Analysis of the Keeling Curve in Terms of Photosynthesis, Respiration, and Combustion
- The Keeling Curve is a groundbreaking graph that has provided critical insight into atmospheric carbon dioxide (CO₂) levels since measurements began in 1958 at Mauna Loa Observatory in Hawaii.
- It reveals two critical patterns:
- Annual fluctuations
- A long-term upward trend.
The Keeling Curve is named after Charles David Keeling, who began these measurements.
Annual Fluctuations: The Breath of the Biosphere
- The Keeling Curve shows a seasonal cycle:
- CO₂ levels rise from October to May.
- CO₂ levels fall from May to October.
Imbalances Between Photosynthesis and Respiration Cause Fluctuations
- Photosynthesis:
- During the northern hemisphere summer (May to October), plants absorb large amounts of CO₂ to grow.
- This reduces atmospheric CO₂ levels.
- Respiration: In winter (October to May), photosynthesis slows down, but respiration continues, releasing CO₂ back into the atmosphere.
Remember that the northern hemisphere has more landmass and vegetation than the southern hemisphere, so its seasonal changes dominate the global CO₂ cycle.
Long-Term Trend: A Steady Rise in CO₂ Levels
- Beyond the annual fluctuations, the Keeling Curve reveals a consistent increase in atmospheric CO₂ since 1958.
- This long-term trend is primarily driven by human activities.
The Role of Combustion
- Combustion is the burning of organic materials, such as fossil fuels (coal, oil, and natural gas) and biomass.
- This process releases CO₂ into the atmosphere:
- Fossil Fuels: Formed from ancient organic matter, burning these fuels releases carbon that was sequestered for millions of years.
- Biomass: Burning wood or other organic materials releases CO₂ that was recently absorbed by plants.
- It’s a common misconception that burning fossil fuels and biomass are equivalent.
- While both release CO₂, fossil fuels add "new" carbon to the atmosphere, whereas biomass burning recycles carbon already in the short-term carbon cycle.
Human Impact
- Industrial Activities: Factories, power plants, and vehicles burn fossil fuels, releasing vast amounts of CO₂.
- Deforestation: Cutting down forests reduces the planet’s capacity to absorb CO₂ through photosynthesis.
- In 2020, human activities released approximately 34 billion tonnes of CO₂ into the atmosphere.
- This is far more than natural processes can absorb, leading to a net increase in atmospheric CO₂.
Interpreting the Keeling Curve: A Balance of Processes
- The Keeling Curve reflects the interplay of three key processes:
- Photosynthesis: Removes CO₂ from the atmosphere.
- Respiration: Releases CO₂ back into the atmosphere.
- Combustion: Adds CO₂, particularly from fossil fuels, driving the long-term increase.
- Think of the atmosphere as a bathtub.
- Photosynthesis acts like a drain, removing CO₂, while respiration and combustion act like faucets, adding CO₂.
- Human activities have turned the combustion faucet on high, causing the bathtub to overflow.
Why Does This Matter?
- Rising CO₂ levels contribute to the greenhouse effect, trapping heat in the Earth’s atmosphere and driving climate change.
- The Keeling Curve provides critical evidence of this trend, highlighting the urgent need to reduce CO₂ emissions.
- How can scientific data like the Keeling Curve influence policy decisions on climate change?
- What role should scientists play in advocating for environmental action?
