The ozone layer is a region of Earth's stratosphere that contains a high concentration of ozone (O3) molecules. It plays a crucial role in protecting life on Earth by absorbing the majority of the sun's ultraviolet (UV) radiation, particularly harmful UV-B and UV-C rays. This absorption prevents most of the harmful radiation from reaching the Earth's surface, where it can cause various health issues in humans, damage ecosystems, and harm organisms.

The ozone layer is not uniform but rather varies in thickness and concentration around the globe. It's thickest near the equator and thinnest near the poles. The concentration of ozone in the ozone layer is measured in Dobson units (DU), with typical values ranging from 250 to 500 DU.

In recent decades, human activities have led to the depletion of the ozone layer, primarily through the release of substances like chlorofluorocarbons (CFCs), halons, and other ozone-depleting substances (ODS) used in various industrial and consumer applications. These chemicals break down ozone molecules when they reach the stratosphere, leading to a reduction in ozone concentration.

Concerns about ozone depletion led to the adoption of the Montreal Protocol in 1987, an international agreement aimed at phasing out the production and use of ODS. Since then, significant progress has been made in reducing the emissions of ODS, resulting in a gradual recovery of the ozone layer. However, full recovery is expected to take several decades.

Monitoring the ozone layer is crucial for understanding its health and detecting any changes that may occur. Satellite observations, ground-based instruments, and atmospheric models are used to track ozone concentrations and study the factors influencing its dynamics.