Our planet is becoming warmer. The heat is melting ice caps, changing weather patterns, and disrupting the Earth's ecosystem. Despite their critical role in the greenhouse effect, we've been hearing how greenhouse gases, or GHGs, play a role in the current climate crisis. In this article, we'll explore GHGs and more.

As you may know, greenhouse gases like CO2, water vapour, methane, nitrous oxide, etc., play a vital role in the greenhouse effect, a natural process for keeping the Earth warm. Earth receives energy in the form of sunlight which passes through its atmosphere. Some of this energy is reflected into space, while others are trapped by greenhouse gases, which keep the Earth warm enough to sustain life. So you see, the greenhouse effect isn't a bad thing nor the GHGs. Without the GHGs, the planet would be frozen and uninhabitable for life to thrive. So what changed? Why are GHGs blamed now for the current climate crisis?

Since the 2000s, the amount of CO2 in the atmosphere has increased significantly, mainly due to the burning of fossil fuels. These human-caused emissions can remain in the atmosphere for long periods, trapping more heat and continuously warming the planet. CO2 especially has a significant impact on the global climate as it lingers for about 300 to 1,000 years. But it's interesting to note that though the concentration of CO2 in the atmosphere is just 0.04% compared to other gases, it is still the primary contributor to global warming.

Oxygen, nitrogen, and argon make up the highest percentage (99%) of gases in the atmosphere, while carbon dioxide is just 0.04%. CO2 and other GHG gases have three or more atoms, and hence they can trap heat enormously. On the other hand, oxygen and nitrogen contain molecules with two atoms, and therefore they are incapable of trapping heat.

Oxygen and nitrogen molecules keep colliding into CO2 and water vapour. As a result, the heat from these GHGs is shared between oxygen and nitrogen molecules. This effect causes the atmosphere to act as a blanket and keeps Earth warm. So when the concentration of GHGs in the atmosphere increases, this blanket starts to become thicker. Hence it becomes more difficult for the heat to rise to the top and escape.

The current CO2 level in the atmosphere is 414 ppm (parts per million). According to the World Climate Research Programme (WCRP) study, if CO2 concentrations double from pre-industrial levels, the Earth's average global temperature will rise by 2 to 5 degrees Celsius, causing devastating effects. The oceans are also getting warmer, increasing the water vapour in the atmosphere, thus amplifying the greenhouse effect.

Today carbon dioxide levels are higher than at any point in the past. We are adding more CO2 into the atmosphere than natural processes can remove. Plants, oceans, and soil are natural carbon sinks that can absorb and store CO2. But at the current rate of CO2 emission, it would take ages to clean up the mess. Hence cutting down GHG emissions and reducing our carbon footprint is the only way to avoid this global catastrophe.

Read Understanding the Greenhouse Gases - CH4 to know about CH4 and its role in global warming.