Met Office: Atmospheric CO2 is now 50% higher than pre-industrial levels ‘It took about 200 years for the atmosphere to see a 25% increase in the atmospheric concentration of carbon dioxide, but only another 35 years to reach this year’s sorry milestone of a 50% increase.’ Image: Shutterstock Carbon dioxide concentration in the atmosphere has now reached 417 parts per million, a 50% increase since people began burning fossil fuels on a large scale during the industrial revolution. That’s the gloomy conclusion reached in a new report from the Met Office, which suggests measurements at the Mauna Loa Observatory (MLO) in Hawaii show that carbon dioxide concentrations are already above that level.