From the tropics to the poles – an introduction to the book, 2015 version

What voice do we choose for this book, our combination of favourite photos close to the written theme and short text, together with details for further voluntary digging by the interested reader.  If only we can imitate the recent and quite wonderful book by Stephen R Palumbi and son Anthony R Palumbi called “The extreme life of the Sea”; their format and style (two voices, one delighting in bringing the unusual facts or slant and the other that of a lyrical and quite wonderful dramaturge) works so well that you just want to keep reading and learning.

We started by wondering what the world truly is these days.  In our previous lives as consultants to government and industry, we had looked hard and wide at the growth processes involved in human activity and in the atmosphere; we knew from experience how quickly transitions can take place.  We could forecast electricity demand and urban ozone levels by realising that the weekly, seasonal and annual cycles of human activity were reflected both in our needs for power and in the resultant contributions of pollutants to regional air-sheds.  We discovered that special days such as national holidays and religious festivals changed the patterns so much that our forecasts had to have a different tilt. And, just add in a few bushfires on a hot, still day and the chemistry of the atmosphere would jump into a quite different and potentially adverse mode.  We constructed forecasting systems for electricity load and price and for urban air quality that had such deductions as their basis .

With (at last!) time on our hands, we could now venture further afield and look at the changes –  along both the long meridians and the broad latitudes, in a world where divisions into north and south are becoming less useful.  We quickly found it necessary to look up and across, down and around in order to make sense of the changes now taking place, both in the environmental and socio-economic worlds.  And many types of animals, insects and birds of the natural world had beaten us to it in their migrations for food, sex or safe habitats.  Whether we like it or not, we all are or will become migrants unless we can adapt to the changes happening now and in our near future.

So, what are we talking about in the title?  Let’s start with some definitions so we do not get too lost on our beachcombing safaris to lands far and near!


Tropic    – (middle English from the Greek tropikost (making a turn)); –  the parallels 23° 26′ north and south of the equator; two circles on the celestial sphere, Cancer in the north and Capricorn in the south.  Cancer the crab is the cardinal water sign, Capricorn the goat is the cardinal earth sign.

The tropics are the regions on Earth between the Tropic of Cancer and the Tropic of Capricorn, whilst tropical is an adjective meaning of tropical location or nature.  Animals of the Tropics can live elsewhere as the bio-physical tropics pass poleward of Cancer and Capricorn!

Allied terms are of the form X-tropic (such as geotropic, neotropic, aerotropic, neurotropic, gonadotropic … etc.) meaning tuned toward, with an orientation toward, having an affinity for, affecting the activity of, maintaining…(the earth, new American tropics, atmosphere, brain, reproductive systems…).

Pole means a type of singularity, an exceptional point in space and/or time.  For the Earth, it is the point at which the axis of the earth, suitably extended, cuts the relevant part of the celestial sphere.   The two points North Pole and South Pole are the northern and southern ends of the axis of rotation of the earth.  All lines of longitude are parallel at the equator and converge to a point at the true north and true south poles.

As they move relatively slowly, the geographic poles can be identified from a time-lapse photograph of the movement of the stars across the night sky, or, if this is not visible, then the directions indicated by marker stars such as the Southern Cross or the Big Dipper.

The two poles are currently glaciated or land covered with ice.  The next largest ice surfaces in the world are the Himalayan/Tibetan mountains that comprise many different countries.  It has become popular to refer to the Third Pole, that band of white surface so obvious from space and consisting of high, ice/snow covered land close to the Tropic of Cancer.  There is as yet no definition of a Fourth Pole!

There are other types of poles besides the geographical ones; magnetic poles where the earth’s magnetic field has a singularity and where the force-field magnetic lines converge.  As the earth’s field is changing over time, the north and south magnetic poles wander slowly across the landscape.  Our magnetic compasses show us the current position of the magnetic poles.

Whilst the geographical poles became the focus of explorers’ aspirations in the early 20th Century, the exact location of the southern magnetic pole was poorly known, see

and it had to wait for other Australians in 1986 to reach properly the southern magnetic pole.

The auroras occur as the magnetic poles are the foci for the solar wind of charged particles as they enter the earth’s upper atmosphere, spiral around the magnetic field lines and ionise the gases in the stratosphere.  The excited atoms then radiate light of the frequencies that match the activation energy.  We see bands of intense greens, reds and yellows and purples that dance before our eyes, if the conditions are right.

The geographical latitude of a given location can be readily measured from the position of the midday sun or the orientation of the night sky but the determination of longitude was much more difficult to determine from measurements.

There are no special places on the endless equator; we have to set our zero somewhere.  The designation of Greenwich in London reflects the historical importance of British explorers.  The determination of longitude required a comparison of a “set by Greenwich” clock with local clocks where midday is defined by the highest position of the sun, or equivalent measure.  Very special clocks were designed for carrying on rough seas in British ships for such a comparison; this method competed with the astronomical determination in the days before satellites and GPS.

The amazing thing about these definitions of the geographical poles is that things were not always this way.  Many millions of years ago we had “tropical poles”, as the polar continents were above the north and south poles; they have since moved away from there by continental drift.  There is coal readily seen in the polar north and found in the polar south, in both cases dated and proven to be formed from tropical vegetation of earlier times.  And once, the continents of Antarctica, Africa, Australasia and South America were one super continent that encompassed the south pole.

The above discourse tends to concentrate on what is happening at the surface of the earth where humans have their regular habitat.  As the climate changes slowly, we are experiencing more tropical weather, as the tropics expand towards the poles.  This action takes place in the troposphere which is the lowest layer of the atmosphere up to a temperature “inversion” some thousands of metres above the surface.  The stratosphere is the next elevated layer and is so important for many of the chemical and ionic processes that determine how and why we exist.

For structures that start low and reach to these heights, consider the emissions from the major volcano of Mauna Loa on the Hawaiian Big Island.  It rises nearly 9 km above the ocean floor; the mountain has depressed the ocean crust by some 8 km suggesting that any volcanic rocks and combustion gases come from 17 km below the tip of cone.  The rocks fall to earth; the gases are very buoyant and in light winds reach the stratosphere.  Such hot gases contain sulphur oxides that can scatter light and provide some shading from the sun for the earth’s surface and so affect both weather and climate.  No wonder then that we need to look at volcanic emissions when deciphering climate change and variability.

It is only in recent years that we have been able to track the motion of, for example, the hot air that rises from the surface of the third pole in summer up through the troposphere into the lower stratosphere.  The air parcels ascend quickly into the stratosphere where they meet polar-seeking winds.  These move the parcels along to be sucked towards the poles and descend again with their chemical signatures almost intact into the troposphere of the polar regions.

We also need to keep this vertical dimension in mind when trying to understand the teleconnections of various parts of the earth’s surface; teleconnections are the “action at a distance” concept of meteorological and climate interactions and are convenient names for a set of important processes (of which we may understand little in detail).  In the above example, we could talk of the teleconnection of the Tibetan plateau with Greenland via the hot air reaching the stratosphere!

Telecouplings are a similar concept for socio-economic systems; we have examples such as the demand of oil in China being a driver for the exploration and extraction of oil under the almost-virgin rainforest of Eastern Ecuador, with a sea passage of semi-processed oil in large tankers along a narrow band of latitudes being the physical representation of the telecoupling.

So we start a journey looking upward and outward, downward and into the depths below us or within ourselves.  We can ponder the present or find ways to delve into the past.   And, by the clever devices of science, we can glimpse the possible and perhaps alternative futures, and even think of how an alien scientist might view us from afar (see the XX post).