The lure of underwater volcanoes

If there is a hierarchy of climate sceptics, those who deny that the observed increase in atmospheric CO2 concentrations is driven by burning fossil fuels and land use change will be near the bottom. Only those who deny that CO2 concentrations are increasing are below them.

The release of the first data on global CO2 concentrations from the NASA’s Orbiting Carbon Observatory-2 (OCO-2) is giving these sceptics some excitement.

Fig 1. Global atmospheric carbon dioxide concentrations from Oct. 1 through Nov. 11, as recorded by NASA’s Orbiting Carbon Observatory-2. Carbon dioxide concentrations are highest above northern Australia, southern Africa and eastern Brazil. Preliminary analysis of the African data shows the high levels there are largely driven by the burning of savannas and forests. Elevated carbon dioxide can also be seen above industrialized Northern Hemisphere regions in China, Europe and North America. Image credit: NASA/JPL-Caltech

The distribution of CO2 over this six week period does not match the naïve expectations of the climate sceptics. Presumably they expected that if anthropogenic activity was responsible for CO2 increase, that the map would look more like Fig 2, which shows NO2 concentrations.

Fig 2. Global atmospheric NO2 concentrations based on 18 months of Envisat observations

So why the differences between the maps for NO2 and CO2? I can think of four interrelated reasons.

First, NO2 has a short atmospheric lifetime, perhaps a week: it doesn’t have time to be transported far from its source before it is removed from the atmosphere. CO2 molecules have an atmospheric lifetime of several years, which gives time for the wind to distribute CO2 away from its source and generate the observed predominantly zonal structure.

Second, related to the first, NO2 emissions are large relative to background atmospheric concentrations, so source regions are strongly highlighted.

Third, NO2 emissions are dominated by anthropogenic sources, whereas the CO2 budget is dominated by approximately equal natural sources and sinks. The large natural source and sinks influence the global distribution of CO2 (but not the trend since 1750).

Fourth, the CO2 map is based on 6 weeks of observations, the NO2 map on 18 months. This, together with the importance of natural fluxes, makes a huge difference. For example the plume over southern Africa has been linked to biomass burning. Burning of grassland can release much of the above-ground carbon as CO2 in a few minutes leading to high CO2 concentrations for a short period. Over the remainder of the year, the grassland is a net sink for CO2, and on an annual basis the carbon budget is approximately in balance. Fossil fuel burning will give a positive flux year round.

Together, these reasons explain why the map of CO2 concentration does not simply show human derived sources even those these are responsible for the long term trend in global CO2 concentrations.

Prediction: when 18 months of OCO-2 data are available, they will 1) show the most important source areas are those with high fossil fuel consumption or deforestation (with some up-welling ocean regions), 2) provoke fake climate sceptics into alleging malpractice.

Martin Hovland, previously best known by international climate sceptics for not renewing his AGU membership (but without stating what he objected to in the AGU statement on climate change), has written a piece for WUWT trying to explain the regional patterns in the OCO-2 data. He blames regionally elevated CO2 over the oceans on tectonic active regions, noting that there are high concentrations near the Emperor Seamounts, Fiji and Timor, all of which are tectonically or volcanically active regions than can be expected to be release CO2 or methane (subsequently oxidised to CO2) into the ocean.

This is rather daft for several reasons.

It is a post-hoc analysis. There are lots of tectonically active regions around the globe. Its not surprising that some are near some of high CO2 regions in the six weeks covered by the first OCO-2 data. A cherry-picked spatial correlation does not impress me.

There are no supporting data to show that the Emperor, Fiji and Timor are particularly active at the moment relative to any of the many other tectonically and volcanically active regions. Where are the seismic data, the temperature data or any other data set that could substantiate his conjecture?

Volcanoes emit relatively little CO2 relative to human sources – about two orders of magnitude less. This flux is fairly well constrained by the helium/CO2 ratio. For underwater geological to release enough gas to materially change regional atmospheric concentrations is inconsistent with what we know about this flux.

CO2 emitted from the ocean floor is trapped in the deep cold bottom water and may take hundreds or thousands of years to reach the surface in an upwelling zone. Hovland proposes a mechanism that could deliver CO2 from the ocean floor to the surface.

The original text to this conceptual drawing is: “Could there be a link between mantle convection and local ocean surface warming and hence atmospheric convection? A burst of mantle convection at a deep-ocean spreading centre would lead to an increased hydrothermal convection, which could lead to a sudden increase in local deep-water warming and upwelling. In turn, this could lead to local accumulation of warm surface water and a temperature gradient that would cause atmospheric convection. T.P.=Tropopause.” (Hovland and Judd, 1988). In the current context, this illustration is also relevant for gases originating on the seafloor and most probably feeding into the above atmospheric column.

