A runaway greenhouse effect is a process in which a net positive feedback between surface temperature and atmospheric opacity increases the strength of the greenhouse effect on a planet until its oceans boil away. An example of this is believed to have happened in the early history of Venus. On the Earth, the IPCC states that "a 'runaway greenhouse effect'—analogous to Venus—appears to have virtually no chance of being induced by anthropogenic activities."
Other, less catastrophic events, that nonetheless can produce a large climate change sometimes are loosely called a "runaway greenhouse" although it is not an appropriate description. For example, it has been hypothesized that large releases of greenhouse gases may have occurred concurrently with the Permian-Triassic extinction event or Paleocene–Eocene Thermal Maximum. Other terms, such as "abrupt climate change", or tipping points could be used when describing such scenarios.
On much longer timescales, such processes can potentially spell the end of life on Earth due to the gradual increase in brightness of the Sun as it expands into a red giant in about one billion years.
Famous quotes containing the words runaway, greenhouse and/or effect:
“The reality is that zero defects in products plus zero pollution plus zero risk on the job is equivalent to maximum growth of government plus zero economic growth plus runaway inflation.”
—Dixie Lee Ray (b. 1924)
“There is not enough exercise in this way of life. I try to make up by active gymnastics before I dress when I get up, by walking rapidly in the lower hall and the greenhouse after each meal for perhaps five to ten minutes, and a good hand rubbing before going to bed. I eat moderately; drink one cup of coffee at breakfast and one cup of tea at lunch and no other stimulant. My health is now, and usually, excellent.”
—Rutherford Birchard Hayes (18221893)
“I have no faith in human perfectability. I think that human exertion will have no appreciable effect upon humanity. Man is now only more activenot more happynor more wise, than he was 6000 years ago.”
—Edgar Allan Poe (18091845)