Kiribati is promoted as a dramatic example of how rising sea levels due to climate change will cause the disappearance of the islands of the Pacific. It's a claim not necessarily supported by science and practical observation.
Three pillars at the ancient marketplace of Pozzuoli, near Naples, led to much speculation among geologists of the 19th century. The activities of marine mollusks on these marble columns seemed to indicate that they had been submerged, then rose again, all within a period of a few thousand years. It was believed by many that this indicated rises and falls in the sea level.
Now we know what actually happened. The area subsided below sea level in Roman times, was uplifted around 700-800AD, subsided again from around 1500 until 1583, when it rose again, then subsided, then rose again. Between 1969 and 1973 the land rose by about 1.7 metres, subsided slightly over the next decade until between 1982 and 1994 it rose some 2 metres.
This is the phenomenon known as bradyseism – the earth's surface can rise and fall without being subject to violent earthquakes.
The UK is tilting – Scotland is rising while southern regions sink. Parts of the English coastline have sunk 6 metres in the last 6500 years. Scotland could rise up to 10cm over the next century, offsetting any sea level rise that might be caused by global warming.
As Australia drifted north over the last 50 million years or so, the land rose and fell. Professor Dietmar Müller of the School of Geosciences at the University of Sydneysays "At the moment we are focused on sea level changes caused by melting ice. But for large portions of the Earth's history there was no ice, however sea level still fluctuated substantially".
Pacific islands form in different ways. The Hawaian and Marquesas Islands were formed as tectonic plates moved over volcanic hot spots. Over a few million years these islands eroded away and become coral atolls, an ongoing process which is dramatically obvious when you visit the area.
Professor Paul Kench of Auckland University co-authored a paper with Dr Arthur Webb, an expert on coastal processes. They concluded that the evidence does not support the idea that the islands of the Pacific are sinking as a result of global warming. In fact, most of them are growing, some dramatically. The three most densely populated islands of Kiribati have grown between 12.5 to 30 per cent since the 1950s.
This would not have surprised Charles Darwin, who proposed a simple theory to explain atoll formation – atolls begin as a fringing reef growing around a volcanic island. If this island sinks beneath the ocean, the reef continues to grow upwards and an atoll forms. His theory was put forward in 1837, but was not proven until 1951 when drilling at Eniwetok Atoll in the Marshall Islands in connection atom bomb testing found the base rock that Darwin predicted.
Journalists visiting Kiribati are often invited to take the two hour boat ride to Tebungnako, a village on Abaiang Atoll to view 'hard evidence' of the ravages of rising sea levels. In 1992 a Canadian report found that El Nino events were responsible for the large waves inundating the coastline. It also found that the sea walls constructed by the islanders exacerbated the damage.
Obviously inundation is not necessarily linked to sea levels, and sea levels are not necessarily linked to global warming. Statistics taken out of context are often meaningless and misleading.
Sea levels are rising, very gradually, but Kiribati and other islands are outgrowing the rise. You can view the relevant BOM statistics for sea levels over the last 24 years at Betio at www.bom.gov.au/ntc/IDO70060/IDO70060SLI.pdf.
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