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So much for geoengineering, 2: Ocean dead zones to expand, “remain for thousands of years”

By Joe Romm on February 17, 2009 at 3:04 pm

"So much for geoengineering, 2: Ocean dead zones to expand, “remain for thousands of years”"


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dead_zone.jpgClimateProgress doubts geo-engineering will ever be practical as a primary strategy for dealing with climate change (see “Part 1: Avoiding the Frankenplanet” and “Geoengineering remains a bad idea”). That said, I don’t consider most of the efforts to pull CO2 out of the air geo-engineering — that is ungeo-engineering our self-inflicted climate wound. And those efforts are only plausible with super-aggressive mitigation that keeps concentrations close to 450 ppm.

It’s strategies like injecting sulfur into the atmosphere that should worry people the most. Those strategies have many flaws, but among the worst is that they do nothing to stop humanity from turning the oceans into one giant acidic deadzone.

A new study in Nature Geoscience, “Long-term ocean oxygen depletion in response to carbon dioxide emissions from fossil fuels,” (subs. req’d, abstract below) makes crystal clear why very serious mitigation must always be humanity’s primary strategy for averting climate catastrophe. As AFP reported on the study:

Global warming may create “dead zones” in the ocean that would be devoid of fish and seafood and endure for up to two millennia….

Its authors say deep cuts in the world’s carbon emissions are needed to brake a trend capable of wrecking the marine ecosystem and depriving future generations of the harvest of the seas.

Precisely. This study makes a matching pair with NOAA stunner: Climate change “largely irreversible for 1000 years,” with permanent Dust Bowls in Southwest and around the globe.

Even worse, of course, is that while there are many plausible, albeit expensive and untried on large scale, strategies for removing CO2 from the atmosphere, it is far from clear how one does that from the ocean.

Here is more detail on this important study and on oceanic dead zones:

In a study published online by the journal Nature Geoscience, scientists in Denmark built a computer model to simulate climate change over the next 100,000 years.

At the heart of their model are two well-used scenarios which use atmospheric levels of carbon dioxide (CO2), the main greenhouse gas, as an indicator of temperature rise.

Under the worst scenario, CO2 concentrations would rise to 1,168 parts per million (ppm) by 2100, or about triple today’s level.

[This worst-case scenario is, of course, just the business-as-usual emissions scenario (see here).]

Dead-Zones-Sidebar.jpgUnder the more optimistic model, CO2 would reach 549 ppm by 2100, or roughly 50 percent more than today.

The temperature rise that either would yield depends on several factors: when the peak in carbon emissions is reached and how quickly it falls, and whether the warming unleashes natural triggers, or tipping points, that enhance or prolong the warming in turn.

Taking such factors into account, the scientists predict a possible rise of around five to seven degrees Celsius over pre-industrial times under the worst scenario. Under the other scenario, there would be warming of roughly between two to four degrees Celsius.

Either scenario spells bad news for the ocean, said Jens Olaf Pepke Pedersen, a physicist at the Technical University of Denmark.

Under the worst scenario, warmer seas and a slowdown of ocean circulation would lower marine oxygen levels, creating “dead zones” that could not support fish, shellfish and other higher forms of marine life — and may not revive for 1,500 to 2,000 years.

“They would start slowly by the end of this century, it’s not something that would happen tomorrow or in the near future but over the next few generations,” Pedersen told AFP.

“But because of the inertia in the ocean, once you have the process going, it’s not feasible to reverse it again just like that, so it would continue for hundreds of years….

Wide oxygen depletion of the ocean, though, poses a far greater threat, touching at the heart of biodiversity, the paper warns.

Around 250 million years ago, a chemical change of the seas led to a massive wipeout of marine species.

Lead scientist Gary Shaffer of the Niels Bohr Institute at the University of Copenhagen said it was unclear, in the grim light of this study, whether future generations could look to the oceans as a major reserve of food.

“Reduced fossil-fuel emissions are needed over the next few generations to limit ongoing ocean oxygen depletion and acidification and their long-term adverse effects,” he said.

