When did global warming start?

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Global Warming Started Long Before Industrial Revolution

People may have begun altering the world's climate as early as 8,000 years ago, says William Ruddiman, a climate scientist with the University of Virginia.

The data show that after the end of the last ice age, about 8,000 years ago, levels of carbon dioxide mysteriously started rising at a time when they should have been dropping.

The same holds true for methane levels from about 5,000 years ago.

Other researchers have tried to attribute those changes to natural causes. According to Ruddiman, however, humans are to blame. He says the following coincidences of timing support his theory:

People started clearing forests for pastures and cropland -- a process that puts more carbon dioxide into the atmosphere -- about 8,000 years ago in Europe and Asia.

People also started raising livestock and flooding rice paddies -- processes that emit methane -- about 5,000 years ago in Asia. Still, Ruddiman says, the work doesn't change the prevailing scientific opinion about greenhouse gases today -- that over the last 150 years, human activities have built up enough of them in the atmosphere to contribute noticeably to the observed global warming.

However the biggest increase was in the 1800s due to the industrial revolution.

See also:

Source: Alexandra Witze, "Theory: Global warming older than we thought," Dallas Morning News, December 10, 2003 and Andrew Bridges, "Scientists Measure Human Impact on Climate," Associated Press, December 10, 2003; based upon Thomas J. Crowley, "When Did Global Warming Start?", Climatic Change, Vol. 61, Issue 3, December 2003.

What is global warming?

What Global Warming Is
As a definition, 'global warming' is the rising of temperature on Earth's surface and atmosphere. This definition has been applied to a controversial issue about why and how that increase in temperature is happening.


Global Warming is the result of not paying attention to the signs, it is the gradual increase in global temperature caused by the emission of gases that trap the sun's heat in the Earth's atmosphere. Gases that contribute to global warming include carbon dioxide, methane, nitrous oxides, chlorofluorocarbons (CFCs), and halocarbons (the replacements for CFCs). The carbon dioxide emissions are primarily caused by the use of fossil fuels for energy.

Global warming is an observed increase in the average temperature of the Earth's atmosphere and oceans. Part of this increase may be due to natural processes, such as the solar cycle, and would have occurred independently of human activity.