Arctic sea ice has seen dramatic declines in recent years. In 2007, Arctic sea ice shrank to its smallest summertime extent ever observed, opening the Northwest Passage for the first time in human memory. This new sea ice minimum came only a few months after a study reported that since the 1950s, summer sea ice extents have declined three times faster than projected
SECTION 7.2Global Climate ChanGe—Causes and ConsequenCesby climate models. In the summer of 2010, Arctic sea ice set a new kind of record: It decreased to the lowest volume ever observed. While the extent (the area of the Arctic Ocean covered by ice) in 2010 was slightly higher than in 2007, the ice was considerably thinner in 2010, mak-ing the volume lower than in 2007. Scientists are concerned that this historically low volume of ice could be more susceptible to melting in the future, causing sea ice loss to accelerate.The importance of sea ice decline comes from the role it plays in both the climate system and large Arctic ecosystems. Snow and ice reflect sunlight very effectively, while open water tends to absorb it. As sea ice melts, the earth’s surface will reflect less light and absorb more. Conse-quently, the disappearance of Arctic ice will actually intensify climate change.Moreover, as the edge of the sea ice retreats farther from land during the summer, many marine animals that depend on the sea ice, including seals, polar bears, and fish, will lose access to their feeding grounds for longer periods. Eventually, this shift will deprive these organisms of their food sources and their populations will not be sustained.If warming continues, scientists are sure that the Arctic Ocean will become largely free of ice during the summer. Depending in part on the rate of future greenhouse gas emissions, the latest model projec-tions indicate that the opening of the Arc-tic is likely to occur sometime between the 2030s and 2080s. The opening of the Arctic has enormous implications, ranging from global climate disruption to national security issues to dramatic ecological shifts. The Arctic may seem far removed from our daily lives, but changes there are likely to have serious global implications.Apply Your KnowledgeThe consequences of abrupt climate change have become so worrisome that some scientists, politicians, and even environmentalists have begun to call for more research into a technique known as geoengineering to help address the problem. Geoengineeringis the deliberate intervention and modification of Earth systems to prevent or reduce climate change. For example, some clouds can reflect incoming sunlight, and so one geoengineering scheme is designed to increase the number of clouds in the sky to help cool the planet. The debate over geoengineering is focused on a number of questions:• Is this a practical and realistic way to address climate change?• Could geoengineering schemes solve one issue (climate change) while triggering other, potentially more serious problems?• Wouldn’t it be better and more direct to address the root causes of climate change—greenhouse gas emissions—than to pursue geoengineering?