News

The Risk of Ocean Death from CO2

December 10, 2010
Planetwork

Cancun – The new trump card in climate change will be ocean acidity, or what might be better called ocean death. This newly recognized threat makes drastically cutting CO2 astronomically more urgent, even as negotiators are just now barely beginning to agree to the emissions reductions required to avert dangerous climate change.

Destabilizing the chemistry of the oceans threatens to irreversibly wipe out the fisheries that humanity depends on for food, while jeopardizing the Earth’s entire ecosystem. It is not an overstatement to describe this as the risk of the death of the oceans as we know them.

There is already enough extra CO2 in the atmosphere to crash the oceans 50 years from now. This is due to the 50-year delay between the CO2 level in the atmosphere, and the effect of that level on ocean acidity. We are already at, or above, an atmospheric level now that could cause a future tipping point in the oceans. This means that within 50 years, or less, we must bring the CO2 level back down to where it is now, and then continue to reduce it further. This is vastly more ambitious than the reductions currently imagined in climate negotiations.

As the amount of CO2 in the atmosphere increases, the oceans absorb more CO2. This has previously been regarded as a good thing, as it has held down the atmospheric CO2 level and thereby slowed global warming. However, when CO2 dissolves in water it forms carbonic acid. This reacts with calcium carbonate in the water, decreasing the amount of calcium available to organisms that need it to build their shells. At even higher concentrations the increased acidity would begin to weaken existing shells by pulling calcium out of them.

Ocean Death now poses a far more severe, certain, and immanent threat than climate change – at much lower CO2 levels. These CO2 levels have long been discounted for climate change, but the new threat to oceans has yet to be understood and considered by negotiators.

The IUCN side event at the UNFCCC COP16 disclosed that a strong consensus of ocean research shows that even 350ppm CO2 might be too high. Researchers say the current level, rapidly approaching 400ppm, is already close to, or beyond, the maximum that oceans could survive. All agreed that 450ppm would cause collapse of the oceans. If we crash the food web in the oceans we would throw the whole world into ecological collapse and famine, and we could do it within less than 50 years if we continued on our current trajectory.

This is in sharp contrast to the CO2 numbers currently under discussion for climate, where politicians and negotiators routinely accept projected temperature increases associated with CO2 levels of 550ppm and beyond. The science around ocean acidity is simpler, more direct, and far more certain than for climate change, yet it is difficult to predict whether the scientific recognition of this new threat will cause the US wake up from well funded denial any faster. We will likely be closer to 400ppm before we begin to act seriously, and a large amount of additional CO2 overshoot is built in to the system. From where we stand now it looks like it would take a miracle to achieve peak CO2 at as low as 450ppm. However, the science now tells us that we face an even more urgent race to take fossil emissions to zero and then begin to rapidly remove net carbon from the atmosphere, before the effects of the carbon we have already emitted catch up with us in the oceans.

Background on avoiding Ocean Death
The first point to understand is that the risk from ocean acidity is purely a function of CO2, not CO2 equivalents, such as methane, nitrous oxide, and other greenhouse gasses. These other gases remain important for temperature, where they could still potentially trigger dangerous runaway feedback loops, but assuming that we do cut CO2 quickly and deeply enough to avoid ocean death, we will also solve climate change.

Secondly, it will not be enough to simply stop emitting fossil carbon; we need to actively remove carbon from the atmosphere to reduce the total atmospheric CO2 level to below where it is now.

Third, we have far less time to do this than has previously been assumed; less than 50 years. After we finish wasting time in well funded denial, we will need to undertake a crash global program to decarbonize the world – on a par with WWII and the space program.

What can we do about it?
The first step will be to simply face the truth, and work to make society understand both the seriousness of the danger and the actions that we must take to address the threat and protect our children. This will be like round two of the climate change debate, but with new science that now shows a simple direct linear relationship between the CO2 level and a new catastrophic global threat. We need to steel ourselves, rise to the challenge, and put PR people rather than scientists in charge of the language and the message.

Taking CO2 emissions to zero – far more rapidly than we have imagined
The first part of the challenge is well understood from climate change. What is frightening is just how rapidly we must do it to avoid the new threat. What is lacking are the will and resources to do it so quickly. While daunting, it is technically achievable to de-carbonize the world’s energy infrastructure in a matter of decades. In addition to efficiency, and the standard renewables, wind, solar, biomass, geothermal, wave and tidal, the other huge wildcard is nuclear, especially the new fast breeder reactor design from Argon National Labs.

