Abrupt Climate Change Inevitable Surprises (2002) / Chapter Skim
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4 Global Warming as a Possible Trigger for Abrupt Climate Change
4 Global Warming as a Possible Trigger for Abrupt Climate Change
Pages 107-117
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From page 107... ...
It is probably no coincidence that stability of the climate increased when ice-sheet size and atmospheric carbon dioxide concentration largely leveled off at the end of the ice age. Greenhouse gases are accumulating in the earth's atmosphere and causing surface air temperatures and subsurface ocean temperatures to rise.
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From page 108... ...
More research is needed to better understand the relationship between human influences on climate, especially global warming, and possible abrupt climate change. CHANGES IN NORTH ATLANTIC THERMOHALINE CIRCULATION A question of great societal relevance is whether the North Atlantic THC will remain stable under the global warming expected for the next few
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From page 109... ...
A possible shutdown of the THC would not induce a new glacial period, as press reports suggested; however, it clearly would involve massive changes both in the ocean (major circulation regimes, upwelling and sinking regions, distribution of seasonal sea ice, ecological systems, sea level) and in the atmosphere (land-sea temperature contrast, storm paths, hydrological cycle, extreme events)
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From page 110... ...
The exceptions to this behavior remind us of the inherent uncertainties present in the simulations. It is not clear whether all relevant feedback mechanisms are considered properly in the current generation of climate models and whether their strength is simulated realistically.
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From page 111... ...
The threshold is approached by a prescribed global warming over about 140 years, equivalent to a doubling of carbon dioxide. Small random fluctuations, as produced by atmospheric disturbances at the ocean surface, can excite large changes in the THC when the system is close to a threshold (Figure 4.1~.
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From page 112... ...
It has been suggested that this change in mode may be a re.~nnn.~e of the tronic~l Pacific to ~nthronn~enic warming ~Trenherth any -r ~~ -- - -- fir -- I- - A -- -- - -A A -- -- -- Or ~~Hoar, 1996~. Comprehensive climate models have just started to include credible representations of ENSO, which makes available tools to investigate the possible responses of the tropical Pacific atmosphere-ocean system to climate change.
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From page 113... ...
POSSIBLE FUTURE ABRUPT CHANGES IN THE HYDROLOGICAL CYCLE One of the most striking predictions of climate models and theory is that global warming will put more moisture into the atmosphere in the tropics and generally accelerate freshwater transport to higher latitudes. Melting of land-fast ice, sea ice, and permafrost and biological or geological
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From page 114... ...
On the basis of the inference from the paleoclimatic record, it is possible that the projected changes will occur not through gradual evolution proportional to greenhouse-gas concentrations, but through abrupt and persistent regime shifts affecting subcontinental or larger regions. The inability to conduct long simulations with coupled models validated against paleoclimatic records, owing to resource limitations, leaves many uncer.
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From page 115... ...
, but behavior in other models is more stable (Hulbe and Payne, 2001~. The major southern sites of formation of oceanic deep-waters are close to the West Antarctic ice sheet, and deep-water formation involves interaction with floating extensions of the ice sheet called ice shelves (e.g., Schlosser et al., 1994~.
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From page 116... ...
sensitivity possibly linked to overly coarse resolution or other shortcomings rather than from improper specification of forcing, future climate anomalies could be surprisingly large. Even if no net cooling results from a substantial, abrupt change in the Atlantic THC, the changes in water properties and regional circulation are expected to be large, with possibly large effects on ecosystems, fisheries, and sea level.
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From page 117... ...
The result from Cuffey and Marshall (2000) that modest warming above recent conditions during the previous interglacial led to major shrinkage of the Greenland ice sheet suggests that large changes in Greenland are likely in the future.
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