Carbon dioxide emissions

Greenhouse gas emissions are a major threat to humanity

Since the 19th century, chemists and physicists have calculated that doubling the amount of CO2 in Earth’s atmosphere would cause a 4°C temperature increase, which could in turn lead to environmental consequences similar to the end of the Ice Age. IPCC researchers (Intergovernmental Panel on Climate Change) now believe that a mere 2°C temperature increase would have very severe consequences. If mankind continues to produce and consume at the current pace, that very temperature change will be unavoidable by the end of the 21st century. To ensure that the 2°C temperature is avoided, emissions of CO2 and other greenhouse gases must be drastically curbed.

The main greenhouse gases are: water vapour (H2O), carbon dioxide or carbonic acid gas (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3), and new gases such as hydrofluorocarbons (HFC), perfluorocarbons (PFC) and sulphur hexafluoride (SF6), whose long-term effects are as yet undetermined. Their atmospheric lifetimes range from twelve years for methane to around one hundred years for carbon dioxide to 50,000 years for sulphur hexafluoride. Their global warming potential (GWP) also differs: 1 kg of methane has the same impact as 21 kg of CO2, and 1 kg of SF6 contributes as much as 24,000 kg of CO2.

The statistics are well-known. Worldwide, human activity produces 6.5 Gt (billion tonnes) of carbon and 23 Gt of CO2 (one CO2 molecule weighs approximately 4 times more than the carbon it contains). However, half that amount, or 3 Gt of carbon a year, should ideally be produced, equivalent to 1960 emissions. It is not an unattainable goal; however the main difficulty is making the emissions equitable, since most human activities associated with “development” have high emissions (industry, intensive agriculture, transportation, heating, etc.).

In an equitable world, where every person had the same emissions rights, the sustainable amount of 3 Gt of carbon production would be divided by the total world population, resulting in a figure of 500 kg carbon per capita per year. To reach that goal, Americans and Australians would have to cut their emissions by 10, Europeans and the Japanese by 4 or 5. Even several developing countries produce more than that level of carbon, including China, though that can be largely explained by its new industrial role in the global economy. On the other hand, most of Sub-Saharan Africa and India, Pakistan, and the Philippines would be able to increase their emissions.