Link and Summary received from Rosemary McQueen
Wed, 6 Jul 2016 at 1:54 p.m.
The New Zealand Climate Science Coalition
Commonsense about climate change Link
Two of Our Coalition Members Reveal the True Facts about Sea Levels
Posted Mon, 4 Jul 2016
“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.”
Professor Vincent Courtillot writes this in his foreword to the Global Waming Policy Foundation paper by which our Coalition members, Dr Willem De Lange and the late Professor Bob Carter rebut alarmist propaganda about rises in sea levels and what causes those levels to rise and fall.
█ SEA-LEVEL CHANGE : Living with uncertainty
By Willem P de Lange and Robert M Carter
Foreword by Professor Vincent Courtillot
SUMMARY [from the paper]
1. Global sea-level corresponds to a notional world-wide average and is determined by the interaction between the volume of the ocean basins, the volume of water that they contain and the effect of Earth’s gravitational field.
2. Change in global sea-level is caused by:
• a change in ocean basin volume, controlled by geological forces
• a change in seawater density, resulting from variations in ocean temperature or salinity;
• the addition or subtraction of water from the ocean by the melting and freezing of glaciers and ice-caps.
Global sea-level is estimated using averaged measurements from a worldwide network of coastal tide-gauges or from satellite-borne instruments. Because they represent a worldwide average, neither of these figures has any useful application to coastal management in specific locations. Instead, a knowledge of local relative sea-level change, as measured at specific coastal locations, is the basis for practical coastal management. Local sea-levels are rising or falling in different parts of the world, depending upon the direction and rate of movement of the underlying land (tectonic change).
3. Sea-level change is mainly a coastal management issue, but the position of sea-level is only one of several important factors that controls the position and changes in the disposition of the shoreline. Other important forces and controls that have to be considered include:
• the rise or fall of the land
• the supply of sediment
• the weather and climate (short and long-term temperature, wind, rainfall)
• the oceans (waves, tides, storms, tsunami)
• erosion and gravitational collapse (for cliffed shorelines).
4. In its natural state, a sedimentary shoreline may shift landwards or seawards by metres to many tens of metres over periods between days and decades. In the past, coastal inhabitants have adapted to such changes, and trying to prevent them by controlling the amount of carbon dioxide in the atmosphere is neither practical nor cost-effective.
5. Coral atolls depend upon the interaction of a shallow ocean sea floor(generally the top of a submerging volcano), the growth and erosion of a coral reef, and the natural forces of winds, waves and tides. The integrity of an atoll is constantly under threat from entirely natural erosive forces. On top of this, human activities such as sand mining, construction project loading and groundwater withdrawal all cause local lowering of the ground surface, and thereby encourage marine incursion. It is this human interference, in combination with episodic natural hazards like tides and storms, and not global sea-level change that provides the alarming footage of marine flooding on atolls that from time to time appears on television news screens.
6. Changes in sea-level over long periods of time (millions of years) are inferred from geological evidence. These long-term changes suggest that any sea-level rises in response to temperature increases decelerate rather than accelerate over time. Such changes also indicate a maximum rate and duration of natural sea-level rise of about 30 mm/y over periods of a century or so.
7. Based on these geological studies, it appears that slow global sea-level rise– typically less than 10 mm/y – has been taking place over the last 10,000 y. At specific localities, this rising trend interacts with changing land levels due to a range of geological processes and multi-decadal climatic oscillations to produce different patterns of local relative sea-level change throughout the world – in some places rising, in others static and in others falling.
8. The long-term tide-gauge data record a 20th century average global sea-level rise of about +1–2 mm/y. It is established by many studies, too, that over the last 150 years global sea-level has been rising at an average rate of about 1.8 mm/y, which is inferred to represent the slow continuation of a melting of the ice sheets that began about 17,000 years ago.
9. Based on the same records, the IPCC has estimated an average rate of global rise between 1900 and 2000 of 1.6 mm/y (2007; 4th Assessment Report) or between 1901 and 2010 of 1.7±0.2 mm/y (2013; 5th Assessment Report). This global average ignores both short-term and multi-decadal changes in sea-level that are known to be associated with meteorological and oceanographic oscillations, and the local and regional effects of land movement. These additional factors are likely to continue to be important for future sea levels, and so should be considered in conjunction with projections of global sea level. The dominance of such processes in sea-level change means that for environmental management purposes sea-level changes should be assessed at local to regional scales, and not globally.
