Bacteria Responsible for Climate Change?

The scientific community is in the midst of one of the strangest controversies. Scientists affirm that climate change is caused by bacteria that use nitrogen and not the carbon dioxide emissions generated by human activities. Did the Intergovernmental Panel on Climate Change (IPCC) fail to take into account a key element in its models?

George V. Chilingar (Department of Civil and Environmental Engineering, University of Southern California) is one of the researchers who support this theory with O. G. Sorokhtin and L. F. Khilyuk. He was an adviser to Ronald Reagan and the United Nations. Moreover, he says that he “advised President George W. Bush not to sign the Kyoto Protocol.” He also states that “George A. Olah, a winner of the Nobel Prize in chemistry, is in agreement with [their] theory.”

O. G. Sorokhtin (Institute of Oceanology of the Russian Academy of Sciences, Moscow)

L. F. Khilyuk (Department of Civil and Environmental Engineering, University of Southern California)

“The hypothesis of current global warming resulting from the increased emission of greenhouse gases into the atmosphere is a myth. Humans are not responsible for the increase in the global surface temperature of 1°F (0.56°C) during the past century and one should explain this increase by natural forces heating the atmosphere,” [1]argue Sorokhtin, Chilingar, and Khilyuk. These authors propose a model that they call the adiabatic theory of the greenhouse effect. According to the latter, “the contemporary global warming, which started in the 17th century (i.e. long before the Industrial Revolution), probably is temporary and determined by the fluctuations in the solar activity.”

This graph, presented by these scientists, is supposed to show the correlation between the temperature change and solar activity.

“Contemporary global warming is developed on the background of general long-term climatic cooling. A new ice age had begun.” In the authors’ opinion, in 400 million years, all continents at moderate latitudes will be covered by glaciers. “At the equatorial belt, the elevated regions will be covered by ice.”This cooling would be caused by bacteria that consume nitrogen, the main constituent of our atmosphere (oxygen represents only 21% of the composition of air). If nitrogen was removed from the atmosphere, this would reduce the pressure of the latter. When the pressure of a gas drops, its temperature decreases—this characteristic of gas is used to generate cold in refrigerators. In our case, this would therefore lead to a cooling of Earth. According to these researchers, past ice ages were also generated by such phenomena related to bacterial activities. Conversely, warmer periods may have been brought about by an increase in atmospheric pressure, for example by an adding of oxygen by plants.

THE END OF LIFE ON EARTH
However, according to this model, in 600 million years, this cold period will come to an end. Oxygen created during the formation of the Earth’s core would no longer be incorporated in the iron contained in our planet’s mantle, the latter being totally “saturated” by this gas. So this oxygen would go in the atmosphere, making its pressure increase. A rise in the pressure of a gas leads to an increase in its temperature (this is the inverse of the case of the cooling of the atmosphere). In this case, the increase in atmospheric pressure would induce our planet’s temperature to rise to 400°C. The situation would continue to worsen: “In 1.5 billion years, the oceans will start boiling.” This would be the end of life on the blue planet.

WHERE IS THE CO2 COMING FROM?
In these authors’ opinion, the rise of the atmospheric carbon dioxide concentration is not the cause of an increase in temperature on Earth but its consequence! According to them, the oceans being the largest CO2 reservoir on Earth—they contain 92 times as much CO2 as the atmosphere—a temperature rise would make carbon dioxide escape from the water and go into the air. The idea is that the warmer a liquid is, the less dissolved gas it can contain. This law can be observed using two glasses and pouring hot water into one and cold water into the other. After a while, bubbles appear on the inner surface of the container that contains the hot water but not on the one with the cold water. These bubbles are made of gas that is “excluded“from the liquid, which can no longer contain it. According to these scientists, in such a situation on Earth, the oceans would therefore release huge quantities of CO2 into the atmosphere.

This graph, created at the Vostok station in Antarctica, charts the parallel change of the temperature and the atmospheric CO2 level. We notice on this chart that the temperature change always precedes the change in atmospheric carbon dioxide concentration.

