Wrong. Human activity is responsible for ALL of the 100 ppm increase. (Actually, it's more like 80 ppm.) That's the whole point of the carbon sink we're discussing. Were it note for human activities, atmospheric CO2 would be decreasing.
The fact that CO2 from anthropogenic sources and CO2 from natural sources (and sinks) mix in the atmosphere does not change that fact. I've used the bathtub analogy before, but: imagine filling your bathtub to the brim, then pulling the drain plug and then adjusting the water flow from the spigot such that the water level remains exactly constant. Subsequently start adding water a cup at a time about once a minute.
What'll happen to the water in the tub? And what's causing that effect?
If you believe they are wrong, go tell the government. That's the source for the 14% number that I previously linked on the thread.
Carbon Dioxide Information Analysis Center