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SEA LEVEL PLANNING MUST BE LOCAL: ICSC CHIEF SCIENCE ADVISOR

December 12, 2014: “Tide turns on sea-level alarmists”, by Professor Bob Carter, ICSC Chief Science Advisor and former head of the Department of Earth Sciences, James Cook University, Queensland, Australia, published in The Australian.

AUSTRALIA is lucky to possess the high-quality, 128-year-long tide gauge record from Fort Denison (Sydney Harbour), which since 1886 indicates a long-term rate of sea-level rise of 0.65mm a year, or 6.5cm a century.

Lucky, because 60-year-long oceanographic atmospheric oscillations mean a true long-term measurement of sea-level rise can be made only when such a record is available.

Similarly low rates of local sea-level rise have been measured at other tide gauges along the east coast. National Tidal Centre records reveal variations between about 5cm and 16cm/century in rates of relative rise. The differ­ences between individual tide gauges mostly represent slightly differing rates of subsidence of the land at each site, and differing time periods.

For example, measurements at Sydney between 2005 and 2014 show the tide gauge site is sinking at a rate of 0.49mm/yr, leaving just 0.16mm/yr of the overall relative rise as representing global sea-level change. Indeed, the rate of rise at Fort Denison, and globally, has been decreasing for the past 50 years.

Shoalhaven, AU (above) city planners taking a sensible approach to
sea level rise adaptation.

Despite this high-quality and unalarming data, it is surprising that some east coast councils have implemented coastal planning regulations based on the computer projections of the UN’s Intergovernmental Panel on Climate Change. For instance, a recent consultancy report for the Shoalhaven and Eurobodalla shire councils, informed by IPCC computer model projections, advised those councils to plan using a rate of rise of 3.3mm/yr, four times the rate at Fort Denison.

The numbers were in part based on experimental estimates of sea-level change provided by satellite altimetry measurements. NASA’s Jet Propulsion Laboratory, which launches the satellite platforms, says these estimates contain errors larger than the sea-level signal claimed and proposes spending more than $US100 million on launching a new GRASP satellite to rectify the matter.

Mindful of these facts, on October 28, Shoalhaven Shire Council rejected advice to use the IPCC’s most extreme emissions Scenario 8.5, applying the still highly precautionary Scenario 6.0, and using their nearest long tide gauge record (Fort Denison) to set future planning policy. The council specifically ruled out the future use of satellite or model-generated sea-level estimates until their accuracy is guaranteed.

In mid-2010, the Eurobodalla council, south of Shoalhaven, introduced a unique interim sea level rise policy that shackled more than a quarter of all properties in the shire to restrictive development controls. Predictably, there was an immediate shire-wide decline in property values.

Figures from RP Data property information specialists show that between 2011 and 2014, Eurobodalla property values suffered a 5.3 per cent loss in value compared with increases of 4.9 per cent and 7.3 per cent for neighbouring coastal shires that didn’t have equivalent restrictive sea-level policies. In the worst cases, individual properties have lost up to 52 per cent of their market value.

In three years, individual Eurobodalla properties lost about $40,000 in value. With 22,000 properties in the shire, this represents a capital loss of $880m at a rate of $293m a year. This steady loss of rateable value means householders will face higher rate increases.

If similar policies were implemented along the entire east coast there would be annual property capital losses of billions of dollars.

So it is not surprising that NSW and Queensland governments are reconsidering their coastal management policies.

Queensland Deputy Premier Jeff Seeney recently notified Moreton Bay Regional Council of his intention to direct it to amend its draft planning scheme “to remove any assumption about a theoretical projected sea level rise due to climate change from all and any provisions of the scheme”. Seeney said his intention was to use a statewide coastal mapping scheme “that will remove the ‘one size fits all’ approach that incorporates a mandatory 0.8m addition to historical data”.

At last, a responsible government has recognised that global average sea-level change is no more relevant to coastal management than average global temperatures are to the design of residential heating and cooling systems — local weather and local sea-level change is what matters.

Satellite measurements and computer model projections are not accurate enough for shire planning. As the NSW Chief Scientist has said, coastal policy needs to be informed by the best available factual measurements.

And as Seeney said: “All mandatory elements of the (planning) scheme must reflect only proven historical data when dealing with coastal hazards such as storm tide inundation and erosion control areas.” Similar policies need to be espoused by all state governments and councils.

Sea-level alarmism has passed high tide and is at last declining. With luck, empirical sanity will soon prevail over modelling.