Ocean acidification - the other CO2 problem
5 January 2009
Climate change has many dangerous consequences, but few of them have risen to prominence as quickly as the threat of ocean acidification. Tom Marshall explores the problem.
In the last half-decade the issue has climbed high up the environmental research agenda from almost-total obscurity. But its consequences still aren't well understood, and more research is urgently needed.
Our economy is so dependent on burning fossil fuels that almost everything people do emits some carbon dioxide (CO2) into the atmosphere. The oceans absorb a large portion of this CO2.
That's a good thing in as far as the seas are soaking up carbon that would otherwise remain in the atmosphere and worsen climate change. Less welcome is the fact that dissolved carbon dioxide is slowly making the oceans more acidic by forming a weak carbonic acid.
So far, this has pushed the oceans from a pH of around 8.2 to 8.1 - on this scale, lower numbers mean more acidity. That might not sound like much, but in the context of such a vast and intricate ecosystem as the world's oceans, it's a big deal indeed. And the number looks set to keep dropping as atmospheric CO2 levels continue to rise.
Dr Ken Caldeira and Dr Michael Wickett from Lawrence Livermore National Laboratory in the US were among the first to point out the problem in a Nature paper in 2003. This was followed up by a Royal Society report two years later. Before these studies, researchers had tended to think ocean acidity remained fairly constant, and that the ocean could absorb large amounts of carbon without coming to harm.
The United Nations Intergovernmental Panel on Climate Change (IPCC) predicted in its 2007 fourth Assessment Report that ocean pH will fall by a further 0.14 to 0.35 units over the 21st century. 'While the effects of observed ocean acidification on the marine biosphere are as yet undocumented, the progressive acidification of oceans is expected to have negative impacts on marine shell-forming organisms (e.g. corals) and their dependent species,' it added.
'By the end of this century, the oceans will be more acidic that they have been for more than 20 million years,' says Dr Ian Joint, a marine microbiologist at Plymouth Marine Library.
More worrying still is that much of the predicted change is already underway because of the carbon we've already emitted; even if we stopped burning fossil fuels today, the oceans would keep getting more acidic for years to come.
N.B. - the remainder of this very good article summarising the current position on ocean acidification can be found on website:
http://planetearth.nerc.ac.uk/features/story.aspx?id=265
Editorial Comment: What a very good article - nicely summarising the present 'state of play' with ocean acidification. 'Planet Earth' is a free NERC publication available to those with an interest in conservation issues |
