Klimaatbeleid is zinloos om de rijzing van de zeespiegel te stoppen
Fred Singer: Opwarming (aannemende dat die ooit nog eens komt) zou tot afremming van de zeespiegelstijging kunnen leiden. Wie had dat ooit gedacht?
Zeespiegelstijging neemt een prominente plaats in in wat door Bjørn Lomborg ooit de 'litanie van milieuangsten' is genoemd. Deze zou worden veroorzaakt door de opwarming van de aarde, die volgens de klimaatalarmisten op haar beurt weer voor een belangrijk deel door de menselijke uitstoot van CO2 zou worden veroorzaakt. Het probleem is dat deze opvatting in strijd is met de waarnemingen.
Onder de titel, 'Sea Level Rise Surprise', schreef Fred Singer voor 'The American Thinker':
Driving the seemingly endless climate-treaty negotiations, the most widely feared consequence of Global Warming appears to be a catastrophic rise in sea level (SLR). Environmental advocacy groups are filling the airwaves with lurid images of flooding of Bangladesh and Pacific islands, and raising the specter of hundreds of millions of environmental refugees demanding care and compensation. Even sober scientists, while not endorsing such obvious scare stories, predict an acceleration of the ongoing global rise, which a system of tidal gauges places at about 18 cm (7 inches) during the 20th century. .
However, more detailed analyses of actual observations suggest an opposite outcome: A climate warming might even slow down SLR -- rather than accelerate it. To understand this counter-intuitive result, one must first get rid of false leads -- just as in a detective story. The misleading argument here is the oft-quoted statement that the climate warmed by 1degF (0.6 C) in the last 100 years and that SL rose by 18 cm. Both parts of the statement may well be true; but the second part does not necessarily follow from the first.
Curiously, Barack Obama predicted a deceleration of SLR when he accepted his party's nomination in 2008: "This was the moment when the rise of the oceans began to slow, and our planet began to heal." Some tidal-gauge data do show deceleration, but starting in 1960. Hey, wasn't that the year during which Obama was conceived?
Singer gaat vervolgens uitvoerig in op de technische moeilijkheden om de zeespiegel nauwkeurig te meten van oudsher met peilschalen en sinds 1993 ook met satellieten.
Wat betreft de toekomstige zeespiegelstijging is er geen bevredigend model dat als basis voor projecties kan dienen wel ruwe schattingen van de belangrijkste determinanten. Dat leidt er onder meer toe dat de opgegeven bandbreedtes van verwachte zeespiegelstijging in de rapporten van het VN-Klimaatpanel (IPCC) erg ruim zijn en van het ene op het andere rapport sterk variëren.
The difficulty with projections of sea level rise is nicely illustrated by the IPCC. The estimates of its first assessment report (1990) showed a range of 10-367 cm for sea level in 2100. The second report, published in 1996, narrowed the range to 3-124 cm. Its third report, published in 2001, showed 11-77 cm. The fourth assessment report, published in 2007, showed 14-43 cm in its draft form but changed it to 18-59 cm in the final printed version.
As can be seen, the maximum SLR decreased successively as estimates improved. All these IPCC projections are very much smaller than the extreme values of about 600 cm by activist-scientist James Hansen (and by climate multi-millionaire Al Gore) -- which assume excessive and rapid melting of the Greenland icecap. This narrowing of estimates by the IPCC has caused great concern among alarmists who feared that the IPCC was being "too conservative." Probably as a result of this peer-pressure, estimates have now increased -- as will be seen in the fifth assessment report, due in September 2013.
As a reviewer of IPCC reports, I have been able to look at the "second order draft," which was recently leaked to the press. It gives values for 2100 of 45-110 cm (16-40 inches) - about double what IPCC estimated just six years ago in their fourth report. (There is no guarantee that these values will survive in the final printed version.) Still, they are very much smaller than some of the extreme estimates that have been written up in newspapers and magazines -- and always blamed on Global Warming (GW) from carbon dioxide, released in the burning of fossil fuels. ...
According to their [IPCC's] 1996 compilation of data, the contributions to SLR of the past century come mainly from three sources: (i) Thermal expansion of the warming ocean contributed about 4 cm; (ii) the melting of continental glaciers about 3.5 cm. (iii) The Polar Regions, on the other hand, produced a net lowering of SL, mostly from ice accumulation on the Antarctic continent. (The mechanism is intuitively easy to understand but difficult to calculate: A warming ocean evaporates more water, and some of it rains out in the Polar Regions, thus transferring water from the ocean to the polar ice caps.) The surprising result: When one simply adds up all these three contributions (neglecting their large uncertainties), they account for only about 20 percent of the observed rise of 18 cm. The climate warming since 1900 cannot be the cause of the SLR; something is missing here. ...
The relevant clue comes from corals and from geological observations: It seems that SL has been rising for the past centuries at about the same rate as seen by tidal gauges in the last 100 years -- about 18 cm per century. In other words, SL was rising even during the colder Little Ice age, from about 1400 to 1850 AD. This provides further support for the hypothesis that the observed global SLR since 1900 is reasonably independent of the observed temperature rise.
The explanation for this riddle had been suspected for some time, based on historic data of SLR derived independently from measurements of coral growth and from isotope determinations of ice volume. But the picture was filled in only more recently through estimates of the rate of melting of the West Antarctic Ice Sheet (WAIS), by tracing its shrinkage during past millennia (through the receding position of its "grounding line," i.e., the line of contact of the ice sheet with the underlying continental land mass.) Note that the WAIS is not floating sea ice; like a mountain glacier, its melting contributes water to the global oceans.
We can therefore describe the broad scenario as follows: The strong temperature increase that followed the Last Glacial Maximum (LGM) of about 18,000 years ago has melted enough ice to raise SL by 120 meters (400 feet). The rate of rise was quite rapid at first and controlled by the melting of the huge ice sheets covering North America and the Eurasian land mass. These disappeared about 8000-5000 years ago; but the WAIS continued to melt, albeit at a much lower rate -- and it is still melting at about the same rate today. Other, smaller WAIS-like ice sheets may have existed in the Antarctic, but have already melted away.
The principal conclusion is that this melting will continue for another 7000 years or so, until the WAIS disappears -- unless another ice age takes over before then. Moreover, there is nothing that we can do to stop this future sea level rise! It is as inevitable as the ocean tides -- as long as the Holocene (the present warm interglacial period) survives.
Fortunately, coral reefs will continue to grow, as they have in the past, to keep up with SL rise. The rest of us will just have to adapt -- as our ancestors did some 10,000 years ago. At least, we are better equipped to deal with environmental changes. ...
We can now try to answer our original question: Can a Global Warming really lower sea level rise? It all depends on the time-scale: Yes -- if GW lasts only for some decades or less. No -- if warmer temperatures persist for millennia, the WAIS melting rate would increase -- and so would SLR. By analogy, a future warming produced, putatively, by an increase in greenhouse gases would give the same result: i.e., reduce the rate of rise of sea level. This is not a recommendation to burn more coal in order to save Venice from drowning. It is a modest appeal to politicians to take note of new scientific developments and recognize that the drastic limits on energy use called for by climate-treaty negotiators will not stop the rising seas.
Lees verder hier.
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