Earth system stabilisation

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Earth System Stabilisation

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It is a remarkable fact that life on Earth has persisted in an unbroken chain for at least 2 or 3 billion years out of the 4.5 billion years of Earth's existence. It appears that the environmental conditions on Earth have never, not even once during this immense interval of time, become so unfavourable as to wipe out every trace of life. Given that all life requires liquid water and hence temperatures between 0 and 100C (or thereabouts, depending on pressure, salinity, etc), this raises the interesting question as to how the planetary environment has been maintained in a habitable state for so long. Why is it that neither temperature nor any other environmental variable has ever in this time deviated so far from the biological comfort zone as to render the whole planet infertile?

Luck may have played a large role (see Anthropic Principle), as may have the incredible ability of evolution to adapt organisms to their environments. Some tenacious microbes may conceivably have persisted in out-of-the-way niches during environmental collapses, only to emerge and repopulate the rest of the planet afterwards. This would help explain the ubiquity of DNA amongst all living organisms, as well as the similarity between living and ancient fossil stromatolites.

Another possibility is that stabilising feedback processes intrinsic to the Earth System

The models featured here allow some insights into these automatic processes which keep the planetary environment in check. Five negative feedback processes are incorporated in the different models, one in each model:

(a) phytoplankton growth and ocean phosphate:

(b) nitrogen-fixer growth and ocean N:P ratio:

(c) diatom growth and ocean silicate:

(d) carbonate compensation and ocean carbonate:

(e) Earth heat emission and Earth temperature: black-body radiation

The properties that these negative feedbacks endow on Earth System behaviour, and the degree to which they impart stability to the Earth environment can be analysed with the different models in several ways:

(1) comet simulations:

(2) time-variable river inputs: Follmi and fast follmi

(3) instantaneous perturbations:

(4) pulse addition experiments: and fossil fuel scenarios

(5) volcanic eruptions:

(6) randomised initial conditions: