A continuous change in the axial inclination of 4° per precessional cycle would alter the amount of radiation reaching the earth's surface in a regular way and the earth would be expected to undergo the same climatic changes during each 360° inversion of the poles, if no other factors were involved. In reality, however, the earth's weather system is an immensely complicated system, involving many interacting variables. Moreover, it is not stated in theosophical literature how long this steady shift in the earth's tilt has been in operation, or how the rate of inversion may have varied in the past; there may have been times when the axial inclination remained virtually constant, including long periods of 'eternal spring'.
Paul Davies underlines our limited understanding of the global climate as follows:
Most computer simulations of the Earth's atmosphere predict some sort of runaway disaster, such as global glaciation, the boiling of the oceans, or wholesale incineration due to an overabundance of oxygen setting the world on fire. . . . Yet somehow the integrative effect of many interlocking complex processes has maintained atmospheric stability in the face of large-scale changes and even during periods of cataclysmic disruption.
Some of the chief factors influencing the climate are mentioned below:
1. The energy output of the sun. Solar flares and sunspots come and go over a cycle of about 11 years (the polarity of the leading spots in each hemisphere reverses at the beginning of each cycle, so that the magnetic period of the sun is considered to be 22 years). There are also thought to be longer variations of 200 or 400 years. Although the sun's overall brightness varies by no more than a fraction of a percentage point over its more or less regular cycle of activity, both individual flare bursts and the average level of flaring activity over a whole solar cycle are known to affect the weather on earth; one possible mechanism may be changes in the intensity of cosmic rays penetrating the atmosphere. During the most intense phase of the Little Ice Age in Europe, from 1645 to 1715, there were very few sunspots. In contrast, sunspot activity peaked between 1100 and 1250, a distinctly warm time in the northern hemisphere
2. The geometry of the earth's orbit, which determines the amount of solar radiation reaching the earth's outer atmosphere. The three main variables are:
a. The tilt of the earth's axis, which determines how much solar radiation is received at different latitudes.
b. Climatic precession (the 21,000-year cycle resulting from astronomical precession combined with apsidal motion), which determines at what time of the year the earth is closest to and furthest from the sun. At present the earth is closest to the sun in midwinter, which means that winters in the northern hemisphere are less severe than they might otherwise be. The most pronounced difference between winter and summer seasons occurs with a large obliquity and a large eccentricity such that winter occurs when the earth is farthest from the sun.
c. The ellipticity of the orbit (the degree of deviation from a circle, involving variations in the earth's distance from the sun). The ellipticity is currently 0.017, and is thought to range between 0.001 (almost circular) and 0.054 over a period of about 100,000 years.
3. The transparency of the atmosphere to either incoming solar radiation or outgoing heat. An important factor is the concentration of greenhouse gases in the atmosphere, such as carbon dioxide, methane, water vapour, nitrous oxide, and ozone. Clouds are the most important element in reflecting solar radiation back into space. Another important variable is the amount of aerosols (small particles) in the atmosphere, including dust thrown up by volcanic eruptions, and meteoric dust from space (resulting from passing through the tail of a comet, a meteorite stream, interstellar dust clouds, etc.). Sulphur dioxide from volcanic eruptions combines with water vapour to form tiny droplets of sulphuric acid, which reflect sunlight and lead to cooler temperatures in the lower atmosphere. Worldwide temperature dropped by about 2°C following the major volcanic eruption of Krakatoa in Indonesia in 1883. After the Tambora eruption in 1815, the extensive volcanic haze caused the following year to be called the 'year without a summer'.
