A number of changes and events have been observed in the stratosphere in the past 30 years: changes in ozone, aerosols from two major volcanic eruptions perturbing the chemical and radiative budgets, water vapour and temperature data that indicate various changes, variations in stratospheric circulation, and climate changes in the Arctic and Antarctic stratospheres especially during the winter-spring seasons. All of them indicating that the stratosphere-troposphere system is changing due to both natural and anthropogenic factors.

The monitoring of those changes in the atmosphere is made possible by measurements of high accuracy and resolution of various quantities. Then modelling tools allow to simulate quantities not directly measurable (See Stratosphere modelling web page), or to reproduce the effect of specific processes, and once fully understood, to predict their future impact on the atmospheric evolution.