What sets the CO2 amount?

Having established that CO2 is in continual exchange with the oceans, so fast that half of all the world's aerial CO2 is gone every 14 years, the next question people  have is more difficult.   Why shouldn't the CO2 come back?    Maybe not as fossil fuel CO2, but still CO2.   That way the fossil fuel increase would be maintained.

Equilibrium is not intuitive.   What matters in equilibrium are ratios, in this case the ratio between the amount of CO2 in the air and the amount in the water.   This ratio is fixed for this physical process of gaseous exchange and the only significant other variables are temperature and air pressure.

It is generally agreed that 98% of all CO2 is in the oceans.   That's 50x as much as in the air.  It is this ratio which is maintained in any gaseous exchange.  We have no control over this.

Now apply this ratio.   Say we doubled aerial CO2 suddenly by burning a great deal of old fossil fuel, yes the total CO2 would go up, and there would be excessive CO2 in the air.   Very quickly the amounts in the air would disappear into the ocean until the old ratio was achieved.  It means that 98% of the new CO2 would be moved quickly to the oceans.   Yes, the concentrations would both go up slightly, but the ratio would be exactly the same.  Remember the concentration of CO2 in the air is very small, less than 1/25th of 1%.

Basically 98% of the fossil fuel CO2 would go into the oceans, something confirmed by the lack of any depression in the C14 ratio in the air.   This was noted by Dr Suess who gave this explanation, an explanation attacked recently by some bodies such as the American Institute of Physics.  At least they recognize it is a critical observation by a pre Global Warming top scientist.

If not from fossil fuel, why is CO2 going up?   To increase the amount of CO2 in the air is simple, heat the water by 1C.   Even this slight release of CO2 has a dramatic effect as you x50, increasing CO2 levels in the air by around 70%

PS Remember when we talk global temperatures and for that matter air pressures, this includes summer and winter, stormy and clear days, night and day, the arctic and the tropics.   We are talking average temperatures and average air pressures.   The chemistry changes across the planet, CO2 being absorbed in very cold areas and more released in hotter areas.   This should not change our conclusions.