Theosophical literature speaks of a veil of meteoric dust surrounding the earth. That the entire atmosphere is permeated with meteoric dust is well established, and an estimated 20,000 to 40,000 tons of cosmic dust fall on the earth every year. It is known that if there were no dust in the atmosphere, there would be little or no precipitation. But the meteoric veil apparently plays a more important role than scientists have yet realized. It is said to be many scores of miles thick, and to consist mostly of very fine cosmic dust but partly of larger bodies. Solar forces reaching the earth arouse electromagnetic currents in this thick shell of meteoric dust; the electromagnetic interchanges between the earth and its meteoric veil produce various meteorological phenomena, such as storms, lightning, winds, droughts, and the auroras, and are also responsible for some 70% of the earth's heat. The associated expansions and contractions of the atmosphere are said to be linked to the succession of glacial and warm periods.
Paul LaViolette has proposed that a cosmic ray volley or galactic superwave, caused by explosions in the centre of our galaxy, can push large amounts of cosmic dust into the solar system. These dust incursions substantially alter the earth's climate through their effect on the sun (perhaps triggering nova-like eruptions) and sunlight transmission through space. He argues that galactic superwaves pass us about once every 26,000 +/- 3000 years (approximating a polar precessional cycle), with the possibility of a 13,000 year recurrence interval. Another important factor is that as the earth revolves around the centre of the galaxy, it oscillates up and down through the galactic plane in a cycle of some 30 million years. When it crosses the plane, as it has been doing for the past 3 million years, it encounters higher concentrations of cosmic debris. The moon is believed to play a role in modulating the influx of meteoric dust.
4. Atmospheric and oceanic circulation patterns, which are set in motion by the different amounts of energy received from the sun at different latitudes and by the rotation of the earth. The circulation of atmosphere and oceans reduces temperature imbalances on a regional scale as well as between high and low latitudes.
5. The albedo (reflectivity) of the surface (due to soil types, presence of ice, snow, and vegetation, etc.), which affects the earth's absorption or radiation of energy.
6. The distribution of land and sea, and the topography of the continents and seafloor (land elevation, sill depth, channel width, etc.), which affect atmospheric and oceanic circulation patterns. Land temperatures reflect both elevation and proximity to the sea (which has a higher heat-storage capacity than land). The average annual temperature decreases by about 4°C for each 550-metre rise in altitude. Hence there is permanent snow on Mt. Kilimanjaro, despite the fact that it is located astride the equator. In the Atlantic, the Gulf Stream carries warm surface water northwards, and keeps northern Europe much warmer than Canada at the same latitude. Conversely, the cool Peruvian coastal current ameliorates the tropical climate of Chile and Peru. The Gulf Stream is thought to have been some 35% weaker during the last glacial maximum, some 21,000 years ago.
The popular dogmas of plate tectonics and continental drift are frequently invoked to explain past climates, but detailed studies show that shifting the continents succeeds at best in explaining local or regional palaeoclimatic features for a particular period, and invariably fails to explain the global climate for the same period. Moreover, drifters say that the continents have shifted little since the start of the Tertiary, yet this period has seen significant alterations in climatic conditions. The geographic distribution of palaeoclimatic indicators such as evaporites, carbonate rocks, coals, and tillites is best explained by stable continents and by periodic changes in climate, from globally warm or hot to globally cool. For instance, 95% of all evaporites (a dry-climate indicator) from the Proterozoic to the present lie in regions that now receive less than 100 cm of rainfall per year, i.e. in today's dry-wind belts. The evaporite and coal zones show a pronounced northward offset similar to today's northward offset of the thermal equator. Horizontal crustal movements are relatively unimportant compared with vertical crustal movements and the associated emergence and submergence of continents
7. Currents of electricity within the earth (telluric currents) and in the atmosphere, and variations in the geomagnetic field. Geomagnetic field patterns closely match the circulation patterns of the atmosphere and also affect ocean currents. It may be significant that during the last ice age, the ice cap was not centred on the geographic north pole but about 15° southward, at a point below Thule, Greenland, at about the same latitude as the present north magnetic pole. A sudden collapse of the magnetic field could cause the air to be chilled into a liquid rain or frozen into snowflakes, followed by super-hurricane winds rushing in to fill the atmospheric vacuum.
