Ocean acidification: Royal Society Report

The Royal Society released its report on ocean acidification on 30/6/2005.

Membership of Royal Society working group:
Professor John Raven FRS, University of Dundee (Chair)
Dr Ken Caldeira, Lawrence Livermore National Laboratory, USA
Prof Harry Elderfield FRS, University of Cambridge, UK
Prof Ove Hoegh-Guldberg, University of Queensland, Australia
Prof Peter Liss, University of East Anglia
Prof Ulf Riebesell, Leibniz Institute of Marine Sciences, Germany
Prof John Shepherd FRS, Southampton Oceanography Centre, University of Southampton
Dr Carol Turley, Plymouth Marine Laboratory
Prof Andrew Watson FRS, University of East Anglia

The full report is available from the Royal Society's website: www.royalsoc.ac.uk

Citation: Royal Society (2005) Ocean acidification due to increasing atmospheric carbon dioxide. The Royal Society; London.

PRESS RELEASE(30 June 2005)
Cuts in carbon dioxide emissions vital to stem rising acidity of oceans says
Royal Society.

Cuts in emissions of the greenhouse gas carbon dioxide are the only way to
stem the rising levels of acidity in our oceans and prevent potentially
damaging consequences for marine life, warns a new report published by the
Royal Society today (Thursday, 30 June 2005).

According to the report, ocean acidification due to increasing atmospheric
carbon dioxide, excess carbon dioxide in the atmosphere, from man's burning
of fossil fuels, has already increased the acidity of the world's oceans to
a level that is irreversible in our life times. This is because the
oceans act as a sponge, taking up carbon dioxide from the atmosphere which
dissolves and forms an acid in the seawater.

Professor John Raven, chair of the Royal Society working group on ocean
acidification said: "Along with climate change, the rising acidity of our
oceans is yet another reason for us to be concerned about the carbon dioxide
we are pumping into the atmosphere. Our world leaders meeting at next week's
G8 summit must commit to taking decisive and significant action to cut
carbon dioxide emissions. Failure to do so may mean that there is no place
in the oceans of the future for many of the species and ecosystems that we
know today. "

Sea creatures such as corals, shell fish, sea urchins and star fish are
likely to suffer the most because higher levels of acidity makes it
difficult for them to form and maintain their hard calcium carbonate
skeletons and shells. For example, even under the 'low' predictions for
future carbon dioxide emissions into the atmosphere, the combined effects of
climate change and ocean acidification mean that corals could be rare on
tropical and subtropical reefs, such as the Great Barrier Reef, by 2050.
This will have major ramifications for hundreds of thousands of other
species that dwell in the reefs as well as for the people that depend upon
them, both for food and to help to protect coastal areas from, for example,

The report says that changes in ocean chemistry, caused by ocean
acidification, means that we can predict that some creatures in the
Antarctic Ocean will be among the first to be affected. For example, some
types of plankton - a major source of food for fish and other animals - may
be unable to make their calcium carbonate shells by 2100. This may have
significant consequences for entire food webs in the region, although the
overall impact of this is unclear.

Higher concentrations of carbon dioxide may also make it harder for some
larger marine animals to obtain oxygen from seawater. For example, squid are
particularly sensitive because they move by jet propulsion - this is very
energy-demanding and requires a good supply of oxygen.

Professor Raven said: "Basic chemistry leaves us in little doubt that our
burning of fossil fuels is changing the acidity of our oceans. And the rate
change we are seeing to the ocean's chemistry is a hundred times faster than
has happened for millions of years. We just do not know whether marine life
- which is already under threat from climate change - can adapt to these

By absorbing carbon dioxide the oceans actually help stave off climate
change. In the past 200 years the oceans have absorbed about half of the
carbon dioxide produced by humans, primarily through the burning of fossil
fuels. They are currently taking up one tonne of this carbon dioxide for
each person on the planet every year.

However, the report warns that rising levels of acidity in the ocean may
mean that the ability of the oceans to mop up carbon dioxide from the
atmosphere will be reduced. This is because the chemistry of the surface
waters of the ocean means that as carbon dioxide is added, its ability to
take up more is decreased. Furthermore, any rise in ocean temperatures, due
to climate change, could reduce the ability of the surface waters to take up
carbon dioxide from the atmosphere.

