Climatewatch: positive feedback cycles I

It seems that some climate alarms are starting to go off, pointing out the appearance of positive feedback cycles. A recent article in the journal Science detailed how one of Earth's largest CO2 sinks - the Southern Ocean - is starting to fail:
Ocean CO2 effect 'starts to fail'
This may be too large a cycle for many of us "non-climatologists" to consider, but here is a positive feedback cycle that I think all of us A/C users can relate to: the hotter it gets = the more we need to cool our house/office/car/etc. = the more often (and higher) we crank up the A/C = using more power = burning more fossil fuels = increasing the CO2 released in the atmosphere.
Now that made me feel better. I cannot assume responsibility for the Southern ocean - but I can assume responsibility for driving with my car windows down as much as I can, instead of using the A/C.
The question is - how many of us need to do this in order for this to make any difference?