One of the biggest greenhouse gases is carbon dioxide. Carbon dioxide is a chemical also called CO2. It is made of molecules, every molecule has one carbon and two oxygen atoms. At room temperature, it is in the gas state, it is also part of the carbon cycle, and atmospheric CO2 is a primary source of carbon for living creatures. In the air, it is invisible, but it acts as a shield for infrared radiation, and due to that, it is one of the main greenhouse gases. CO2 is found in groundwater, lakes, ise caps, and seawater. Carbon dioxide can dissolve in water, and when it does, it becomes bicarbonate (HCO3), which makes the ocean more acidic. Burning fossil fuels is the primary cause of the increased CO2 level in the atmosphere and, therefore, the main cause of climate change. CO2 is also emitted into the atmosphere from deforestation, land clearing for agriculture, and the degradation of soils.

How exactly does carbon dioxide trap heat on Earth? When the heat from the Sun reaches the Earth’s surface, some of the heat absorbs on the ground, and the other part reradiates from the ground. We can feel it as heat. Maybe you have heard the heat leaving the ground when you walk on darker surfaces, they feel very warm or even hot. The infrared waves reach up to the atmosphere, and they are trying to get back to space. Oxygen and nitrogen are the main components of the atmosphere. Oxygen and nitrogen don’t interface with infrared waves in the atmosphere. That’s because all the molecules are absorbing different types of wavelengths, and the wavelength that is leaving the Earth’s surface doesn’t match the oxygen and nitrogen wavelengths. Each wavelength carries energy. Since carbon dioxide is made out of carbon and oxygen, their molecules are perfect together to absorb wavelengths between 2000 and 15 000 nanometers, which is the same range as infrared energy has. CO2 absorbs the infrared energy and then sends it back in all different directions. Half of the energy goes back to space, and the other half reaches the earth’s ground as heat.

In the atmosphere, there is less than 0.04% CO2, so how can the impact be so major? Because of greenhouse gases, life on Earth is possible. Nowadays, the CO2 level in the atmosphere is higher than it has ever been in three million years. The presentage might seem very little, but it adds up to billions and billions of tons of CO2, which is trapping the heat around Earth. In 2019, people released more than 36 billion tons of extra CO2 into the atmosphere, and it will stay there for hundreds of years.

Carbon dioxide has naturally increased in the past. On Earth, there have been several ice ages, and between them have been warm episodes called interglacials. They all began with a small increase in incoming sunlight in the Northern Hemisphere because of the change in Earth’s orbit around the Sun. Due to more sunlight, the oceans got warmer, and they outgassed CO2. Extra carbon dioxide acted as a shield in the atmosphere for the infrared light, and therefore the ice on Earth started to melt. In the past million years, the amount of carbon dioxide has never exceeded 300 ppm (parts per million). If the fossil fuel burning is going to continue, then the CO2 level may exceed 800 ppm or even higher.
 
You have probably learned that plants use CO2 to make oxygen, and because of that, you might think that the extra CO2 in the atmosphere wouldn’t be a big problem. Also, the ocean and the soil absorb some of the carbon dioxide, they store it underground, underwater, or in the roots and tree trunks. Without human activity, a larger amount of oil, coal, and natural gases would stay underground and wouldn’t disturb the carbon cycle. Fossil fuels contain carbon that plants absorbed out of the atmosphere millions of years ago, and now we have been using most of the fossil fuels for hundreds of years. By using them, the carbon cycle is out of balance, and plants and the ocean are unable to absorb the extra carbon fast enough. It would take thousands of years to absorb the extra amount of carbon, and sadly, we don’t have that much time.
 
In conclusion, we have to think of better ways to produce energy. By decarbonizing our energy supply, removing CO2 from the atmosphere, and adopting more sustainable practices, we have the potential to significantly reduce the harm and hardship caused by climate change.

Sources:
https://en.wikipedia.org/wiki/Carbon_dioxide
https://www.epa.gov/ghgemissions/overview-greenhouse-gases
https://news.climate.columbia.edu/2021/02/25/carbon-dioxide-cause-global-warming/
https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide