Why carbon matters
Carbon is called the "backbone of life" because it forms the structural basis of all biological molecules: carbohydrates, proteins, fats, and DNA. Carbon's unique ability to form four stable bonds allows it to build the complex, large molecules that life requires. It is also the primary greenhouse gas driver of Earth's climate through CO₂ and methane.
Fast cycle and slow cycle
⚡ Fast Carbon Cycle (days to years)
Operates through living organisms:
- Photosynthesis: Plants absorb CO₂ + H₂O + sunlight → glucose + O₂. Carbon removed from atmosphere.
- Respiration: All organisms break down glucose → CO₂ + H₂O + energy. Carbon returned to atmosphere.
- Decomposition: Bacteria and fungi break down dead organisms, releasing CO₂ back to atmosphere.
🐢 Slow Carbon Cycle (millions of years)
Operates through geological processes:
- Weathering: Rain (slightly acidic) dissolves rocks, releasing carbon into rivers and oceans.
- Sedimentation: Marine organisms die and sink, forming carbonate rocks (limestone) over millions of years.
- Volcanism: Tectonic activity releases CO₂ stored in rocks back to the atmosphere.
The problem: Burning fossil fuels releases carbon from the slow cycle (stored over millions of years) into the fast cycle in just decades. This overwhelms natural carbon sinks and causes rapid CO₂ accumulation.
The Keeling Curve and its consequences
📈 The Keeling Curve
In 1958, American scientist Charles David Keeling began continuously measuring atmospheric CO₂ at Mauna Loa Observatory, Hawaii. The resulting graph — the Keeling Curve — shows CO₂ rising from ~315 ppm in 1960 to over 420 ppm in 2025. It also shows a seasonal "sawtooth" pattern: CO₂ drops each Northern Hemisphere summer as plants absorb it, then rises in winter when they shed leaves. This is the planet "breathing."
🌡️ Global Warming
Rising CO₂ enhances the greenhouse effect, raising global average temperatures. Earth has warmed ~1.2°C since pre-industrial times. The Paris Agreement (2015) aims to limit warming to 1.5–2°C to avoid the worst impacts.
🌊 Ocean Acidification
Oceans absorb CO₂, forming carbonic acid (H₂CO₃). Ocean pH has dropped from 8.2 to 8.1 since industrialisation — a 26% increase in acidity. This dissolves coral skeletons and shellfish shells, threatening marine ecosystems.
🌾 Eutrophication
Excessive use of nitrogen fertilisers adds nitrogen compounds to rivers and lakes. This triggers rapid algae growth (algal blooms). When the algae die and decompose, bacteria consume oxygen, creating "dead zones" where aquatic life cannot survive. This is a major problem in India's rivers and lakes near agricultural areas.
India is the world's third-largest CO₂ emitter but has committed to net-zero emissions by 2070 and 500 GW of renewable energy by 2030. India's forests absorb approximately 300 million tonnes of CO₂ per year — a significant natural carbon sink.