The Greenhouse Effect on Earth and Other Planets
How Earth’s Climate differs from that of Mars and Venus due to Greenhouse Gases
Written by Amirali Banani | December 18, 2023
The Greenhouse Effect
Greenhouse gases absorb the long wave thermal infrared energy radiated by the Earth’s surface and reemit that thermal infrared energy in all directions; this is what causes the greenhouse effect.
The greenhouse effect accounts for the trapping of longwave thermal infrared energy (or heat energy) within the Earth’s atmosphere which increases the Earth’s overall temperature, similar to how a greenhouse works. The more greenhouse gases there are in the atmosphere, the more thermal energy (heat) radiated by the Earth’s surface will be trapped within its atmosphere and, consequently, the hotter the climate of planet Earth will become.
The greenhouse effect essentially regulates the Earth’s climate and sustains the surface temperature of planet Earth. Therefore, we need to control the amount of greenhouse gases in the atmosphere to keep the Earth’s overall climate stabilized and to slow down global warming and climate change. By doing so, we can prevent the potentially devastating effects that excess greenhouse gases can have on life on Earth.
Why Is Carbon Important?
- Carbon dioxide (which obviously consists of carbon) helps Earth preserve the energy that it receives from the sun so that it doesn’t all escape back into space. If there wasn’t any carbon dioxide in the atmosphere, the Earth’s oceans would be frozen solid and the climate of planet Earth would probably be similar to that of Mars.
- All living things on Earth contain carbon. It’s one of the 4 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 consists of 18% carbon and most plants consist of 45% carbon.
- Plants absorb carbon dioxide (CO2). They extract the carbon and release the oxygen. On the other hand, animals breathe in the oxygen (O2) released by plants and breathe out carbon dioxide (CO2), which is what plants depend on for cellular respiration. Ultimately, plants and animals depend on each other. For hundreds of millions of years, plants and animals have lived and died together. Their remains have been buried deep beneath the Earth’s surface, and for hundreds of millions of years, this material has been intensively compressed and heated by the incredible amount of pressure and heat beneath the Earth’s surface. Eventually, the ancient remains of the dead animals and plants turn into what we call fossil fuels: oil, coal, and natural gas. Today, we use fossil fuels as the main source of energy production in the world. We combust these carbon-rich materials to power vehicles, heaters, barbecues, drive power plants, and many other things that require energy to operate. Therefore, in a sense, everything that powers our society depends on living organisms as they are all carbon-based. This entire process that I just explained is the epitome of what’s called 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 become warmer. Throughout Earth’s history, whenever the amount of CO2 in the atmosphere has increased, the overall temperature of Earth has also increased. Thus, there is a proportional relationship between the amount of CO2 in the Earth’s atmosphere and the temperature of the planet.
Comparing Earth’s Atmosphere with those of Mars and Venus
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 the moderate amount of greenhouse gases (GHG) within it, works to trap enough radiant heat within the atmosphere to create a temperate, habitable planet. Mars, meanwhile, has a very thin atmosphere with an atmospheric density of 1% that of Earth’s. Even though Mars’s atmosphere is composed mostly of carbon dioxide (which is a GHG), since its atmosphere is so thin, the greenhouse effect is almost ineffective on Mars, therefore making it a cold planet. Oppositely, Venus has an incredibly thick and dense atmosphere consisting of 96% carbon dioxide which traps a significant amount of radiated thermal energy (heat) within the atmosphere of the planet, and this is what primarily accounts for its extremely hot temperatures.
As rocky planets, Earth, Mars, and Venus have similar atmospheres, interiors, and surfaces, and even the same greenhouse gases in the atmosphere. However, the different levels of greenhouse gases in the atmosphere 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 on the planets 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 partially the incident solar radiation on the planets which mainly has to do with their proximity to the sun.
To conclude…
The distinct greenhouse effects on Earth, Mars, and Venus underscore the profound impact of atmospheric characteristics on planetary climates. Earth’s moderate atmosphere, coupled with a well-balanced mix of greenhouse gases, facilitates 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 which is 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 emphasizes the importance of understanding the delicate equilibrium required for a planet to sustain habitability.
In the face of global warming and climate change due to increasingly rising temperatures on planet Earth, it is more crucial than ever before to understand the greenhouse effect’s extraordinary influence on planetary climate.
