An article series by Hadi Issa

Deep in the hearts of stars, the basic chemical elements supporting life were first formed from hydrogen and helium, including carbon, nitrogen, and oxygen, contributing to the formation of celestial bodies in the solar system – the orbiting planets of Solar Nebula, including Earth. When the Earth was formed, it was covered with a hot liquid of molten minerals, known as magma. Meanwhile, magma started erupting as volcanoes, releasing gases to the atmosphere, including water vapor, nitrogen, carbon dioxide, and sulfur dioxide, forming the Earth’s atmosphere. Consequently, clouds started appearing, and heavy rain started falling, thus the Earth’s hydrosphere was formed. Afterwards, volcanoes started erupting again in the form of lava that, under cooling conditions, crystallized and formed igneous rocks, and under weathering, igneous rocks were transformed to sedimentary rocks, and later, under heat and pressure beneath the Earth’s surface, to metamorphic rocks, in a perpetual rock cycle, hence the Earth’s lithosphere was formed, and the biogeochemical cycling of chemical elements started, giving rise to life-incubating conditions.

As an essentially closed system, the Earth has a finite amount of matter. The availability of some nutrients, however, is vital for the continuity of life; therefore, those nutrients flow through continuous cycles between Earth’s subsystems, aka spheres, and from one reservoir to another, as part of the planet’s life-driving biogeochemical system. According to the law of conservation of mass – discovered by Russian scientist Mikhail Lomonosov in the mid-eighteenth century – in a closed system, matter can neither be created nor destroyed, in which both mass and energy remain constant. Mass and energy, however, undergo various physical and chemical changes that have no influence over their overall quantity in the system.

The natural processes influencing the dynamics of the carbon cycle include chemical reactions in the atmosphere, biological processes in the biosphere (respiration, photosynthesis, and decomposition), weathering and deposition of rocks along the lithosphere, and various processes in the hydrosphere (including transport, uptake, chemical reactions, and precipitation). Moreover, human activity is affecting the cycle through anthropogenic practices, mainly industrial carbon emissions that are increasing the greenhouse effect above the permissible levels, intensifying ocean acidification, and bringing up multiple pollution-related illnesses.

Article 1: Carbon in the Atmosphere

Mainly, carbon exists in the atmosphere (troposphere) in two chemical forms: carbon dioxide (CO₂) and methane (CH₄). Each of these two compounds is transferred to the atmosphere from a variety of sources.

Figure (1) Drivers of Carbon Dioxide in the Atmosphere

Respiration: Every time an organism (including humans) exhales, carbon dioxide is released to the atmosphere. Cellular respiration – a sub-process of respiration - is a vital cellular activity that drives the forces of life, in which cells break down chemical molecules for energy. Although it may differ from one person to another, excluding trained athletes and people with higher physiological capabilities, the average person can only maintain a functional body, without breathing, for a duration of 3 minutes; any period that exceeds that timescale might put the person at risk of brain injury, cardiovascular struggles, and other related illnesses; an extended period of time leads to death.

Figure (2): Glucose or Krebs Cycle

Decomposition: Decomposition is a key factor in the overall recycling-of-matter process. When an organism dies, its body decays under the effect of decomposition by microorganisms, where the organic matter forming the body organs is broken down into its simplest molecules, releasing nutrients, carbon dioxide, and water into the soil, where plants absorb it and use it as a source of energy for growth. Throughout the process, excess carbon dioxide is transferred to the soil through pore space, creating a difference in carbon concentration between the soil and the atmosphere; that difference drives diffusion of carbon dioxide from soil to the atmosphere.

Volcanic Eruptions: In the depths of the Earth lower crust and upper mantle, magma – which is a hot fluid that’s composed of molten and semi-molten minerals and rock mixtures – rises through open cracks in the Earth’s surface as lava, releasing volcanic ash, volcanic dust, and gases – including carbon dioxide, nitrogen, sulfur dioxide, and water vapor – to the atmosphere.

