Since the industrial revolution began over two centuries ago, the oceans have absorbed an estimated 500 billion tons of carbon dioxide. This is about a quarter of the total amount spewed into the atmosphere as the burning of coal, oil and natural gas gathered pace and agriculture replaced forests.
As a result, the basic chemistry of seawater is being altered on a scale scientists say has not occurred for at least 20 million years. Moreover, it is happening at a rate not seen in the last 65 million years.
Does it really matter? More specifically, will it affect future food security in a world where 1 billion people already rely on fisheries for their primary source of animal protein and another three billion depend on the sea to meet at least 15 percent of their protein needs?
This is a pressing question for Japan where fish has long played an important part in the national diet.