Earth's atmosphere is a complex mixture of gases, each playing a unique role. Nitrogen and oxygen dominate, but trace gases like and have outsized impacts. These greenhouse gases trap heat, warming our planet and shaping our climate.
Greenhouse gases come from both natural and human sources. Burning fossil fuels releases CO2, while agriculture produces methane. Some gases linger for centuries, while others break down quickly. Understanding these differences helps us tackle climate change effectively.
Atmospheric Composition and Greenhouse Gases
Composition of Earth's atmosphere
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Nitrogen (N2) makes up approximately 78% of the atmosphere by volume is the most abundant gas
Oxygen (O2) is the second most abundant gas at around 21% by volume is essential for life on Earth
Argon (Ar) is the third most abundant gas constituting about 0.93% by volume is an inert noble gas
Water vapor (H2O) varies in spatially and temporally typically ranging from 0.1% to 4% by volume influences weather and climate
Carbon dioxide (CO2) currently makes up approximately 0.04% by volume (as of 2021) concentration has been increasing due to human activities like fossil fuel and deforestation
Trace gases include neon (Ne), helium (He), methane (CH4), krypton (Kr), and xenon (Xe) each constitutes less than 0.002% by volume but can have significant impacts on the atmosphere and climate
Role of greenhouse gases
Greenhouse gases are atmospheric gases that absorb and emit infrared radiation primary ones include water vapor (H2O), carbon dioxide (CO2), methane (CH4), (N2O), and ozone (O3)
Trap heat in the atmosphere by absorbing outgoing infrared radiation emitted by Earth's surface and re-emitting this energy in all directions including back towards the surface leading to warming
warms Earth's surface and lower atmosphere without greenhouse gases Earth's average temperature would be around -18°C (0°F) much colder than current conditions
Increasing concentrations of greenhouse gases lead to an enhanced greenhouse effect causing global warming and climate change impacts ecosystems, sea levels, and weather patterns
Sources of greenhouse gases
Carbon dioxide (CO2)
Anthropogenic sources include fossil fuel combustion (coal, oil, natural gas), deforestation, and cement production
Natural sources include , volcanic eruptions, and decomposition of organic matter
Methane (CH4)
Anthropogenic sources include agriculture (livestock and rice cultivation), landfills, and fossil fuel extraction and distribution (natural gas leaks)
Natural sources include wetlands, termites, and wildfires
Nitrous oxide (N2O)
Anthropogenic sources include agricultural soil management (fertilizers), industrial processes, and biomass burning
Natural sources include microbial processes in soils and oceans
Water vapor (H2O)
Anthropogenic sources include irrigation and combustion of fossil fuels
Natural sources include evaporation from oceans, lakes, and rivers as well as transpiration from plants
Ozone (O3)
Anthropogenic sources include photochemical reactions involving nitrogen oxides and volatile organic compounds from vehicle emissions and industrial processes
Natural sources include the stratospheric ozone layer and lightning
Atmospheric lifetime of gases
Atmospheric lifetime is the average time a molecule of a gas remains in the atmosphere before being removed or chemically altered through processes like chemical reactions, photolysis (breakdown by sunlight), deposition on Earth's surface, or uptake by oceans or vegetation
Greenhouse gases with longer atmospheric lifetimes have a more persistent impact on the greenhouse effect carbon dioxide (CO2) has an atmospheric lifetime of centuries to millennia
Greenhouse gases with shorter atmospheric lifetimes can still have significant impacts if their emissions are large and continuous methane (CH4) has an atmospheric lifetime of about 12 years but has a strong greenhouse effect
Understanding atmospheric lifetimes helps predict the long-term effects of greenhouse gas emissions on climate change and develop mitigation strategies reducing emissions of long-lived gases is crucial for limiting long-term warming