The anatomy of climate

The Earth’s climate is constantly changing. Everyone has heard of ice ages: it used to get very cold on Earth, and vast areas were covered with ice for thousands of years. There were also times when the whole planet turned into tropics, and it was humid and warm even near the poles. To find out how the climate has changed, people study plants and animals of the past, deposits in the soil and at the bottom of the oceans, and isolate gas bubbles from years of ice. But is it possible to know what the climate will be like in the future?

In general terms

The climate is the «average weather». It includes all meteorological characteristics, like temperature, precipitation, and wind. They can be averaged over any area: «the climate of France», «the climate of Europe», or «the climate of the Earth». The period that we average should not be too short. Today, the climate is estimated for 30 years, but you can look at a longer period: for example, «the climate of the Holocene» (the last 12 thousand years). In general, «climate» is a very diverse concept. But most often, when we talk about climate, we mean the average temperature for 30 years, because, in this case, the trends are more obvious, and all characteristics are easy to observe.

The climate can be predicted in the same way as the weather: with computers and equations. Here is roughly how it works:

Find out what natural processes affect the climate
Determine the physical laws by which these processes «work»
Prepare a mathematical model and run it on a supercomputer

The task is very complicated because of the interconnection of many processes on the surface of the Earth and in its atmosphere, as well as the influence of the Sun and other celestial bodies. In general, the climate can be compared to a living organism, like a human being. Our condition depends on both external conditions and what is going on inside the body. Let´s imagine that the Earth is a person, and the climate is its state of being.

Weather Outside

For us to be comfortable, good weather is very important: it shouldn’t be too hot or too cold. For our planet, «weather» is the intensity of the sun’s radiation, because most of the Earth’s heat comes from the Sun.

Since the birth of the Sun, the intensity of its radiation has been slowly increasing, and the Earth receives more and more heat. We know this from observations of other stars and from the history of the Earth itself, and we can make predictions.

But there are also cyclical changes in the Sun, that is, alternating periods of increased and decreased activity. There are several such cycles: one is an 11-year cycle, another is 22 years, a century, and millennia. We are also forecasting based on them, but we still do not fully understand the reasons for their occurrence.

How to dispose of energy

But even with the same solar activity, the climate can be very different, depending on how the sun’s energy is distributed around the planet. There are two main processes this depends on.

Milankovitch cycles

These are slow, changes in the parameters of the Earth’s orbit, occurring over many thousands of years. The orbit in which the Earth revolves around the Sun is not a circle (as we always imagine), but an oval. It constantly changes shape: it either shrinks and becomes almost a circle, or stretches out. And the Sun is never in the center of this oval, but closer to one of its edges.

Valerya Milovanova / Windy.app

Now take the northern hemisphere of the Earth, and imagine this coincidence: winter comes, and the Earth is far away from the Sun. It would be colder than usual. And in summer, the Earth is close to the Sun, and summer is hotter. The climate has highcontrasts. At the same time, in the southern hemisphere, it is the opposite: winter is very warm, and summer is cold, the climate has evened out.

We should also remember that the axis of rotation of the Earth is tilted by about 23° to the plane of the orbit, and, because of this, winter and summer alternate. But over the millennia, this angle changes cyclically, too. As the angle increases, the seasons become more pronounced; as the angle decreases, they become less pronounced.

Valerya Milovanova / Windy.app

Milankovitch cycles happen because of the influence of the Moon, the Sun, and other planets on the Earth. We understand this well, and can make predictions based on it. For example, now the shape of the orbit is close to a circle (and continues to strive for a circular shape), and in January, the Earth is slightly closer to the Sun than in June. The climate is fairly flat now, and will not change anytime soon.

Tectonics

Continents are constantly moving, changing the face of the Earth. As the continents move, air circulation, sea currents, and the entire climate change.

Here, too, the Earth goes through cycles: the continents come together to form one giant supercontinent, and then they diverge again.

Valerya Milovanova / Windy.app

The Earth’s climate strongly depends on where the continents are located. For example, if they all join together at the equator, the Earth will get very warm. And if the continents unite at the pole, they will be covered by an ice cap, as Antarctica is now, and very cold times will ensue.

