Nature, Not Human Activity, Rules the Climate - Science ...

! ‘Bottoms-up’ modeling of future sea levelsdoes not uniformly predict rising sealevels.The four IPCC reports have all used a‘bottoms-up’ modeling analysis of global averagechange in sea level. They estimate separately thepositive contribution to SL rise from meltingmountain glaciers (eustatic) and thermal expansionof a warming ocean (steric). Obviously, this holdsonly for the upper ocean layer as icy-cold deep-seawater is neither increasing in temperature nor wouldexpand if warmed. They then add the estimated netvalues (ice loss minus ice accumulation) for theGreenland and Antarctic ice sheets.The observed lack of acceleration of SL(Figures 17 and 18) may indicate a fortuitous yetplausible balance, in which ice accumulation on theAntarctic plateau roughly balances the effects ofexpanding ocean and melting glaciers forshort-lived (decades-long) global temperaturechanges [Singer 1997, p. 18]. This is plausiblebecause a warming ocean releases more moistureinto the atmosphere, which increases precipitationand ice accumulation, mainly over the Antarcticcontinent. If true, sea level would continue toincrease at about the same rate – roughly 18 cm percentury – in spite of temperature changes of shortduration, measured in decades, whether warming orcooling.! Each successive IPCC report forecasts asmaller sea-level rise.Successive IPCC reports have reduced theirestimates of projected sea-level rise, as shown inFigure 19, and are coming closer to a value of 18cm per century. Because this is also close to theongoing rate of rise, this is equivalent to sayingthere will be no acceleration by AGW, i.e., noadditional sea-level rise due to warming.There is, however, another problem: The IPCCfigures do not match the observed rate of rise[IPCC-AR4 2007, Table TS.3, p. 50]. Most of theongoing SL rise may therefore be due to the slowmelting of the West Antarctic Ice Sheet (WAIS)[Conway 1999]. It has been slowly melting since theLGM of 18,000 years ago. If it continues at thisrate, it will disappear in about 7,000 years[Bindschadler 1998] – unless another ice agecommences.Figure 19: Estimates of sea-level rise to Year 2100 from IPCCreports of 1990, 1995, 2001, and 2007. Note the strongreduction in estimated maximum rise, presumably based onbetter data and understanding. Also shown are the publishedseal level rise values of Hansen (H) [2006], Rahmstorf (R)[2007], and Singer (S) [1997]. Both H and R are well outside ofthe maximum IPCC values. The ongoing rate of rise in recentcenturies has been 18 cm per century; therefore, theincremental rate of rise for IPCC 2007 would be 0 to 41 cm,and about 0 to 2 cm for Singer.! Forecasts of more rapid sea-level rise arenot credible.Recently, Stefan Rahmstorf [2007] haspublished a ‘top down’ approach to SL-riseprediction that exceeds the current IPCC estimatesabout threefold. He simply assumes the rate of riseis proportional to global mean temperature. There isno theoretical basis to support this assumption – andindeed, it is contradicted by observational evidence:SL rise continued at the same rate even when theclimate was cooling from 1940 to 1975. As Nobelphysicist Wolfgang Pauli once said whenconfronted with a similar silliness, “This theory isworthless; it isn’t even wrong.”Hansen [2006] has suggested even moreextreme estimates of future SL rise – nearly 15 (oreven 60) times the mean IPCC value and 30 (oreven 120) times that of Singer. His 20-feet estimateis based on speculation about the short-term fate ofpolar ice sheets, assuming a sudden collapse andmelting; his 80-feet estimate is derived bycomparison with previous interglacials. However,the MWP and the much greater warmings during theearlier Holocene showed no evidence of suchimagined catastrophes. Hansen and Rahmstorf cantherefore be considered ‘contrarians’ on this issue.18