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Islands Rimming Pacific Atolls: Their Response to Sea Level Rise
Volume 16, Number 4: 23 January 2013

On 17 October 2009, members of the Maldives' Cabinet donned scuba gear and used hand signals to conduct business at an underwater meeting that was staged to highlight the purported threat of global warming to the very existence of their country's nearly 1200 coral islands, where they signed a document calling on all nations of the earth to reduce their carbon emissions, based solely on climate-alarmist claims that the growing greenhouse effect of anthropogenic CO2 is raising temperatures, melting both glacial and polar ice, and causing seawater to expand, rise and inundate their country's low-lying islands.

But is this contention correct? In a study that integrated field observations, differential global positioning system data, historical aerial photographs and ultra-high resolution remote sensing images that examined the nature, spatial patterns and rates-of-change of the shorelines of 17 islands on the Maiana and Aranuka atolls of Kiribati's Gilbert Island chain, Rankey (2011) obtained a wealth of data that come to bear on this important question. And the conclusions he derives from that information are vastly different from the data-sparse contentions of the world's climate alarmists.

Rankey found, for example, that short-term (four-year) rates of shoreline changes can indeed be dramatic, with significant intrusion of seawater over sloping shores. However, much longer (forty-year) rates of change are much smaller; and not all of his analyses depict shrinking dry-land surfaces, as some of the studied islands have actually been accruing above-water area. And so it is that he forthrightly and correctly states that "the atoll islands are not washing away."

Similar island surface responses have been found by Webb and Kench (2010), who studied 27 other atoll islands in the central Pacific, using historical aerial photography and satellite images over periods ranging from 19 to 61 years, during which time interval they say that instrumental records indicated a rate of sea-level rise of 2.0 mm per year in the central Pacific. Yet in spite of this sea level rise, they too found "no evidence of large-scale reduction in island area," noting that the islands "have predominantly been persistent or expanded in area on atoll rims for the past 20 to 60 years," adding that 43% of the islands "increased in area by more than 3% with the largest increases of 30% on Betio (Tarawa atoll) and 28.3% on Funamanu (Funafuti atoll)."

Years earlier, Connell (2003) had also found no evidence for the oft-repeated island doomsday claims of radical environmentalists. And thus we see the great importance of real-world data - as opposed to climate model simulations - when it comes to considering the current and future status of the earth's many islands. And we thereby also better understand the concluding counsel of Rankey, i.e., that in matters such as those that he and the others cited herein have studied, "solutions must consider the natural complexity of these [island] systems, rather than advocate overly simplistic notions of the causes of, and the solutions to, coastal change."

Sherwood, Keith and Craig Idso

References
Connell, J. 2003. Losing ground? Tuvalu, the greenhouse effect and the garbage can. Asia Pacific Viewpoint 44: 89-107.

Rankey, E.C. 2011. Nature and stability of atoll island shorelines: Gilbert Island chain, Kiribaati, Equatorial Pacific. Sedimentology 58: 1831-1859.

Webb, A.P. and Kench, P.S. 2010. The dynamic response of reef islands to sea-level rise: Evidence from multi-decadal analysis of island change in the Central Pacific. Global and Planetary Change 72: 234-246.