The results also suggest that exoplanets located in residential areas may be sensitive to the ice age.
At least twice in Earth’s history, almost the entire planet has been surrounded by sheets of snow and ice. These dramatic events in Snowball Land occurred one after the other, about 700 million years ago, and evidence suggests that successive global ice ages have laid the groundwork for a further explosion of complex, multicellular life on Earth.
Scientists have considered several scenarios that could have overthrown the planet in each ice age. Although no driving process has been identified, it is assumed that what caused the temporary freezing had to be done in a way that pushed the planet beyond a critical threshold, such as reducing incoming sunlight or atmospheric carbon dioxide to a level low enough to detect due to the global ice spread.
Bet WITH Scientists now say the snowballs were the result of “speed-induced glaciers.” That is, they found that the Earth could enter the global ice age when the levels of solar radiation it receives change rapidly in a geologically short period of time. The amount of solar radiation must not fall to a certain threshold point; until the incoming sunlight decreases faster than the critical speed, there will be a temporary icing or “Snowball”.
These findings, published Publications of the Royal Society, show that any processes that caused the age of the Earth ‘s ice age were likely to reduce the amount of solar radiation reaching the surface, such as widespread volcanic eruptions or biologically induced cloud formation, which could have significantly prevented sunlight.
The results can also be applied to the search for life on other planets. The researchers wanted to find an exoplanet in a living area – at a distance from a star whose temperature would be such as to support life. New research suggests that these planets, like Earth, could also glaciate temporarily if their climate suddenly changed. Even if they are in a residential area, Earth-like planets may be more sensitive to the global ice age than previously thought.
“You can have a planet that holds up well in a classic living area, but if the incoming sunlight changes too fast, you can get a snowball,” says Constantin Arnscheidt, a major at MIT’s Department of Earth, Atmosphere and Planetary Sciences. (EAPS). “This highlights the idea that there are so many more nuances in the concept of accommodation.”
Arnscheidt is the author of this article along with Daniel Rothman, professor of geophysics at EAPS, founder of the Lorenz Center and one of the directors.
Despite the specific processes that caused the glaciers of the past, scientists broadly agree that the Snowballs resulted from a “running” effect that includes feedback from the ice albedo: As the sun’s rays decrease, the ice expands from the poles to the equator. As more ice covers the globe, the planet becomes more reflective or higher than the albedo, which further cools the surface for the ice to spread. Eventually, if the ice reaches a certain degree, it becomes a running process and leads to a global glacier.
The global ice age on Earth is temporary due to the planet’s carbon cycle. When the planet is not covered with ice, the level of carbon dioxide in the atmosphere is somewhat controlled by weather conditions associated with rocks and minerals. When a planet is covered in ice, weather conditions are greatly reduced, causing carbon dioxide to accumulate in the atmosphere, creating a greenhouse effect that eventually distracts the planet from the ice age.
Scientists basically agree that the formation of the globe has some connection between the incoming sunlight, the ice albedo feedback, and the global carbon cycle.
“There are a lot of ideas about what caused these global glaciers, but they all stem from some kind of implied modification of solar radiation,” Arnscheidt says. “But usually it was investigated across the threshold.”
He and Rothman had previously explored other periods in Earth’s history when the speed or speed of certain climate changes had implications for events such as the mass extinction of the past.
“Through this exercise, we realized that there was an immediate way to be serious about applying such speed-induced descent ideas to Snowball Earth and adaptability,” says Rothman.
“Be careful about speed”
The researchers developed a simple mathematical model of the Earth’s climate system that includes equations depicting the relationship between incoming and outgoing solar radiation, Earth’s surface temperature, atmospheric carbon dioxide concentration, and the effects of weather conditions on the uptake and storage of atmospheric carbon dioxide. The researchers were able to adjust each of these parameters to monitor the conditions under which the snowball occurred.
Eventually, they found that the planet would freeze faster if the radiation from the incoming sun dropped rapidly, at a rate that was faster than critical rather than up to a critical threshold or a certain level of sunlight. It is not known exactly what that critical speed will be, as the model is a simplified view of the Earth’s climate. Nevertheless, Arnscheidt estimated that in order to enter the global ice age, the Earth would have to suffer about 2 percent. The resulting sunlight falls in about 10,000 years.
“It is reasonable to assume that the glaciers of the past were caused by geologically rapid changes in solar radiation,” says Arnscheidt.
The specific mechanisms that could have quickly darkened the skies over tens of thousands of years still need to be discussed. One possibility is that widespread volcanoes have been able to release aerosols into the atmosphere and block incoming sunlight around the world. Another is that primitive algae may have had mechanisms that facilitated the formation of light-reflecting clouds. The results of this new study suggest that scientists may consider processes that rapidly reduce incoming solar radiation as likely causes of the Earth’s ice age.
“Despite the fact that humanity will not be shaken by the current trajectory of our climate, the existence of such a ‘speed point’ on a global scale can still be worrying,” Arnscheidt said. For example, he teaches us that we must be careful not only about the magnitude of change, but also about the pace at which we change the Earth’s climate. There may be other points caused by this rate that can be caused by anthropogenic warming. This identification and limitation of critical value is a worthy goal of further research. “
Reference: 2020 July 29 Constantin W. Arnscheidt and Daniel H. Rothman, The Ways of Universal Icing. Publications of the Royal Society.
DOI: 10.1098 / rspa.2020.0303
This study was co-funded by the MIT Lorenzo Center.