The idea that there might come a time when the ability to absorb airborne CO2 is maxed out doesn't necessarily imply that that point has yet been reached.

Also, if it's app. the same proportion over time, that still means that in one year we put .7 x 35GT = 24.5 GT/a, vs. .7 x 2GT = 1.4 GT/a... we still pump more than two decades worth of CO2 in one year than we did 160 years ago.

Finally, while it may be true that the oceans can still absorb a lot of CO2, how long will it be before that means there aren't any more shellfish or coral? While I can easily see the oceans continuing to absorb CO2 long after the disappearance of shellfish or coral, it doesn't mean that I think it's a good idea to continue to do so and just write those biological niches off... I like shrimp.

Tasty tasty shrimp.