For decades, climate change has been almost only understood in one direction: the Earth is getting hotter and hotter. But a new study by scientists at the University of California, Riverside (USA) and the University of Bremen (Germany) offers a paradoxical scenario: Extreme warming could trigger a "mistake" in the climate system, pushing the planet back to the ice age.
According to this study, heat does not lead to cold because of natural "balance", but because the Earth's self-regulating system overreacted.
For millions of years, the Earth has maintained a relatively stable state thanks to slow but sustainable geological mechanisms. As CO2 levels rise and global temperatures rise, rainfall also increases.
Rain erodes rocks, sweeping carbon from the continent to the ocean. Here, phytoplankton - microplankton - uses carbon for growth. When they die, they sink to the seabed, "locking" CO2 out of the atmosphere for thousands of years, reducing the greenhouse effect and making the climate cooler.
This mechanism has long been seen as the planet's natural "heat regulator". But new research warns that if the warming is too strong and prolonged, that heat regulator may overactive.
When the ocean warms to an extreme level, nutrients - especially phosphorus - will increase sharply. This stimulates phytoplankton to explode widely. As a result, the amount of carbon absorbed from the atmosphere and buried in the seabed increases much faster than the ability to replenish CO2 from natural sources such as volcanoes.
Once the ocean floor "swallows" CO2 faster than the speed of Earth's emissions, greenhouse gas concentrations will drop sharply. Global temperatures can then plummet in a relatively short time on a geological scale, pushing the planet into a period of severe freezing, similar to the glacial periods that once existed in history.
In this scenario, phytoplankton - often seen as the "alliance" of climate - becomes a dangerous factor. In very warm and oxygen-deprived oceans, phosphorus can be released back from seabed sediments, continuing to nourish plankton. The cycle continues to accelerate: More nutrients, more phytoplankton, more CO2 retained, and a faster cold climate.
Although it sounds scary, scientists emphasize that this is just a hypothesis based on modeling and geological data. Even if this scenario happens, the time is counted in hundreds of thousands of years. Modern humans will almost certainly no longer exist to witness a new ice age triggered by global warming itself.
In the near future, the threat remains unchanged: extreme heat, drought, sea level rise and increasingly severe weather phenomena. Cold, if it comes, will appear long after humans disappear.
The final unpleasant message: Earth does not exist to ensure stability or convenience for humans. This planet is only seeking its own balance, even if the price to pay is the disappearance of a "conscious" creature.
And that awareness may be the last chance to slow down climate change, before "climate defects" become irreversible.
