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Feb 21, 20215 min read

Understanding the Reality of Climate Change: CO2 emissions

A look into the historical trends greenhouse gases and their contribution to climate change


Writers: Akshaya, Haritha, Kavya


Thus far we have discussed the weather phenomenon and natural disasters that have been exacerbated by climate change. Here, we take a step back to the core inquiry at hand - climate change. In this blog, we delve into the effects of greenhouse gases, specifically about carbon dioxide and its relevance to climate change.

Understanding Climate Change: Historical Perspective

To better understand how humans have exacerbated climate change, let’s look at the historical trends of carbon emissions. But first, what is carbon dioxide? Carbon dioxide is considered a greenhouse gas. By definition, a greenhouse gas is able to readily absorb and release heat (2). Other greenhouse gases include methane and nitrous oxide. Although greenhouse gases have a negative connotation, they are important in maintaining the habitable temperatures of our planet. Greenhouse gases have the characteristic of absorbing energy from the sun and releasing them over time (2). This allows for the temperature of the atmosphere to be maintained relatively constant throughout the year. Different greenhouse gases have varying capacities in how long they are able to sustain the energy. CO2, unlike methane and nitrous oxide, absorbs less energy, exists longer, and is more abundant in the atmosphere (2).


Yearly Carbon cycle:

As we will discuss later, carbon emission levels have risen and have displayed a clear upwards trend in the past century, but yearly fluctuations are another pattern to observe. Generally, the CO2 levels drop during the spring and summer due to an increase in plant life which takes in a higher amount of CO2. Comparatively, the levels rise during the fall and winter, when there is less plant life.

More specifically, CO2 levels have increased as a result of the burning of fossil fuels as well as from land use change. Findings have shown that from 2007 to 2016, we humans have added 10.7x10^15 grams of carbon every year. The ocean has taken in about 22% of the carbon, the land biosphere absorbed 28%, and 6% from the sink reservoirs were not counted for (5). Although the general increase in CO2 levels can be seen, there is a seasonal cycle of CO2 concentration which can be observed by the yearly fluctuations we see. Along with this, scientists have reported an increase in the global “breathing” pattern, indicating that the vegetation is absorbing more of the CO2, and forests have even grown as a result (6). This can especially be seen in the northern areas of the planet, in the boreal forest, as well as the tundra.


Carbon dioxide is even more present at night than it is during the day, but it is more present in fall and winter because the plants take up less CO2. In the spring and summer, they absorb more of the CO2 through photosynthesis, and also release less of it back through respiration. Because humans have impacted the natural cycle greatly, the growing season of plant life has expanded to a duration of a month longer than it was from 1961 to 1990 (7). The fluctuations that can be observed yearly through the gradual increase in levels, as mentioned before, is termed the “sawtooth” graph, which reveals the changes over the year that occur (7). Additionally, the season of growing plant life which has increased can be seen by the bigger ‘teeth’ on the graph, where plants take in and then release more CO2. The variation in the fluctuations of CO2 levels depend on the geographical location, but it is clear that the northern hemisphere takes in more CO2 in the winter because there is more land and plant life (7).


Trends:

At the beginning of the Industrial age, carbon dioxide was measured to be at 280 ppm (parts per million). Since then, the atmospheric concentration of CO2 has risen by 47% and is estimated to be 412 ppm as per recent measurements (1). So you might be wondering, what were the historical carbon emissions rates? How do they compare to what we are measuring right now? Why is this so threatening?

Carbon dioxide emissions had once been this high around 3 million years ago. During that time, the average global temperature was 2-3oC higher and oceans levels were 15-25 meters higher (2). Earth’s CO2 emission exceeded above 400 ppm 16 million to 25 million years ago, where the climate and the environment of the planet were significantly different than what it is today. There is a natural carbon cycle that coincides with the ice age cycle of our planet. When the axis of the earth changes slightly, more sunlight is exposed. This would lead to the higher temperatures and the eventual warming of the planet as CO2 was released (2). Glacial periods of colder climate occurred as the water and life on our planet absorbed the CO2, reducing the greenhouse effect (3). As we can see, the carbon cycle is closely associated with the climate of our planet and is crucial for maintaining moderate temperatures. The measurements of historic carbon dioxide levels are measured through ice cores from glaciers. These ice cores have trapped air that can be used to analyze the components.



Unlike the historical trends, the carbon dioxide emission levels are increasing at an unprecedented rate. Natural carbon emission maximums were achieved over longer periods of time, allowing for the life on our planet to adapt. However, the current rate of carbon emission is 100 times higher than that of the naturally occurring phenomenon (2). At the current rate, we are expected to reach around 500 ppm in the next 50 years (4). This means that global food supply, extreme weather events, and wildlife will be severely impacted. Many organisms on the planet, including humans, will struggle to adapt to a quickly changing climate.


What contributes to the rising CO2 and methane levels?

The meat and poultry industry contributes significantly to the rising carbon dioxide levels in the atmosphere. Greenhouse gases like carbon dioxide and methane are produced as a result of increased consumption of plants (feed) by cattle and livestock. The beef industry, for instance, emits around 3.6 to 6.8 pounds of CO2 into the atmosphere for every pound of beef that is produced. (5) Cultivating feed also produces a lot of CO2 and cattle require a lot of feed in order to grow before they are slaughtered. Producing a pound of beef also requires up to 10 grams of plant protein. Cultivating this results in the release of large amounts of CO2 and methane. (5) Additionally, animal waste releases a large amount of methane into the atmosphere. (5)


The burning of fossil fuels has also significantly increased the atmospheric concentration of CO2. Humans have been responsible for increasing the concentration of atmospheric CO2 by around 47% since the industrial revolution. Factories and vehicles have changed the natural greenhouse of the Earth. The burning of fossil fuels like coal and oil leads to the production of CO2 when oxygen combines with carbon. The increase of carbon dioxide in the atmosphere has led to heating up of the atmosphere and the surface of the earth. The effect of this heating has led to more evaporation and precipitation, however, some regions may become hotter and dryer while others become wetter. Another effect has been melting of glaciers and ice sheets, thereby increasing the sea levels. This is a dangerous consequence, as rising sea levels will lead to sinking of landmass, thereby causing destruction to populations. Climate extremes


Closure:

97 million cars were produced in 2018 alone, meaning more fossil fuels burned. In society today, technological innovations are certainly needed, but at the same time, we must determine and allocate which technologies we must pursue and implement. New phones and cars are not necessary for an improved lifestyle and environment. We need to collectively contribute to reducing waste and explore creative solutions to combat climate change. If rising sea levels, hotter climate, increase in extreme weather events, and extinction of life are not enough to convince us to take action, what else are we waiting for?


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