Sea-level change: Living with uncertainty
de Lange, W. P., & Carter, R. M. (2014). Sea-level change: Living with uncertainty (GWPF Report No 15). Sea-level change: Living with uncertainty. London: The Global Warming Policy Foundation.
Permanent Research Commons link: https://hdl.handle.net/10289/9443
Sea level change is a naturally occurring process. Since the last glacial maximum, some 18,000 years ago, de-glaciation has taken place and this natural global warming has led to sea-level rise of on average 120 m or so. At some times, pulses of melt water coming from large peri-glacial lakes led to rates of sea-level rise as high as 3 m per century. The rate slowed down some 7000 years ago and since then has been naturally fluctuating by only a few meters. The remaining global sea-level rise has been about 20 cm in the 20th century. Has this led to global disasters? The answer is no. If the projected rise over the 21st century is double what was seen in the 20th, is it likely that it will result in global disasters? Again, the answer is most likely no; human ingenuity, innovation and engineering, and the proper material and financial resources should solve local problems if and when they arrive, as they have in the 20th century (see the Dutch example). In this short and accessible monograph, Willem de Lange and Robert Carter describe and explain sea-level change, including the many remaining uncertainties in our full understanding of what exactly drives this change, and discuss the implications, mainly regarding coastal management. The monograph is intended for policy makers, but it should be informative for any educated reader. De Lange and Carter analyse the causes of sea-level change, and describe how it has been measured – with tide gauges over the past 100 to 150 years and from satellites over the past 30 years. Their key message is to recall that sea-level change is a local phenomenon, with high variability and multiple causes. In the 20th century, for a global average rise of 20 cm, there has been sea-level rise of up to twice that value in some places, but in others a drop of the same amount! Because of the melting of a large former ice cap over the Baltic area, the Earth’s viscous mantle is slowly deforming and as a result sea-level is decreasing in the North of the British Isles at the same time as it is rising on the south coast. Moreover, we have known since Darwin and understood since the plate tectonics revolution that atolls in the Pacific form over slowly subsiding volcanoes and will eventually drown (but at a slower ‘geological’ rate, due to thermal subsidence of the lithosphere on which they stand). In any case, the global average has no practical value in local or regional coastal management.
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