what is the composition of earth's atmosphere today
Atmosphere of Earth By volume, dry air contains 78.09% nitrogen, 20.95% oxygen,[1] 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Air content and atmospheric pressure vary at different layers, and air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in Earth's troposphere and in artificial atmospheres.
Main-group element Main-group elements (with some of the lighter transition metals) are the most abundant elements on Earth, in the Solar System, and in the Universe. They are sometimes also called the representative elements.
Greenhouse gas Human activities since the beginning of the Industrial Revolution (taken as sometime between the years 1740 and 1754) have produced a 40% increase in the atmospheric concentration of carbon dioxide, from 280 ppm in 1750 to 406 ppm in early 2017.[6] This increase has occurred despite the uptake of a large portion of the emissions by various natural "sinks" involved in the carbon cycle.[7][8] The vast majority of Anthropogenic carbon dioxide (CO2) emissions (i.e., emissions produced by human activities) come from combustion of fossil fuels, principally coal, oil, and natural gas, with comparatively modest additional contributions coming from deforestation, changes in land use, soil erosion, and agriculture (including animal agriculture), though some of the emissions of this sector are offset by carbon sequestration.[9][10]
Northern Hemisphere Its surface is 60.7% water, compared with 80.9% water in the case of the Southern Hemisphere, and it contains 67.3% of Earth's land.[2]