Publication Date:
2013-01-03
Description:
[1] The impact of changes in the abundance of greenhouse gases (GHGs) on the evolution of tropospheric ozone (O 3 ) between 1960 and 2005 is examined using a version of the Goddard Earth Observing System chemistry-climate model (GEOS CCM) with a combined troposphere-stratosphere chemical mechanism. Simulations are performed to isolate the relative role of increases in methane (CH 4 ) and stratospheric ozone depleting substances (ODSs) on tropospheric O 3 . The 1960 to 2005 increases in GHGs (CO 2 , N 2 O, CH 4 , and ODSs) cause increases of around 1–8% in zonal-mean tropospheric O 3 in the tropics and northern extratropics, but decreases of 2–4% in most of the southern extratropics. These O 3 changes are due primarily to increases in CH 4 and ODSs, which cause changes of comparable magnitude but opposite sign. The CH 4 -related increases in O 3 are similar in each hemisphere (∼6%), but the ODS-related decreases in the southern extratropics are much larger than in northern extratropics (10% compared to 2%). This results in an interhemispheric difference in the sign of past O 3 change. Increases in the other GHGs (CO 2 and N 2 O) and SSTs have only a small impact on the total burden over this period, but do cause zonal variations in the sign of changes in tropical O 3 that are coupled to changes in vertical velocities and water vapor.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
Permalink
