· The unique combination of factors on the Earth, viz. gravity, oxygen-rich atmosphere, an abundance of polar fluid (water), and the trajectory around the Sun are primarily responsible for rendering it habitable.
· The favourable thermal regime in the biosphere is conspicuous by its absence in the above list. The temperature on the Earth is a consequence of the greenhouse phenomena. Without gravity and (consequently) the atmosphere, the Earth will get much cooler and would have acted as a ‘heat sink.’
· The 'warmth' further differentiates the Earth from her celestial sisters. While the other planets have become either heat emitters or sinks, the Earth is perched ‘on the fence.’ It can either become a heat sink or become hot enough to act as heat emitters.
· ‘Life’ balances the Earth on the fence.
· Together, all the above-stated attributes entrapped the Earth between the two extremes (heat radiator and sink). The heat received on the earth began to be passed around between the three spheres (lithosphere, hydrosphere, and atmosphere).
· It is important to acknowledge the centrality of gravity in this cycling.
· The differential rate of energy release from each sphere cumulatively added the stress on the energy cycle.
· Living organisms propped up as moderators that regulate the energy flow and thereby relieve the stress on the energy cycle.
· The moderation was achieved by sequestering energy in the living body for some time.
· Living organisms can be visualised as energy check dams.
· It was logical to find more living mass in those regions on the Earth that receives more solar energy and has adequate water (the tropics). While the hot arid and the arctic regions of the Earth represent micro-theatres of the above-stated heat radiator and sinks.
· The abundant polar fluid (water) became the baton (medium) of the energy cycle.
· A host of elements piggy-back on this baton.
· Left to itself, the probability of the Earth becoming a heat-sink seems to be higher. [While there were multiple ice ages, there were no heat-age(s) during the planetary evolution.]
· One species has altered this probability. Unless under some unexpected, unforeseen planetary-scale events, the Earth is unlikely to have an ice-age shortly (planetary time scale).
· However, indiscriminate human actions have begun to destabilise the planetary level equilibrium. Our action has released vast amounts of energy stored in innumerous check dams both on the lithosphere (plants) and hydrosphere (marine life). The equilibrium is slowly but surely shifting to the right side (warmer atmosphere).
· There are two options in front of us:
either wait for the Earth to restore the equilibrium
or
intervene to recreate energy check dams.
