It seems the answer would require observing plankton populations, and even though I personally find it hard to picture that propellers would do it (more likely oceanic pollutants, I should think) it is an interesting idea to look not just at the rates of CO2 emission but also at the rates of removal. Can we all agree the CO2 is increasing? This means we are not in equilibrium, and unless something is done either at the emission end or the removal end, we won't be in equilibrium any time soon. But I thought the purpose of the thread was to debate if there is in fact GW, not why?