Carbon dioxide (CO2) makes up about 0.04% of the Earth's atmosphere, or 400 parts per million (400ppm). CO2 is a greenhouse gas. Concentrations of CO2 in the atmosphere have varied from 7,000 ppm during the Cambrian period about 500 million years ago to 180 ppm during the Quaternary glaciation of the last two million years.
Recently, some climatologists have started to suggest that efforts to control human emissions of carbon are working. Whilst, on the face of it, this seems like complete poppycock, it may not be as crazy as it seems. The world is slowly moving out of the smoke stack industry era and newer, more sophisticated technologies tend to emit less CO2.
The problem with the idea, however, is that the amount of CO2 in the atmosphere is not reducing. In fact the increase in CO2 seems to be gathering pace.
The daily average concentration of atmospheric CO2 at Mauna Loa Observatory first exceeded 400 ppm on 10 May 2013. It is currently rising at a rate of approximately 2 ppm/year and accelerating. See https://www.esrl.noaa.gov/gmd/ccgg/trends/index.html
Good news about CO2: Emissions from the energy sector stayed flat ...The International Energy Agency announced Friday that the global energy sector produced 32.1 billion metric tons of CO2 in 2016, about the same as in 2015 and 2014, even while the world economy grew by more than 3 percent. (source Grist-17 Mar 2017)
Guardian Wednesday 6 May 2015