Figure (3): Well-Measured Volcanic Eruptions throughout the 20^th Century (Siegel & Starts With A Bang , 2017)

Deforestation: Vegetation plays a key role in the reduction of the amounts of carbon dioxide escaping to the atmosphere through photosynthesis. Unlike other organisms, plants and trees, while do normal respiration at night, perform a reverse-respiration process, known as photosynthesis, when exposed to the sun, i.e., in the daytime. Forests are also estimated to hold about half of the net population of animal and plant species on Earth, in other words, preserving forests means preserving biodiversity. And last but not least, forests are responsible for a good amount of oxygen production, which is a vital process for the continuity of life along the biosphere.

The Amazon, for example, is the largest rainforest and river basin in the world, accounting for about 20% of overall oxygen production. Rainforests play a crucial role in the overall oxygen production process on Earth that scientists refer to them as the ‘lungs of the planet.’ However, continuous and extensive deforestation activity, taking place on a global scale, is limiting forests and vegetation’s proper functionality. According to a study by the World Carfree Network (WCN), around 15% of total carbon emissions to the atmosphere are driven by deforestation. (Scheer & Doug, 2018)

Burning of Fossil Fuels and Wildfires: Burning fossil fuels is quite a reliable, economically-feasible source of energy, which led humanity to rely on them for ages to generate power. However, today we know that they have enormous drawbacks; a big price tag attached, in fact, and what we also are aware of, today, is that there are better, ‘cleaner’ sources of energy – including solar energy, geothermal energy, wind energy, and nuclear energy – that we could rely on without having to pay that tremendous price. There are multiple of issues that have arisen as a result of extraction and burning of fossil fuels. First, the amount of carbon dioxide released to the atmosphere throughout the process exceeds that coming out of all the natural sources combined. Aside from polluting our air, water, and soil, there are also plenty of pollution-related illnesses that appeared, consequently. According to a study by the World Health Organization, about 4.2 million people die annually because of diseases linked to exposure to poor outdoor air quality, and about 91% of the global population lives in places with air quality that doesn’t match the international standards.

Figure (4): Global CO2 Emissions From Fossil Fuels, 1960-2017 (Canadell, Quéré, Peters, Andrew, Jackson, & Haverd, 2017)

Wildfires, moreover, give fossil fuels a hand when it comes to carbon emissions. While part of wildfires occur naturally, to some extent, fueled by lightning or extreme weather conditions, there’s a considerable portion that’s directly driven by anthropogenic factors, and that’s either intentional, to perform activities, or accidental, due to carelessness. Such factors include power-line invasion; either by direct connection or through wind, arsons within or neighboring wild lands, campfires within or neighboring wild lands, waste and debris incineration, or discarding lit cigarettes. A study by researchers at the University of Colorado has concluded that about 84% of wildfires that took place in the U.S., between 1992 and 2012, were directly driven by human activity (Daley, 2017). While wildfires are themselves carbon emitters, extreme temperatures that are caused by overmuch greenhouse effect resulting from carbon emissions can also give them rise; increasing their strengths and frequency – as the climate warms, moisture and precipitation levels are changing in various regions of the planet, variably – boosting extreme wet and dry conditions, accordingly. Another study by researchers at the National Aeronautics and Space Administration (NASA) shows that about 40,000 wildfires took place, in the western U.S. alone, over the past six decades, 61% of which are concentrated in the duration between the years 2000 and 2017.

Figure (5): NASA’s Observations of Wildfires in the Western U.S. Over the Past Six Decades (Patel, 2018)

