Science is largely in agreement when it suggests that the Earth’s temperature it increases more and moreand logic could lead us to think that the world is going to become in a real desert like the one in Almería. But to everyone’s surprise, what can happen is a great ice agethat is, everything ends up covered in ice. And although it may seem illogical, science wanted to give light about this topic.
They have been new models from the University of Bremen and the University of California Riverside, published in Sciencewho have located right there one of the great unexpected dangers of terrestrial geochemistry: under certain conditions, excess heat can activate “biological accelerators” that then cool the planet beyond its original state. Even to reach an ice age.
Beyond the rocks. Something that may be unknown to many is that the Earth has a temperature control system like the thermostat in our home. The most accepted was regulation by the slow wear of silicate rocks.
However, geological records show episodes in which this natural “thermostat” fails: the Earth freezes from pole to pole, as during the Precambrian glaciations. What is missing from the equation? The new study points to the decisive influence of marine biology and nutrient cycles, especially phosphorus and oxygen.
An unexpected loop. When CO₂ emissions and global temperatures rise, the arrival of phosphorus into the oceans also increases, fertilizing the proliferation of algae. These remove CO₂ thanks to photosynthesis in the water, and when they die, they transport that carbon to marine sediments, where it can be trapped for millions of years. As if it were a dumping ground for carbon dioxide on the seabed..
But the key to the loop is oxygen: the explosion of algal productivity consumes the oxygen in the water, meaning that almost no living being can live here. Under these conditions, phosphorus stops being buried and instead of being eliminated it is recycled from the sediment. This fuels new “super blooms” and closes a vicious cycle: ‘More nutrients → more algae → less oxygen → more nutrient recycling → extreme cooling’.
The result is that the biological thermostat goes crazy, sequestering carbon at a frenetic pace that the rocks’ slow thermostat cannot compensate for.
The new model. The new model integrate these quick feedbacksadding sedimentary chemistry, the phosphorus cycle and the oxygenation state to the traditional silicate weathering models. Surprisingly, when predicting the effect of the “great human experiment” of releasing CO₂, he finds that the system does not always smoothly return to the previous statebut it can overcompensate and take the planet to colder times, in deep glaciations, for tens of thousands or hundreds of thousands of years.
This only occurs when the atmosphere is less rich in oxygen, something common in Earth’s past, which may explain why ice ages coincide with intermediate periods of planetary oxygenation. Today, that same loop would make the “reward” much smoother, although there would still be the risk of long-term cooldown.
If we continue burning fossils. In this way, other scientific studies already suggest that large inputs of phosphorus, whether due to massive mining or increased weathering induced by climate change, can increase the risk of anoxia and abrupt cooling events, although this scenario would take centuries or millennia to develop.
This is why the acceleration of the phosphorus cycle together with the increase in CO₂ concentrations is conditioning us to the climate changes that we will see in a few million years. And although the Earth system may have the mission of stabilizing, the reality is that this system cannot always be trusted.
Images | Denise Schuld
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