Weekly average CO2 at Mauna Loa observatory, Hawaii
Measurements taken by the National Oceanic and Atmospheric Administration

Week beginning on Aug. 16, 2015:   399.13 parts per million
Weekly value from one year ago:     396.81 ppm
Weekly value from 10 years ago:     378.79 ppm

Global data:
400.11 ppm for June 2015 
397.52 ppm for June 2014