10. Satellite measurements of global sea-level have only been available since 1992, and the technology is therefore in its infancy. Complex computation and statistical analysis is required to transform raw satellite measurements into a sea-level curve, including the correction and piecing together of records collected over many years by ageing, and ultimately different, satellite vehicles. In recent years, it has been claimed on the basis of satellite measurements that the rate of sea-level rise since 1992 is greater than 3 mm/y – twice that measured using tide-gauge data for earlier periods, although the IPCC’s 5th Assessment Report considers it likely that similar rates occurred between 1930 and 1950. This apples-to-oranges comparison has formed the basis of claims that the rate of rise is accelerating, as required by the global warming hypothesis.
11. Most policy discussions regarding sea-level change are conducted in terms of computer modelled projections, rather than of factual information. In its 4th Assessment Report in 2007, the IPCC used physics-based computer simulations of the Earth and its climate to project a rise of sea-level of between 18 and 59 cm by 2100. The bottom end of this range corresponds with the 18-cm rise in sea-level predicted by empirical models and matches the long-term tide-gauge rate of rise of 1.8 mm/y.
12. Semi-empirical models produce the highest and most alarming estimates of rates of future sea-level change so far published (between 0.8 and 1.8 m by 2100). Strong controversy exists over the likely accuracy and policy usefulness of these results. Given that both empirical and deterministic modelling yield more modest projec- tions of future sea-level, the semi-empirical models can at best only be viewed as a work in progress.
13. The IPCC estimates that 1.1 mm of the 20th century sea-level rise of 1.8 mm/y can be accounted for by the combined effects of continuing ice melt (~0.7 mm/y) and ocean expansion due to warming (~0.4 mm/y), with the remaining ~0.7 mm/y relating to dynamic oceanographic and meteorological factors. The relatively small contribution from melt water indicates that there is no scientific basis for the claim that global warming will imminently melt so much ice that sea levels will rise dra- matically; by 20 ft in the imagination of Al Gore (Gore, 2006) or by 5 m in that of Jim Hansen (Hansen, 2007; Hansen and Sato, 2012).
Current global sea-level policy, supported by many governments, is to reduce the quantity of carbon dioxide in the atmosphere in order to slow a global warming that is apparently no longer happening, in a vain attempt to reduce the rate of global sea-level rise. This policy attempts to moderate a theoretical environmental variable, ignores local sea-level and coastal management realities, is ineffectual in significantly reducing sea-level rise and is not cost effective compared to incremental adaptation.
Global sea-level policy as currently practiced by governments is therefore scientifically uncertain and both financially and politically unsustainable.
Based on the material presented in this paper we recommend the implementation of three policy guidelines.
● Abandonment of ‘let’s stop global sea-level rise’ policies: No justification exists for continuing to base sea-level policy and coastal management regulation upon the outcomes of speculative deterministic or semi-empirical sea-level modelling. Even were the rate of global sea-level change able to be known accurately, the practice of using a notional global rate of change to manage specific coastal locations worldwide is irrational, and should be abandoned.
● Recognition of the local or regional nature of coastal hazard: Most coastal hazard is intrinsically local in nature. Other than periodic tsunami and exceptional storms, it is the regular and repetitive local processes of wind, waves, tides and sediment supply that fashion the location and shape of the shorelines of the world. Yes, local relative sea-level is an important determinant, but in some localities that is rising and in others falling. Accordingly, there is no ‘one size fits all’ sea-level curve or policy that can be applied. Crucially, coastal hazard needs to be managed in the context of regional and local knowledge, using data gathered by site-specific tide-gauges and other relevant instrumentation.
● Use of planning controls that are flexible and adaptive in nature: Many planning regulations already recognize the dynamic nature of shorelines, for example by applying minimum building setback distances or heights from the tidemark. In addition, engineering solutions (groynes, breakwaters, sea-defence walls) are often used in attempts to stabilise a shoreline. To the degree that they are both effective and environmentally acceptable, such solutions should be encouraged. Nevertheless, occasional damage will continue to be imposed from time to time by large storms or other unusual natural events, and that no matter how excellent the pre-existing coastal engineering and planning controls may be. In these circumstances, the appropriate policy should be one of careful preparation for, and adaptation to, hazardous events as and when they occur.
It is the height of folly, and waste of money, to attempt to ‘control’ the size or frequency of damaging natural events by expecting that reductions in human carbon dioxide emissions will moderate climate ‘favourably’ – whether that be putatively sought from a moderation in the frequency and intensity of damaging natural events or by a reduction in the rate of global average sea-level rise itself.
Posted by Elizabeth Kerr
Election Year. This post is offered in the public interest.
*Image: clipartpal.com – Hippo