I came across the above photo on Reddit the other day (original link here). As one Redditor so aptly put it, “The stupid, it burns!!!” Interestingly, there are multiple layers of stupid here. Like a giant stupid onion. Leaving aside the fact that water dumped into a sink would eventually wash back into the ocean, how many buckets of water would each Earthling need to dump to cancel out the rising sea levels?
According to the Wikipedia entry for "Current sea level rise", predicted values for the ocean rise due to global warming range anywhere from 90 to 880 mm. I'll take 90 mm and just calculate the lower bound. The total area of the oceans is roughly 3.4 ×1014 m2, meaning that the total volume is about 3.0×1013 m3. One bucket might hold 50 L and there are 6.7 ×109 people in the world. Form this, we can compute the total number of buckets needed,
# of buckets = (total volume) / [ (volume per bucket per person) × (number of people)]
= (3.0×1013 m3) / [ (50 L per bucket per person) × (6.7×109 people)]
= 90,000 buckets.
Even neglecting the fact that the water will just wash back into the ocean, this method would still require every person on the planet to dump 90,000 buckets of sea water down their sink. As Shakespeare might once have said, "The stupid, it doth burn."