Comment: CO2 reflects sunlight and does indeed cool the planet.  However, the total amount of CO2 released by volcanoes averages about .26 gigatons per year, compared with 32 gigatons per year by human activity worldwide (US Energy Information Administration, for the year 2012).  Also, it is a major factor in ocean acidification.  The pH has fallen by .1 unit over the last few hundred years, which is about 30 percent more acidic.  By the end of this century, it will be nearly 150% more acidic, which will affect the entire food chain upon which about a billion people depend on for their livelihood and food (NOAA, et al).  Massive amounts of CO2 in the atmosphere is not our friend.