The impact of increasing carbon dioxide on ozone recovery

Abstract

[1] We have used the Goddard Space Flight Center coupled two-dimensional model to study the impact of increasing carbon dioxide from 1980 to 2050 on the recovery of ozone to its pre-1980 amounts. We find that the changes in temperature and circulation arising from increasing CO 2 affect ozone recovery in a manner which varies greatly with latitude, altitude, and time of year. Middle and upper stratospheric ozone recovers faster at all latitudes due to a slowing of the ozone catalytic loss cycles. In the lower stratosphere the recovery of tropical ozone is delayed due to a decrease in production and a speedup in the overturning circulation. The recovery of high northern latitude lower stratospheric ozone is delayed in spring and summer due to an increase in springtime heterogeneous chemical loss, and is speeded up in fall and winter due to increased downwelling. The net effect on the higher northern latitude column ozone is to slow down the recovery from late March to late July, while making it faster at other times. In the high southern latitudes the impact of CO 2 cooling is negligible. Annual mean column ozone is predicted to recover faster at all latitudes, and globally averaged ozone is predicted to recover approximately 10 years faster as a result of increasing CO 2 .

The sensitivity of stratospheric ozone changes through the 21st century to N<sub>2</sub>O and CH<sub>4</sub>

“…The magnitude of the increase is listed as O 3 in the rightmost column of Table 1. In general, this increase is caused by a combination of a slowing of the gas-phase ozone loss cycles due to stratospheric cooling (Rosenfield et al, 2002), and decreasing concentrations of stratospheric chlorine and bromine resulting from the phase-out of halogenated ODSs under the Montreal Protocol (Bekki et al, 2011). The simulations with larger N 2 O surface concentrations lead to a smaller increase in ozone (4.3 DU in N 2 O-8.5 compared with 10 DU in N 2 O-2.6), while those with larger CH 4 surface concentrations lead to a larger increase in ozone (16.7 DU in CH 4 -8.5 compared with 4.4 DU in CH 4 -2.6).…”

“…CO 2 , the dominant anthropogenic greenhouse gas (GHG), elevates ozone by cooling the stratosphere, which slows the gas-phase ozone loss cycles (e.g. World Meteorological Organization, 1998; Rosenfield et al, 2002;IPCC/TEAP, 2005). Of the GHGs controlled under the Kyoto Protocol, those with the highest radiative forcing after CO 2 are N 2 O and CH 4 , both of which lead to changes in ozone via chemical processes.…”

Key drivers of ozone change and its radiative forcing over the 21st century

“…S3a), driving enhanced heterogeneous ozone loss chemistry (WMO, 2014). In contrast, cooling in the upper stratosphere results in ozone increases associated with a slowdown of catalytic O x cycles (Haigh and Pyle, 1982;Rosenfield et al, 2002).…”

“…Stratospheric cooling leads to further ozone loss in the lower stratosphere (through enhanced heterogeneous ozone destruction) and ozone increases in the upper stratosphere (through reduced NO x abundances and HO x -catalysed ozone loss, and 30 enhanced net oxygen chemistry) (Haigh and Pyle, 1982;Rosenfield et al, 2002). In addition, a projected acceleration of the BDC leads to an enhanced STE of ozone (e.g.…”

The potential to narrow uncertainty in projections of stratospheric ozone over the 21st century

“…Many recent studies have pointed to the role that future changes in GHG concentrations might play in determining both global and regional ozone abundances over the 21st century (Shepherd, 2008,Waugh et al, 2009, Jonsson et al, 2009, Oman et al, 2010a. GHGs can affect ozone concentrations through the additional HO x and NO x production from increases in CH 4 and N 2 O decomposition, through acceleration of catalytic ozone destruction cycles in the colder stratosphere and indirectly by influencing the strength of the Brewer-Dobson circulation and hence the meridional and vertical transport of ozone (Barnett et al, 1974;Randeniya et al, 2002;Rosenfield et al, 2002;Haigh and Pyle, 1982;Chipperfield and Feng, 2003;Portmann and Solomon, 2007;Ravishankara et al, 2009;Butchart et al, 2006).…”