Probably, with the heat that is felt, the idea of having the planet completely covered with snow may not even seem credible. However, a sudden and rapid change in the level of solar radiation caused the ice to cover the Earth completely 717 million years ago.
Despite the fact that the last time happened many millions of years ago, scientists believe that such an event has happened several times. So, the question is: can it happen again?
Earth, the snowball
According to scientists, the Earth, 717 million years ago, was covered by a large layer of snow and ice. This event was called “Snowball Earth” and may have occurred several times throughout the history of our planet. Average temperatures reached fifty degrees below zero and the ice at the poles spread to the equator.
A magnificent and gloomy landscape
Most likely, the trigger was a blockage of sunlight caused by an unclear event. However, the hypotheses may point to massive volcanic eruptions, which release aerosols into the atmosphere, or primitive algae that, by some mechanism, facilitate the formation of clouds that reflect light.
A team of MIT researchers has developed a mathematical model that sheds light on the formation of these extremely cold eras. According to what the study, published in Proceedings of Royal Society A, concludes is that global glaciations occur when the level of solar radiation received by the planet's surface changes rapidly in a geologically short period.
So, the key issue here is not the amount of solar radiation decreasing at a specific point, but the key is the speed with which it does this.
The key is in radiation
The research carried out by the specialists takes into account several parameters. Thus, it is important to understand the relationship between incoming and outgoing solar radiation, the temperature of the Earth's surface, the concentration of carbon dioxide in the atmosphere and the effects on the absorption and storage of atmospheric carbon dioxide. The experts were able to adjust each of these parameters to see which conditions generated a “Snowball Land”.
What was understood is that for our planet to become an ice ball it was necessary that the solar radiation received to decrease quickly. That is, if that radiation were to reduce, for example, to a rate of 2%, it would take approximately 10,000 years for the Earth to enter the global ice age. However, there is no certainty what the critical rate for the event would be faster.
The causes may actually be those mentioned above, that is, massive eruptions or a biological process.
Can we cause this event?
What scientists have concluded may help humanity to think. That is, if there is no global environmental plan, the problems will surely start to be more and more serious.
Although humanity does not unleash a snowball glacier on our current climate trajectory, the existence of a 'speed-induced tipping point' on a global scale may remain a cause for concern.
Explained Constantin Arnscheidt, from the Department of Science. Earth, Atmospheric and Planetary (EAPS) and main author of the study.
Regardless of the specific processes that triggered past ice ages, scientists agree that "Snowball Earth" arose from an "uncontrolled" effect. This means that as the sunlight decreases, the ice expands from the poles towards the equator.
As more ice covers the globe, the planet becomes more reflective, or higher, in albedo (reflection coefficient) which further cools the surface so that more ice expands. Eventually, if the ice reaches a certain degree, it becomes an uncontrolled process, resulting in the global ice age. Obviously, the world's glaciations on Earth are temporary in nature, due to the planet's carbon cycle.
In summary, scientists agree that the formation of the “Snowball Land” has something to do with the balance between sunlight received, ice albedo feedback and the global carbon cycle.
What happened on Earth may explain what exists on other planets
The findings can also be applied to the search for life on other planets. The researchers were interested in finding exoplanets within the habitable zone, at a distance from their star that would be within a temperature range that could sustain life. The new study suggests that these planets, like Earth, may also temporarily freeze if the climate changes abruptly. Even if they are within a habitable zone, planets similar to ours may be more susceptible to global glaciations than previously thought.
We could have a planet that was well within the classic habitable zone, but if the sunlight changes too fast, we could have a 'snowball on Earth. What this highlights is the notion that there are much more nuances to the concept of habitability.