Professor Raven said: "The oceans play a vital role in the earth's climate
and other natural systems which are all interconnected. By blindly meddling
with one part of this complex mechanism, we run the risk of unwittingly
triggering far reaching effects."

The report looks at various ways of tackling rising acidity such as adding
limestone to the oceans to make them more alkaline. However, it found that
the only practical way to minimise the risk to the oceans and marine life is
to reduce emissions of carbon dioxide into the atmosphere.

The report point out that there is still much uncertainty around the impacts
of ocean acidification and recommends that a major international effort be
launched into this relatively new area of research.

Conclusions and recommendations of the report


1.      The oceans are absorbing CO2 produced from human activities from the
atmosphere and this is causing chemical changes in the oceans by making them
more acidic (i.e., decreasing the pH of the oceans).

a.      Ocean acidification, like global warming, is a predictable response
to those human activities that increase the atmospheric concentration of
CO2. The magnitude and rate of the acidification of the oceans can be
predicted with more confidence than the rise in temperature due to global
warming, as they are less dependent on climate-system feedbacks.

b.      Predictions of the consequences of CO2 emissions must take into
consideration the close chemical and physical coupling between the oceans
and the atmosphere. For example, changes in the chemistry of the ocean will
affect its ability to absorb additional CO2, which will in turn affect the
rate and scale of global warming. Rising sea temperatures caused by global
warming also affect ocean chemistry, as well as other physical and
biological processes.

c.      The oceans are currently taking up about 1^tonne of human-derived
CO2 per year for each person on the planet. Almost a half of the CO2
produced in the past 200 years from burning fossil fuels and cement
manufacture has been absorbed by the oceans. Calculations based on
measurements of the surface oceans and our understanding of ocean chemistry
indicate that this uptake of C02 has already  reduced  surface seawater pH
by about 0.1, which corresponds to an increase of about 30% in the
concentration of hydrogen ions.

d.      As CO2 continues to enter the atmosphere from human activity, a
proportion will be taken up by the oceans. If CO2 emissions are not
regulated, this could probably result in the pH decreasing by a further 0.5
units below 2000 levels, by 2100; this is beyond the range of current
natural variability and probably to a level not experienced for at least
hundreds of thousands of years and possibly much longer. Critically, the
rate of change is also probably at least 100 times higher than the maximum
rate observed during this time period.. These changes are so rapid that they
are overwhelming the buffering capacity of the natural processes that have
moderated changes in ocean chemistry over most of geological time.

e.      The chemical changes in the oceans caused by increases in the
concentration of CO2 in the atmosphere will include a lowering of the pH, an
increase in dissolved CO2, a reduction in the concentration of carbonate
ions, and an increase in bicarbonate ions. All of these will affect the
organisms and processes in the ocean.

f.      There appears to be no practical way to remove this additional CO2
from the oceans after it has been absorbed, nor any realistic way to reverse
its widespread chemical and biological effects. It will take many thousands
of years for natural processes to remove this excess CO2 and return to a
level close to their pre-industrial state. Thus, it appears that the only
practical way to minimise long-term consequences for the oceans is to reduce
CO2 emissions to the atmosphere.

2.      These changes in ocean chemistry will impact on marine organisms and

a.      Seawater pH is a critical variable in marine systems; even small
changes will have a large impact on ocean chemistry. These changes are
likely to change the biodiversity of marine ecosystems, and may affect the
total productivity of the ocean. The impacts will be greater for some
regions and ecosystems. However, apart from a few ecosystems such as coral
reefs and the Southern Ocean, the direction and magnitude of these impacts
are very uncertain. Most of the available evidence suggests that these
changes are likely to reduce the resilience of marine ecosystems.

b.      The best scientific information currently available suggests that
these changes in ocean chemistry will almost certainly have major adverse
effects on corals and the reefs they build in tropical and subtropical
waters. This will affect the stability and longevity of the structures
supporting these ecosystems with implications for the biodiversity and their
ecological sustainability. Cold-water coral reefs are also likely to be
adversely affected.