THE COOLING EFFECT OF CO2
Once this carbon dioxide in the atmosphere, what consequences does it have? According to the Intergovernmental Panel on Climate Change (IPCC) carbon dioxide is a greenhouse gas and therefore induces a warming of the planet. In these researchers’ opinion, this is the contrary: it leads to a decrease in temperature! They state that if our atmosphere were replaced by another one entirely made of carbon dioxide, it would be colder. They reach this surprising conclusion considering that the elements constituting such an atmosphere (the molecules) are 1.5 times as heavy as the ones of air. These ”weighty” molecules have a strong propensity to absorb the sun’s heat by starting to move. These movements of molecules cause the gas to become less dense. This situation can be illustrated by bumper cars; during the night, when they are stationary, it is possible to park them side by side so that they do not take up a lot of room. But during the day, when they move, they use a larger area. It is the same with a gas, which expands once heated. In so doing, it becomes lighter—since it is less dense—and, according to these scientists, rises into the stratosphere, a layer of the atmosphere located between 10 and 50 km. (6-30 miles) above Earth’s surface. It would be a phenomenon similar to that used to operate hot-air balloons. In this case, the air inside the envelope is heated up. The gas expands and so becomes lighter than the one around it. Then it rises up, taking the basket along with it.

In their climate model, once this hot air is in the stratosphere, it cools by radiation, i.e. the heat of the gas changes into waves that go off into space. The hot air, after its ascent into the atmosphere, is replaced by cold air, which is heavier than the surrounding air and therefore goes down. Such movements of air masses are called convection. Thus, in these scientists’ opinion, carbon dioxide has a cooling effect by intensifying these movements.
Another gas that is generally regarded as warming the planet is methane. According to the authors, as in the case of CO2, it would have the effect of cooling the air through the same mechanism.

OTHER SCIENTISTS’ POINT OF VIEW
Regarding the possibility that nitrogen-consuming bacteria could lead to climate changes, Frank Poly, a scientist at the Laboratoire d’Ecologie Microbienne (Laboratory of Microbial Ecology) in Lyon (France), notes that “One must not lose sight of the fact that other theories linking climate to bacteria exist. For example, such microorganisms, also related to nitrogen, produce N2O, a greenhouse gas.” This phenomenon would therefore exert an opposite effect compared to the cooling generated by bacteria according to the mechanism set out by Chilingar, Sorokhtin, and Khilyuk. Bacteria are important in other processes, as in the creation of methane (a greenhouse gas) or dimethyl sulfide, an aerosol that has the curious property of inducing cloud formation. Werner Aeschbach-Hertig (Institute of Environmental Physics at the University of Heidelberg in Germany) works on reconstructions of past climates. He wrote an article in the Journal of Environmental Geology that contradicted the three scientists’ theory. He fears that this has enabled the authors to publish a new article to respond to it. “So I think now that it is better that I ignore these strange theories and concentrate on my scientific work. I don't want to answer questions about these obscure ideas,” he remarks. As for the famous skeptic Willie Wei-Hock Soon, he is also not convinced by the bacterial hypothesis. This astrophysicist at the Solar and Stellar Division of the Harvard-Smithionian Center for Astrophysics in the United States thinks that “The nitrogen-consuming bacteria probably play a role in climate. But is this phenomenon important?” To answer this question, we must go further in understanding the involvement of bacteria in this issue since no assessed estimate is provided in relation to this hypothesis at the present time by the scientists who support it. Nitrogen, carbon, phosphorus, oxygen, and sulfur are necessary for life. Among them, nitrogen has the greatest abundance in the atmosphere and the oceans. The amount of all this nitrogen is larger than that of the four other elements combined. But most of that nitrogen is in the air and cannot be used by the greater part of living beings. That’s where bacteria come in and transform nitrogen that is in the air into other forms that can be incorporated into organisms. For instance, the clover plant hosts such bacteria capable of converting nitrogen into protuberances on its roots.

Clover modifies nitrogen that is in the air. Thanks to this, living creatures like this ladybug can use this element. (Photo: Gius Cescu/http://www.fotocommunity.fr/pc/pc/mypics/979350)

MAN AND THE NITROGEN CYCLE

Since the nitrogen usable by organisms is quite scarce after all, in many environments plants stop developing due to the lack of this precious element. Regarding agriculture, mankind decided to remedy this problem by transforming its useless nitrogen into usable nitrogen in order to give it to cultivated plants so that they can better proliferate. But the quantities of this gas that must be modified through a chemical process (called Haber-Bosch) are such that human beings became a more significant player than nature in this transformation on the continents. This situation has various consequences, notably in terms of pollution. But the one that interests us here is that as the useless nitrogen is taken from the air, 100 million tons of this gas are captured through this process out of the atmosphere each year [2].

