Publication

Journal	Atmospheric Chemistry and Physics
Volume (Issue)	16(20)
Page(s)	13067 - 13080
Title of proceedings	Atmospheric Chemistry and Physics
DOI	10.5194/acp-16-13067-2016

URL	www.atmos-chem-phys.net/16/13067/2016/
Type of Open Access	Publisher (Gold Open Access)

Stratospheric water vapour (SWV) is an impor- tant component of the Earth’s atmosphere as it affects both radiative balance and the chemistry of the atmosphere. Key processes driving changes in SWV include dehydration of air masses transiting the cold-point tropopause (CPT) and methane oxidation. We use a chemistry–climate model to simulate changes in SWV through the 21st century fol- lowing the four canonical representative concentration path- ways (RCPs). Furthermore, we quantify the contribution that methane oxidation makes to SWV following each of the RCPs. Although the methane contribution to SWV maxi- mizes in the upper stratosphere, modelled SWV trends are found to be driven predominantly by warming of the CPT rather than by increasing methane oxidation. SWV changes by −5 to 60 % (depending on the location in the atmosphere and emissions scenario) and increases in the lower strato- sphere in all RCPs through the 21st century. Because the lower stratosphere is where water vapour radiative forcing maximizes, SWV’s influence on surface climate is also ex- pected to increase through the 21st century.