During the next few days the level of carbon dioxide in the atmosphere is expected to reach 400 parts per million (ppm) for the first time in millions of years.
Recordings from the Earth Systems Research laboratory in Hawaii were logged at a daily average of 399.72ppm on 25 April. On Monday, the weekly average was 398.5. Further, hourly readings have registered above 400pm 6 times during the past week at the Hawaii station, and sometimes up in the high Arctic as well. The Hawaii laboratory at Mauna Loa is 3,400m away from major pollution sources, and is considered very reliable in terms of CO2 readings.
As most of us now know, CO2 levels in the atmosphere have been rising since the start of the industrial revolution around 200 years ago, when they were recorded as being about 280ppm. In 1958 a level of 316ppm was recorded at the Mauna Loa station, when the observatory first started operating.
Scientific consensus has determined that the primary cause of the rise in CO2 levels is the ever-increasing burning of fossil fuels by humans. The last time CO2 levels were this high is thought to be around 3.2 million to 5 million years ago, when the global climate was a lot warmer than it is today.
Even as levels reach 400ppm and beyond, it still remains to be seen when the world will begin to take serious action to reduce emissions, and to begin to decrease the heavy use of fossil fuels. Governments from around the world are again meeting in Bonn, Germany to attempt to make progress on the glacial pace of international climate talks.