Oceans in Crisis - Ocean Worlds: The Story of Seas on Earth and Other Planets - page 174

over one-tenth of one-third of 1 per cent of the atmosphere—can
have such far-reaching consequences. Astonishing, and of course to
many still unbelievable. But the natural world is complicated and
often a little counter-intuitive, and the oceans are, in some ways, more
vulnerable to change than the land.
Emissions of carbon from their ancient storehouses in the
ground—of coal, oil, and gas—into the air are broadly known. They
currently stand at about 10 billion tonnes per year (just a few years
ago one was talking about 7 billion tonnes a year, but then that is the
nature of progress). That translates into about 30 billion tonnes of car-
bon dioxide, because two oxygen atoms (atomic weight ~16) are added
to each carbon atom (atomic weight ~12). That's just a figure. We can't
absorb figures in any real fashion, or at least most of us can't.
A kilogram of carbon dioxide, if in solid 'dry ice' form, makes up a
cube with each edge a little over 8.5 centimetres long, like one of the
larger children's play bricks. In gas form, at normal atmospheric tem-
perature and pressure, it swells out to something over five hundred
litres, which is about the volume of a very large family refrigerator.
A transatlantic flight in a 747 releases over 200 tonnes of carbon diox-
ide, or 200,000 refrigerators full. As the New York Times commentator
Andrew Revkin once said, if carbon dioxide was pink, we would be
very aware of what we are producing (and if it was smelly, we would
have turned to another energy source forthwith).
What about other sources? Volcanoes are huge carbon dioxide
emitters, surely? They are, but not on the gigantic scale at which
humans are now operating. The 1990 eruption of Mount Pinatubo
in the Philippines was the largest of the past century, explosively
expelling about 10 cubic kilometres of magma which spread over
the surrounding countryside as ash and pumice fragments. That
eruption—a catastrophic, gas-rich one—released something like
42 million tonnes of carbon dioxide, which is certainly large but