How does the residence time of atmospheric exhaust plumes contrast with spent upper stages left in high orbit?

Exhaust plumes disperse relatively quickly, while high-orbit stages persist for centuries.

The environmental impact of a launch occurs across vastly different timescales depending on altitude. The intense burning of propellants releases exhaust plumes containing water vapor and other compounds directly into the stratosphere and mesosphere. These atmospheric pollutants are subject to global air currents and disperse relatively quickly, meaning their direct impact on atmospheric chemistry is short-lived, measured in days or months. Conversely, a spent upper stage left in a high orbit, like GEO, is outside the reach of atmospheric drag. This hardware becomes space debris that can remain in a stable orbit for hundreds or even thousands of years, creating a persistent, long-term threat to active satellites through potential collision.