Removing net CO2 from the atmosphere
The other new factor that separates the risk of ocean death from previously understood risks of climate change is the need to actively remove CO2 from the atmosphere – very quickly. We will need to actively remove a huge amount of CO2 from the atmosphere over the next 50 years.

While many policy makers assume that CCS (carbon capture and storage) will be the solution to both CO2 emissions and removing net CO2, CCS actually remains an unproven technology, and may potentially still be fatally flawed do to problems with produced water (dirty liquids and gas forced to the surface), CO2 leakage, and the sheer volume of suitable formations required. At best CCS may help reduce point-source fossil emissions, such as from coal-fired power plants. Using CCS to sequester carbon released from biomass energy to achieve net carbon removal remains one of the big speculative solutions for removing net carbon from the atmosphere.

In response to concerns about ocean acidity a few scientists in the geoengineering community have suggested adding calcium carbonate to oceans, but this would require massive additional energy inputs and would also raise new unanswered questions for ocean ecosystems. At the far end of sci-fi geoengineering ideas are proposals for synthetic trees to actively scrub CO2 out of the atmosphere. These would also require vast amounts of extra energy and presuppose that CCS will work to actually store the CO2 removed from the atmosphere.

Increased net forest cover and low carbon agriculture and rangeland management techniques are the lowest cost way of achieving one-time increases in total terrestrial carbon storage. Preserving and ultimately re-expanding, tropical forests are at the core of the REDD+ initiative and are certainly the first place to start. Soil carbon is also beginning to be discussed and is expected to become important at COP17 in South Africa, but all land use changes combined will not be able to provide more than a fraction of the total carbon removal needed. There is simply not enough capacity to remove the bulk of the net surplus fossil carbon from the atmosphere.

So far, perhaps the best-proven method of removing and storing large amounts of excess carbon from the atmosphere may be biochar. Biochar can also initially be cost-effective based on value-added benefits from soil fertility, pollution mitigation and increased total biomass. Sustainable biochar made from only a small fraction of available agricultural residues could remove almost a gigaton per year of carbon, while other calculations suggest that biochar could remove as much as 5 gigatons per year using 10% of all available waste biomass. The biggest benefit of biochar over CCS alone is that it can increase total productive lands by reclaiming depleted tropical land and thereby taking pressure off intact tropical forests. If seawater were used to irrigate salt tolerant plants on coastal deserts the total might exceed those numbers.

Increased carbon cycling in the oceans is the other major potential source of photosynthetic activity. The ocean scientists at the IUCN event at COP16 did not like the idea of seeding the ocean with iron, and claimed that all of the major ocean NGO’s agree with their position on this. However, photosynthesis in the oceans is the most likely place to look beyond terrestrial biomass to achieve gigaton-scale carbon removal over time.

The direct photosynthetic capture of CO2 by algae for biofuels production shows promise as an alternative to fossil carbon feedstocks, but it is not clear whether this will ultimately be helpful for net carbon removal from the atmosphere.

How much carbon?
CO2 absorbed by the ocean has accounted for about 1/3 of all fossil emissions, while terrestrial sinks are estimated to have absorbed about another 1/3 of fossil emissions. The oceans will give up CO2 on the way back down to lower atmospheric levels, but terrestrial sinks will not.

One ppm of atmospheric CO2 is equivalent to about two metric tonnes of solid carbon, so once we get to zero fossil emissions, we will need to remove about two gigatons of carbon per 1ppm reduction in the atmospheric CO2 level. Once we reduce the atmospheric CO2 level enough that the oceans begin to emit CO2 rather than absorb it, then we will need to remove more like three gigatons of carbon per 1ppm reduction in the atmospheric CO2 level.

The apparently insurmountable challenge over the next 50 years will be to keep the oceans from seeing atmospheric CO2 levels above 400ppm for any significant period. To avoid this, we will need to undertake crash programs to both slash fossil emissions and to actively remove net carbon from the atmosphere – as rapidly as possible. If we can do so, the same programs can continue to remove net carbon once we curtail fossil emissions and take us back down to 350ppm, or below. To hold the CO2 level at 400ppm will require slashing total emissions much faster than we currently imagine possible, while also removing several gigatons per year of net carbon from the atmosphere. To eventually go from 400ppm back down to 350ppm will require removing more like 150 gigatons of carbon, as once the oceans start to release CO2 that extra carbon will need to be removed and retired as well.

Risk of Ocean Death PDF download
Background on Avoiding Ocean Death PDF download

 

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