DATE RESOURCES AND MEASUREMENT

Changes in atmospheric oxygen levels are measured at the Scripps Institution of Oceanography at La Jolla, California under the Scripps O2 Program. Since 1991, air samples have been collected on a consistent basis from stations around the world to provide a global and hemispheric perspective on oxygen variability. The Scripps O2 Program is under the direction of Professor Ralph Keeling.

The Scripps Institute report oxygen measurements as changes in the O2/N2 ratio of air relative to a reference.  

They compute:

     δ =

((O2/N2)sample – (O2/N2)reference)/ (O2/N2)reference)

• (O2/N2)sample is the O2/N2 mole ratio of an air sample
• (O2/N2)reference is the O2/N2 mole ratio of their reference

Their reference is based on tanks of air pumped in the mid 1980s which are stored at the Scripps Institute laboratory in La Jolla, California.

CLIMATE CHANGE :  THE MAGNITUDE OF THE PROBLEM    

Atmospheric oxygen levels are fundamentally linked to the evolution of life on Earth. The present-day concentration is about 20 percent of Earth's atmosphere.