ilmakeää

Ilmakeä (more commonly spelled ilmakehä) is the Finnish word for the atmosphere, the layer of gases surrounding a planet. In Finnish usage the term refers primarily to Earth's atmosphere and is used in scientific, educational and everyday contexts; it also appears in cultural works such as poetry, music and place names.

Earth’s atmosphere is a mixture of nitrogen (about 78%), oxygen (about 21%), argon, carbon dioxide and trace gases, together with variable amounts of water vapor and suspended particles. Structurally it is divided into layers by temperature gradients: the troposphere, stratosphere, mesosphere, thermosphere and exosphere. The troposphere contains most weather phenomena and nearly all atmospheric mass.

Functions of the atmosphere include providing breathable air, regulating surface temperatures through the greenhouse effect, protecting the surface from harmful solar and cosmic radiation, and enabling weather and climate systems. Human activities have altered atmospheric composition and dynamics through greenhouse gas emissions, aerosol release and ozone-depleting substances, with consequences for global climate, air quality and ecosystems.

Scientific study of the atmosphere spans meteorology, atmospheric chemistry, climatology and planetary science. Observational and modeling tools range from ground-based stations and balloons to satellites and global climate models. In public discourse and policy, ilmakeä is central to discussions on air pollution control, climate mitigation and adaptation, and international environmental agreements.