Greenhouse gases (GHGs) absorb and emit radiation in Earth’s atmosphere, leading to a greenhouse effect. The greenhouse effect is necessary – without it, Earth’s average temperature would be much colder. However, increasing the greenhouse effect by increasing the levels of GHGs in the atmosphere is contributing to climate change.
Use lower case for the names of GHGs:
carbon dioxide methane nitrous oxide chlorofluorocarbon hydrofluorocarbon water vapour
short-lived tropospheric ozone
For publications for a general audience, the names of other gases should be spelt out in full. For more technical publications, they can be shortened to chemical formulas:
carbon dioxide
or CO
2 not CO2, CO
2
methane or CH4
nitrous oxide or N2O
ozone or O3
water vapour or H2O
See Chemical formulas for more information on presenting chemical names.
NOx is a generic term for nitric oxide and nitrogen dioxide, or nitrogen oxides. Note that the x is lower case, subscripted and italic; other variations (eg NOx) are not correct.
Chlorofluorocarbons and hydrofluorocarbons are groups of compounds that can be referred to in their shortened forms:
chlorofluorocarbons or CFCs hydrofluorocarbons or HFCs
If shortened forms for chemical compouinds are used, identify them in full at first use in the text:
… carbon dioxide (CO2) … hydrofluorocarbons (HFCs) … nitrogen oxides (NOx)
GHG emissions are generally reported as parts per million (ppm) or parts per billion (ppb) (see Relative units). The carbon dioxide equivalent is often displayed as CO2 equivalents (CO2-e) and is often reported as parts per million by volume (ppmv), megatonnes of carbon dioxide equivalents (MtCO2-e) or gigatonnes of carbon dioxide equivalents (GtCO2-e).
Reminder. Use lower case for the initialisms ppm, ppb and ppmv.
Use a lower case, italic p for the unit ‘partial pressure of CO2’:
Emissions is generally plural when referring to GHGs:
carbon dioxide emissions emissions targets
