The magazine of the european research area European Commission Copenhagen, a missed chance?

Interview by Yves Sciama

(1)  IPCC: International Panel on Climate Change. Jean-Pascal 

van Ypersele is a physicist, climatologist and professor 

at the Institute of Astronomy and Geophysics at the 

Catholic University of Louvain (BE).

---

10 research

*

eu No. 63 | APRIL 2010

SPECIAL REPORT

 

CLIM

A

T

E

OCEANS

W

e know that oceans play a key 

role in regulating climate. 

These vast carbon reservoirs 

retain a quarter of the carbon 

dioxide released by human activities over the 

past 200 years. This absorption capacity is 

explained essentially by a physical process (see 

sidebar). As nature always tends towards a bal-

ance and as carbon dioxide dissolves in water 

it is easily transmitted from air to sea. If this 

were not the case, climate change would be 

much greater. But there is the other side to the 

equation: ocean acidification.  

“Until recently we did not believe that 

the chemistry of sea water would be thrown 

off balance to the point of having an impact 

on the biology of organisms and marine eco-

systems,” explains Jean-Pierre Gattuso, an oce-

anographer and coordinator of EPOCA, a vast 

European research programme launched in 

2008 to determine the impact of ocean acidi-

fication on marine biotopes.  

Snowball effect

CO

2

 is an acidic gas. When it dissolves in 

the oceans it reacts with the water and the car-

bonate ions to form bicarbonate ions. This 

reaction increases the quantity of H

+

 ions in 

the sea water, thereby increasing its acidity, 

measured by a fall in its pH. It also decreases 

the concentration of carbonate ions, a funda-

mental element for certain kinds of marine life. 

Corals, shellfish and crustaceans are examples 

of organisms threatened directly by this change. 

Their common feature is to produce their shell 

or skeleton by capturing the calcium ions and 

carbonate ions present in the sea water. This 

provides them with the necessary elements to 

produce calcium carbonate.  

With less carbonate in seawater, calcareous 

organisms have to use up more energy to 

develop. “At first we thought that calcification, 

which is the ability to produce calcium, would 

simply be reduced. But the reality is more com-

plex. While calcification has slowed in some 

CO

2

 emissions do not only 

add to the greenhouse effect, 

they also have a more insid-

ious impact on the acidity 

of oceans. An impact that 

could destabilise marine 

ecosystems.   

The Big Blue

 turns acidic

© Jean-L

ouis 

Te

yssié/I

nt

ernational A

tomic Ener

gy A

genc

y