Author: Amirali Banani
Editors: Chiara Chen and Misha Wichita
Artist: Kevin Lin
Greenhouse gases absorb the long-wave thermal infrared energy radiated by the Earth’s surface and reemit it in all directions, causing the greenhouse effect. This effect traps long-wave thermal infrared energy, or heat, within the Earth’s atmosphere, similar to how a greenhouse works. As the amount of greenhouse gases in the atmosphere increases, so does the amount of trapped thermal energy, leading to an overall increase in Earth’s temperature.
The greenhouse effect plays a crucial role in regulating the Earth’s climate, sustaining its surface temperature. Therefore, we need to control the number of greenhouse gases in the atmosphere to stabilise the Earth’s overall climate and slow down global warming. By doing so, we can prevent the potentially devastating effects of excess greenhouse gases on life on Earth. Carbon dioxide helps Earth preserve the energy it receives from the sun, preventing it from escaping back into space. If the atmosphere did not contain any carbon dioxide, the Earth’s oceans would be frozen solid, and the climate of planet Earth would be similar to that of Mars. All living things on Earth contain carbon, one of the four essential elements in plants and animals, along with oxygen, hydrogen, and nitrogen. Carbon combines with other elements to form vital biomolecules such as carbohydrates, nucleic acids, proteins, and lipids. The human body comprises 18% carbon, and most plants are 45% carbon.
Plants absorb carbon dioxide (CO2) during photosynthesis, extracting carbon from the molecule and releasing oxygen. On the other hand, animals breathe in the oxygen (O2) released by plants and breathe out carbon dioxide. Ultimately, plants and animals depend on each other. For hundreds of millions of years, they have lived and died together. Their remains have been buried deep beneath the Earth’s surface, and over time, this material has been intensively compressed and heated by the incredible pressure and heat beneath the Earth’s surface. Eventually, the ancient remains of the dead animals and plants turn into what is known as fossil fuels: oil, coal, and natural gas. Today, fossil fuels serve as the main source of energy production worldwide. We combust these carbon-rich materials to power vehicles, heaters, barbecues, run power plants, and operate many other things that require energy. Therefore, in a sense, everything powering our society depends on living organisms, as they are all carbon-based. This entire process is known as the carbon cycle. Carbon dioxide is very effective at absorbing long-wave thermal infrared energy radiated by the Earth’s surface and remitting that energy in all directions; therefore, even a small increase in carbon dioxide in the atmosphere can cause the Earth’s overall temperature to rise. Throughout Earth’s history, whenever the amount of CO2 in the atmosphere has increased, the planet’s overall temperature has also risen. Thus, there is a proportional relationship between the amount of CO2 in the Earth’s atmosphere and the planet’s temperature.
The greenhouse effect isn’t the same on all planets and differs considerably based on the thickness and composition of a planet’s atmosphere. The thickness of the Earth’s atmosphere, combined with its moderate amount of greenhouse gases (GHG), traps enough radiant heat to create a temperate, habitable planet. Meanwhile, Mars has a very thin atmosphere with an atmospheric density of 1% of that of Earth. Although Mars’s atmosphere is composed mostly of carbon dioxide, a greenhouse gas, the thinness of its atmosphere makes the greenhouse effect almost ineffective on Mars, resulting in a cold planet. On the other hand, Venus has an incredibly thick and dense atmosphere consisting of 96% carbon dioxide, which traps a significant amount of radiated thermal energy within the atmosphere of the planet, explaining Venus’s extremely hot temperatures.
As rocky planets, Earth, Mars, and Venus have similar atmospheres, interiors, and surfaces, and they even have the same greenhouse gases in the atmosphere. However, their atmospheres can change the temperatures of the planets significantly. Carbon dioxide dominates the greenhouse gases in the atmospheres of all these planets, but the level of warming varies significantly based on the amount of carbon dioxide and other greenhouse gases in their respective atmospheres, the thickness and density of their atmospheres, and the incident solar radiation on the planets, mainly associated with their proximity to the sun.
The distinct greenhouse effects on Earth, Mars, and Venus underscore the profound impact of atmospheric characteristics on planetary climates. Earth’s moderate atmosphere and a well-balanced mix of greenhouse gases foster a temperate and habitable environment. In contrast, Mars, despite its abundance of carbon dioxide, grapples with a thin atmosphere, rendering the greenhouse effect virtually ineffective and resulting in cold conditions. Conversely, Venus’s exceptionally thick atmosphere, predominantly composed of carbon dioxide, intensifies the greenhouse effect, contributing to its scorching temperatures.
These divergent outcomes reveal the nuanced relationship between atmospheric thickness, composition, and the resulting impact on a planet’s climate. Despite their shared rocky composition and similar greenhouse gas constituents, the varying levels and distribution of these gases, coupled with atmospheric density, play pivotal roles in determining the overall temperature conditions. This exploration highlights the intricate interplay of factors influencing planetary climates and emphasises the importance of understanding the delicate equilibrium required for a planet to sustain habitability. In the face of climate change and increasingly rising temperatures on planet Earth, it is more crucial than ever before to understand the greenhouse effect’s extraordinary influence on planetary climate.
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Education, UCAR Center for Science. “Center for Science Education.” Comparing Planetary
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Education, scied.ucar.edu/activity/planetary-gases. Accessed 2 Jan. 2024.
“Carbon Cycle.” Encyclopædia Britannica, Encyclopædia Britannica, Inc.,
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