Far worse than the current and expected global warming is the possibility of abrupt climate change. Feedback mechanisms may cause the current warming to become runaway. Should this happen mankind's survival may not be possible.
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An abrupt climate change occurs when the climate system is forced to transition to a new climate state at a rate that is determined by the climate system energy-balance, and which is more rapid than the rate of change of the external forcing.[1] Past events include the end of the Carboniferous Rainforest Collapse,[2] Younger Dryas,[3] Dansgaard-Oeschger events, Heinrich events and possibly also the Paleocene-Eocene thermal maximum.[4] The term is also used within the context of global warming to describe sudden climate change that is detectable over the time-scale of a human lifetime. One proposed reason for the observed abrupt climate change is that feedback loops within the climate system both enhance small perturbations and cause a variety of stable states.[5]
Timescales of events described as 'abrupt' may vary dramatically. Changes recorded in the climate of Greenland at the end of the Younger Dryas, as measured by ice-cores, imply a sudden warming of +10°C within a timescale of a few years.[6] Other abrupt changes are the +4 °C on Greenland 11,270 years ago[7] or the abrupt +6 °C warming 22 000 years ago on Antarctica.[8] By contrast, the Paleocene-Eocene Thermal Maximum may have initiated anywhere between a few decades and several thousand years. Finally, Earth Systems models project that under ongoing greenhouse gas emissions as early as 2047, the Earth's near surface temperature could depart from the range of variability in the last 150 years, affecting over 3 billion people and most places of great species diversity on Earth.[9]
The IPCC states that global warming "could lead to some effects that are abrupt or irreversible".[11]
In an article in Science, Alley et al. said "it is conceivable that human forcing of climate change is increasing the probability of large, abrupt events. Were such an event to recur, the economic and ecological impacts could be large and potentially serious."[12]
A 2013 report from the U.S. National Research Council called for attention to the abrupt impacts of climate change, stating that even steady, gradual change in the physical climate system can have abrupt impacts elsewhere—in human infrastructure and ecosystems for example—if critical thresholds are crossed. The report emphasizes the need for an early warning system that could help society better anticipate sudden changes and emerging impacts.[13]
One source of abrupt climate change effects is a feedback process, in which a warming event causes a change which leads to further warming. This can also apply to cooling. Example of such feedback processes are:
http://en.wikipedia.org/wiki/Abrupt_climate_change#Current_situation
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An abrupt climate change occurs when the climate system is forced to transition to a new climate state at a rate that is determined by the climate system energy-balance, and which is more rapid than the rate of change of the external forcing.[1] Past events include the end of the Carboniferous Rainforest Collapse,[2] Younger Dryas,[3] Dansgaard-Oeschger events, Heinrich events and possibly also the Paleocene-Eocene thermal maximum.[4] The term is also used within the context of global warming to describe sudden climate change that is detectable over the time-scale of a human lifetime. One proposed reason for the observed abrupt climate change is that feedback loops within the climate system both enhance small perturbations and cause a variety of stable states.[5]
Timescales of events described as 'abrupt' may vary dramatically. Changes recorded in the climate of Greenland at the end of the Younger Dryas, as measured by ice-cores, imply a sudden warming of +10°C within a timescale of a few years.[6] Other abrupt changes are the +4 °C on Greenland 11,270 years ago[7] or the abrupt +6 °C warming 22 000 years ago on Antarctica.[8] By contrast, the Paleocene-Eocene Thermal Maximum may have initiated anywhere between a few decades and several thousand years. Finally, Earth Systems models project that under ongoing greenhouse gas emissions as early as 2047, the Earth's near surface temperature could depart from the range of variability in the last 150 years, affecting over 3 billion people and most places of great species diversity on Earth.[9]
The IPCC states that global warming "could lead to some effects that are abrupt or irreversible".[11]
In an article in Science, Alley et al. said "it is conceivable that human forcing of climate change is increasing the probability of large, abrupt events. Were such an event to recur, the economic and ecological impacts could be large and potentially serious."[12]
A 2013 report from the U.S. National Research Council called for attention to the abrupt impacts of climate change, stating that even steady, gradual change in the physical climate system can have abrupt impacts elsewhere—in human infrastructure and ecosystems for example—if critical thresholds are crossed. The report emphasizes the need for an early warning system that could help society better anticipate sudden changes and emerging impacts.[13]
One source of abrupt climate change effects is a feedback process, in which a warming event causes a change which leads to further warming. This can also apply to cooling. Example of such feedback processes are:
- Ice-albedo feedback, where the advance or retreat of ice cover alters the 'whiteness' of the earth, and its ability to absorb the sun's energy[20]
- The dying and burning of forests, as a result of global warming[21]
http://en.wikipedia.org/wiki/Abrupt_climate_change#Current_situation
