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Five Decades of Shoreline Change on Diego Garcia Atoll

Paper Reviewed
Purkis, S.J., Gardiner, R., Johnston, M.W. and Sheppard, C.R.C. 2016. A half-century of coastline change in Diego Garcia - The largest atoll island in the Chagos. Geomorphology 261: 282-298.

One of the major concerns about global warming is the fear that rising temperatures will cause an acceleration of sea level rise, which some believe will cause extensive inundation and flooding of low-lying coastal areas in the years and decades ahead. But is this really the case?

One way to test this model-based projection is to examine historic trends in atoll island land area to see if they are, in fact, succumbing to rising seas; for in the words of Purkis et al. (2016), "being low and flat, atoll islands are often used as case studies against which to gauge the likely impacts of future sea-level rise on coastline stability." If rising oceans are indeed linked to global warming and are a force to be reckoned with, then the oft-described (by climate alarmists) unprecedented global warming and sea level rise of the past few decades should surely have made their mark on these low-lying land areas by now.

A recent test of this hypothesis can be seen in the work of Purkis et al., who examined remotely sensed images from Diego Garcia, an atoll island situated in the remote equatorial Indian Ocean, to determine how the shoreline of this island has changed over the past five decades (1963-2013), during which time sea level in the region has been rising over 5 mm per year, over at least the last 30 years, based on data they obtained from the National Oceanographic Data Center. And what did their study reveal?

In the words of the four scientists, "the amount of erosion on Diego Garcia over the last 50 years is almost exactly balanced by the amount of accretion, suggesting the island to be in a state of equilibrium." Commenting on the significance of this finding, Purkis et al. write that their study "constitutes one of the few that have documented island shoreline dynamics at timescales relevant to inform projections of future change." And the information it delivers is a damming indictment of alarmist projections of low-lying island demise in response to CO2-induced global warming. And this point is further driven home by the researchers' additional observation that "the areas of shoreline erosion and extension bear little relationship to prevailing ocean climate, a finding which should guard against attempts to predict sites of future land loss through natural processes."

Posted 23 September 2016