Past Events
Several periods of abrupt climate change have been identified in the paleoclimatic record. Notable examples include:
- About 25 climate shifts, called Dansgaard-Oeschger cycles, which have been identified in the ice core record during the glacial period over the past 100,000 years. The most recent of these events was the Younger Dryas which began 12,900 years ago and moved back into a warm-and-wet climate regime about 11,600 years ago.
- The Younger Dryas event, notably its sudden end. It has been suggested that: "The extreme rapidity of these changes in a variable that directly represents regional climate implies that the events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the North Atlantic climate system." A model for this event based on disruption to the thermohaline circulation has been supported by other studies.
- The Paleocene-Eocene Thermal Maximum, timed at 55 million years ago, which may have been caused by the clathrate gun effect, although potential alternative mechanisms have been identified. This was associated with rapid ocean acidification
- The Permian-Triassic Extinction Event, also known as the great dying, in which up to 95% of all species became extinct, has been hypothesized to be related to a rapid change in global climate. Life on land took 30 million years to recover.
- The Carboniferous Rainforest Collapse occurred 300 million years ago, at which time tropical rainforests were devastated by climate change. The cooler, drier climate had a severe effect on the biodiversity of amphibians, the primary form of vertebrate life on land.
There are also abrupt climate changes associated with the catastrophic draining of glacial lakes. One example of this is the 8.2 kiloyear event, which associated with the draining of Glacial Lake Agassiz. Another example is the Antarctic Cold Reversal, c. 14,500 years before present (BP), which is believed to have been caused by a meltwater pulse from the Antarctic ice sheet. These rapid meltwater release events have been hypothesized as a cause for Dansgaard-Oeschger cycles,
Read more about this topic: Abrupt Climate Change
Famous quotes containing the word events:
“We have defined a story as a narrative of events arranged in their time-sequence. A plot is also a narrative of events, the emphasis falling on causality. “The king died and then the queen died” is a story. “The king died, and then the queen died of grief” is a plot. The time sequence is preserved, but the sense of causality overshadows it.”
—E.M. (Edward Morgan)
“Just as a mirror may be used to reflect images, so ancient events may be used to understand the present.”
—Chinese proverb.