Stratospheric ozone depletion from halocarbons is partly countered by pollution‐driven increases in tropospheric ozone, with transport connecting the two. While recognizing this connection, the ozone assessment's evaluation of observations and processes have often split the chapters at the tropopause boundary. Using a chemistry‐transport model we find that air‐pollution ozone enhancements in the troposphere spill over into the stratosphere at significant rates, that is, 13%–34% of the excess tropospheric burden appears in the lowermost extra‐tropical stratosphere. As we track the anticipated recovery of the observed ozone depletion, we should recognize that two tenths of that recovery may come from the transport of increasing tropospheric ozone into the stratosphere. Plain Language Summary The world has made great strides in phasing out the halocarbons that drive ozone loss, such as the chlorofluorocarbons 11 and 12. While living with the well‐documented depletion of the ozone layer, we are now watching the slow recovery (increase) of stratospheric ozone over this century after our phaseout of halocarbon production and use. Projecting this recovery date also depends on the impact of other changing greenhouse gases on stratospheric chemistry as well as changes in tropospheric ozone. Both observations and models identify tropospheric ozone as increasing due to air‐quality pollution in the lower atmosphere. Here, using a global chemistry‐transport model, we find that this ozone increase carries over into the stratosphere at rates affecting the recovery expected from the decay of atmospheric halocarbons. This process is inherently included in our chemistry‐climate models but is not diagnosed as such. The ozone assessments need consider that what happens in the troposphere does not stay in the troposphere, complicating our of interpretation of ozone changes over this century. 1. Prologue The Climatic Impact Assessment Program (CIAP, 1974) in the early 1970s completed an integrated U.S. assessment of the ozone (O3) layer as being under future threat from a proposed fleet of high‐flying Concorde‐like supersonic transport aircraft (SSTs). The threat of depletion of the ozone layer was based on the catalytic ability of oxides of nitrogen (NOx) emitted from the engines to destroy stratospheric ozone (Johnston, 1971; McElroy et al., 1974). The hypothetical threat of SSTs was quickly replaced by real ozone depletion caused by chlorofluorocarbons (Molina & Rowland, 1974; Stolarski & Cicerone, 1974; Wofsy & McElroy, 1974). Ozone assessments became international and remained focused on halogen‐driven ozone depletion (e.g., WMO, 1981, 1985, 2022). In 1988 the NASA High Speed Research Program revived the dream of a commercial SST fleet and initiated the Atmospheric Effects of Stratospheric Aircraft (AESA) to re‐assess SST impacts based on the maturity of stratospheric science. In the first AESA report, a figure appeared (Schmeltekopf, 1992; reproduced here as Figure 1) that predicted increases in lowermost stratospheric O3 from the aircraft NOx due to “smog reactions” that include methane (CH4). This result was surprising at first to those focusing on O3 depletion, and it may be the first assessment to show increased lower stratospheric O3 production associated with human pollution.