A Rising Tide Sinks All Coasts
Sea Level Rises Could Create Tens of Millions of Climate Refugees
SOURCE: Susmita Dasgupta, et al.
A flood of recent reports indicate that as a result of global warming, oceans levels are creeping upward far faster than originally predicted. Above: the project impact of flooding in the Nile delta region of Egypt, from "The impact of sea level rise on developing
countries," Susmita Dasgupta, et al., Climatic Change (Oct)(2008).
A torrent of new reports and scientific studies released over the last two months have made the same disconcerting prediction: sea level rise is accelerating and could overtake many areas within the century. Experts already understood that many countries in Southeast Asia and the South Pacific were already vulnerable to sea level rises, but the new findings have dramatically raised the stakes for others once thought to be relatively safe—including several parts of the United States. If these predictions hold true, nations around the world could soon face the prospect of having millions of climate refugees on their hands.
Most experts now agree that the estimates made by the Intergovernmental Panel on Climate Change in 2007, which predicted that a sea level rise between 7 inches and 2 feet by 2100, were much too conservative because they did not take the contributions from rapidly melting glaciers and ice sheets into account. Ocean thermal expansion, which occurs when oceans grow in volume when they absorb more heat, was once considered the driving factor behind sea level rise. But new melt rate data collected from Greenland and Antarctica in recent years now suggests that deglaciation is a more significant factor. A landmark study published in 2005 made the threat starkly clear, as it found that the complete melting of the Greenland and Antarctic ice sheets could raise sea levels by about 70 meters.
By some estimates, a 3-foot rise could still be too optimistic.
Here in the United States, a joint report co-authored by the Environmental Protection Agency, the National Oceanic and Atmospheric Administration, the US Geological Survey, and the Department of Transportation unveiled this past week concluded that Florida, Louisiana, North Carolina, and Texas were the most susceptible states. The report, entitled “Coastal Sensitivity to Sea Level Rise: A Focus on the Mid-Atlantic Region,” warned that coastal erosion will quicken as sea levels rise, causing the sandy shores that make up the region’s coast to slowly crumble and put millions at risk. Because some parts of its coast are already sinking, North Carolina would be especially hard-hit. Under the report’s worst-case scenario, sea levels could rise by as much as 3 feet by century’s end, which would result in some of the Mid-Atlantic’s barrier islands “crossing a threshold” and collapsing.
By some estimates, a 3-foot rise could still be too optimistic. According to a study published earlier this month in the journal Climate Dynamics, sea levels could rise between 0.9 and 1.3 meters by 2100—or roughly three times higher than what the IPCC forecasts. To predict what would happen in the future, the authors, an international team of researchers from Denmark, England, and Finland, looked to the past—specifically at the connection between average global temperatures and the sea level two millennia ago. They discovered a direct relationship between the two: warm episodes were often marked by periods of sea level rise, while cool periods, like the “little ice age” that took place during the 18th century, were marked by periods of sea level decline.
If this relationship still applies today, and global temperatures rise by about 3 degrees by century’s end (if not more), as is widely expected, the authors conclude that the seas could rise over a meter, which would have disastrous consequences for many parts of the world. For this to happen, ice sheets and glaciers would have to melt at a much faster rate than most scientists have been forecasting—something that many, in the face of gloomy 2007 and 2008 melt rate measurements, now believe could be the new normal. Indeed, according to Wilfried Haeberli, the director of the World Glacier Monitoring Service, glaciers are melting so fast that most could be gone by the middle of the century.
While the United States and other developed countries will eventually be forced to adapt to the impacts of rising sea levels, poor nations, which largely lack the resources to do so, will be in for a world of hurt if present trends continue. A World Bank report published last year in the journal Climatic Change determined that tens of millions of people in 84 coastal developing countries will likely be displaced by rising sea level over this century alone. As Science Progress noted last week, the country that could suffer the most devastating losses is Vietnam.
According to the report, a one-meter sea level rise could displace over a tenth of the country’s population—roughly 8.6 million people—which lives in low-lying areas and along the coast. Mauritania, Guyana, Jamaica, and the Bahamas—the latter of which could lose over a tenth of its land to sea level rise—would be some of the other hardest-hit countries. Overall, a one-meter rise would affect about 56 million people spread over 194,000 square kilometers. An earlier report commissioned by the IPCC identified the South Pacific, including the island nations of Kiribati and Tuvalu, as ground zero for sea level rise; the 7 million Pacific Islanders, most of whom live within 1.5 kilometers of the shore, could join the growing numbers of early climate refugees.
To help these countries avoid the worst, the developed world should begin to disburse aid according to the degree of threat, the authors conclude, and help their governments develop national adaptation plans. Which is easier said than done, of course. Even most developed countries are struggling to come up with strategies to forestall future losses caused by erosion, agricultural degradation, and coastal flooding. According to the U.S. Climate Science Program report, most current mitigation policies—rebuilding at the same location, relocating, coastal engineering, or some combination thereof—would fail to hold back the faster sea level rises that are now widely predicted. Existing structures are designed for current sea level and do not take into account the effects of coastal erosion. Better land-use planning, retrofitting, and science-based management are all necessary to prevent the worst from happening.
Jeremy Jacquot is a graduate student in marine environmental biology at the University of Southern California and is a contributing writer for The Huffington Post, Discover Magazine, DeSmogBlog, and TreeHugger.
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