A new University of California, Davis, study by a top ecologicalforecaster says it is harder than experts thought to predict whensudden shifts in Earth's natural systems will occur -- a worrisomefinding for scientists trying to identify the tipping points thatcould push climate change into an irreparable global disaster.
"Many scientists are looking for the warning signs that herald suddenchanges in natural systems, in hopes of forestalling those changes,or improving our preparations for them," said UC Davis theoreticalecologist Alan Hastings. "Our new study found, unfortunately, thatregime shifts with potentially large consequences can happen withoutwarning -- systems can 'tip' precipitously.
"This means that some effects of global climate change on ecosystemscan be seen only once the effects are dramatic. By that pointreturning the system to a desirable state will be difficult, if notimpossible."
The current study focuses on models from ecology, but its findingsmay be applicable to other complex systems, especially ones involvinghuman dynamics such as harvesting of fish stocks or financial markets.
Hastings, a professor in the UC Davis Department of EnvironmentalScience and Policy, is one of the world's top experts in usingmathematical models (sets of equations) to understand naturalsystems. His current studies range from researching the dynamics ofsalmon and cod populations to modeling plant and animal species'response to global climate change.
In 2006, Hastings received the Robert H. MacArthur Award, the highesthonor 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 aresearch scientist in the Department of Computational and SystemsBiology at the John Innes Center in Norwich, England.
Scientists widely agree that global climate change is already causingmajor environmental effects, such as changes in the frequency andintensity of precipitation, droughts, heat waves and wildfires;rising sea level; water shortages in arid regions; new and largerpest outbreaks afflicting crops and forests; and expanding ranges fortropical pathogens that cause human illness.
And they fear that worse is in store. As U.S. presidential scienceadviser John Holdren (not an author of the new UC Davis study)recently told a congressional committee: "Climate scientists worryabout 'tipping points' ... thresholds beyond which a small additionalincrease in average temperature or some associated climate variableresults in major changes to the affected system."
Among the tipping points Holdren listed were: the completedisappearance of Arctic sea ice in summer, leading to drastic changesin ocean circulation and climate patterns across the whole NorthernHemisphere; acceleration of ice loss from the Greenland and Antarcticice sheets, driving rates of sea-level increase to 6 feet or more percentury; and ocean acidification from carbon dioxide absorption,causing massive disruption in ocean food webs.
Source: University of California - Davis