“A COMPLETE LACK OF UNDERSTANDING OF THE MECHANISMS”
Does this have an influence on climate according to the model proposed in this theory? It is relatively easy to realize that this is not the case. If we assume that during the past 100 years this amount of nitrogen has been taken out of the atmosphere annually, the total represents only one hundredth of the carbon dioxide added to the atmosphere by the emissions caused by human activities (this is in fact an overestimation for nitrogen since its transformation intensified in the last century). The authors of the theory estimate that the influence of anthropogenic emissions (generated by human activities) of CO2 on temperature is less than 0.03°C. They get this result by calculating the temperature rise according to the change in partial pressure of CO2 due to anthropogenic emissions according to the mechanism described above. Yet they “forget“ to take into account the greenhouse effect! In any event, it is difficult to see how it would be possible for anthropogenic emissions of CO2 to have a negligible effect on climate whereas a quantity of nitrogen at least 100 times smaller can lead to a cooling of Earth by taking into account the same phenomena. When they classify nitrogen-consuming bacteria into the “first-order climate drivers,” which they define as having “an importance 10,000 times greater than anthropogenic emissions of greenhouse gases,” we realize that the mistake is huge. “Changes in partial pressures caused by modifications of the atmosphere composition have a very small effect on climate,” explains Urs Neu, who conducts research on past climates within the Swiss Academy of Sciences. “There is a difference in temperature between the poles and the equator or between day and night even though the average atmospheric pressure between these geographic regions or different times of the day does not change,” continues this scientist, co-author of the book Climate Variability and Extremes during the Past 100 Years. Taking nitrogen up from the atmosphere does not significantly influence the Earth’s temperature, as this element is not a greenhouse gas. Gavin A. Schmidt, a climate modeler at the NASA Goddard Institute in New York City, agrees with this point of view and considers that the scientists who have put forward this hypothesis show “a total lack of understanding of the way the atmosphere works.”

CO2 AND CLIMATE
The bacterial hypothesis is not the only one formulated by Chilinar, Khilyuk, and Sorokhtin. What should we think about the idea that CO2 has the effect of cooling the atmosphere? Is the mechanism set out above real? Let’s recollect the theory: CO2 absorbs heat and so expands, becomes lighter, and rises into the stratosphere, where it cools by radiating out into space. Once cold, it descends in the atmosphere and refreshes it. “One of the problems with this theory is that a heated air parcel rises only if its temperature is higher than the one of the air that is around it,” explains Urs Neu. This is indeed what we saw in the example of the montgolfier: it rises up because the air is hotter inside the envelope than around it. “Because CO2 is relatively evenly distributed throughout the atmosphere, the warming due to the heat absorption of CO2 occurs everywhere.” adds the researcher. Given the fact that for convection phenomena to take place there must be parts of the atmosphere that are warmer than others to have mass differences, in such a case these air movements are nonexistent. Even if the convective processes described by the authors were real, hot air could not go to the stratosphere and cool there. Indeed, one might imagine intuitively that the more one goes up into the atmosphere, the more its temperature decreases. This is in fact not the case. The stratosphere is warmer than the top of the layer beneath it, the troposphere (inside which we are). “Because of that, convection phenomena cannot go through the boundary between these two layers,” underlines Urs Neu. Warm air arriving at this layer is colder than the surrounding air, so it is heavier than the air around it and stops its ascent.