Agricultural Activities: While the climate affects the farming process (for example, crop yield and crop stability) by the influence of multiple factors, including temperature, precipitation, and day-to-day weather conditions, agricultural activities can also have severe impacts on the climate, making it an interdependent relationship. Together, the impact of climate change on agriculture and the amount of greenhouse gases emitted from an agricultural area of land (for example, a farm) could be determined by how ‘climate-smart’ the practices adopted in the process are. There are several factors in the farming process that are responsible for carbon emissions. First, the selection of land is a key factor as to how far the process would impact the environment – if the selected land is a valuable natural resource, then destructing it not only threatens biodiversity, but could also have severe impact on the populations of species (including humans) relying on it and the overall balance in the ecosystem. Deforestation and clearing of parent vegetation prior to farming furthermore adds up carbon to the atmosphere when plant and tree residuals undergo decomposition. Soil cultivation and tillage also contribute to carbon emissions – where the carbon-based organic matter stored in the soil is aroused, leading to diffusion of carbon dioxide from soil into the atmosphere – the more fertilizers are added in the process, the more nutrient residuals get stored in the soil, thereby the more carbon is emitted. It’s estimated that the overall food production process – including farming, manufacturing, processing, and packaging – is responsible for one-third of the global greenhouse gas emissions (Gilbert, 2012).

Industrial Manufacture: Energy and raw materials are two essential driving forces in industrial processes, and the reliance on carbon-based resources means an additional amount of carbon emissions released to the atmosphere. The major carbon emissions in manufacture are attributed to the processes involved in the production of construction materials. Cement is mainly used in construction sites as a material-agglutinating substance – mostly in the concrete-production process – and is composed of lime (CaO), silica (SiO₂), alumina (Al₂O₃), and minor additives. In order to produce lime, calcination of limestone (CaCO₃) takes place, where it’s heated under high temperature and reduced to calcium oxide. Production of cement emits carbon dioxide from two different sources: fossil fuels – used as a source of energy – and during the calcination sub-process. The overall concrete production process accounts for about 5% of global anthropogenic carbon emissions (NRMCA, 2008).

Figure 6: Sources of Carbon Emissions during the Cement Production Process (Cement Industry Federation, 2018)

Steel production is also one of the construction industry’s major-contributor processes to greenhouse gas emissions. Steel is an alloy composed mainly of iron and carbon. The carbon content of steel is made up by transforming coal into coke – a fuel that mostly consists of pure carbon, with minimized impurities. However, the process is a huge carbon emitter – accounts for about 25% of the industry’s total carbon emissions (Global Greenhouse Warming, 2018).

Like carbon dioxide, methane (CH₄) is a greenhouse gas that has similar adverse effects on the climate system. While some carbon dioxide-emitters can also release methane to the atmosphere in the process – including fossil fuels and wildfires, where methane is also a by-product of the burning process – there are other sources of emission that are more of methane-emitters.

Figure 7: Drivers of Methane in the Atmosphere

Anaerobic Decomposition (Wetlands):Under anaerobic (oxygen-free) conditions, microorganisms, specifically anaerobes, breakdown organic substances, in a series of chemical reactions, where methane gas is a reaction-product. Wetlands are ideal environments for such process since they provide the anaerobic conditions needed by anaerobes to perform work. Wetland soil loses its air content when it becomes saturated, where soil pores are mostly or fully filled with water content, thus the anaerobic conditions become present. The Production of methane in anaerobic soil is done through a process known as fermentation.  In the first stage, aka hydrolysis, a group of microorganisms secrete hydrolytic enzymes to breakdown nutrients into smaller organic molecules, which are then transformed to volatile fatty acids through acidogenesis. Another group of microorganisms then use the fatty acids for the generation of acetate, carbon dioxide, and hydrogen in a sub-process known as acetogenesis. Finally, mehtnogenesis takes place, were a third group of microorganisms degrade the products into methane and minor amount of carbon dioxide, which may also be reduced to methane afterwards.

Figure (8):Flowchart of the Stages Undertaken in the Fermentation Process (Clifford, 2018)

Anaerobic Decomposition (Cultivation of Rice): Rice is one of the most common food ingredients in the world. On a global scale, about 3 billion people, almost half of the global population, rely on rice as a source of nutrition. Cultivated rice, however, has not proven to be environmentally ideal due to the massive amounts of greenhouse gas emissions linked to it. Since rice yield is extremely dependent on water availability, farmers manage to maintain flooded conditions across the field (paddies), which provides an ideal environment for anaerobic decomposition to take place in the soil. The climate-rice cultivation relationship is interconnected, since the more amount of carbon dioxide available in the atmosphere, and consequently the more presence of relatively high temperatures, the faster the rice crops are likely to grow, and the more anaerobic decomposition takes place in the soil. According to a study conducted by a team of researchers at the University of California, the increased amount of carbon dioxide in the atmosphere contributes to about 25% more productivity and about 43% more methane emissions in the rice field (Kerlin, 2012).

