Imprimer
/ Idées

A world unexpected: II

A world unexpected: II

Constantly contemplate the whole of time and the whole of substance,
and consider that all individual things as to substance are a grain of a fig,
and as to time the turning of a gimlet.

– Marcus Aurelius, Book X, Dictum 17

 

Chronos

 

In 1883, Krakatoa, a volcano in what was then the Dutch East Indies, erupted with such force that it pulverized an entire island and darkened the global sky for many months, creating spectacular sunsets of which we can still see traces in paintings such as Munch’s The Scream.

 

A world unexpected: IIIIII

 

Even though this may sound impressive today, it is nothing compared to what earlier records tell us. Life on earth has gone through several massive environmental changes. It may be hard to imagine, but there has been times when our planet was entirely submerged by a single ocean, when it had a single big continent, when it was almost entirely covered with ice, and when it was a hot greenhouse devoid of any continental glaciers (respectively referred to as ‘snowball’ and ‘hothouse Earth’ by scientists). It has seen massive asteroidal impacts and gigantic volcanic eruptions by far more powerful than Krakatoa.

 

All of this happened while living things roamed the planet. Single-cell organisms have probably existed for more than two billion years. The rise of visible forms of life can be dated with more precision: the beginning of the Phanerozoic eon, about 540 million years ago. There has been a variety of mass extinctions since then, the last of which occurred following the advent of an ice age about 33.9 million years ago (after the dinosaurs became extinct).

 

Most of us grasp the magnitude of such periodic changes, although it remains much harder to grasp the scale of time over which the events take place. Homo sapiens, who has existed for about 200 000 years, covers an extremely short episode in the evolutionary saga of life. In fact, if the timescale for life on Earth was represented by the length of the Eiffel tower, human existence would be less than half an inch long. Industrialized society, covering the last 200 years, would be thinner than a human hair.

 

Likewise, we have affected the Earth in ways that can only be evaluated and understood over very long periods of time, far beyond that of a mortal life. The CO2 that we have so far put into the atmosphere will likely remain there for many millennia. The resources we have extracted from the Earth, some of which took hundreds of millions of years to form, are quickly being consumed and reduced to waste in just a few generations. Understanding environmental change effectively requires that we reframe our own existence in time.

 

Gaia

 

Accumulating evidence suggests that we are changing the balance of the Earth’s ecosystem. We are creating stressors in a system that has long remained stable. We know that there are limits to the extent we can extract and transform the Earth’s resources. We can also anticipate the potential consequences of our continued production and consumption of earthly materials (rare-mineral depletion, ocean acidification, water scarcity, mass extinction of wild plants and animals).

 

However, it is important to point out that we are disturbing this ecosystem in ways never recorded and never experienced before. Because of this, it is extremely difficult to grasp the effects and duration of the undergoing change. In fact, there is little way of really knowing what lies ahead. There are many ‘unknown unknowns’ on the road before us, that is, unforeseeable effects that cannot be imagined before they happen.

 

This unpredictability makes environmental change even more dreadful, since it leaves us ill-prepared to face the potential negative consequences (‘Black Swans’) that Mother Nature could bring upon us.

 

It should be noted that the Earth experienced several other ‘traumas,’ or extreme climatic disruptions, in its agelong past. As a matter of fact, Mother Nature has its own backup mechanisms for dealing with stressors. One of these is the geological carbon cycle.

 

Over time, atmospheric carbon dioxide reacts with silicates on the ground to form carbonate rock. As the physicist Ugo Bardi explains, ‘the reaction is slow by human standards, but not so by geological ones,’ and it gradually consumes atmospheric CO2.

 

Carbonates are soluble in water in the form of ions. As such they are progressively drained towards the oceans by rain. There carbonates enter the shells of marine organisms, which then sediment at the bottom of oceans. With the movement of the tectonic plates, the ocean floor is gradually pushed down and absorbed into the mantle, along with its sediment carbon, which is eventually brought back to the surface as the result of volcanic activity.

 

The geological carbon cycle is believed to be the principal mechanism ensuring that there is enough carbon dioxide in the atmosphere for plant photosynthesis, without which there would be no life on Earth.

 

But the cycle also effectively acts as a ‘planetary thermostat’ because it regulates atmospheric greenhouse effects. When Earth cools down, volcanic eruptions predominate over CO2 removal by silicate. The opposite happens when the Earth warms up.

 

Even when the Earth was almost completely covered by ice, volcanic activity ensured that it properly heated up again. This ‘thermostat’ mechanism is one of the reasons explaining why surface temperatures have remained within a range that is favorable to the continued development of life.

 

The problem with the geological carbon cycle, of course, is that it operates over several millions of years and as such is of no help whatsoever on a civilizational timescale. Mother Nature is antifragile, but we are not.

 

Read the following article in the series here.

 

comments powered by Disqus