OCEAN DEGASSING
We now come to the last point of this theory: is the rise in the atmospheric level of carbon dioxide caused by the ocean degassing resulting from the increase in temperature? Many factors lead to the refutation of this hypothesis. Techniques (isotopes C12/C13, radiocarbon) permit scientists to determine if the carbon is of natural origin or generated by combustion. One knows, thanks to these studies, that the increase of the atmospheric concentration of carbon dioxide is anthropogenic. The acidification of oceans, which is due to a rise in the quantity of CO2 that they contain, is also an indication pointing in the same direction. Furthermore, reconstructions of past climates carried out at Vostok Station in Antarctica (see graph above) show that in the transitions between glacial and interglacial periods, a temperature increase leads to a rise in atmospheric CO2. There is an 800-year latency between these two events. It is therefore not possible that the warming induces an increase in the atmospheric CO2 level in the current climate change. The authors also do calculations using Henry’s law, a physical law that allows connecting the concentration of a gas dissolved in a liquid and the pressure of this gas in the air. This leads them to the conclusion that CO2 has leaked out of the oceans, which would be consistent with the hypothesis of degassing. Yet only temperature variation is taken into account and not the change in the partial pressure of CO2. By introducing the latter, one can reach the opposite conclusion (depending on the chosen temperature). In addition, Urs Neu draws attention to the fact that Henry’s law is not valid for such considerations. “Many other processes and factors play a role in such a question. For example, there are colder areas in the oceans that can contain a lot of carbon dioxide. This cold water, denser than the one that surrounds it, will then descend into the ocean and therefore remove CO2 from the atmosphere.”

Yet even assuming that the calculations made by the scientists supporting the idea of degassing (using a temperature change of 1°C) are right, their own result contradicts their theory. Thus they come to the conclusion that the CO2 released by the oceans has induced an increase of 13.5 ppm (parts per million, unit of concentration) in the atmosphere. This would only explain a fraction of the actual rise, which is of 100 ppm. Among the first-order climate drivers also appear, according to Sorokthin, Chilingar, and Khilyuk, variations in solar activity. They justify this point of view with the graph correlating solar activity with the temperature on Earth (see above). Two scientists, Eigil Friis-Christensen and Knud Lassen, published a chart similar to the one presented by these researchers in the scientific magazine Science in 1991.

The 1991 graph. In blue: solar activity. In red: the terrestrial temperature.

Part of the scientific community remained skeptical of this paper. The reason for this was that some thought that the statistical treatment used had the effect of distorting the curve of solar activity for the recent periods. In 2000, new information permitted scientists to determine that the graph was wrong.

The corrected chart of 2000. Note that the correlation between solar activity and temperature no longer exists for the recent period of the curve.

Gavin A. Smith, who was named as one of the 50 leaders in science on a global scale by Scientific American magazine, thinks that “These authors’ theory does not make sense. It’s equivalent to writing a book about gravity and assigning all the effects to the sucking of a hypothetical giant turtle.”

                                                               Gaëtan Dübler

[1] The quotations in this part come from the book Global Warming and Global Cooling, Evolution of Climate on Hearth published by Elsevier and authored by the three above-mentioned scientists.

[2] For more information about the nitrogen cycle and man's influence on the latter, see for example Galloway et al., 2003, 1995; Burns and Hardy, 1975; Jaffe, 1992; McElroy et al., 1976; Schlesinger and Hartley, 1992; Stedman and Shetter, 1983; Söderlund and Svensson, 1976; Mackenzie, 1998.

How Was the Greenhouse Effect Discovered?

The greenhouse effect is central to the issue of global warming. But do you know how it was revealed? A look back at the history of climatology reveals unexpected elements.

On this evening of 1859, the rain fell on the cobblestones of Piccadilly Circus (a famous square located in London, England) on which long silvery reflections, emanating from the gaslights, stretched out. A carriage arriving from Shaftesbury Avenue broke the silence of the night. It took Regent Street, where it vanished, leaving only the fading echo of the noise of hooves in the maze of streets behind it. Nearby, on Albemarle Street, was a large building. Under the pediment, supported by heavy columns and on which letters carved into the stone read, “The Royal Institution of Great Britain,” a window was still lit despite the late hour. Under the flickering light of Bunsen burners (a piece of laboratory equipment that permits the production of a flame with gas), a scientist examined a strange machine that he had just finished assembling. He then went near its pipes and turned stopcocks; a hiss was heard, and carbon dioxide filled a long tube. The goal of this experiment was to solve one of the greatest mysteries of science at the time. It was known that Earth had gone through ice ages; how was it possible that the climate had altered so drastically? Science already had addressed this issue. In 1824, Joseph Fourier, a French physicist, proposed that these climate changes stemmed from changes in the composition of the terrestrial atmosphere. How did he reach this conclusion? Researchers knew that our planet, considering the heat that it receives from the sun, should be so cold that its entire surface could be covered with ice. It was therefore postulated that something in the atmosphere retained heat. Joseph Fourier carried out the following experiment: he put a box on which stood a window pane in the sun. He observed that the temperature rose inside this system. According to him, the atmosphere played the same role for the globe as the glass for the box. This experiment would later inspire the name of the phenomenon that he discovered: the greenhouse effect.