8. The impact of asteroids, meteoroids, or comets of varying sizes. It is fashionable at present to assign impacts a major role in triggering climate change and global catastrophes. However, polar ice core studies show no evidence that the climatic transitions of the last ice age were precipitated by comet impacts, though cosmic bodies certainly hit the earth from time to time.
9. Interactions between life and its environment. According to the Gaia hypothesis, the earth's biota does not simply respond passively to climate but helps to modulate and even control it, by regulating the concentration of atmospheric carbon dioxide and other organically derived substances so as to keep temperature and precipitation at advantageous levels. James Lovelock describes the earth as a self-regulating organism, capable of ensuring the survival of a life-sustaining global climate. Humans, however, are also known to exercise an adverse influence, through desertification, deforestation, emissions of greenhouse gases, etc., though their impact is probably of little significance compared to what nature itself is capable of.
According to the widely accepted Milankovitch model of the ice ages, the history of glaciation and deglaciation is primarily determined by the insolation changes resulting from the three orbital cycles -- the obliquity cycle (i.e. the postulated axial oscillation between 21.6° and 24.6°) with a period of 41,000 years; climatic precession with periods of 23,000 and 19,000 years; and the eccentricity cycle with a period of 100,000 years. It is commonly asserted that studies of the climate record have found evidence of climatic variations with essentially the same frequencies. However, the picture is rather more complicated than is often implied. The periodicities found in the Pleistocene climate record include: 140,000, 104,000, 100,000, 44,000, 43,000, 41,000, 40,000, 25,000 24,000, 23,400, 23,000, 20,000, 19,000, 18,600, 15,700, 9300, 9200, 6400, and 5700 years. It seems at times that scientists are more interested in fitting data into the Milankovitch theory than in objectively testing it or looking for alternative explanations.
Even if the approximately 41,000-year periodicity found in the climate record is genuine -- and age determinations become increasingly uncertain the further back we go in time -- it would be premature to conclude that this proves the existence of the obliquity cycle postulated by science, since other factors may be responsible. The general belief that the 100,000-year periodicity is related to the eccentricity cycle has also occasionally been challenged. LaViolette says that galactic superwaves may be related to the 23,000-year climatic cycle, and could also account for the 100,000-year cycle, which approximates four superwave periods.
Alistair Dawson has concluded that some of the Late Quaternary palaeoclimatic data can certainly not be explained in terms of the Milankovitch cycles. He also warned that any correlations should be tempered with caution since the calibration between Milankovitch astronomical chronology and radiometric ages is not know with certainty, and it is not at all clear how Milankovitch effects are translated into changes in global climate.
The main problems facing the Milankovitch model are as follows.First, it fails to explain the vast epochs in which the earth was free of polar ice sheets. Second, the relatively small seasonal and latitudinal radiation variations resulting from the orbital parameters are insufficient to account for the magnitude of climatic changes. Third, the 100,000-year cycle appears to dominate in the Pleistocene climatic record, whereas scientists calculate that the 100,000-year eccentricity cycle is the weakest of the orbital parameters. Fourth, the pattern of the climatic record is asymmetrical: ice ages appear to start slowly and take a long time to build up to maximum glaciation, only to terminate abruptly and go from maximum glacial to full interglacial conditions in less than 7000 years. In fact, major temperature changes of up to 10°C can even occur in a matter of decades.
Fifth, climatic changes in the northern and southern hemispheres appear to be synchronous, whereas the precession cycle operates in different directions in the two hemispheres. Finally, solar flares have probably altered the amount of solar radiation received at the outer atmosphere, whereas the Milankovitch theory assumes that it has remained constant.
In theosophical literature poleshifts are mentioned as one of the causes of sudden climatic changes and ice ages. Blavatsky says that the 'karmic disturbance of the axis' has produced periodical deluges and glacial periods. W.Q. Judge writes:
Ice cataclysms come on not only from the sudden alteration of the poles but also from lowered temperature due to the alteration of the warm fluid currents in the sea and the hot magnetic currents in the earth, the first being known to science, the latter not. The lower stratum of moisture is suddenly frozen, and vast tracts of land covered in a night with many feet of ice. This can easily happen to the British Isles if the warm currents of the ocean are diverted from its shores.
2. Climate and axial tilt
The most important single variable in the climate is the temperature, which is determined by two main factors: the angle of incidence at which the sun's rays strike the earth's surface, and the length of time the sun remains above the horizon each day The amount of solar radiation reaching the earth's surface is reduced by the thickness of the atmosphere through which it must pass. The heating effect per unit area (insolation) is at its maximum when the sun is vertically overhead and at its minimum when it is on the horizon.
The earth's axial tilt divides it into three main climatic zones: the tropical or torrid zone, the temperate zones, and the polar or frigid zones. The tropical zone lies between the tropic of Cancer and the tropic of Capricorn, where the midday sun is vertically overhead at the summer and winter solstices respectively. The temperate zones lie between the tropics and the polar circles (23.4° and 66.6° N and S). Within these regions, the sun is never vertically overhead, and the intensity of insolation becomes increasingly seasonal with distance from the equator. At 50° latitude, there are just over 16 hours of daylight at the summer solstice, but only about 8 hours at the winter solstice. At 60° latitude, the figures are 19 hours and 6 hours respectively. In the polar zones, seasonality is taken to extremes. At the arctic and antarctic circles, there is a day of 24 hours daylight at the summer solstice and 24 hours darkness at the winter solstice. At 79° there are two months of permanent daylight during summer and two months of winter darkness. At the poles, there would be six months of daylight during the summer and six months of winter darkness, were it not for the fact that atmospheric refraction reduces the period of darkness by about half.
Although the earth's tilt defines the theoretical boundaries of the tropical, temperate, and polar zones, actual climate conditions can differ significantly from this simple picture due to the influence of all the many other climatic factors. Thus, although, theoretically, the temperate zones are the regions of the earth between the tropics and the polar circles, in terms of actual climatic conditions the temperate zone currently lies between about 40° and 50° in the northern hemisphere and 35° and 55° in the southern hemisphere. Moreover, not even these more restricted zones can be described as temperate in their entirety, since although the northern zone includes western Europe and similar regions such as New Zealand, it also includes the heartlands of continents, such as Siberia and the central-northern US and Canada, where conditions are much more extreme. These far from temperate regions are generally described as having continental climates, while the only true temperate regions are those on the western sides of continents, dominated by the arrival of successive weather systems sweeping in from the oceans further to the west. The prevailing winds off the ocean keep the temperate regions cool in summer and warmer than they would otherwise be in winter.
An increase in the inclination of the axis to, say, 26° would enlarge the (theoretical) tropical and polar zones, and compress the temperate zones. Only at the midlatitudes of 45° N and S would there be little noticeable change. The temperature range in continental interiors would probably change for the worse. Increased extremes of temperature in summer and winter would require a more vigorous atmospheric and oceanic circulation to transport the heat from the tropics to the poles, resulting in increased storminess, fierce winds, and general unpredictability of the weather. If the obliquity were to decrease to about 20°, the temperate zones would expand at the expense of the tropical and polar zones. Temperate flora and fauna would be able to extend their ranges north and south of the present limits. The variations between summer and winter insolation would be reduced, and the range of temperature in continental regions would be much more equable. The temperature gradient between the tropical and polar regions would be greatly reduced and less heat would need to be transferred across the temperate zone. Weather patterns would become more stable and predictable.
