheric radiation is emitted to all sides, including downward to the Earth’s surface. Thus, greenhouse gases trap heat within the surface-troposphere system. This is called the greenhouse effect."

Summary of "What Is Global Warming?"

Global warming refers to the increased temperature of Earth's surface, including land, water and near-surface air.

Per most of the scientific community, Earth has warmed significantly since the mid-20th century due to an increase in greenhouse gases that trap heat on Earth.

See other quick-reading articles in this series:

For an in-depth look at "What Is Global Warming," see A Guided Tour Through Global Warming: A Critical and Complex Environmental Issue by Larry West, About.com's Guide to Environmental Issues.