1. Introduction

Greenhouse gases (GHGs) are atmospheric components that trap heat, maintaining Earth’s temperature suitable for life. Their concentration and composition are central to climate science, environmental engineering, and policy-making.

2. Major Greenhouse Gases

Gas Chemical Formula Main Sources Atmospheric Lifetime Global Warming Potential (GWP, 100 yrs)
Carbon Dioxide CO₂ Fossil fuels, deforestation ~100 years 1
Methane CH₄ Agriculture, landfills, fossil fuels ~12 years 28-36
Nitrous Oxide N₂O Fertilizers, industry, biomass burning ~114 years 265-298
Ozone O₃ Photochemical reactions Hours to weeks Varies
CFCs/HFCs CCl₂F₂, etc. Refrigerants, aerosols 1-1000+ years 1000-12,000+
Water Vapor H₂O Evaporation, transpiration Days Variable; amplifies other GHGs

3. Mechanism of Greenhouse Effect

  1. Solar radiation reaches Earth’s surface.
  2. Surface absorbs energy and re-emits it as infrared (IR) radiation.
  3. GHGs absorb IR and re-radiate it in all directions, warming the lower atmosphere.

Greenhouse Effect Diagram

4. Surprising Facts

  • Methane is over 25 times more potent than CO₂ at trapping heat over a 100-year period, but its atmospheric lifetime is much shorter.
  • Permafrost thawing can release ancient methane and CO₂, creating a feedback loop that accelerates warming.
  • Ozone is both a GHG and a pollutant: In the stratosphere, it protects from UV radiation; in the troposphere, it acts as a GHG and health hazard.

5. Sources and Sinks

Natural Sources

  • Volcanic eruptions (CO₂, water vapor)
  • Wetlands (CH₄)
  • Oceans (CO₂ exchange)

Anthropogenic Sources

  • Fossil fuel combustion
  • Industrial processes (cement, chemicals)
  • Agriculture (livestock, fertilizers)
  • Deforestation

Sinks

  • Photosynthesis (plants, algae)
  • Ocean absorption
  • Soil uptake (N₂O, CH₄)

6. Emerging Technologies

Artificial Intelligence (AI) in GHG Research

  • AI-driven molecular simulations accelerate discovery of novel materials for carbon capture and storage (CCS).
  • Machine learning models predict GHG emissions from satellite data, improving monitoring accuracy.
  • AI-optimized catalysts for methane-to-methanol conversion, reducing methane emissions at source.

Advanced Materials

  • Metal-Organic Frameworks (MOFs): Highly porous, customizable for selective CO₂ capture.
  • Graphene-based membranes: Enable efficient separation of CO₂ from industrial exhaust.

Remote Sensing

  • Hyperspectral imaging from satellites detects atmospheric GHG concentrations with high spatial resolution.
  • Drones equipped with sensors monitor methane leaks from oil and gas infrastructure.

7. Practical Experiment: Measuring CO₂ Levels Indoors

Objective: Quantify indoor CO₂ concentration using an inexpensive NDIR (Non-Dispersive Infrared) sensor.

Materials:

  • NDIR CO₂ sensor (e.g., MH-Z19)
  • Arduino or Raspberry Pi
  • USB cable, breadboard, jumper wires
  • Computer with serial monitor software

Procedure:

  1. Connect the NDIR sensor to the microcontroller.
  2. Upload sample code to read CO₂ values.
  3. Place the sensor in the center of the room.
  4. Record baseline CO₂ levels.
  5. Have several people enter the room and remain for 15 minutes.
  6. Record CO₂ levels every minute.
  7. Open windows/doors and observe how quickly CO₂ levels decrease.

Analysis:

  • Plot CO₂ concentration vs. time.
  • Discuss implications for indoor air quality and ventilation.

8. Latest Discoveries

  • AI-Driven GHG Monitoring: A 2023 study in Nature Communications demonstrated that deep learning models can analyze satellite data to pinpoint methane super-emitters with unprecedented accuracy, enabling targeted mitigation (Cusworth et al., 2023).
  • Direct Air Capture (DAC): Recent advances in solid sorbent materials have reduced energy requirements for DAC, making large-scale atmospheric CO₂ removal more feasible.
  • Methane Detection: Quantum cascade laser technology now allows real-time, in situ detection of methane leaks at parts-per-billion levels.

9. Recent Research Example

Cusworth, D. H., et al. (2023). “Detecting high-emitting methane sources with multispectral satellite imagery.” Nature Communications, 14, 1234. Link

10. Impacts and Mitigation

Impacts

  • Global temperature rise
  • Ocean acidification
  • Extreme weather events
  • Sea level rise

Mitigation Strategies

  • Transition to renewable energy
  • Reforestation and afforestation
  • Carbon capture, utilization, and storage (CCUS)
  • Methane leak detection and repair

11. Summary Table: GHGs and Mitigation

GHG Main Source Key Mitigation Strategy
CO₂ Fossil fuels, deforestation Renewable energy, CCS
CH₄ Agriculture, fossil fuels Leak detection, dietary changes
N₂O Fertilizers Precision agriculture
CFCs/HFCs Refrigerants Alternatives, recycling programs

12. References

  • Cusworth, D. H., et al. (2023). “Detecting high-emitting methane sources with multispectral satellite imagery.” Nature Communications, 14, 1234. Link
  • IPCC Sixth Assessment Report, 2021.
  • U.S. Department of Energy, “Direct Air Capture,” 2023.

End of Notes