With an axial tilt of 30°, the tropics are at 30° latitude and polar circles at 60° latitude, so that the tropics, temperate zone, and polar zone each cover 30° of latitude in each hemisphere. With a tilt of 45°, the tropics and polar circles are at 45° latitude, and the temperate zone disappears (though temperate conditions may still exist in certain regions). With a tilt of 60°, the tropics are at 60° latitude and the polar circles at 30° latitude, which means that latitudes between 30° and 60° are within both the tropics and the 'polar' zone! At higher tilts, the overlap between the two zones increases, until at 90° (and 270°) it reaches 90°, so that the whole earth lies in both the tropics and the 'polar' zones, resulting in seasonal variations of extreme intensity even at midlatitudes. With a tilt of 0°, on the other hand, the temperate zone would cover the entire earth, and day and night would everywhere be 12 hours long. This would be the ideal world for human habitation, as there would be no pronounced seasons, little heat flow, and the weather system would be reduced to only the gentler circulations of atmosphere and oceans resulting from the earth's rotation.
An article in Astronomy magazine in 1992 attempted to describe the conditions that would prevail if the earth's axis was tilted at 90°.3 In spring and autumn all parts of the earth would still have daily cycles of daylight and darkness, but there would be extended periods of constant daylight in summer and constant darkness in winter. Twice a year every latitude would experience tropical heating as the sun passed directly overhead. At a latitude of about 34° N or S, the day-night cycle would last for a total of 7.5 months of the year, while for the other 4.5 months there would be constant day or constant night, coupled with harsh summers and winters. The lengths of these periods would vary at different latitudes.
The seasonal heating cycle prevents the formation of permanent polar ice caps. The polar regions would experience the same tropical heating and high temperatures as the equatorial regions of old Earth. However, the polar regions in winter are exceptionally cold, so seasonal polar ice caps may form. Because the polar caps aren't permanent, the oceans -- and the shorelines on the continents -- are higher than those on old Earth.
If seasonal polar ice caps form, the dominant force controlling weather may shift from jet streams which circle the Earth along lines of latitude to a pole-to-pole flow. This mimics the condensation flows seen on Mars, caused by the freezing and thawing of the Red Planet's polar caps. Thermal flows created by intense heating at one location and cooling at others may replace old Earth's trade winds and other east-west winds.
New Earth residents probably also experience significant seasonal variations in the shoreline, depending on whether the thawing of one polar ice cap occurred at the same rate as freezing at the other pole. This change in sea level would occur on top of a change in the range of tides due to gravitational effects from the Moon and Sun. . . .
Biological clocks, also called circadian rhythms, help animals and plants make the best use of their waking hours, driving urges to eat, sleep, seek shelter, or store food for the winter. . . . Most living things have biological clocks that run with cycles of between 23 and 25 hours. Earth's cycle of day and night constantly realigns these cycles to keep them in sync with the changing seasons. In contrast, during experiments in which no day-night change occurs in lighting, people resort to their natural biological clock of around 25 hours to regulate their actions, such as sleep cycles.
But life on new Earth, where protracted periods of daylight and darkness exist, would have to adapt differently. Life-forms may depend exclusively upon their biological clocks to avoid the problem of the changing day-night cycle and the periods of prolonged daylight and darkness. Or perhaps the biological clocks would take over only during the periods of continuous daylight and darkness. When day and night cycles finally returned, the day-night cycle would control activities. (Would life-forms suffer from a massive dose of jet lag during the period when the day-night cycle takes over from the internal biological clock?) Perhaps life wouldn't have biological clocks at all. Or perhaps life-forms would have a complex set of rhythms that control activities during the periods of prolonged darkness and prolonged light and that adjust to changes in the day-night cycle. Clearly, whatever dominates the biological rhythms, social and emotional aspects of humans would evolve differently on new Earth.
3. The climate record
The global climate has undergone major changes over the course of geologic history. The earth's climate has fluctuated episodically between periods of worldwide warming and worldwide cooling. Right-hand deflections of the curve represent periods when the earth was uniformly warm with no frigid zone, and left-hand deflections of the curve represent periods when the earth was cool.
