3.5% to be exact. But nature's 200 Gt per year gets reabsorbed in the spring and summer and man's 7Gt is all output. Therefore the increase in CO2 in atmosphere that is being observed is 100% manmade.
Another way to look at it, were the CO2 rise natural, it would amount to 5-10 ppm due to the warming after the Little Ice Age. Instead we have gone from 280 to 400 and rising. For that to be natural, there would have be a 10-12C ocean warming within the last few centuries or so. That's not at all plausible.
Glad I got the full explanation at Free Republic instead of having my ears carved off by a pathological Leftist.
That's actually fairly disturbing news.
From 2000-2010 we went up 22 PPM.
That's a 20% increase in one decade.
Has that trend increased from 2011-2014?
Should we comforted by the fact that we are still dealing with parts-per-million?
How does nature know which CO2 is nature made and which is man made?
Long term satellite survey ( last three decades ) indicates an increase of vegetation in warm arid regions worldwide as Co2 has risen.