The Guardian 18 Jun 08;
Bill Hare, Greenpeace adviser and visiting scientist at the Potsdam Institute for Climate Impact Research, Germany, responds to Wallace Broecker's call for carbon storage experiments in the depths of the Pacific Ocean
The urgency of reducing emissions of CO2 has never been greater. The science of climate change has revealed that the risks are much higher and more imminent than we had estimated only a few years ago. But just as with a deadly emergency in a heavy passenger jet: the crew should never, ever rush into hasty actions that will ultimately make a very bad situation a lot worse. Ocean disposal of CO2 is one such option.
A careful, rational and scientific analysis of the option of CO2 disposal in the ocean leads to the conclusion that it is not viable. In 2006 the German government's scientific Advisory Council on Global Change (WBGU) came down against this option: "introducing CO2 into seawater should be prohibited, because the risk of ecological damage cannot be assessed and the retention period in the oceans is too short." The main arguments were "the largely incalculable ecological risk" and the fact that over longer timeframes a significant fraction of the stored CO2 would get back to the atmosphere.
In the long run (hundreds to thousands of years) which, given the very long lifetime of CO2 we must always keep in mind when devising climate policies to limit warming, this option would not help reduce CO2 below levels that would have otherwise occurred.
As the IPCC Fourth Assessment Mitigation report, in which I was a lead author, has shown, conventional options to rapidly reduce emissions in the next few decades are available now. What is lacking to deploy these at scale and quickly are the appropriate policy settings. The absence of these is most acute in Dr Broecker's own country, the USA.
It is not just Greenpeace and other environmental groups that think that ocean disposal is a bad option. The decision by OSPAR, for example, to explicitly rule out the disposal of CO2 into the ocean and on to the sea bed, is by no means irrational, nor the result of "strong-arm tactics". Neither is it a decision in which Greenpeace played any major role.
Turning to some of the details in Dr Broecker's arguments.
Deep water injection CO2 would cause inevitable and potentially irrevocable damage to those deep-water ecosystems directly impacted (smothering, asphyxiation, acidification), and at scale would result in far more widespread effects in the abyssal zone over time as the clathrates dissolve. Over far longer timescales it would result in changes to abyssal ecosystems which in turn feed back to the global carbon cycle.
To suggest that there is "no indication that the projected rise in upper ocean CO2 content will have adverse impacts on fish" and, on this basis, to argue that spread of CO2 through the deep sea would therefore also be benign, is misleading in the extreme. This statement ignores the growing evidence that projected rises in upper ocean CO2 and consequent acidification is likely to have profound impacts on calcification rates and calcifying organisms. It is predicted that upper ocean pH levels will drop to levels lower than those recorded at any time over tens of millions of years, and at a rate orders of magnitude greater than any previous change. There is also evidence that deep water crustacean species, sediment dwelling organisms and associated ecosystem processes could also be adversely affected, including changes to nutrient cycling thought to occur through impacts on sediment microflora.
The fact that deep water CO2 concentrations are currently lower than those of surface waters should not be taken as an indication of a vast unexploited capacity for CO2 disposal. Our knowledge of the biogeochemical processes which have contributed to the current distribution of CO2 in the deep oceans remains limited, as does our capacity therefore to predict the consequences of multi-billion tonne injections of CO2 at depth. To assume that uniformity of concentration is somehow an acceptable target, or one which will have minimal impact on marine ecosystems and the carbon cycle, is oversimplistic.
Dr Broecker argues that a series of experiments involving the release of one tonne quantities of CO2 at depths greater than 3,500m are the next logical step. One tonne release experiments to observe behaviour and determine impacts is one thing. However, one tonne experiments intended as proof of the concept for multi-gigatonne injections in the future is quite another.
An obvious critical aspect is the potential for cumulative impacts resulting from continuous injections over long periods, or a large number of injections, such as would be a necessary characteristic of any deep injection strategy for climate change mitigation. The nature and likelihood of these cumulative impacts simply could not be assessed from the results of the experiments he suggests.
Existing ocean dumping laws are designed to protect the marine environment from irresponsible and unsustainable waste disposal operations. The London Convention and its 1996 Protocol, which are currently in force in parallel, preclude the disposal at sea of industrial waste, including CO2, with the specific exception to enable carbon capture and storage in sub-sea bed geological formations under strict conditions of operation, verification, monitoring and control.
By definition, injection of CO2 at the sea bed deliberately and immediately relinquishes any control over the waste. Such disposal operations are effectively irreversible, and any adverse consequences, on whatever geographical and time scales they may occur, cannot be prevented or mitigated. If the models Broecker suggests we should rely on prove to be inadequate or inaccurate, or both, what do we do?
In short, ocean disposal of CO2, in common with other proposals for geoengineering our way out of climate change, is simply a dangerous distraction and draws attention away from the real solutions. There is no alternative but to drastically reduce emissions and this is best done at source using renewable energy, energy efficiency, reducing deforestation and improving the efficiency of industry and agriculture.
Many in the scientific community and in environmental groups such as Greenpeace share Dr Broecker's deep sense of frustration at the lack of action to date and his great sense of foreboding over the fate of the planet if we do not succeed in getting emissions reduced quickly.
Dr Broecker's work and writings since at least the mid-1970s warning of the dangers of rising CO2 helped to inspire a generation of scientists such as myself to work on this subject, and moreover to work hard and long to develop a global agreement to reduce emissions and limit the risk of rapid human-induced and dangerous climate change. As such his views are to be taken seriously and considered carefully. But in this case we must agree to disagree.
