"By mole fraction (i.e., by number of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases."
The study of gases and particles in the Earth's atmosphere, including their chemical and physical properties and interactions.
The Earth's Atmosphere: Understanding the layers of Earth's atmosphere and their characteristics.
Oxygen and Nitrogen: The two most abundant gases in Earth's atmosphere — their properties, and their contributions to the Earth's atmosphere.
Carbon Dioxide: Understanding the role of carbon dioxide in the atmosphere and its contribution to the greenhouse effect.
Greenhouse Gases: Understanding the various greenhouse gases that contribute to global warming.
Pollutants: Understanding the various pollutants that can affect the Earth's atmosphere.
Aerosols: Understanding the impact of aerosols on atmospheric chemistry and climate.
Ozone: Understanding the role of ozone in the atmosphere and how it affects air quality and climate.
Air Quality: Understanding the factors that affect air quality and how air quality is monitored.
Weather: Understanding how atmospheric composition affects weather patterns.
Climate Change: Understanding the causes and effects of climate change and the role of atmospheric composition.
Acid Rain: Understanding the causes and effects of acid rain on atmospheric composition.
Atmospheric Dynamics: Understanding the physical processes that govern the motion and behavior of the Earth's atmosphere.
Atmospheric Chemistry: Understanding the chemical reactions that take place in the Earth's atmosphere.
Radiation Balance: Understanding the balance between incoming solar radiation and outgoing infrared radiation that governs the Earth's climate.
Radiation Transfer: Understanding how radiation interacts with the Earth's atmosphere and affects atmospheric composition.
Aerosol-Cloud Interactions: Understanding the interactions between aerosols and clouds and their impact on atmospheric composition and climate.
Remote Sensing: Understanding how satellites and other remote sensing technologies are used to study atmospheric composition.
Earth System Modeling: Understanding how computer models are used to simulate and study the Earth's atmosphere and its interactions with other components of the Earth system.
Nitrogen: The most abundant gas in the atmosphere, making up 78% of the air we breathe.
Oxygen: The second most abundant gas in the atmosphere, making up around 21% of the air we breathe.
Argon: A noble gas that makes up about 0.9% of our atmosphere, and is also used in light bulbs and welding.
Carbon dioxide: A trace gas that is a greenhouse gas, allowing energy from the sun to be trapped in the atmosphere.
Neon: Another noble gas that is used in signs and lighting, and makes up about 0.0018% of the atmosphere.
Helium: A lighter than air gas that is also used in balloons and airships, and makes up about 0.0005% of the atmosphere.
Methane: A potent greenhouse gas that is produced by natural processes as well as by human activities such as farming and industry.
Water vapor: A variable gas that can cause weather changes and is also a greenhouse gas.
Ozone: A gas that is formed in the atmosphere and acts to protect the Earth from the sun's harmful ultraviolet radiation.
Trace gases: Various gases that are present in the atmosphere in small quantities but can have significant impacts on the environment, including nitrogen oxides, sulfur dioxide, and hydrogen chloride.
"The atmosphere of Earth creates pressure, absorbs most meteoroids and ultraviolet solar radiation, warms the surface through heat retention (greenhouse effect), allowing life and liquid water to exist on the Earth's surface, and reduces temperature extremes between day and night."
"Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere."
"Air composition, temperature, and atmospheric pressure vary with altitude."
"Within the atmosphere, air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in Earth's troposphere."
"The atmosphere changed significantly over time, affected by many factors such as volcanism, life, and weathering."
"Recently, human activity has also contributed to atmospheric changes, such as global warming, ozone depletion and acid deposition."
"The atmosphere has a mass of about 5.15×10^18 kg."
"Three quarters of the atmosphere's mass is within about 11 km (6.8 mi; 36,000 ft) of the surface."
"The atmosphere becomes thinner with increasing altitude, with no definite boundary between the atmosphere and outer space."
"The Kármán line, at 100 km (62 mi) or 1.57% of Earth's radius, is often used as the border between the atmosphere and outer space."
"Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km (75 mi)."
"Several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition."
"The study of Earth's atmosphere and its processes is called atmospheric science (aerology)."
"Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann."
"Atmospheric science includes multiple subfields, such as climatology and atmospheric physics."
"The study of historic atmosphere is called paleoclimatology."
"The atmosphere [...] reduces temperature extremes between day and night (the diurnal temperature variation)."
"The atmosphere of Earth creates [...] absorbs most meteoroids and ultraviolet solar radiation."
"The atmosphere of Earth creates [...] allowing life and liquid water to exist on the Earth's surface."