(ORDO NEWS) — The Harvard researcher analyzed the likelihood of complete glaciation of the entire surface – including the equator – for terrestrial planets. It turned out to be a common scenario. And he can be the cause of the destruction of all complex life.
The work shows the unexpected vulnerability of our planet to this course of events. According to calculations, in the last 20 thousand years, the Earth has passed literally a few degrees from complete and permanent glaciation, which excludes the survival of large terrestrial multicellular organisms.
Traditionally in the scientific world, it was believed that the climate of terrestrial planets – including ours – has a “built-in thermostat” or, as it is also called, “carbon air conditioner”. When the planet is cold, carbon dioxide is weakly bound by rocks (the rate of chemical reactions of CO2 binding by basalts decreases).
Due to this, the main greenhouse gas accumulates in the atmosphere, and the temperature rises again. When it is hot on Earth, the rate of carbon dioxide binding accelerates sharply, its concentration in the air decreases, causing the greenhouse effect to fall – and lower the temperature on the planet.
Robin Wordsworth, the author of a new paper aimed at publication in The Astrophysical Journal Letters, decided to test whether the hypothesis of a carbon conditioner, supposedly automatically stabilizing the Earth’s climate, is compatible with the latest data on the climate of our planet in the past.
To do this, he calculated how often natural periodic fluctuations in the level of CO2 in the earth’s air can lead to the emergence of the “Earth-snowball” state. This is the name for the phase of complete and permanent glaciation of the planet, including the equatorial zone. For the Earth, it occurs at +7 ° C. Today, the average temperature on the planet is +15, and at the last peak of glaciation, 20 thousand years ago, it dropped to + 9-10 ° C.
The author makes detailed calculations of how the temperature on the simulated Earth will change with fluctuations in the CO2 level, identified from the analysis of ancient rocks. It turned out that with a serious cold snap, the oceans of the planet begin to actively absorb carbon dioxide, reducing the greenhouse effect and increasing cold snaps. It turns out that with a constant level of solar radiation, the planet should fall into a state of complete glaciation after 300 million years.
When the researcher entered into the calculations the fact that the radiation of the Sun increases with time, the speed of the onset of full glaciation did not suddenly decrease. It turned out that as the luminosity of the Sun increases, the tendency of terrestrial planets to glaciation does not decrease. The point is this: ice reflects solar radiation so well that the observed increase in the star’s luminosity cannot significantly reduce the chances of its planet for global glaciation.
The researcher comes to the conclusion that his modeling predicts: “the historically observed levels of CO2 fluctuations in the next hundreds of millions of years will be enough for the planet to transition to the state of “Snowball Earth”.
The author notes that this is the most general description of the process. In reality, such a scenario – in the absence of anthropogenic influence on the climate – can be realized even faster. Wordsworth recalls that the last peak of glaciation (20 thousand years ago) was literally a few degrees short of enough to start the unstoppable movement of glaciers towards the equator. Modeling shows that virtually all terrestrial exoplanets orbiting stars like the Sun should often fall into the “Snowball Earth” state.
Based on the data available today, this condition leads to the death of all terrestrial multicellular species. If the scientist’s calculations are correct, it turns out that the terrestrial planets do not have a “built-in thermostat”, but a built-in mechanism for the periodic destruction of all complex terrestrial life.
This can clarify the reasons for the Tsiolkovsky-Fermi paradox – the fact that with a very large number of stars and planets in the Universe, there are no signs of extraterrestrial civilizations. The likelihood of the emergence of civilization will be significantly reduced if the biological evolution of complex species is periodically “zeroed”, erasing all intelligent species before they can influence the climate and save themselves from its fluctuations.
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