Editing Global warming potential (section)

=== Water vapour ===
{{See also|Greenhouse gas#Special role of water vapor|Climate change feedbacks#Water vapor feedback (positive)}}
[[Water vapour]] does contribute to anthropogenic global warming, but as the GWP is defined, it is negligible for H<sub>2</sub>O: an estimate gives a 100-year GWP between -0.001 and 0.0005.<ref>{{cite journal | doi=10.1088/1748-9326/aae018 | title=The global warming potential of near-surface emitted water vapour | year=2018 | last1=Sherwood | first1=Steven C. | last2=Dixit | first2=Vishal | last3=Salomez | first3=Chryséis | journal=Environmental Research Letters | volume=13 | issue=10 | page=104006 | bibcode=2018ERL....13j4006S | s2cid=158806342 | doi-access=free | hdl=1959.4/unsworks_57193 | hdl-access=free }}</ref>

H<sub>2</sub>O can function as a greenhouse gas because it has a profound infrared absorption spectrum with more and broader absorption bands than {{CO2}}. Its concentration in the atmosphere is limited by air temperature, so that radiative forcing by water vapour increases with global warming (positive feedback). But the GWP definition excludes indirect effects. GWP definition is also based on emissions, and anthropogenic emissions of water vapour ([[cooling tower]]s, [[irrigation]]) are removed via [[precipitation]] within weeks, so its GWP is negligible.