The evidence for very warm temperatures at high latitudes and glaciation at low latitudes clearly shows that the width of climatic zones has changed radically since the mid-Proterozoic. Since the width of climatic zones and the range of seasonal change are largely determined by the degree of axial tilt, this would suggest significant changes in obliquity. Nevertheless, the reigning scientific belief is that since the climatic record shows that in the past, as today, the earth was generally divided into three primary zones -- a mainly warm climate at low latitudes, with cooler climates at high latitudes -- there is no need to invoke major changes in obliquity. However, a number of scientists disagree with this.
Since the warming and cooling trends shown in figure 1 generally lasted many millions or tens of millions of years, they can certainly not be explained simply in terms of a steady shift of the axis -- even allowing for the fact that according to theosophy the geological periods are much shorter than the exaggerated periods postulated by science on the basis of radiometric dating . It should be borne in mind, however, that our planet's history is reconstructed by studying the properties of the various strata of the earth and the fossils found in them, and that the record of the rocks is very incomplete: more than 95% of all the sedimentary rocks formed since the origin of the planet have been eroded and recycled. In addition, many former land areas are now submerged beneath the oceans. Nevertheless, there is mounting evidence that superimposed on the long-term warming and cooling trends there have been significant oscillations in climate. For instance, the Pleistocene ice age consisted of a succession of glacial and interglacial periods, whose number was initially put at 4, whereas nowadays it is put at 17.
The prevailing view today is that Antarctica has been subject to continuous polar climates for the last 15 million years (since the mid-Miocene), though some scientists believe that East Antarctica may have been relatively deglaciated 3 to 5 million years ago (in the early Pliocene). The Arctic is thought to have been a warm ocean until approximately 2 million years ago, followed by a permanent ice pack about 850,000 years ago. There have been many times during the history of the globe when the polar regions had a warm climate. For example, fossil plants and animals (including the first-known amphibians) indicate that warm conditions existed in the arctic regions in the Devonian. Large Permian reptiles, which must have required a warm climate, are found along the Dvina River of Russia, just below the arctic circle. A forest of Late Permian age, interpreted to have lived between 80 and 85°S, has been discovered on Mt. Achernar in the Transantarctic Mountains.
The overall climate of the Mesozoic, and more specifically of the Cretaceous, was warmer than that prevailing over the globe today. Modern tropical to subtropical conditions extended to at least 45°N and possibly to 70°S, with warm- to cool-temperate climates beyond this zone. This warm global climate was also notably equable. In the Triassic some amphibians ranged all the way from 40°S to 80°N. In the Cretaceous large dinosaurs and trees existed in such high-latitude localities as Svalbard and the present North Slope of Alaska. In the late Palaeocene-mid-Eocene, there were forests on Ellesmere Island (80°N) with crocodilian bones, palm trees in west-central Greenland and southern Alaska, and mangrove swamps in the London-Paris basin. During the late middle Eocene, tropical rain forest occurred at least 20° and possibly 30° poleward of the present northern limit. The Miocene floras of Grinnell Land, Greenland, and Spitzbergen all required temperate climatic conditions with plentiful moisture.5 Large Pliocene trees in fossil forests have been discovered at 82.5°N in northern Greenland and 83.5°S in the Beardmore Glacier area of Antarctica.
Large trees live in parts of the Arctic today in a much colder climate than usually prevailed in the past, and some sizable trees in Siberia live as far north as 73°N. However, controversy surrounds the question of whether the big trees, widespread vegetation, and abundant, large animals that occupied these regions in the past could have survived under polar-light conditions such as those that exist with an axial tilt similar to the present one. Some scientists argue that the earth's obliquity must have been as low as 5-15° to explain the occurrence of subtropical floras in high latitudes during the Cretaceous and Palaeogene (early Cenozoic). H.A. Allard argued that the weak zonations of climate that have characterized certain geological eras are difficult to harmonize with a strongly tilted axis such as now prevails; he believed that in the Cretaceous, when there was little seasonal change, the obliquity was around 0°
Opponents of this view argue that although a smaller obliquity would increase the winter solar insolation at high latitudes, the mean annual insolation would decrease, leading to cooler polar temperatures, whereas the evidence points to warmer polar temperatures in Mesozoic and early Cenozoic time; an alternative explanation is that life may have adapted to a polar-light regime. However, the climatic models on which such views are based have been challenged. Jack Wolfe suggested that at some critical value of axial inclination, the atmospheric circulation changes from one that is predominantly cellular (as it is today) to one that is predominantly meridional, which would have more than compensated for decreased annual insolation values at high latitudes.
