[THS] Climate Tipping Points May Arrive Without Warning

[Peter Webster]

http://www.physorg.com/news184963823.html

Climate 'Tipping Points' May Arrive Without Warning, Says Top Forecaster
February 9, 2010 Climate 'Tipping Points' May Arrive Without Warning, Says Top
Forecaster

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This graphic shows the extent of Arctic sea ice in September 2009 (in white)
compared with the median ice extent for September from 1979 to 2000 (in magenta).
(U.S. National Snow and Ice Data Center/map)

(PhysOrg.com) -- A new University of California, Davis, study by a top ecological
forecaster says it is harder than experts thought to predict when sudden shifts in
Earth's natural systems will occur -- a worrisome finding for scientists trying to
identify the tipping points that could push climate change into an irreparable global
disaster.

"Many scientists are looking for the warning signs that herald sudden changes in
natural systems, in hopes of forestalling those changes, or improving our
preparations for them," said UC Davis theoretical ecologist Alan Hastings. "Our new
study found, unfortunately, that regime shifts with potentially large consequences
can happen without warning -- systems can 'tip' precipitously.

"This means that some effects of global climate change on ecosystems can be seen
only once the effects are dramatic. By that point returning the system to a desirable
state will be difficult, if not impossible."

The current study focuses on models from ecology, but its findings may be applicable
to other complex systems, especially ones involving human dynamics such as
harvesting of fish stocks or financial markets.

Hastings, a professor in the UC Davis Department of Environmental Science and
Policy, is one of the world's top experts in using mathematical models (sets of
equations) to understand natural systems. His current studies range from researching
the dynamics of salmon and cod populations to modeling plant and animal species'
response to global climate change.

In 2006, Hastings received the Robert H. MacArthur Award, the highest honor given
by the Ecological Society of America.

Hastings' collaborator and co-author on the new study, Derin Wysham, was
previously a postdoctoral scholar at UC Davis and is now a research scientist in the
Department of Computational and Systems Biology at the John Innes Center in
Norwich, England.

Scientists widely agree that global climate change is already causing major
environmental effects, such as changes in the frequency and intensity of
precipitation, droughts, heat waves and wildfires; rising sea level; water shortages in
arid regions; new and larger pest outbreaks afflicting crops and forests; and
expanding ranges for tropical pathogens that cause human illness.

And they fear that worse is in store. As U.S. presidential science adviser John Holdren
(not an author of the new UC Davis study) recently told a congressional committee:
"Climate scientists worry about 'tipping points' ... thresholds beyond which a small
additional increase in average temperature or some associated climate variable
results in major changes to the affected system."

Among the tipping points Holdren listed were: the complete disappearance of Arctic
sea ice in summer, leading to drastic changes in ocean circulation and climate
patterns across the whole Northern Hemisphere; acceleration of ice loss from the
Greenland and Antarctic ice sheets, driving rates of sea-level increase to 6 feet or
more per century; and ocean acidification from carbon dioxide absorption, causing
massive disruption in ocean food webs.

More information: The study, "Regime shifts in ecological systems can occur with no
warning," was published online today by the journal Ecology Letters, in its Early View
feature: http://www3.interscience.wiley.com/journal/123276879/abstract .

Provided by University of California - Davis