General circulation models and chemistry-climate models predict that the Brewer-Dobson circulation (BDC)—a slow circulation pattern that determines stratospheric ozone and water vapor distributions and is related to climate change processes—will strengthen in response to an increase in greenhouse gases. Several modeling studies have also shown that the BDC will weaken as ozone recovers (or strengthen as ozone is depleted), however modeled predictions need to be checked against observational climate datasets. A new study, funded in part by CPO’s Climate Observations and Monitoring (COM) Program, examines observations from the past four decades and shows that the data support general circulation and chemistry-climate model predictions of ozone impacts.
Observing BDC strength has been challenging because its changes cannot be measured directly. However, nearly 25 years of research has advanced scientists’ ability to detect BDC changes from existing observations. Using satellite observations and ERA-Interim reanalysis data, researchers from NOAA’s Geophysical Fluid Dynamics Laboratory, Massachusetts Institute of Technology, and the University of Washington, examined BDC changes over the last 40 years in relation to the periods of ozone depletion (1980-1990) and ozone recovery (2000-2018). They found that the annual mean BDC accelerated during the ozone depletion period but decelerated for the ozone recovery period, thus supporting the general circulation and chemistry-climate model predictions of ozone impacts. Their results show differences between Northern Hemisphere and Southern Hemisphere cells, but overall the satellite data suggest an emerging response of the BDC to greenhouse gas increases in the Northern Hemisphere.