Raising Livestock: Animal agriculture is a major contributor to greenhouse gas emissions. As a high-resource consuming process, raising livestock requires massive amounts of energy, water, and land, and as the world population grows, the demand for animal products is, consequently, growing, and the amounts of resources needed in the process are increasing. There are three main processes by which animal farms are emitting greenhouse gases: deforestation, manure management, and enteric fermentation. First, ranching is one of the major causes of deforestation, on a global scale, where vast areas of vegetation are being cleared for pasture expansion.  About 80% of the Brazilian land is now dedicated for cattle ranching – which has become a primary threat to the Amazon rainforest’s biodiversity and oxygen productivity (Global Forest Atlas, 2018). Anaerobic decomposition of manure is another parameter to consider when it comes to methane emissions. The amount of emissions resulting from soil fermentation relies on a number of factors: the amount of manure used, livestock type, number of livestock being raised, and other environmental conditions, including, the abundance of carbon dioxide in the atmosphere, moisture, and temperature. Furthermore, one of the major factors contributing to methane emissions in cattle ranching is enteric fermentation – a process by which carbohydrates is broken down into simple molecules by microorganisms, in a herbivore’s digestive system, for absorption into the bloodstream. The products then go through anaerobic fermentation by methanogenic microorganisms, where methane is a chemical by-product. Animals consequently emit methane gas every time it escapes from their body, through gas expelling or burping. Therefore, the higher the feed was, the higher the emissions will be (Dong, Mangino, & McAllister, 2006).

Figure (9): Average Global Methane Emissions From Enteric Fermentation Between 1990 and 2016 (FAOSTAT, 2016)

The sun is the essential source that fuels the forces shaping the Earth’s climate. Electromagnetic radiation, transmitted to Earth by the sun, is the only form of energy that’s capable of traveling through space’ vacuum. Electromagnetic radiation is a spectrum of electromagnetic waves of various wavelengths and frequencies, aka the electromagnetic spectrum. The wavelength potion visible to the human eye, about 390 nanometers to700 nanometers, is known as visible light, where to either side of the visible spectrum lie different portions of invisible radiation, including gamma rays, X-rays, ultraviolet, infrared, microwaves, and radio waves.

Figure (10): The Electromagnetic Spectrum (L\Annunziata, 2016)

Incoming radiation from the sun is absorbed by the Earth’s surface, providing it with the heat energy needed by the Earth systems to remain functioning. Electromagnetic energy then radiates back from Earth’s surface to space in the form of infrared radiation. The importance of naturally-occurring greenhouse gases is that they trap that outgoing radiation and keep the Earth as warmed as needed for life to thrive, in a phenomenon known as the greenhouse effect. However, as the amount of greenhouse gases, in an anthropogenic manner, dramatically increased, the global mean standard temperature has risen above the permissible level, driving a change in the average weather conditions over long periods of time – the climate – giving rise to a global critical phenomenon known as climate change. Climate can be defined as the average weather, including extreme records, over a long period of time, and since it varies from one year to another, scientists usually use a period of 30 years as a standard reference. 

Currently, the global scientific consensus – as concluded and peer-reviewed by over 97% of the world’s Earth and climate scientists – is that the climatic changes taking place on Earth at the present time are driven by anthropogenic factors, and while the Earth’s climate has had several changes that were mainly driven by natural conditions, throughout history, it’s firmly agreed upon by the vast majority of the scientific community that the current change is not a natural phenomenon. Some of the major greenhouse gases currently existing in the atmosphere are water vapor, carbon dioxide, methane, and nitrous oxide.

Figure (11): Estimated Atmospheric Concentrations of CO2, CH4, and N2O (SEOS, 2007)