If you look at a map of the world, you’ll see that all the continents have now split apart, and this contributes to a milder climate. In the next 200 million years, the continents may reunite, but we don’t yet know exactly where or when that will happen.

Solar activity and Milankovitch cycles are the two main «external» processes affecting the Earth’s climate.

Something is begging to come out.

All human organs are constantly busy with something, but do you often think about it? Only when something goes wrong!

When volcanoes erupt, magma, the molten rocks, comes from deep within the Earth’s crust to the surface. All the gaseous substances that used to be contained in the magma: water vapor, carbon dioxide, and many others, immediately escape into the atmosphere.

Volcanic gas emission. Gary Saldana / Unsplash

Carbon dioxide has a strong greenhouse effect. The more of it in the atmosphere, the higher the air temperature will be, and vice versa. Therefore, the concentration of carbon dioxide is one of the main factors influencing the climate. Throughout the history of the Earth, the concentration of carbon dioxide has been constantly changing, but on average, it has been decreasing. So has the temperature. The planet is aging, «exhaling,» and there are fewer and fewer volcanic eruptions. And volcanoes are the primary natural source of carbon dioxide. It turns out that there is almost no inflow, but the outflow remains. After all, carbon dioxide is used by living organisms to build their bodies (plants take it directly from the atmosphere, and animals take it from plants). After they die off, carbon can remain in the ground in the form of coal, oil, and natural gas reserves and disappear from the cycle of matter.

It is true that now the reserves of coal, oil, and gas have become actively used by people. Carbon dioxide buried in the ground is returning to the atmosphere, increasing its concentration. This is the main reason for the climate warming we are experiencing today.

Population

Hundreds of bacteria, fungi, and protozoa live inside humans, and they help us digest food and resist viruses. You don’t even need an analogy here: the Earth is teeming with life, and the main «climate trendsetters» on Earth are plants.

Plants are closely related to the climate. Compare a tropical forest with a desert. Or the Arctic tundra. Plants want to avoid growing in hostile environments, but if they have grown, they can change the climate to suit them!

Here’s an interesting thought experiment called «daisy world». Let’s imagine that only two plants grow on Earth: black daisies and white daisies. Now let’s imagine that there is now a minimum temperature on Earth suitable for daisies. Black absorbs more energy and gets hotter, so black daisies will be much more comfortable and warmer. Plus, they will heat up the ambient air from them, which will also help. Bottom line: there will be many more black daisies than white daisies, and the Earth will be warmer than it would be without them.

Kai Wenzel / Unsplash

Now let’s start gradually increasing the temperature on the planet. At some point, it will exceed the comfort level for the flowers. Black daisies will get hot. White daisies will have the advantage of reflecting all the sunlight, so they cool themselves and the air around them. Bottom line: there are more white daisies than black ones, and it’s colder on Earth than it would be without the flowers.

It turns out that daisies not only adapt to change, but also change the climate themselves: they «pull» it to the one that is most comfortable for them. Let’s not forget about animals, either. During their life, they can eat plants and emit greenhouse gases into the atmosphere, greatly complicating the picture described. But in the end it turns out that the more diverse the biosystem of the planet, the more stable its climate will be.
And one more interesting fact: if plants mitigate climate changes, it is the snow that intensifies them...! It, like white daisies, reflects most of the incident light back into space. So where there is snow, the Earth gets very little warmth. But if the climate suddenly starts getting colder (no matter the reason), snow falls more often and lies longer. It has time to reflect more light, and the cooling increases. And when it gets warmer, there is less snow and the climate gets even warmer.

What kind of climate do the models predict?

When we put all the pieces together, we get a prediction of the Earth’s climate. And now all the models are predicting continued warming. Since the 19th century, the average global temperature has already risen about 1°C. And by the end of the twenty-first century, the temperature increase is estimated to be between 2 to 5 °C.

True, not all scientists agree with the current climate projections. Critics say that we do not predict the entire climate, but only what we know about it. And that many important processes are still not accounted for in the models, so the results are inaccurate. But this means only one thing: we have to continue research. And then we will better understand what to prepare our descendants for in hundreds and thousands of years.

Text: Eugenio Monti, a meteorologist and a climatologist

Cover photo: Simon Maage / Unsplash

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