Pretty much all models that are trying to predict how much danger we are (on global warming) suggest that all current carbon syncs will continue to work, however, that does not appear to be the case.
We have emitted roughly 1500 giga tonnes of carbon dioxide since the industrial revolution, and the total amount of carbon dioxide in the atmosphere is 3200 giga tonnes. Before this point, there was roughly 2200 giga tonnes in the atmosphere. These numbers suggest that around 1 quarter has been absorbed by the planet (these numbers could well be wrong but are worked out from well known figures).
This suggests that at least 1 quarter of our emissions have been absorbed, which if this study is right, means 1 third more carbon being added each year, if we simply keep our emissions stable or conversely, we need to cut emissions by an extra third to meet our goals, if this holds true.
Given our difficultly cutting emissions so far, this is going to prove hard.
And yet, we need to do it very fast.