section_path: Concentrations and role in the environment/Atmosphere
section_name: Atmosphere
paragraph_text: Atmosphere
  
  In Earth's atmosphere, carbon dioxide is a trace gas that plays an integral part in the greenhouse effect, carbon cycle, photosynthesis and oceanic carbon cycle. It is one of several greenhouse gases in the atmosphere of Earth. The current global average concentration of carbon dioxide (CO) in the atmosphere is 421 ppm (0.04%) as of May 2022. This is an increase of 50% since the start of the Industrial Revolution, up from 280 ppm during the 10,000 years prior to the mid-18th century. The increase is due to human activity.
  
  As of March 2024, the monthly average concentration of CO reached a new record high of 425.22 parts per million (ppm), marking an increase of 4.7 ppm over March 2023. By the latest measurement, levels had further escalated to 427.48 ppm. This continuous increase in CO concentrations is a clear indicator of ongoing global environmental stress, primarily driven by the burning of fossil fuels, which is the principal cause of this rise and also a major contributor to climate change. Other significant human activities that emit CO include cement production, deforestation, and biomass burning.
  
  Carbon dioxide is a greenhouse gas. It absorbs and emits infrared radiation at its two infrared-active vibrational frequencies. The two wavelengths are 4.26 μm (2,347 cm) (asymmetric stretching vibrational mode) and 14.99 μm (667 cm) (bending vibrational mode). CO plays a significant role in influencing Earth 's surface temperature through the greenhouse effect. Light emission from the Earth's surface is most intense in the infrared region between 200 and 2500 cm, as opposed to light emission from the much hotter Sun which is most intense in the visible region. Absorption of infrared light at the vibrational frequencies of atmospheric CO traps energy near the surface, warming the surface of Earth and its lower atmosphere. Less energy reaches the upper atmosphere, which is therefore cooler because of this absorption.
  
  The increase in atmospheric concentrations of CO and other long-lived greenhouse gases such as methane increase the absorption and emission of infrared radiation by the atmosphere. This has led to a rise in average global temperature and ocean acidification. Another direct effect is the CO fertilization effect. The increase in atmospheric concentrations of CO causes a range of further effects of climate change on the environment and human living conditions.