Don't Go Off At Half Cock On Sea Levels, Minister

22 May 2009 FOR IMMEDIATE RELEASE

*Sea levels must be measured against earth’s tectonic plate movements*

Environment Minister Nick Smith has been warned not “to go off at half-cock” with his proposal announced this week of a possible national environment standard on sea-level rise. The warning comes from the New Zealand Climate Science Coalition which says that rises in sea levels are regional rather than “global” and need to take account of tectonic plate movements that cause land to move up and down in places.

“The scoping project proposed by the Minister should not be left to solely to the Ministry for the Environment (MfE), but should be the responsibility of the agency best able to measure both sea and land movements. The logical approach would be for the sea level observations to be fed into GeoNet, under the auspices of GNS Science. Then we would not have to wait for snippets of data to make their way to present mean sea level (PMSL) reports, and both sea level and land movement data would be at the same site, and could be integrated with continuous GPS measurements. They could even plot relative sea level for the public and managers,” says the coalition statement.

“At the same time, the Minister should end the situation in which NIWA currently controls access to sea level data. This is a conflict of interest because NIWA’s consulting wing that earns a considerable amount of income from advising councils to adopt guidelines of something like 0.5 m sea level rise within the foreseeable future. Sea level information should be as freely available as is weather data from MetService.

“The Minister also needs to explain why New Zealand should adopt values higher than the UN IPCC projections (39 cm by 2100, with plus or minus 20cm due to ice cap uncertainty) , and make sure that we account for regional effects. What is important for our coastline is relative sea level rise, not global sea level rise. Taku’u Island, wrongly quoted in a recent TV One programme, is an excellent example of land sinking rather than sea rising. However, even around New Zealand there are locations where tectonic uplift is greater than sea level rise, and others where subsidence due to ground water removal and compaction causes a higher rate of sea level rise.

“From satellite monitoring of sea levels worldwide, we know that sea level rise its currently about 3mm per year -- a barely noticeable amount. It has been relatively constant at this value for the last 150 years. Recently it has reduced to about 2mm but this could be a temporary effect. From the records that we already have we know that ground movement on an annual basis can be greater than 3mm per year in either direction and we also know that, during an earthquake, it can be very large indeed, as the Napier earthquake of 1931 demonstrated.

“A more recent example is the Edgecumbe earthquake of 1987 where the sea level effectively rose 40cm at Thornton Beach, Bay of Plenty, the same as the projected IPCC rise by 2100, but there has been no erosion of the shoreline. There was a temporary erosion of the lower beach face, but overall erosion at this site is dominated by ENSO (El Nino Southern Oscillation) and PDO (Pacific Decadal Oscillation) cycles. Further, dune restoration by volunteers with minimal finacial input has resulted in shoreline accretion, despite the sea level rise. These local factors should be able to be included in coastal hazard assessments,” the coalition statement concluded.

ENDS

© Scoop Media