About 700 million years ago, the Earth experienced several unusual events that led to virtually the entire planet being completely or almost completely ice-covered. This took place at the end of the Precambrian and the hypothesis is called “Snowball Land”. There are debates about what caused these severe frosts.
Without enough sunlight, we would expect the Earth to turn into an icy world. Constantin Arnscheidt of MIT suggested that it is not necessary for the amount of radiation captured to drop below a certain level. Instead, a sufficiently rapid drop in temperature could also initiate the process, even if the temperature at the end point were high enough to keep the planet frost-free.
Many factors influenced the cooling of the Earth. The sun could be dim and volcanoes could fill the sky with sulfur dioxide. Any such change would create a feedback loop. Some of them, such as reduced rock weathering, would counteract cooling. Others, including the expansion of the polar ice caps, would make this stronger. If the latter phenomena were to dominate, they would lead to an uncontrolled process leading to temperatures well below the temperatures when cooling begins.
Arnscheidt proved that reinforcing factors dominate when changes are rapid. When the process is slow, there is no snowball effect. The MIT scientists presented a model in which a 2% fall in sunlight in less than 10,000 years initiated a feedback loop that covered the entire surface of the planet with ice. This is just a basic model – analyzing additional factors can help you estimate the exact cool-down time.
“It is reasonable to assume that past glaciations were triggered by rapid geological changes caused by changes in solar radiation,” said Arnscheidt.
This discovery has important ramifications. Climatologists know this, but many people are still unaware of it – global warming is dangerous not because of the mere fact of heating our planet, but because of the speed of the process.