Annual Carbon Dioxide Minimum is Now Above 400 ppm

Ice core records show that until the Industrial Revolution atmospheric CO2 levels remained fairly steady at around 280 ppm (parts per million). By 1961, CO2 data collected at a monitoring station at the summit of Hawaii volcano showed that atmospheric CO2 levels were rising steadily by about 2 ppm per year. In 2005 the station recorded that CO2 concentrations had increased to 380 ppm. In May 2013, the station documented CO2 levels above 400 ppm for the first time.

The launch of the NASA Jet Propulsion Laboratory’s Atmospheric Infrared Sounder (AIRS) in 2002 made it possible for researchers to map CO2 levels in the troposphere-the lowest region of the earth’s atmosphere- on a global scale by taking measurements over the ocean, land, and poles and tracking these changes over time. The information gathered from AIRS includes the global average value of CO2 in the troposphere, which is the atmospheric level where most all the earth’s weather occurs.

The AIRS system allowed scientists to confirm a significant landmark: the annual minimum CO2 level has now exceeded 400 ppm over the entire globe. This is significant because during spring, as photosynthesis ramps up, plants breathe in carbon dioxide (CO2), and atmospheric levels of CO2 begin to drop. When trees lose their leaves in the fall and winter CO2 levels begin to rise again. This natural process means that there is an annual cycle of minimum and maximum levels of atmospheric CO2 during the year. Finding that global concentrations are above the 400 ppm threshold at a time of year when atmospheric CO2 is typically at its lowest level is a critical turning point in our climate. Scientists say that unless something dramatic happens with humans and the planet, it will never be 400 ppm again, at least over the next several decades.

For more information see: Satellite data confirm annual carbon dioxide minimum above 400 ppm.