Knowledge Of Natural Cycles Of Global Warming And Cooling
Major climatic cycles in the Quaternary appear to be 40,000 years long, with subsidiary cycles of around 20,000 years. These cycles are caused by predictable changes in the Earth’s orbit round the Sun as discovered by Milankovitch in 1941. However, this is not the whole story: it explains the periodicity of temperature cycles but not why we have Ice Ages, because the latter have not been recycling throughout all of geological time. Thus, there must be another factor which has recently changed from the earlier to the later periods. However, this is not far to seek: the topographical changes in the Earth’s surface also affect its temperature distributions. Thus, the Panama Gap between North and South America closed in the Quaternary, and the Arctic Ocean became isolated when the very shallow Bering Straits became dry land at times of low global sea level in the Quaternary. In addition, these changes in ocean circulation were accompanied by changes in atmospheric circulation when the Himalayas, the Tibetan Plateau, and the western cordillera of the Americas began to rise and to cause late Tertiary cooling. Thus, the rising of these mountains could have been a major cause of change in the dominant periodicity of glaciations which led to the intensification of Quaternary glaciation in the Tertiary.
It is now time to apply Peter Toghill’s review of geological knowledge to the current belief in anthropogenic global warming. The current ice sheets of Greenland and Antarctica represent frozen atmospheric water up to 0.25 million years old. Older ice has recycled back to the oceans by mass flow of the ice sheets to melt water. Thus, current ice contains air representative of the atmosphere over this recent time interval. Sampling and chemical analysis of such air samples taken from differing ice-core depths show that greenhouse gases (carbon dioxide and methane) were low during glacials and high during interglacials. However, I wish to bring to the attention of my readers the knowledge that this relationship does not enable us to decide whether high concentrations of atmospheric carbon dioxide and methane are the cause of the warming or the effect of the warming. Thus, we have to consider the existence of a natural mechanism for global warming which would enable us to decide which of the foregoing alternatives is operative. However, as of now, we know that studies of pollen and beetles at the end of the last glacial episode (the Devensian) around 13,000 years ago in southern Britain show remarkable temperature rises of 10 centigrade degrees in 100 years. Indeed, there appears to have been 20 of these rapid temperature surges in Britain during the last 60,000 years and all apparently due to natural causes (i.e. no anthropomorphism). To account for these changes, Peter Toghill proposes, in a subsection of Chapter 13, entitled global warming, that south moving icebergs melt into the northward moving warm/tropical/saline water of the Gulf stream; that this northwards flow of warm water is accompanied by its cooling, its increasing density, and its sinking to greater depths; that the southwards moving cold and relatively fresh water progressively lowers the density of the northward flowing water, inhibits its sinking, and thus reduces its flow; that this in turn reduces its warming effect; but that when the southward flow is thus also reduced, the Gulf Stream flow increases again; and that this oscillation has been the cause Britain’s temperature rising by up to 10 Centigrade degrees in 100 years, between cooling periods of a few thousand years. In the last 8000 years, conditions have been stable, but this is an unusual situation and may not last. At this point Peter Toghill provides Fig. 158 which gives the major divisions of the Quaternary Period and their temperate/glacial sub-divisions of which there have been eight since the Tertiary, for which he cites G.S. Boulton, in Geology of England and Wales, together with P. D. Duff and A. J. Smith, eds. Geological Society of London, 192, p.41, fig. 14.4. However, I suggest that the subsection, entitled Global Warming in Peter Toghill’s Chapter 13, is a compromise between what he wanted to write and what his publishers permitted him to write (c. f. the Publisher’s overall disclaimer, which I cited in introducing Peter Toghill’s Book.
As to anthropogenic global warming Peter Toghill goes on to state that we should not pollute the atmosphere, but it seems that natural changes are far more important than those produced by humans. However, while it has become popular to suggest that global warming has been occurring only since our industrial revolution; and that such warming is thus anthropogenic: I prefer to conclude that when two ocean currents meet head to head, at least one of them must reverse at lower depths and return from whence it came, accompanied by the other. Thus, I maintain that when the north flowing Gulf Stream encounters the south flowing Arctic current, there is a region where the warming Arctic current is of equal density with the cooling Gulf Stream; that in this region, these equally dense waters sink to to greater depths; that these now combined waters then move south at these greater depths, the Gulf Stream being the major component of the pair; that were this southern movement to cease, both surface currents would cease; that, instead of this ceassetion the encounter-region of the surface waters moves northwards in warming periods and southwards in cooling periods; but that we cannot determine from these movements the cause or the causes of the warming or of the cooling periods themselves.
However, Peter Toghill notes that the Quaternary is often equated with the Ice Age; but that this is a relative view; that though some temperatures did fall in the Tertiary by around 10 Centigrade degrees, it was still relatively warm in the tropics, and during the inter glacial periods, in the north, it was warmer than at present; and that if you asked the current inhabitants of Greenland if they thought the Ice Age had finished, they would say ‘No’, and if you asked the same question of the people of Antigua, they would say, ‘What Ice Age’. He then goes on to review the evidence for glacial and inter-glacial conditions in Britain, and to a lesser extent, in north-west Europe with reference to their names and dates (the latter derived from magnetic reversals) as set out in the Duff/Smith Table referenced above, but these details need not concern as here. It is, however, worth noting here, that there is evidence that the fossilised flora and fauna include evidence for oak and elder, warm-water shells, and elephants, lions and horses, and at Swanscombe, for the presence of scull fragments and the stone tools of early Homo sapiens in the Hoxian sub-period of the Pleistocene. Again, in the Devensian, there is evidence of a major cooling around 115,000 years ago, but with little in the way of ice-cover. However, a further marked cooling occurred 73,000 years ago and from then on, the climate oscillated to give maximum glaciation between 23,000 and 14,000 years ago, but with ice having largely disappeared by 13,000 years ago. Again, a sudden climate deterioration between 11,000 and 10,500 years ago produced the Loch Lomond re-advance, to be followed just as quickly by the climatic warming of the Holocene (Flandrian Stage) 10,000 years ago, in which we now live. But, I say, none of this identifies the cause of this re-cycling of temperatures.