c.      Future concentrations of the carbonate ion are likely to fall to
levels that will make it more difficult for animals to produce hard
structures such as carbonate skeletons and shells. The evidence available
suggests that this will probably adversely affect most of these organisms.
For example many coastal animals and specific groups of phytoplankton and
zooplankton will be affected.

d.      Increased CO2 and the associated reduction in seawater pH may be
particularly stressful for organisms with high metabolism such as squid.
Whilst the physiology of other large marine animals will also be affected,
possibly restricting their growth, reproduction or both

e.      Benthic ecosystems, especially on the seabed of shallow waters,
provide an essential service for other organisms in the surface oceans:
receiving food from the sunlit waters above in the form of sinking
particles, they also recycle nutrients from the sediments, which are
required for the growth of other organisms. Differences in the response of
these diverse organisms to reduced pH could have a considerable impact on
the functioning of marine sediments and the 'ecosystem goods and services'
they provide.

f.      Organisms will continue to live in the ocean wherever nutrients and
light are available, even with ocean acidification. However, from the data
available, it is not known if organisms at the various levels in the food
web will be able to adapt or if one species will replace another. It is also
not possible to predict what impacts this will have on the community
structure and ultimately if it will affect the services that the ecosystems
provide. Without significant action to reduce CO2 emissions into the
atmosphere, this may mean that there will be no place in the future oceans
for many of the species and ecosystems that we know today.

3.      Oceans play a very important role in the global carbon cycle and
Earth's climate system.

a.      There are potentially important interactions between changes in the
state of the oceans (including its pH) and changes in the global climate and
atmospheric chemistry. Our knowledge of these impacts and effects is
currently poor and requires urgent consideration.

b.      In addition to ocean acidification climate change - a better known
effect of increasing atmospheric C02 emissions - will also affect marine
ecosystems. Occurring at the same time, these effects, particularly of
increased ocean temperature, will be additional to (and possibly synergistic
with) those due to increased CO2 and acidification.

4.      The socio-economic effects of ocean acidification could be

a.      Serious damage to coral reef ecosystems, and the human activities
that are based on them such as fisheries and recreation, could amount to
economic losses of many billions of dollars per year. This will have very
serious impacts on the vulnerable societies that depend upon them.

b.      Ocean acidification is likely to have significant impacts on some
marine fish and shellfish species. The economic value of many of these
impacts cannot be determined, but would present a risk to some unknown
fraction of the global economic value of these resources (about $100 billion
per year).

c.      Ocean acidification will probably cause significant changes in the
whole marine biogeochemical system and the ecosystem services that it
provides, to an extent and in ways that cannot at present be foreseen.

d.      Changes to the stability of coastal reefs in tropical and
subtropical parts of the globe may lead to serious decreases in coastal
protection over longer time periods. These changes could fundamentally
change the nature of entire coastlines and the resources available to human
societies that depend on them.

5.      Reducing the scale of future changes to the chemistry and acidity of
the oceans is only possible by preventing the accumulation of CO2 in the

a.      Solutions other than preventing CO2 emissions reaching the
atmosphere, such as adding chemicals to counter the effects of
acidification, are likely to be only partly effective and only at a very
local scale. It would be impossible at a regional or global level, and could
also cause damage to the marine environment.

b.      There are many possible approaches to preventing the accumulation in
the atmosphere of CO2 produced by human activities: for example, improved
energy efficiency, use of renewable energy, and carbon sequestration in
geological reservoirs. However, some approaches, such as direct injection of
CO2 into the deep ocean, have the potential to further exacerbate chemical
changes to the ocean.

c.      Unless significant reductions are made to the rate of emissions of
CO2 into the atmosphere (to less than those leading to a doubling from
current atmospheric CO2 concentrations by 2100 ) the entire depth of the
Southern Ocean will become under-saturated for aragonite, which is required
by some organisms to make carbonate skeletons and shells. Further increases
in atmospheric concentration of CO2, above this doubling, would make the
impacts progressively worse for the ocean as a whole.

