It is not good enough, in terms of either scientific research sensu stricto or intellectual endeavour sensu lato, “to not use” the available information bearing directly on the question - the satellite-derived global coverage of atmospheric temperatures, which we know would show IPCC’s hypothesis to be wrong.

Furthermore, to use instead “measurements from weather balloons and look at the trends in temperature that have occurred since about 1960” is scientifically and intellectually insupportable, because there is no such trend.  The balloon record of atmospheric temperatures since 1958 comprises a long period showing little trend, a single warming step at 1976/77, and another long period of little trend.

As demonstrated in Sections 6 and 7 above, the step-change in atmospheric temperature at 1976/77 reflects a major re-ordering of oceanic circulation at that time - which entailed abrupt warming in the equatorial and NE Pacific, and abrupt cooling in the subtropical South Pacific.  It was not caused by the Greenhouse Effect.

Because there is no substantial greenhouse-related warming of the lower atmosphere in the period of available records, ie the 43 years 1958-2000, the second tranche of observed surface warming in the 20th century (1977-2000) must be largely the result of natural variability; although various human influences would have played some secondary role.

There is a second ghost which also needs to be laid.

Here quoting back the words of the ‘flag’ in Nature of 5 October 2000 (see Section 5.5 and 5.6) pointing to a review of model-based climate predictions, it is hard to see how “an objective analysis of the uncertainty in predictions” could be content with describing the occurrence of a sudden nonlinear transition between climatic regimes as ‘highly improbable’.  What is ‘highly improbable’, is an ability of numerical climate-change models to handle in an adequate fashion either past or future nonlinearities - of which that witnessed in 1976/77 is a well-documented real-life example.  Observation and deduction are the alternative to numerical models.

Davies and Hersh (1986) put mathematical abstraction in its place:
 ..... the computer does bring a new spirit into science.  By turning attention away  from underlying physical mechanisms and towards the possibility of once-for-all  algorithimization, it encourages the feeling that the purpose of computation is to  spare mankind of the necessity of thinking deeply.

 8.2  Nonlinear transitions on the grand scale
As discussed in Foster (1999) and illustrated in figures 3-9 therein, the largest climate excursions (warmings of 5 degrees C or more, in a few decades or less) during the last Glacial were in the North Atlantic Basin mega-region.

These climate excursions each follow Heinrich events, the outburst of iceberg armadas into the North Atlantic mostly from the North American ice-sheet, which leave trillion-tonne layers of ice-rafted detritus on the floor of the North Atlantic.  There were six of these major climatic events between 70,000 years before the present and the end of the Glacial at about 15 kyBP.

Continental ice launched into the sea from high latitudes becomes sea-level rise in the world’s oceans, including those girdling the equator.  The direct result is an increase in Earth’s radius of gyration, and a consequent slowing in its rate of rotation as its level of angular momentum is preserved.  But the ocean currents which transport heat around the globe are not glued to the stony Earth, and must move relative to their containing basins in an endeavour to preserve their linear momentum.  Sudden nonlinear transition between climatic regimes is the outcome.

That inertial factors are the driver here, is confirmed by McGuire et al (1997) who note a correlation between abrupt global sea-level changes during this period and frequency of explosive vulcanism in the Mediterranean.  Liquid magma is subject to the same forces as liquid oceans.

 8.3  Glacial/Interglacial continuity
The Heinrich events combine with smaller intervening ice-rafting events to form a pacing of ice-rafted detritus deposition in the North Atlantic at a frequency of 1500 +/- 500 years, as shown in Figure 25.  These smaller iceberg outburst also have an impact on climate.

The left hand graph in the Figure shows a proxy for surface air temperature over the past 30 ky, as preserved in a Greenland ice-core.  The Glacial, the Glacial/Interglacial transition, a brief return to near-glacial conditions in the Younger Dryas, and the 10 ky of relatively benign conditions in the Holocene - which we still enjoy - can be seen.

The right graph records the layers of ice-rafted detritus recovered from North Atlantic sediment cores.  Although very much smaller than during the Glacial, these layers - presumably now originating from Greenland - maintain their pacing right through the present Interglacial.  The latest such layer (not shown in the graph) is that related to the Little Ice Age.

8.4  Explaining the Little Ice Age in inertial terms
The Little Ice Age (see Figure 3) is the last in a series of periodic colder intervals, of which there appear to have been seven, in the North Atlantic Basin during the past 10 ky.  Like its predecessors, it appears to have been triggered by the launching of continental ice into the sea.

Figure 26 (copied in colour) shows in red the surface current which transports heat from the equatorial Pacific to the northern reaches of the North Atlantic.

My ‘Oceanic Impedance’ hypothesis of global climate change envisages that launching of icebergs (from Greenland) raises equatorial sea-level, with a consequent slowing of Earth’s rate of rotation and increase in LOD.

The chain of events here is likely to be complicated.  Initially, the rate of LOD change will increase as equatorial sea-level rises, peak, and die away (much as illustrated for the 1890-1930 period in Figure 23, although the duration and magnitude of changes are likely to be much larger) as the ice surge is exhausted.  From then on, LOD will be longer, but LOD change will have ceased and so will the inertial impacts.

However, added to this simple conceptual model will be hunting (ie over/under compensating) effects, and resonance effects engendered by the very non-uniform Atlantic topography.

At times, these effects will tend to force more of the warmth-bearing current into the Caribbean, and reduce the proportion which passes unimpeded to the north en route to the Nordic seas.  Impeded flow in the Caribbean means less ocean-transported heat reaching the Arctic, and positive feedbacks (more sea-ice and more land covered by snow will cause reflection of incoming solar heat) will accelerate  the cooling process.

