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The deep unknown: ocean acidification’s murky waters

February 16, 2010

Let us presume for a moment that the sceptics are right: the current global warming trend, rather than being the unproven consequence of humans pumping carbon dioxide into the atmosphere, is largely just the latest manifestation of a natural process experienced by the earth at various times in its long existence.

Does it then matter that we continue burning fossil fuels and don’t bother reining back our carbon emissions?  According to many, it does: just look at what is happening in our oceans.

The ocean acts as a carbon dioxide sink, absorbing our emissions.  But when there is too much CO2 for the water to dissolve, there is a build-up of carbonic acid.  This acidification limits the access marine organisms have to carbonate ions, which they need to form their hard shells and skeletons.  This means an uncertain future for the likes of plankton and molluscs, and for the coral reefs which shelter the species of fish so many of the world’s poorer nations rely on for sustenance.

But ocean acidification, too, is an area in which scepticism abounds.

The contrarians point out that there is not enough reliable data.  The ocean’ s chemistry is complicated, and there is no simple way of measuring pH.  Laboratory experiments on the effects of CO2 on salt water’s acidity don’t precisely mimic natural processes.

It’s been pointed out that the freshwater mussel has lived for aeons in waters which have a very variable pH, though being largely acidic, with this variation being geographical as well as seasonal.

Some organisms lived through the last period of major ocean acidification around 55 million years ago, which was a much more dramatic scenario than anything that we are experiencing now, quite happily; their adaptation apparently was to grow thicker shells to compensate.

Like the bird species that can now live further north as a result of the changing climate, so ocean acidification isn’t bad news for every sea-living organism.  It’s been noted that sea grasses, which form an important feeding and spawning location for commercially-useful fish, grow better in carbon rich waters. 

So, oceans have experienced increases in acid since the last Ice Age, and seem to have adjusted to these – just as, some would say, the Earth has ridden out changes in temperature.  On the other hand, the environmentalists could fairly claim that the rate at which the oceans are becoming acidic is happening alarmingly fast (mirroring the intensifying progress of global warming) – giving organisms much less time in which to adapt.

In this debate, the science seems to be even more complicated than that surrounding climate change.  Proponents and sceptics come up with formula-filled explanations which are very hard for the layperson to understand.  And pretty hard for a SolarUK blogger to summarise.

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