carbon dioxide

History

In 1756, Scotsman Joseph Black called CO₂ 'fixed air,' showing that it is released from limestone and absorbed by alkalis. Later, Lavoisier identified it as a compound of carbon and oxygen. In 1859, Irish physicist John Tyndall measured the heat absorption of CO₂, laying the foundations of the greenhouse effect theory.

How it works

In a plant leaf, CO₂ enters through microscopic pores into green cells, where sunlight splits water and forces carbon dioxide to turn into sugars. This process—photosynthesis—feeds almost all living things. In the ocean, CO₂ dissolves, but excess acidifies the water, threatening corals and shells, like a weak acid shower eroding calcareous shells.

History

In 1756, Scotsman Joseph Black called CO₂ 'fixed air,' showing that it is released from limestone and absorbed by alkalis. Later, Lavoisier identified it as a compound of carbon and oxygen. In 1859, Irish physicist John Tyndall measured the heat absorption of CO₂, laying the foundations of the greenhouse effect theory.

How it works

In a plant leaf, CO₂ enters through microscopic pores into green cells, where sunlight splits water and forces carbon dioxide to turn into sugars. This process—photosynthesis—feeds almost all living things. In the ocean, CO₂ dissolves, but excess acidifies the water, threatening corals and shells, like a weak acid shower eroding calcareous shells.

History

Black (1756) isolated CO₂ from limestone; Lavoisier (1770s) determined its composition. Tyndall (1859) measured heat absorption. Arrhenius (1896) quantitatively predicted global warming from rising CO₂. Keeling (from 1958) began monitoring at Mauna Loa, proving the trend. The carbon in CO₂ is formed in stars through the triple-alpha process, explained by Fred Hoyle and Margaret Burbidge in 1957.

How it works

The greenhouse effect of CO₂ is based on its ability to absorb Earth's infrared radiation. The Earth radiates as a blackbody with a maximum near 10 µm (Wien's displacement law). Vibrations of the CO₂ molecule (antisymmetric stretching with a dipole moment) resonate with IR photons, re-emitting some energy back to the surface. Radiative forcing depends logarithmically on concentration: ΔF = 5.35·ln(C/C₀). According to the second law of thermodynamics, heat flow from a cold atmosphere to a warm surface is impossible without an external source, so re-emission merely slows cooling.

Open problems & fun facts

Quantitative assessment of climate sensitivity (ECS)—the temperature rise from doubling CO₂—remains in the range 2–5°C due to uncertainties in feedbacks (clouds, ocean); Creating efficient and cheap direct air capture (DAC) systems for CO₂ with subsequent mineralization; Forecasting the regional impacts of ocean acidification on marine ecosystems

💡 Every day, an average tree absorbs about 22 kg of CO₂, and a hectare of forest—up to 2 tons. But volcanoes emit even more CO₂ into the atmosphere: one eruption can release as much as all the world's cars in a year. In the distant past, when carbon dioxide was 10 times higher, giant ferns grew on Earth, becoming coal.