[strommen]

3.75ppm, but yes - to be clear, worldwide emissions are continuing to increase, so the CO2 level should be rising by more and more every year.

If we can level off our greenhouse emissions (and we're very close), the CO2 level should continue to rise each year, but at a roughly-constant rate.

And if the world can get approach net-zero greenhouse emissions (a reasonable goal for 2050), the CO2 level should stop growing.

And then, we would need a few centuries of negative greenhouse emissions to get back to pre-industrial temperatures. I suspect we'll never bother to do this.

[danieltillett]

According to the NOAA link I provided the CO2 concentration at Mauna Loa rose from 402.80 ppm in June 2015 to 406.81 ppm in June 2016 (most recent data) which is 4.01 ppm in a year :(

I think you mean the growth rate of CO2 emission is starting to level (actually looking at the data not even this is true), not growth of CO2. We are still headed for disaster if the CO2 goes up by 4ppm every year. I see no sign that emissions of CO2 are slowing, or that we are doing anything serious to stop emitting GHG. Just look at the growth of CH4 which is continuing to increase [1].

1. http://www.esrl.noaa.gov/gmd/ccgg/trends_ch4/