Carbon dioxide
A gas with the chemical formula CO₂, released by processes including respiration, fossil fuel combustion and land-use change.
Example
Human activities add CO₂ faster than natural sinks remove the extra amount, increasing its atmospheric concentration.
The catch
Its warming effect persists across several timescales; there is no single simple lifetime.
Related terms
Fossil fuel, Albedo, Atmospheric lifetime, Carbon budget, Climate change, Climate feedback
In more depth
Carbon dioxide, explained.
Carbon dioxide is the main driver of human-caused warming, and its effect builds up because each release adds to a stock that lingers. Warming tracks the cumulative total, so the IPCC finds that warming from CO₂ stops rising only when net emissions reach zero. Oceans absorb part of each release, and that uptake makes seawater more acidic, a separate harm known as ocean acidification.
Units trip people up. A tonne of carbon and a tonne of carbon dioxide are different quantities, because the oxygen atoms add weight, so a figure quoted in carbon looks far smaller than the same amount quoted as CO₂. Loose phrases such as 'carbon emissions' cause a related muddle, since writers often use them to cover every greenhouse gas, methane included.
In the journal