evidence: On the other hand, animals – including humans – breathe out CO₂ in the process of respiration. When plants and animals die, their stored carbon is also released as CO₂. Natural processes such as respiration and decay, forest fires and volcanic eruptions add an additional 190.2 billion tonnes of CO₂ to the atmosphere per year. [...] Humans generate CO₂ when burning fossil fuels such as gas, petrol, oil, and coal. This adds an additional 9.1 billion tonnes of CO₂ to the atmosphere each year. [...] As a result of increasing emissions, the global atmospheric CO₂ concentration has increased by 50 per cent since pre-industrial times, rising from 277 ppm in 1750 to 416 ppm in June 2023.