Greenhouse gases

Greenhouse gases and their impact on our climate

Greenhouse gases (GHG) are gases that trap heat from the sun in the Earth’s atmosphere. They act like the glass walls of a greenhouse, which is why they are called greenhouse gases. This effect is important because it helps to keep our planet at a suitable temperature for life. However, human activity since the Industrial Revolution has caused an immense increase in greenhouse gases, leading to global warming and  climate change. The consequences include higher global temperatures and a higher likelihood of extreme weather events such as hurricanes, floods, and droughts. They can also harm biodiversity and disrupt entire ecosystems.

What are the main greenhouse gases?

Countries worldwide are working together to combat climate change to set targets and rules for reducing greenhouse gas emissions. Because of their powerful impact on the climate, the main GHGs are regulated by the United Nations Framework Convention on Climate Change (UNFCCC). All parties to the Convention, especially the industrialised countries, are expected to reduce their emissions drastically. The Kyoto Protocol was an international treaty negotiated under the guise of the UNFCCC that aimed to combat climate change by reducing greenhouse gas emissions. It was the first international agreement to regulate how these countries would reduce these emissions.

The UNFCCC identifies seven primary greenhouse gases, although many others exist:

• Carbon dioxide (CO₂)
• Methane (CH₄)
• Nitrous oxide (N₂O)
• Hydrofluorocarbons (HFCs)
• Perfluorocarbons (PFCs)
• Sulphur hexafluoride (SF₆)
• Nitrogen trifluoride (NF₃)

The Intergovernmental Panel on Climate Change (IPCC) estimates that rising atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have already caused the global surface temperature to rise by 1.4°C during the industrial era, independent of other greenhouse gases (GHGs).

What causes greenhouse gases?

• Carbon dioxide (CO2): Carbon dioxide emissions are the main cause of global warming. This gas enters the atmosphere mainly from the burning of fossil fuels such as coal, natural gas, and oil, but also from solid waste and trees. It can also be removed from the atmosphere or sequestered through biogenic processes. This happens when plants or trees absorb CO2 through photosynthesis, or through technical processes, including direct air capture (DAC). According to the World Meteorological Organization, global carbon dioxide emissions from fossil fuels will reach a record high in 2024 and continue to rise.
• Methane (CH4): Methane is estimated to be responsible for approximately a third of the warming we are experiencing today. Methane is released during the extraction and transport of coal, natural gas, and oil. Livestock, various agricultural activities, land-use changes, and the decomposition of organic waste in municipal solid waste landfills also emit methane.
• Nitrous oxide (N₂O): Nitrous oxides are produced by various human activities, such as agricultural and land-use practices, industrial processes, combustion of fossil fuels and solid waste, and wastewater treatment.

How long do Greenhouse Gases (GHG) remain in the atmosphere?

The length of time a greenhouse gas remains in the atmosphere depends on the type of gas. The period can vary from a decade to hundreds or thousands of years. According to NASA, carbon dioxide can remain in the atmosphere for hundreds to thousands of years, while methane lasts only about a decade. Nitrous oxide, which is 40% man-made and 60% natural, can stay in the atmosphere for about 110 years.

How can greenhouse gases be reduced?

Mitigating climate change requires reducing the amount of greenhouse gases in the atmosphere through a variety of strategies. This can happen through avoiding or removing emissions. Avoiding means preventing emissions from entering the atmosphere in the first place. It focuses on actions that reduce or eliminate sources of emissions, such as:

• Switching to renewable energy: Using solar, wind, or hydropower instead of fossil fuels to generate energy.
• Improving energy efficiency: Adopting energy-saving technologies, such as LED lighting or fuel-efficient vehicles
• Sustainable land use practices: Protecting forests from deforestation and promoting sustainable agriculture to avoid emissions from land degradation and habitat destruction.

Removing emissions involves extracting greenhouse gases that are already in the atmosphere. Common methods include:

• Increasing carbon sequestration: Expanding forests, conserving ecosystems, and restoring degraded lands to capture carbon dioxide through natural processes like photosynthesis.
• Technological carbon removal: Using innovative technologies, such as direct air capture or carbon capture and storage (CCS), to physically remove CO₂ from the atmosphere and store it underground or in other secure locations.