It is also conceivable that trees could have grown in polar regions if the earth had a much higher obliquity than at present. Fred Dick suggested that with an inclination of say 45°, an orbit of considerable eccentricity, and midwinter at perihelion, the Greenland summers would have been long and warm enough for the trees that used to grow there.9 This possibility illustrates how difficult it is to draw firm conclusions about the inclination of the axis on the basis of palaeoclimatic and palaeontological data.
It is stated in theosophical literature that the poles have been cold and warm in turn,10 and this is supported by the climatic record. According to an ancient Commentary, the third (Lemurian) root-race was at about the midpoint of its development when: 'The axle of the Wheel tilted. The Sun and Moon shone no longer over the heads of that portion of the Sweat Born; people knew snow, ice, and frost, and men, plants, and animals were dwarfed in their growth.' This may refer to the cooling period that began in the early Cretaceous .
An overall gradual warming took place from the Palaeocene to the mid-Eocene,
followed by gradual cooling until the major climatic deterioration at the end of the Eocene, though there were several fluctuations during this period. Since then, one major trend of northern hemisphere climates has been a decrease in the mean annual range of temperature and thus increased equability, though again there have been several fluctuations. Jack Wolfe postulates that if the major climatic trends during the Tertiary were largely the result of changes in the inclination of the axis, then from the Palaeocene to the mid-Eocene, the inclination gradually decreased from around 10 to 5°. It then began to increase slightly until the end of the Eocene, when the inclination increased rapidly to 25-30°. Since then, he believes that the inclination has gradually decreased to the present average value of 23.5°. He admits that this model does not explain several fluctuations in mean annual temperature, which might result from fluctuations in the amount of solar radiation reaching the earth. Xu Qinqi has argued that the main cause of the alternation of glacial and nonglacial periods is the variation of the obliquity between about 10 and 25°.13 Clearly such scenarios are still very conservative by comparison with the changes in axial inclination implied in theosophical writings.
Since early Pliocene time the width of the temperate zone is said to have changed by more than 15° (1650 km) in both the northern and southern hemispheres. If we apply the rule of a 4° axial shift per precessional cycle, the theoretical temperate zone (as defined solely by the axial tilt) should have changed by 90° in each hemisphere since the beginning of the Pliocene (about 1.87 million years ago on the theosophical timescale), though this could be obscured by the complexity of the climate system. At the start of this period, the inclination of the axis would have been about 48°, and it proceeded to pass through 90°, 180°, and 270°, before reaching its current value of about 336.6° (23.4°).
At the beginning of the Pleistocene (about 870,000 years ago on the theosophical timescale), the tilt would have been about 200°, and the earth's north pole would have made an angle of 20° with the south ecliptic pole. A series of glacial and interglacials ensued, and the last ice age ended about 11,000 years ago, when the earth's tilt would have been about 25°. We do not know for certain whether this is the theosophical scenario, since we have not been given any details of exactly how the axial tilt has evolved during this period.
The end of the last ice age between 13,000 and 8000 years ago was accompanied by a 120-metre rise in sea level and widespread flooding. The Late Pleistocene also saw large-scale volcanic activity, and the extinction of large animal species in many parts of the world. Blavatsky says that the last major cataclysm occurred about 12,000 years ago, but she does not explicitly link this with a poleshift. This cataclysm was followed by the submergence of Poseidonis, the last remaining Atlantean island in the Atlantic, in 9565 BC.