THE GREENHOUSE EFFECT IS ILL-NAMED!

Even so, this analogy is wrong. The reason that the temperature increases inside the box or the greenhouse is that the air is confined. One can realize this by opening a window in a greenhouse: the temperature then decreases until it is identical to the one outside. As regards the greenhouse effect of the atmosphere, it comes from the fact that the latter lets sunlight in but absorbs infrared radiation, as we shall see below. A pane has no such properties. The greenhouse effect is therefore ill-named!
However, this model was then accepted as valid; the question was how the atmosphere acts as a glass. The experiments developed by a scientist at the Royal Institution, John Tyndall, were precisely designed to address this issue.

John Tyndall

The first step was to extract gases constituting the air as oxygen, nitrogen, water vapor, and CO2. Carbon dioxide was obtained by distilling the air (distillation is a process that allows the separation of chemical substances by heating). A question that arises then is the following: the sun’s rays pass through the atmosphere and heat Earth. If this energy came from the universe, why does it not completely return there so that it warms the world? The reason for this is that the ground and oceans will cool by emitting what Joseph Fourier called “chaleur obscure” (”dark heat”). But the latter will be trapped by the atmosphere.

AN INVISIBLE LIGHT

What is this mysterious heat? In 1800, a discovery revealed its true nature. An English composer and astronomer, Sir Frederick William Herschel, was doing an experiment with a prism (a transparent object that disperses light into different colors. The same phenomenon can be observed with the raindrops when there is a rainbow).

Here we see a prism (the pyramid). On the right side, at the bottom, a ray of light hits it. A second beam is reflected and moves upward, whereas another part goes through it and is separated into colors.

By chance, a thermometer was placed on his desk, but beside the spectrum, i.e. the dispersion of light into colors. To this scientist’s great surprise, the temperature indicated by this instrument increased even though the light was not reaching it! Sir Herschel then realized that the thermometer was right next to the red part of the spectrum—which we see on the image at the top of the shaft of light transmitted through the prism. He deduced from that that there must be, beyond the red, an invisible light that carries heat. That is what we currently call infrared light. Though this light is not visible to humans, it is perceptible by other animals like certain snakes thanks to receptors located on their heads. Since Earth gives off the heat that it receives from the sun in the form of infrared light, John Tyndall had to use the latter to measure the heat absorption of the gases found in our atmosphere. How to generate such a light? The answer is surprisingly simple: any warm body gives out this light.

Your pet gives off light! Here, a cat seen in infrared. The light parts—the eyes, mouth, and ears—are those that emit the most, i.e. those that are warm or have significant heat losses.One also observes that its nose is relatively cold compared to the rest of the body.

This is the reason that some reptiles can detect infrared light: this enables them to perfectly locate their prey, even in the darkest night. But let’s get back to John Tyndall’s experiment. For the generation of infrared light, he would therefore create a warm body by pouring heated water into a container. Such an apparatus is called a Leslie’s cube because it had been developed by an English physicist, Sir John Leslie, in 1804.

View of the instruments used by John Tyndall for his experiment.

THE GREENHOUSE EFFECT MECHANISM CLARIFIED

In this picture, on the left-hand side of the piece of furniture on the left, we notice a cube, underneath which there is a Bunsen burner. This is a Leslie’s cube (the ”rod” striking out of it is a thermometer to measure the temperature of the water). A similar piece of equipment is mounted on the right side of the long horizontal tube. Inside the latter is the gas of which one wants to study the heat absorption. Its ends are sealed with a transparent material in order to confine the fluid of interest while letting the infrared light produced by the second Leslie’s cube go through it. We notice on the right-hand table an object composed of a stand and two cones. It is a thermopile. What is that? Inside it there is a special coil of wire that has the property, if one heats part of it up, of creating electricity. This type of battery has some applications today, such as to supply electricity to industrial processes requiring rapidly large quantities of energy. But this phenomenon is not used on a big scale because of its poor efficiency. In the experiment, the infrared light coming from the cubes will enter the thermopile through the cones. The greater the temperature difference between the two sides, the more electricity will be generated. It is connected by wires to another instrument placed on the stool; this is a galvanometer, a device capable of measuring electrical currents. So the more heat is absorbed by the gas inside the tube, the greater the temperature difference inside the thermopile and the more current it generates. Therefore, this equipment permits the measurement of the heat absorption of a gas. (Regarding the other instruments used for this experiment, one sees a screen on the right of the thermopile. The others are used to generate the fluids in question).
What were the results of this experiment? Among the perfectly translucent and invisible gases constituting our atmosphere, some absorb heat when infrared light goes through them. This is the case for water vapor and carbon dioxide. The mechanism of the greenhouse effect was thus clarified some 150 years ago!