6.      We conclude on the basis of current evidence and that acidification
of the oceans, caused by emissions of CO2 into the atmosphere, is
inevitable, and the magnitude of this acidification can be predicted with a
high level of confidence. However, its impacts, particularly on marine
organisms, are much less certain and require a substantial research effort.

a.      Research into the impacts of an ocean with a high CO2 concentration
is in its infancy and needs to be developed rapidly. Among the priority
areas for further research are the identification of those species,
functional groups and ecosystems that are most sensitive to, and the rate at
which organisms can adapt to, increased surface ocean CO2; the interaction
of increased CO2 in the surface ocean with other factors such as
temperature, with the carbon cycle, with sediment processes, and with the
balance of reef accretion and erosion; feedbacks of increased ocean surface
CO2 on air-sea exchange of CO2, DMS and other gases important for climate
and air quality; and larger-scale manipulation experiments on the effect of
increased CO2 on biota in the surface ocean.

7.      Ocean acidification is a powerful reason, in addition to that of
climate change, for reducing global CO2 emissions.


1.      There is a clear risk of significant adverse effects from ocean
acidification. We recommend that this should be taken into account by policy
makers and other relevant national and international bodies (perhaps
including the United Nations Framework Convention on Climate Change) at all
discussions and negotiations about climate and other global changes.

2.      Any targets set for CO2 emission reductions should take account of
the impact on ocean chemistry and acidification as well as climate change.
We recommend that if the risk of irreversible damage arising from ocean
acidification is to be avoided, the cumulative future man-made emissions of
CO2 to the atmosphere should be less than 900^Gt^C by 2100 (2100). Even at
this level the direct impact of ocean acidification, is very likely to cause
serious harm to the Southern Ocean.

3.      Ocean acidification and its impacts on the oceans needs to be taken
into account by the Intergovernmental Panel on Climate Change and kept under
review by international scientific bodies such as the Intergovernmental
Oceanic Commission, the Scientific Committee on Oceanic Research and the
International Geosphere-Biosphere Programme.

4.      Tackling ocean acidification cannot be done by any country alone. We
believe that the UK could and should take a lead internationally on both
policy and research. However, it will only be able to do so by developing
and extending its research activity and its international scientific

5.      Marine ecosystems are likely to become less robust as a result of
the changes to the atmosphere outlined in this report and are likely to be
more vulnerable to other environmental impacts (for example climate change,
water quality, coastal deforestation fisheries and pollution). This
increased fragility and sensitivity of marine ecosystems needs to be taken
into consideration during the development of any policies that relate to
their conservation, sustainable use and exploitation, or effects on the
communities that depend on them.

6.      Research into ocean chemical changes needs additional investment.
Given the potential impacts, we recommend that a major internationally
coordinated research effort (including monitoring) should be launched. The
scale of this needs to be commensurate with that on the effects of climate
change arising from enhanced greenhouse emissions. The impacts of ocean
acidification are additional to, and may exacerbate, the effects of climate
change. For this reason, the necessary funding should be additional and must
not be diverted from research into climate change.

International collaboration should be enhanced, particularly on the
questions associated with effects on ocean chemistry and impacts on
sensitive organisms, functional groups and ecosystems. These efforts need to
focus on establishing a better understanding of the various metabolic
processes at different parts of the life cycle and how these are expressed
at an ecosystem level. Approaches required include global monitoring,
experimental, mesocosm and field studies, and models that include effects of
pH on scales ranging from that of the organism to that of the ecosystem.
Greater understanding of the likely changes will help inform the management
strategies by which human populations can mitigate or adapt to these
changes, and can also be linked to climate change models to predict
synergistic impacts. The existing research projects of Surface Ocean-Lower
Atmosphere Study (SOLAS) and Integrated Marine Biogeochemistry and Ecosystem
Research Project (IMBER) should be part of any new initiative.

7.      Action needs to be taken now to reduce global emissions of CO2 to
the atmosphere to avoid the risk of large and irreversible damage to the
oceans. We recommend that all possible approaches be considered to prevent
CO2 reaching the atmosphere. No option that can make a significant
contribution should be dismissed.