Now, the bad news is we have already reached the 400 ppm level this year. The daily average reading from January 1, 2015 was for 400.37 ppm.
NOAA actually reports it as 401.56 ppm. We can expect it to fluctuate up and down, so it won't stay above 400 and, in fact, NOAA reports the level as 399.91 ppm for January 2nd. But, the earliest it reached this level in 2013 was in May. The earliest it reached this level in 2014 was March. And, now we are seeing this level in January. There can be no doubt we are nearing the time when the CO2 level will never again drop below 400 ppm. My guess? 2016 will be the last year that will ever have CO2 levels less than 400 ppm. At least, for the next thousand years, or more. Here is the two-year plot of CO2 levels as measured at Mauna Loa, Hawaii.
But don't forget, the new fossil fuel industry tactic is to tell you this is a good thing and we should be doing more of it. What do you think?