Climate research | The Earth’s temperature regulation will eventually work – but the stony thermostat will not have time to curb human-caused warming

Terrestrial temperature has fluctuated wildly throughout the history of life.

About 600 million years ago, the Earth is believed to have been so cold that a large part of the Earth was covered in ice and snow for millions of years.

In the Cretaceous period, it was so hot that the surface temperature of the sea water could have been as high as 36 degrees. A tropical forest grew in Antarctica.

Why the earth’s temperature has seen up and down throughout its history? Why does a cold period end at some point and is followed by a warmer period?

You can also wonder why the heat doesn’t just rise all the time, but a hot phase is always followed by a cool phase.

The explanation could be that the Earth has a thermostat that regulates the temperature of the planet so that the temperature always returns close to some kind of equilibrium state.

Question Earth’s planetary thermostat has puzzled geologists for decades, but no clear answer has been obtained. There has been no material to test the theory.

In recent years, however, material has been obtained when researchers have drilled samples from deep-sea fossils and from Greenland and Antarctica and analyzed their isotopes.

For example, oxygen isotopes tell about the past climate, whether it was cold, hot, dry or rainy.

When this information is compared to known events in prehistory, such as volcanic eruptions or mass extinctions, a picture of the Earth’s climate history is built.

Researchers at the Massachusetts Institute of Technology (MIT) used this new material in a recent study. They built a comprehensive picture of global temperature history in a study they published Science Advances – science journal.

The material has been searched for signs of thermostat operation. That is, if the Earth’s climate cools or heats up, would the data show a feedback mechanism that prevents temperatures from developing too extreme, in which case the climate starts to change in the opposite direction.

Researchers the conclusions are twofold.

According to the first, during the period of 4,000 to 400,000 years, the Earth actually has a thermostat that returns the climate back to equilibrium. However, for longer periods than this, the effect of the thermostat seems to disappear.

“According to the research, there seems to have been no dead man’s switch on Earth for long periods of time, which would surely return the system to its initial state,” says the doctoral researcher Sanni Turunen From the Geosciences and Geography Department of the University of Helsinki.

In this case, the preservation of life on Earth could have depended on chance.

Terrestrial the most important part of the climate thermostat is stone, especially fresh volcanic stone or rock species of fold mountains. When these types of rock weather, the process removes carbon dioxide from the air.

Weathering begins when positive ions are released from the weathering stone, which eventually end up in the sea.

In the sea, ions combine with bicarbonate ions, which are carbon dioxide dissolved in water. The compounds begin to precipitate.

“The process creates limestone or, over time, even marble, and thus the carbon dioxide they contain is permanently out of the atmosphere,” says Turunen.

Because the earth has a huge amount of rock, weathering is a really powerful temperature regulator.

It is known, for example, that the Earth’s climate began to cool down about 430 million years ago, when plants with roots appeared.

According to Turunen, this is believed to be partly due to the fact that the roots of the plants eroded the stone to an unprecedented extent.

The weathering of the rock also contributed to the cooling of the giant continent Pangaea in the past.

When the giant continent was formed, several folded mountain ranges appeared on the Earth. Because fold mountains contain the most weatherable rock, this caused a cool period at the end of the Carboniferous period.

According to Turunen, our current climate is also cooler than average from a geological point of view, thanks to the weathering of the rock.

The thing that cools our current climate the most is the Himalayan folded mountain range, which is still rising. However, you don’t notice it because it wears down as fast as it rises.

What makes weathering a thermostat? How weathering reacts to temperature.

In warmer weather, decay accelerates, so more carbon dioxide is absorbed and the climate starts to cool.

In the cold, decay slows down, so carbon dioxide begins to accumulate in the atmosphere, and thus the climate warms up again.

This is the thermostat that was revealed in a recent study in the medium term.

Human from a perspective, the thermostat is slow. Last year Science Advances-science magazine published a study that investigated the functioning of the thermostat during the Paleocene-Eocene thermal peak, approximately 55 million years ago.

At that time, the global temperature rose by 8–10 degrees in a short time and remained high for 50,000–100,000 years. Large terrestrial mammals died from the heat, the seas became acidified and the calcareous plankton disappeared completely.

German researchers analyzed lithium isotopes by studying that when the climate warmed so strongly, the rate of rock erosion tripled.

Evaporation, heavy rains and storms further increased erosion. Still, the cooling effect of the thermostat only began to show after 20,000 to 50,000 years.

How about those long-term climate events where the thermostat has no effect?

A good example of that is the Permian mass extinction about 250 million years ago. It was the biggest extinction wave in Earth’s history. During that time, almost all species living on land and in the sea disappeared from the earth.

The extinction was triggered by volcanic eruptions lasting about half a million years, which increased the carbon dioxide concentration in the atmosphere sixfold. The global temperature rose by more than ten degrees.

One of the mysteries of the Permian extinction is why the thermostat did not return the climate to cool, but temperatures remained high for as many as five million years.

In these conditions, the rocks eroded at a tremendous rate, but it did not affect the climate.

One the answer was received earlier this year Nature Geosciencesfrom the study published in the scientific journal. Paleontologists from the University of Ottawa discovered that the oceans have been full of dissolved silicon during the Permian period.

Normally, there is little dissolved silicon in the sea, as diatoms use it to build their shells.

However, during the Permian period, the oceans were so acidic that all silicon-using single-celled life forms were dead. So there was no user for silicon.

However, the dissolved silicon explains why the thermostat didn’t work. When there is a lot of dissolved silicon in the sea, the positive ions released from the weathered rock do not combine with carbonates, but with silicon.

This creates clay minerals, but it does not remove carbon dioxide from the atmosphere, but on the contrary produces it. So silicon froze the thermostat and, on top of that, increased carbon dioxide emissions.

Only when the silicon-using plankton bodies returned to the sea and bound the silicon to themselves did the thermostat start working and the climate cooled.

How about what does the climate thermostat mean in terms of current climate change?

Obviously, nothing for us, but it can be a joy for those who come after us.

According to MIT researchers, it is likely that the thermostat will eventually cool the climate. It can take 20,000–50,000 years, and you shouldn’t wait for that.

“What is worrying is what happens in between,” says Turunen.

Previous climate upheavals have brought with them large waves of extinction.

The most worrying According to Turunen, the characteristic of current climate change is its speed.

“The biggest climate changes associated with mass extinctions have two characteristics: the total temperature change has been more than 5.2 degrees and the rate of change is more than 10 degrees per million years,” he says.

In the current climate change, the speed of change is accelerating beyond a dangerous level and 5.2 degrees should not be exceeded now, nor in five hundred years.

However, from a geological point of view, the current climate change is hardly even at the beginning. The good news is that humans can also intervene.