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Abrupt climate change—large shifts in climate that take place within decades or even years—is the topic of increasing scientific research because of the potential for such changes to happen faster than society or ecosystems could adapt. A new report from the National Research Council evaluates the potential for abrupt changes in the ocean, atmosphere, ecosystems, and high latitude regions to help decision makers and communities make informed decisions about how to prepare for sudden changes. The report calls for an early warning system to help society better anticipate abrupt changes. Credit: Left, Larsen B ice shelf collapse, Landsat 7 Science Team and NASA GSFC; Right, drought in Gujarat, Ahmad Masood/Reuters
The report expands the idea of abrupt climate change, stating that even steady climate change can cross thresholds that trigger abrupt changes in other physical, natural, and human systems. For example, gradual climate change can cause abrupt changes in the utility of human-built infrastructure, such as when rising sea levels suddenly surpass sea walls, or when thawing permafrost causes the sudden collapse of pipelines, buildings, or roads. Credit: Jane Hawkey, climatechange.maryland.gov
A growing body of research is helping scientists to distinguish the imminent threats of abrupt climate change from those less likely to take place this century. Some abrupt climate changes are already underway, making these changes a primary concern for near-term societal decision making and a priority for research. For example, warmer polar temperatures have caused a rapid decline in Arctic sea ice over the past decade. Credit: National Snow and Ice Data Center
The rapid decline in Arctic sea ice–an abrupt climate change that is already underway–has potentially large and irreversible effects on various components of the Arctic ecosystem, as well as impacts on Arctic shipping and resource extraction with significant geopolitical ramifications. The photo shows a ship that has crossed the Northern Sea Route that is now open because of sea ice disappearance. Credit: Nordic Bulk Carriers
Another abrupt change already underway is an increased extinction pressure on many plant and animal species. The effects of climate change, such as increasing air and water temperatures, add to other pressures on ecosystems such as pollution, resource extraction, and deforestation / land-use changes. These changing conditions can cross thresholds beyond which some species cannot survive. For example, as the climate changes species such as the Hawaiian Silver Sword (left) and the mountain pika (right) will be pressured to relocate or rapidly adapt—and those populations that are unable to do so will be in danger of extinction. Credits: Left, Wikimedia Commons
; Right, National Park Service
Other species may fare better as the climate changes, causing abrupt shifts in the balance of ecosystems. For example, the warmer temperatures brought by climate change have led to outbreaks of mountain pine beetles (left) by speeding up their reproductive cycles and allowing more beetles to survive over winter. Increased populations of the insects have destroyed large areas of this Colorado forest (right). Credit: Left: Dion Manastyrski; Right: Anthony Barnosky.
Some abrupt changes, widely discussed in the scientific literature because they were once identified as possible threats, are now considered unlikely to take place over the near term. For example, the probability of a rapid shutdown within this century of the Atlantic Meridional Overturning Circulation—an ocean current that moves warm water from the upper layers of the Atlantic northwards and brings colder water south—is now understood to be low. Credit: H. Furey, WHOI.
A second example of an abrupt climate change that was previously identified as a possible threat is the potential rapid release of large amounts of carbon currently stored in high latitude regions as permafrost soils and methane-containing ices. According to current scientific understanding, as temperatures rise, these carbon stores are poised to play a significant amplifying role in the century-scale buildup of greenhouse gases in the atmosphere—but are unlikely to do so abruptly within this century. Credit: NASA Earth Observatory
But there are still large uncertainties about the likelihood of some potential abrupt changes, highlighting the need for expanded research and monitoring. For example, as Earth’s climate warms, the destabilization of the West Antarctic Ice Sheet could raise sea level rapidly (left; red represents areas where temperatures have increased the most during the last 50 years), with serious consequences for people living in coastal communities. However, current ice-sheet models do not account for all the physical processes that make the glaciers of West Antarctica particularly sensitive to warming climate. Because large uncertainties remain, the probability of an abrupt change in the West Antarctic Ice Sheet within this century is unknown, but probably low. Credit: Left: NASA/GSFC Scientific Visualization Studio
; Right, Shutterstock.com
Further scientific research and enhanced monitoring of the climate, ecosystems, and social systems may provide information that a tipping point is imminent. The report calls for the development of an early warning system for abrupt changes that builds upon existing programs like the National Integrated Drought Information System, which produces seasonal drought outlooks. Anticipating abrupt changes before they occur could allow time for society to take action to adapt or make preparations to help mitigate the impacts of sudden changes. Credit: NOAA
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