Global warming could swing Earth’s climate regulation system in the opposite direction, creating the basis for an ice age.
Could global warming create the conditions for a new ice age on Earth? Theoretically… yes: the climate “control system” which, like a thermostat, corrects the earth’s temperatures, bringing them back towards acceptable ranges, could respond to excessive warming by reversing the situation, and laying the foundations for a period of extreme cold.
A group of Californian scientists has identified a missing piece in the understanding of the Earth’s carbon cycle, which could explain this seemingly absurd oscillation. The discovery could help us better understand how such extreme ice ages developed in the past.
An automatic adjustment system
For decades, a climate process based on the erosion of Earth’s rocks was thought to be a stabilizing force, keeping temperatures on Earth from swinging too far toward one extreme or the other. Rain absorbs carbon dioxide from the atmosphere before falling back to the Earth’s surface; the CO2 brought by the rain interacts with the rocks, degrades them, and the dissolved material ends up in the oceans with the previously captured CO2.
In the sea, carbon combines with calcium released from rocks and forms marine animal shells and limestone. These materials settle on the seabed and retain carbon for millions of years, partly contributing to reducing the level of CO2 in the atmosphere. Here is the regulation system we were mentioning: «as the Earth warms up – explain the authors of the study, published in Science – rocks degrade more rapidly and absorb more CO2, again contributing to cooling the Earth.”
An exaggerated correction
But if this climate “self-regulation” system works so well, why then were the ice ages that affected the Earth so extreme? In some of the first, ice and snow covered virtually the entire Earth’s surface. Such a level of freezing cannot be explained by a climate that settles in such a refined way: what process then could have sent the earth’s thermostat into overdrive?
A group of geologists from the University of California – Riverside have identified a possible cause of the “jam,” which has to do with how carbon is buried in the ocean. When CO2 increases, and with it temperatures and precipitation increase, rain transports greater quantities of nutrients removed from the emerged lands towards the seas. These substances, such as phosphorus, stimulate the growth of plankton in the oceans, which absorb CO2 through photosynthesis, like plants do on Earth.
When it dies, the plankton settles to the seabed along with the captured carbon: this process also removes CO2 from the atmosphere. In warmer conditions, however, excess nutrients cause plankton to overgrow and consume excessive amounts of oxygen in the ocean. With less oxygen, phosphorus is more likely to be released back into the water rather than remain permanently captured: this recycled phosphorus in turn causes even more plankton to grow in a loop that continues to drain oxygen reserves in the sea and which increases carbon capture by plankton.
It is this excessive “zeal” in removing CO2 and mitigating temperatures that risks reversing the situation and creating much less cooling than desired. In short, this is how the foundations for an ice age are created.
How it was, and how it will be
According to the authors, lower oxygen levels in the early Earth may have made the described climate control system less stable and triggered more extreme ice ages. Today there is more oxygen in the atmosphere and in the seas: if we continue to add CO2 to the atmosphere, in the short term the Earth will continue to warm, with the catastrophic effects on the climate that we have already begun to see. In a subsequent phase, the system described could generate a cooling period, however less extreme, because the presence of oxygen in abundance reduces the recirculation of nutrients and the excess of plankton described.
