The core message contained in the WBGU’s special experts’ report: “The Future of the Oceans” sounds uncomfortable. In future the world’s oceans will be too high, too warm and too acid because mankind is continuing to release too much CO2 into the atmosphere, thus boosting the greenhouse climate (global warming). ETH professors and WBGU advisory council members Nina Buchmann and Renate Schubert are certain that, “this is triggering processes that will have catastrophic consequences in the next few decades. We must do something as quickly as possible now.”

Carbon dioxide is dissolving in seawater

In fact the new WBGU special experts’ report (1), on which the two professors collaborated, leaves no doubt that politicians really must act now on the climate issue. The reason is that the carbon dioxide which mankind is producing is threatening the seas and coastal regions not only via climate warming, rising sea levels and more frequent and more powerful storm tides, but also indirectly. The WBGU draws attention to this new development which can cause the entire oceanic ecosystem to topple over within a few decades: insidious acidification resulting from the input of CO2. This is changing the chemistry of the seas.

The oceans have now already absorbed about half the CO2 emissions worldwide. However, the gas has not simply evaporated but has dissolved in the seawater to form mainly bicarbonate. This has caused the water to become more acidic. According to the WBGU, the pH of seawater throughout the world has already dropped by an average of 0.1 pH unit. That sounds like a small amount. However, the scale is logarithmic, not linear. “This development has been appreciated and studied only in the last few years,” says Buchmann. “And the politicians have not yet got it into their heads!”

For all marine organisms such as molluscs or corals that form limestone, acidification is more devastating than the mere warming of the water. These animals can no longer form calcium carbonate shells or limestone reefs respectively. Fish, which have in any case already been severely harassed by fishing, also suffer in acidic water. Nor is the acidification of the oceans easily reversible. The damage will persist for thousands of years.

Where can we house environmental refugees?

The other consequences of climate change highlighted in the report are not new, but in the proportions described they are nevertheless shocking. The oceans are warming up increasingly and the Arctic sea ice is melting faster than the proverbial snow in the spring sun. According to the forecasts forming part of the WBGU report, by the end of this century the Arctic will be ice-free each summer unless climate precautions are taken. The sea level will also rise more rapidly than suspected. Satellite measurements confirm a rise of three centimetres during the past decade – more than ever before. If the level rises by more than one metre compared to the pre-industrial era, the WBGU predicts difficult times ahead for people living near the coast. After all, one person in five lives less than 30 km from the sea.

“The industrialised nations might possibly cope with a one metre rise in sea level,” says Renate Schubert, ETH Professor of Political Economics. On the other hand poor countries such as Bangladesh are much more vulnerable to this. In addition there is the fact that a few island states such as Tuvalu would simply disappear. The inhabitants of regions inundated in the future would have to flee.

At present more than 60 million people worldwide live in zones situated only one metre above mean sea level, and 275 million in the 5-metre zone. This is why Schubert expects significant migratory flows of environmental refugees in the future, for which the world community is currently unprepared. “The international dispensation of justice must clarify the status of such refugees as soon as possible. Environmental refugees have not existed up to now. No-one knows who is willing to or ought to accept them, or who should pay for them.”

Protection regions and threshold values called for

The special experts’ report is not just a collection of facts, but also contains points of reference, known as guiding principles, that show politicians the necessity to act. Among other things, the WBGU regards the creation of large-area ocean reserves as advisable so the sensitive ecosystems and their inhabitants can recover.

ETH professors Renate Schubert (l.) and Nina Buchmann present the new experts’ report on the state of the oceans. large

Up to 30 percent of the sea area should be designated as protection regions (nature reserves). In addition the WBGU calls for the average global temperature rise to be limited to a maximum of 2°C compared to the pre-industrial value. This is also necessary to protect the oceans. The committee has also imposed an upper limit on the increase in the acidity value: the pH is allowed to drop by a maximum of 0.2 units so as not to destabilise the ocean’s equilibrium. Also the sea level should not rise by more than 5 centimetres per decade, and in the long term by a maximum of one metre compared to the pre-industrial level.

The WBGU’s recommendations are aimed directly at German politicians. Ambitious climate protection is the only thing that can help to limit the consequences of global warming, acidification and sea level rise for the marine environment and mankind. Buchmann is convinced that the WBGU’s messages really will reach the target audience for the experts’ report and will initiate something. As an entirely general principle, one ought not to underestimate the significance of the scientific community in this context. In the case of the ozone hole, for example, the international community quickly adopted appropriate measures after its “discovery”. In addition, 160 countries have since also ratified the Kyoto Protocol. Finally, even major companies such as British Petroleum have now started to change their ideas. BP is now also called “Beyond Petroleum”.

Don’t “submerge” carbon dioxide underwater

There are frequent demands for climate policy to be pursued by disposing of CO2 in and under the sea. The WBGU’s response to this suggestion is highly critical. Schubert und Buchmann emphasize that “We strictly reject ‘storing’ carbon dioxide in the sea, not least because of the acidification problem.” The WBGU would accept storage below the seabed only subject to the imposition of strict conditions. For such projects the Advisory Council calls for stringent checking of the suitability of the geological formations and a containment time of at least 10,000 years. “It is always much better not to release CO2 at all,” says Buchmann. But this really would require a proactive climate policy.