What are greenhouse gases?

Greenhouse gases (GHG) are gases that absorb and emit thermal radiation and whose wavelength is within the infrared range.

While greenhouse gases exist in nature, human activities have exponentially increased their presence. The accumulation of these gases in the atmosphere is the main cause of climate change.

What are the main greenhouse gases?

• Carbon dioxide (CO₂): also called carbon dioxide gas or carbonic anhydride, this is the most common greenhouse gas. Its main source of emission is the burning of fossil fuels (oil, natural gas, and coal). It is also produced as a result of deforestation and in the anaerobic putrefaction of plants and soil.
• Methane (CH₄): it is mainly generated in the production and transportation processes for fossil fuels, though it is also emitted from rice cultivation and livestock farming (livestock digestion produces large amounts of methane). Despite the fact that its concentration in the atmosphere is very low, it has a heating capacity 25 times higher than that of CO₂.
• Chlorofluorocarbons (CFCs): these are derivatives of saturated hydrocarbons whose production is tied to aerosols and refrigeration. Once released into the atmosphere, they decompose and release chlorine atoms that destroy ozone molecules; this is why they are primarily responsible for the loss of density in the ozone layer.
• Nitrogen oxides (NO_x): these include all chemical compounds made up of the combination of oxygen and nitrogen molecules. They are produced in combustion.
• Fluorinated gases: these are emitted by industry during the manufacture of electrical and electronic equipment and by refrigeration and air conditioning systems.

What impact do greenhouse gases have?

Since the Industrial Revolution, greenhouse gases have increased in concentration in the atmosphere more and more, and this has led to a number of changes in global ecosystems. Some of the main consequences of greenhouse gases in the atmosphere include:

• An increase in the average temperature of the planet.
• Extreme weather events that are more frequent and drastic, such as droughts, floods, storms, and heat waves.
• Glaciers and polar ice caps melting.
• Sea level rise.
• Ocean acidification due to the absorption of carbon dioxide, which threatens marine ecosystems and marine life.
• Alteration of precipitation patterns, which can impact life cycles in ecosystems, freshwater availability, and agricultural productivity.
• Loss of biodiversity.

How can the impact of greenhouse gases be mitigated?

The impact of the concentration of greenhouse gases is visible, and some consequences are unavoidable. Therefore, it is an urgent necessity to implement mitigation and prevention measures, such as protecting coastal communities, improving agricultural resilience, strengthening infrastructures, etc.

How can greenhouse gas emissions be reduced?

The reduction of greenhouse gas emissions is critical for slowing down climate change and supporting the Sustainable Development Goals. Some of the main efforts that can be made in this regard are:

• Accelerating the transition toward sources of renewable energy.
• Improving energy efficiency.
• Reforestation.
• Adopting sustainable agricultural practices.
• Increasing re-use.
• Redirecting consumption habits.
• Promoting the transition to a zero-waste economy.

Other actions seek to reverse the production of greenhouse gases through technology. Geoengineering (also called climate engineering or climate intervention) seeks large-scale modification of the Earth’s climate to reverse the effects of human activity on the planet. These processes can be categorized into two main branches:

1. Solar Radiation Management (SRM), which aims to reduce the amount of solar radiation that reaches the Earth’s surface through various measures, such as cloud seeding or the introduction of stratospheric aerosols.
2. The reduction of carbon dioxide, both directly and through the promotion of natural mechanisms for gas removal. Some of these methods include:
   • Direct air capture to extract carbon dioxide or store it in the surface agricultural soil.
   • Bioenergy with carbon capture and storage (BECCS): proposes the production of biomass from which to extract energy by capturing CO₂.
   • Ocean fertilization: enhancing the growth of phytoplankton by introducing iron and other nutrients. During their photosynthesis process, phytoplankton use atmospheric CO₂. When they die, these aquatic organisms drag the pollutant to the bottom of the sea.
   • Afforestation: creating new forests in places where there have never been any.

Institutions like NASA (US) and the Royal Society (UK) have done research in these fields. However, to this day, there is significant controversy on the effectiveness of these methods, particularly around their side effects.