What exactly is Greenhouse Gas?
“Greenhouse gases (GHGs) are a set of gases that accumulate in the lower layer of the atmosphere, the troposphere, and absorb infrared radiation, which contributes to increasing the average temperature of the Earth’s surface”
– Photovoltaic Solar Energy Conversion, 2020
The air around us holds various greenhouse gases like water vapor, chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone (O3). These gases act like a cozy blanket, trapping heat from the sun and making the Earth warm. This phenomenon is called the greenhouse effect, and it comes in two forms: natural and enhanced.
1. Natural Greenhouse Effect
This happens because of the natural presence of greenhouse gases and is super important for life on Earth. Without it, our planet would be about 33°C cooler.
2. Enhanced Greenhouse Effect
The enhanced greenhouse effect occurs when there’s extra heat trapped due to higher levels of greenhouse gases caused by human actions. These emissions are changing our climate faster than ever before. This change messes with weather patterns and natural balances, putting us and all living things at risk. Human activities are mostly to blame for the majority of the 1.1°C global warming we’re experiencing.
Out of all the greenhouse gases, FOUR are getting major global attention due to their role in climate change: carbon dioxide, methane, nitrous oxide, and fluorinated gases. In the next part of this blog, I’ll explain these gases and where they come from.
Figure: Recent enhancement in GHGs emissions (Source: World Meteorological Organization)
Most Significant Greenhouse Gases
Carbon dioxide (CO2)
Carbon dioxide is the big player in climate change, and here’s why it matters:
First off, there’s a huge amount of it: We’re pumping over 35 billion tons of CO2 into the air every year. This mainly happens when we burn stuff like coal and oil that used to be buried underground.
Secondly, CO2 sticks around for a long time. The CO2 we release today will hang out in the atmosphere, trapping heat, for hundreds of years. Even if we magically stopped emitting CO2 tomorrow, it would take many lifetimes before the effects of our past emissions disappeared.
Lastly, lots of industries rely on fuels or processes that produce CO2. Think burning fossil fuels for power and transportation, making concrete and steel, refining oil and gas, fermentation (for instance, to make alcohol or pharmaceuticals), and even natural processes like plants decaying. Each of these sectors can cut down on CO2 emissions, but it’s not a one-size-fits-all solution.
Methane (CH4)
The second biggest contributor to climate change is methane, which is a major component of natural gas. Methane has about 100 times the heat-trapping power of CO2, but it doesn’t hang around in the atmosphere for as long—it sticks around for about 10 years. Measuring methane emissions is tricky because they don’t mainly come from factories. Instead, they come from sources like livestock, changes in forests and wetlands, rotting organic waste in landfills, and leaks from gas wells and pipelines.
Nitrous oxide (N2O)
Nitrous oxide is a potent greenhouse gas that lingers in the atmosphere for more than 100 years. While it’s famously known as laughing gas, its commercial usage contributes only a small fraction to our emissions. The primary source of nitrous oxide in the atmosphere is from growing crops with fertilizers containing nitrogen. Additionally, it can be released during land use changes, industrial processes, combustion of fossil fuels and solid waste, and wastewater treatment.
Fluorinated gases
Hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride are synthetic greenhouse gases that pack a punch. They’re released from various household, commercial, and industrial activities. These gases, especially hydrofluorocarbons, are sometimes used as replacements for ozone-depleting substances like chlorofluorocarbons and halons. Even though fluorinated gases are emitted in smaller amounts compared to other greenhouse gases, they’re super potent. They have what’s called a high global warming potential (GWP), meaning they trap a ton more heat than CO2 for the same amount of mass. Their GWPs usually range from thousands to tens of thousands, earning them the nickname “high-GWP gases.”
Major greenhouse gases (Source: IPCC, Climate change 2021; MIT Climate Portal)
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