Plot of global CO2
This graph shows the monthly mean atmospheric carbon dioxide at Mauna Loa Observatory, Hawaii, measured since 1958. A single data point has been added for the concentration recorded on May 9. The black curve represents the seasonally corrected data. (high resolution graphic)

The global concentration of carbon dioxide in the atmosphere hit 400 parts per million for the first time in recorded history on Thursday, according to data from the Mauna Loa Observatory in Hawaii.

Since 1958, the Mauna Loa Observatory has been gathering data on how much carbon dioxide is in the atmosphere. Carbon dioxide has increased by about 24 percent since the beginning of this record. Thursday's level was an unprecedented 400.03 ppm. (Source: NOAA)

Carbon dioxide is an important heat-trapping (greenhouse) gas, which is released through human activities such as deforestation and burning fossil fuels, as well as natural processes such as respiration and volcanic eruptions. It is the primary driver of recent global climate change.