Here is the study abstract:

Ongoing global warming could persist far into the future, because natural processes require decades to hundreds of thousands of years to remove carbon dioxide from fossil-fuel burning from the atmosphere. Future warming may have large global impacts including ocean oxygen depletion and associated adverse effects on marine life, such as more frequent mortality events, but long, comprehensive simulations of these impacts are currently not available. Here we project global change over the next 100,000 years using a low-resolution Earth system model, and find severe, long-term ocean oxygen depletion, as well as a great expansion of ocean oxygen-minimum zones for scenarios with high emissions or high climate sensitivity. We find that climate feedbacks within the Earth system amplify the strength and duration of global warming, ocean heating and oxygen depletion. Decreased oxygen solubility from surface-layer warming accounts for most of the enhanced oxygen depletion in the upper 500 m of the ocean. Possible weakening of ocean overturning and convection lead to further oxygen depletion, also in the deep ocean. We conclude that substantial reductions in fossil-fuel use over the next few generations are needed if extensive ocean oxygen depletion for thousands of years is to be avoided.

Any geo-engineering strategy that lets the oceans die is no cure at all.

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18 Responses to So much for geoengineering, 2: Ocean dead zones to expand, “remain for thousands of years”

  1. thingsbreak says:

    Off-topic, but I assume you’ve seen the Wonk Room post about Morano’s email list. I just wanted to note my total lack of surprise to see the Pielkes on it.

    The line between denier and “denier-eq” is a thin one indeed…

  2. Anthony, rabid doomsayer says:

    Sooner or later we are going to panic and do something really stupid. It would be a good idea to study all the geo engineering ideas so that we can avoid the absolute worst.

    Scale can cause unexpected problems. It may be the optimum solution, well least bad, might be a combination of partial answers.

    No doubt we will miss some potential problems, but can we at least avoid what should be obvious even now.

  3. paulm says:

    “This worst-case scenario is, of course, just the business-as-usual emissions scenario …”

    things could get worse than BAU….

  4. David B. Benson says:

    Some partial solutions are quite clear:

    (1) plant tens of billions of trees;
    (2) make and bury biochar;
    (3) enhanced mineral weathering.

    I think of these a benign geo-engineering, although I’d like another term without the negative connotations of “‘geo-engineering”.

  5. Gail says:

    this is making me miss cigarettes.

    Since we are all doomed, can I start up again? I was thinner too..

  6. David B. Benson says:

    Gail — Yup.

    Also eat less red meat.

    Good for the climate and your pocletbook.

  7. Gail says:

    oh well, my “pocketbook” is pretty empty these days.


    no really I won’t…

  8. tidal says:

    Is it just me, or is the news getting progressively dismal lately? It feels like the old Monty Python sketch “Four Yorkshireman” and we keep trying to outdo each other with “the environment is getting worse than we imagined!” snippets… except, this is for real and going forward… and not funny….

    “We were evicted from our hole in the ground. We had to go and live in the ocean!”

    “You were lucky to have a non-acidic ocean! There were a hundred and fifty million of us living in a small shoebox in the middle of the Spanish desert.”

  9. OO says:

    Who cares about dead zones? We’re toast anyway…

  10. llewelly says:

    That said, I don’t consider most of the efforts to pull CO2 out of the air geo-engineering — that is ungeo-engineering our self-inflicted climate wound.

    Does that make iron fertilization ungeo-engineering?
    In otherwords – I’d like an explanation of what you consider geo-engineering vs ungeo-engineering.

    [JR: I think I'm pretty clear here. Air capture, trees, algae, biomass -- are ungeo-engineering. I grant that iron fertilization may be a bit unique. So far, it's unclear it is doing much net capture, so I remain unenthused about it.]

  11. Gail, just call it carbon sequestration into the lungs.

  12. jorleh says:

    No problem, would our friend Lomborg say. Try only to give antibiotics to the poor and so the world economy is better.