In support of this hypothesis is the observation of a warmer Caribbean from about AD 1300, as the impounding of warm-water flow within the confined basin suppresses the usual upwelling of cold, deep water.

It is likely that the onset of the Little Ice Age in the higher latitudes of the North Atlantic Basin represents an inertially-related nonlinear transition between climatic regimes.

That this inertial driver had little apparent impact at equivalent latitudes in the Southern Hemisphere is not surprising.  The Antarctic Circumpolar Current lies in a geometrically-simple setting which offers no opportunity for the impedance of oceanic heat-transportation similar to that afforded by the Caribbean.

8.5  Modern-day surging of the West Antarctic ice-sheet
There is not much water stored in glaciers, but there is in ice sheets.  It was the surging of continental ice into the sea, largely but not exclusively from North America, which caused the sudden sea-level rises that triggered the prominent (and inertially-driven) climate fluctuations in the North Atlantic Basin region during the last Glacial.

Similar, but lesser, surges from the Greenland ice sheet appear to have been responsible for the continuation of this ca 1500-year pacing of climate fluctuations right through the Holocene, albeit at a lesser amplitude (at least since removal of the North American ice sheet was essentially complete some 6-7 kyBP).  Continental ice remains today on Antarctica (90%) and Greenland (10%).

Ice is too good an insulator for the vagaries of contemporary climate to have a discernible impact on the quantity or frequency of launching of continental ice.  Instead, it appears that surging is related to the internal mechanics of the individual ice sheet.  In the case of the East Antarctic continent and Greenland, snowfall appears to more-or-less replace the ice lost from surges.  Surges are rapid, but their replacement by new snow-fall is gradual; therefore inertial impacts are feasible, even in an ice-sheet which shows no net change with time.

But West Antarctica is very different.  As shown in Figure 27(a), the West Antarctic ice sheet (now containing some 10% of Antarctic ice) is founded on a deeply-submerged continental shelf.  Furthermore, the WAIS appears to have been destabilised by the 120-135 metres rise in global sea-level since the Last Glacial Maximum some 20 kyBP.

Figure 27(b) depicts the retreat of the grounding-line of the WAIS on the Ross Sea coast since the LGM.  Here, the grounding-line has retreated along the foot of the Transarctic Mountains of East Antarctic by some 1300 km during that time.  The WAIS is collapsing, and its collapse has contributed some 11 metres to world sea level - mostly during the past 8 ky.

The WAIS is much more active than are the ice sheets on East Antarctica and Greenland; and its complete disappearance over, say, the next millennium is not implausible - with a concomitant eustatic sea-level rise of some 5 or 6 metres.  Whether this happens or no, is entirely beyond human influence.

Recent work has led to the discovery of present-day surging in several West Antarctic ice-streams.  Streams debouching onto the Ross Shelf - see Figure 27 (c) - are moving at speeds of up to a kilometre per year, and those into the Amundsen Sea by twice as much.

It makes no difference where ice enters the sea.  Greenland or Antarctica, its inertial impact will be the same - and will be most-readily detected in the northern North Atlantic Basin.

In his address to the National Press Club (see Footnote 6) Church was reported as saying that he thought:
 ..... it was unequivocal that the oceans are warming and even after 500 years of  stabilisation of greenhouse gases in the atmosphere, sea-level rise through  thermal expansion will continue.

I would like to see more attention by Australian scientists to the current surging of ice-streams on the West Antarctic ice-sheet.  Much could happen here in 500 years - or less.

8.6  Defining the ‘Oceanic Impedance’ hypothesis
There have been many (probably ocean-related and inertially-triggered) climate changes in the North Atlantic Basin region over the past 100 ky, at several time-scales; and that these are linked in some way to changes in equatorial sea-surface temperature is becoming accepted (see for instance Curry and Oppo18, 1997).

The Oceanic Impedance hypothesis of global climate change is founded on the belief that large and small changes with a similar cause are a plausible future expectation, and that sudden nonlinearities of this sort are beyond the predictive capacity of today’s climate models.

In particularly, observed climate change in the 1945-2000 period is best explained by the new hypothesis.  Granted, variations in solar activity, human-caused GHG emissions, and non-greenhouse anthropogenic factors, are all likely to have played a role.  Nevertheless, the main cause of observed warming in the period is a sudden re-ordering of oceanic heat-transportation in 1976/77.  This event is associated with contemporary changes in strength and location of the upwelling of cold deep water, particularly in the equatorial Pacific, and is likely to be inertially-triggered.

The more-complex basinal geometry of the Northern Hemisphere implies that the free circulation of oceanic waters, deep or surface, is more likely to be impeded in the north than the south at the time of inertial changes.  Therefore, the impact of such changes will be most obvious in the Northern Hemisphere, particularly in the lands surrounding the northern North Atlantic Basin, than elsewhere.

In summary, the 1976/77 changes represent the main climatic event of the 20th century; and the Oceanic Impedance hypothesis grants them but a single driver - the oceans.
______________________________________________________________________________
18.  Those readers who seek out this useful paper will be surprised indeed.  By way of explanation for its observations, the summary at the end of the paper offers only:
 One likely possibility is the nonlinear response of climate to variations in solar insolation at low  latitudes, as has been suggested by several authors.
The abstract also offers but one (different!) explanation - natural variation in atmospheric GHGs:
 The apparent synchroneity of equatorial SST and polar air temperature changes, as well as the  amplitude of the SST changes at the equator, are consistent with the climate effects expected from  changes in the atmosphere’s greenhouse gas content .....
Greenhouse is to scientists, as nectar to bees.

You read it first here

© 2001  Bob Foster  Posted   9, April, 2001
www.globalwarming-news.com
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