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Spring 2014 Vol. 13 Number 2

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Abrupt Climate Change

Early Warning System Could Help Predict Rapid Changes in Climate Before It's Too Late

Photos courtesy U.S. Geological Survey

With unprecedented levels of carbon dioxide in the atmosphere, scientists are certain that Earth's future climate will be warmer, sea levels will rise, global rainfall patterns will change, and ecosystems will be altered. But what remains uncertain is exactly how and when we will arrive at that future.

Many climate projections forecast steadily changing conditions that suggest society and ecosystems will have time to adapt. But the scientific community has been paying increasing attention to the possibility that at least some changes will happen abruptly -- over the course of years to decades, rather than gradually over centuries -- leaving little time to react.

Some abrupt changes are already underway, for example the rapid decline of Arctic sea ice due to warming temperatures and the increases in extinction rates of both marine and terrestrial species. Recent research has eliminated the possibility that other large and abrupt changes will happen this century, such as a shutdown of the Atlantic Ocean circulation patterns or a rapid release of methane from Arctic and sub-Arctic latitudes, although these processes are still worrisome over longer timelines. Still other scenarios, such as the destabilization of the West Antarctic ice sheet, are plausible but their probabilities of occurring this century are less certain and require more scientific research.

Abrupt changes in the physical climate system are not the only cause for concern, however. Even changes that occur gradually may cross a threshold and trigger sudden and permanent ecological or socio-economic impacts. An example of such a "tipping point" is a slight increase in ocean acidity levels, which would affect many species' ability to survive. In addition, human infrastructures may be affected by rises in sea levels or thawing permafrost.

Although research has helped distinguish more imminent threats from those that are less likely to happen this century, there is still significant work to do to understand these tipping points in the climate, natural, and social systems.

The ability to anticipate what would otherwise be surprises requires both careful monitoring of climate conditions and improved models for projecting changes, according to a recent National Research Council report. It recommends an early warning system that would allow for the prediction of abrupt changes and facilitate more informed decisions on the balance between mitigation and adaptation.

Building upon existing land and satellite monitoring networks, the early warning system would also capture and analyze new information on the interconnectedness of climate and human systems. Among the critical needs for anticipating abrupt changes with a moderate-to-high likelihood of occurring this century are expanded and standardized monitoring of ocean oxygen content, pH levels, and temperature; enhanced observations of atmosphere, sea ice, and ocean characteristics in the Arctic; and better understanding of how species interactions and interactions between climate-caused extinctions and other drivers intensify extinction rates.

New and existing information should be integrated into numerical models, which in turn should regularly alternate between data collection, model testing and improvement, and model predictions that suggest future data needs. An early warning system will need to be refined as understanding of abrupt climate changes, impacts, and social vulnerabilities evolves.

The system should be part of an overall risk management strategy, providing required information for hazard identification and risk assessment. Ultimately this could inform decisions to tailor preparedness efforts, ensuring that warnings result in appropriate protective actions and ultimately pre-empt catastrophes.

-- Lauren Rugani

Abrupt Impacts of Climate Change: Anticipating Surprises. Committee on Understanding and Monitoring Abrupt Climate Change and Its Impacts, Board on Atmospheric Studies and Climate, Division on Earth and Life Studies (2013, 250 pp.; ISBN 978-0-309-28773-9; available from National Academies Press, tel. 1-800-624-6242; $59.95 plus $5.00 shipping for single copies).

The study was chaired by James W.C. White, professor of geological sciences at the University of Colorado, Boulder. The study was funded by the National Oceanic and Atmospheric Administration, National Science Foundation, U.S. intelligence community, and the National Academies.

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