  13. Sasparilla says:

    I have to second what “Anthony, rabid doomsayer” is saying here. At some point, since we’re not going to make dent in this ride before alot of poorer countries feel serious effects (whether its smaller sea level rise or severe continuous droughts and destruction of food production capacity – i.e. the starvation of citizens), some desperate country(s) is going to do something stupid.

    I would like these possible eventualities (the cheap ones anyone could do) seriously researched (and tested as best they can) so we know what might happen – right now they are just somewhat impervious blogosphere ideas and they’re multiplying rapidly (and will continue to do so as things get worse and people start getting more desperate).

    Some of these “levers”, (Sulfur in the atmosphere to reduce temps) will be in the hands of nearly any country thats wants to pull them – as they won’t cost much and won’t require much technology. JMHO.

  14. David B. Benson says:

    Don’t think “ungeo-engineering” is going to be the most helpful phrasing.

  15. Cynodont says:

    Joe, I agree that we’re completely sunk without radical emission reductions happening soon. However, we also need to defuse the runaway CO2 emission time bomb(s) that threaten to make human GHG emissions trivial. There’s a 1000 GtC of methane in the Arctic Permafrost, which equates to more than 10 times the *historical* total of human emissions. If we don’t preserve the Arctic sea ice, then this will be released within 100-200 years. It’s very likely that only geoengineering can save the arctic sea ice now, so why not be a little bit more proactive about promoting intelligent discussion on geoengineering research?

    There are other GHG emission feedback loops that are kicking in, (e.g. tropical forest drought an wildfires, diminished ocean circulation, etc…). So we don’t have much time to waste! Your diatribes are not helping promote intelligent discussion.

    BTW, as the only mammalian survior of the Permo-Triassic mass extinction, we Cynodonts completely agree that diminished ocean circulation (triggering anoxia and hydrogen sulfide gas) is the worst possible outcome of human CO2 emissions.

  16. Cynodont says:

    Another thing… you need to get the science straight on this issue. Dead zones from ocean anoxia are completely different from the problem of ocean acidification. Also, acidification is a relatively trivial problem compared to the threat of “Ocean Anoxic Events” as described in the Shaffer et al paper. Acidification only kills some species, whereas anoxia kills them all – particularly when anoxia gets so bad that hydrogen sulfide gas is produced.

    Ocean Anoxic Events (OAE) are caused by radiative forcing imbalances that produce changes in climate which alters ocean circulation and hence oxygen penetration. Acidification has absolutely nothing to do with this process (and may even help if less organic carbon is exported to the deep ocean). It is very possible that radiative forcing management techniques (e.g. stratospheric aerosols, marine cloud seeding, DMS production) could actually maintain or restore natural ocean circulation patterns, which would prevent OAE from occuring. Researching how this could be done should be one of the highest priorities.

  17. I think the Nature Geoscience authors have identified the process by which sulfur bacteria take over enough of the oceans to put H2S into the atmosphere. H2S was identified as the kill mechanism in the Permian-Triassic mass extinction event by several paleontologists. I have read only the abstract because I have neither a subscription to Nature nor a new enough computer to read the whole article. Thank you Cynodont for the clarification. Joe Romm should have published more details.




    http://www.astrobio.net is a NASA web zine. See:





    “Under a Green Sky” by Peter D. Ward, Ph.D., 2007.

    “Six Degrees” by Mark Lynas. See:

    If the global warming gets to 6 degrees centigrade, the above people say that we humans will go extinct because of H2S. The authors are the first oceanographers that I know of to support this idea. Their mechanism of O2 loss is new. Other oceanographers have scoffed at the idea that the ocean could get hot enough to loose its oxygen, but heating isn’t the mechanism. H2S coming out of the ocean seems all too plausible to me. Humans WILL NOT survive breathing H2S. H2S reacts with O2 and H2O to become H2SO4 in your lungs. This is a very painful way to die. I am terrified.

    We MUST end the burning of coal immediately or very soon, world wide. We don’t have time to wait for world politics as usual.

  18. Theodore says:

    Agricultural run-off as a contributor to dead zone expansion should, all by itself, be a sufficient reason to oppose agricultural biofuel production.