TOWARDS A TEMPERATURE RISE?
Though this theory was seen at the time as a way to explain the past glaciations by variations of atmospheric CO2 concentration, it did not appear interesting regarding the contemporary climate. It was not until 72 years later, in 1896, that two Swedish scientists, a geologist, Arvid Högbom, and a chemist, Svante Arrhenius, made estimates and came to the conclusion that the CO2 generated by burning coal could lead to an increase in the terrestrial temperature. But this did not appear to be of concern given the fact that, with the quantities of carbon dioxide that were discharged, a long time would have been necessary to reach a problematic situation. Furthermore, for Nordic scientists, an increase in temperature would have been rather welcome. The idea arose of deliberately changing the Earth’s climate. The German physicist Walter Nernst, a Nobel Prize winner, fantasized about setting fire to useless coal seams in order to warm the climate!
In the years that followed, CO2 continued to be perceived as harmless. Indeed, many thought that the oceans could soak up the carbon dioxide that was released into the atmosphere. Soon another regulatory mechanism of nature was proposed: if the oceans contain more CO2 than the atmosphere, the same is true for living matter. It was therefore considered that even if the water could not absorb all the CO2 released, vegetation would take it up. The idea is that an increase in the atmospheric carbon dioxide level causes plants to grow faster. The latter using CO2 for photosynthesis, more plants would mean that more CO2 would disappear from the atmosphere and finally everything would return to normal. Yet in 1938, an English engineer named Guy Steward Callendar realized that the carbon dioxide concentration and the temperature increased. This discovery would revive scientific interest in this issue, and the measurements of atmospheric CO2 concentration would be improved progressively from 1960 onwards. Terrestrial temperature records would also get more sophisticated. Since the late 70s, satellites have been used for this task. New areas of research would open up such as the study of past atmospheric CO2 variations and their implications for the climate.

THE MAGNOLIA’S MEMORY
For instance, the 90s saw works dealing with plants that haven’t evolved much since the dinosaur era, such as the magnolia.

A magnolia flower. As these organisms evolved while bees did not exist, they are designed to be pollinated by beetles! (Beetles are insects, such as ladybugs, that are distinguished by their special wings. Today, this is the animal order that numbers the greatest number of species).

If these plants are exposed to significant levels of CO2, the shape of their leaves will be different. Fossils revealed such modifications. Given the fact that the climates of the dinosaur age were generally warmer than the present ones, this confirms that large carbon dioxide concentrations were connected with them.
The perception of the greenhouse effect has become more complex with the passing of time, though the one popularized by the media since the 60s is equivalent to the Joseph Fourier’s. More precisely, the infrared radiation given out by the soil will be gradually filtered during its passage through the atmosphere, so some of the light is absorbed by the air that thus heats up. The latter itself begins to give off infrared light in all directions, which in turn warms the surrounding air, etc. One can visualize the atmosphere as a juxtaposition of layers. The infrared light escapes into space only at the level of the uppermost layer of the troposphere, a layer of the atmosphere extending from the surface to an altitude of about 6 to 20 km (4-12 miles) depending on the geographic location.(The upper layers play an insignificant role in these phenomena.) What happens if we increase the CO2 level in the atmosphere? This last layer will contain more carbon dioxide, and thus infrared light will have more difficulty going through it. This reduces the amount of this light emitted by Earth. This layer therefore heats up, giving out infrared light that warms the layers beneath it, which themselves start to emit infrared light…This is how the whole atmosphere warms.
This model, which is used in the computer simulations of the temperature evolution in the future, shows that concerning warming, everything is conditional upon the uppermost layer of the stratosphere. The latter determines how much infrared light leaves the globe. The warming or the cooling of our blue planet depends on this layer.

Gaëtan Dübler