Fig. 3. Hovland’s caption: The original text to this conceptual drawing is: “Could there be a link between mantle convection and local ocean surface warming and hence atmospheric convection? A burst of mantle convection at a deep-ocean spreading centre would lead to an increased hydrothermal convection, which could lead to a sudden increase in local deep-water warming and upwelling. In turn, this could lead to local accumulation of warm surface water and a temperature gradient that would cause atmospheric convection. T.P.=Tropopause.” (Hovland and Judd, 1988). In the current context, this illustration is also relevant for gases originating on the seafloor and most probably feeding into the above atmospheric column.

This is nonsense. There is a large temperature difference between the ocean floor and the ocean surface. Vast amounts of energy would be required to heat the ocean enough to induce the circulation envisaged by Hovland. That energy simply isn’t there. Plumes of geothermally heated water rise a few hundred metres in to the ocean (perhaps a thousand metres), and can be tracked by He isotopes. Even large plumes have a temperature anomaly of only ~0.1 °C.  They would need far more energy to rise to the surface to release CO2 (and enormously more energy to affect atmospheric circulation. Hovland’s claims simply are not plausible.

In a few weeks time, NASA will release the next map of CO2 concentrations. It is likely that the high CO2 regions will have shifted. Will Hovland conclude that different tectonic regions are active?

 

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About richard telford

Ecologist with interests in quantitative methods and palaeoenvironments
This entry was posted in Fake climate sceptics, Silliness, WUWT and tagged , . Bookmark the permalink.

17 Responses to The lure of underwater volcanoes

  1. Andy Skuce says:

    The fact that CO2 concentrations were more-or-less stable for most of the Holocene suggests that natural emissions and sinks were in rough balance. Had emissions of volcanoes suddenly taken off to produce the increased rate of increase of concentrations in the 1950’s, surely we would have noticed, it’s not as if volcanoes, especially the CO2-rich ones, go off without a bang.

    There’s a good review of volcanic emissions by Burton et al 2013 http://www.minsocam.org/msa/rim/RiMG075/RiMG075_Ch11.pdf

    Total volcanic outgassing is about 640 Mt CO2/year, which is about one-third of the amount we emit from making cement, never mind the fossil fuels emissions, of which the emissions fit the concentration curves like a glove, in shape and size, once you account for ocean and biosphere carbon uptake.

    Then there is volcanic “ingassing”, take up by weathering of volcanic rocks on land. Dessert et al (2003) estimate this to be about 180 Mt CO2/year, so the net volcanic contribution may be smaller still.

    As for just seafloor volcanism, that’s about 100Mt CO2/year of outgassing, although the estimates vary a fair bit, However, there are also carbonation reactions going on with basalts at the seabed and according to Alt and Teagle (1999) the ocean floor may even be a net sink of CO2.
    http://www.sciencedirect.com/science/article/pii/S0016703799001234

    Senator Lisa Murkowski still doesn’t get it though:
    http://www.motherjones.com/mojo/2014/11/sen-murkowskis-climate-comments-are-completely-wrong

  2. David R says:

    What’s your view on this project, ATTP? http://global.jaxa.jp/press/2014/12/20141205_ibuki.html

    • Hei,

      Richard here. It looks like the data from that Japanese satellite match what I expected – that the long-term mean CO2 concentrations would show human emissions.

      • Sorry, it seems that some seem to think that this is my blog, which it clearly isn’t. I think it’s because I normally tweet your posts and that somehow makes people think they’re mine. I have been pointing out that they’re not when people do make that mistake, but maybe I need to add something whenever I tweet one of your posts to make it clear that it’s not mine.

      • It seems to be a fairly common problem – I’ve had comments addressed to other people before when the reader has arrived via someone else’s link on twitter. Perhaps I should put my name somewhere obvious, rather than just having it hidden in the about page.

  3. Forgot to mention that the Emperor Seamounts have been extinct for tens of millions of years. There is probably some residual emission of CO2 and heat, but you really would not expect substantial quantities of either.

  4. Eli Rabett says:

    NO2 is an excellent marker of fossil fuel combustion because it requires a very hot temperature to activate the N2 so that NO2 forms and such temperatures are mostly seen in lightening bolts and fossil fuel combustion.

    CO is a marker of agricultural burning which tend to be fuel rich. So by looking at CO2, CO and NO2 you can tease out what is happening.

  5. nobodySpecial says:

    Volcanoes emit relatively little CO2 relative to human sources
    It’s the warming of the ocean water that causes the water to release CO2. The volcanic activity warms the water. You seem to not understand basic chemistry

      • Marco says:

        I am quite sure it isn’t. There really are people who think they just know this stuff better than actual scientists.

        Usually I then ask such people to calculate by how much the oceans must warm to allow the observed increase in atmospheric CO2 to be due to ocean warming. Much handwaving follows, as they either are completely unable to do the calculation, or when they do, they calculate warming they think is absurd – those latter people then divide into those who think they must have made a major mistake and therefore dismiss the results, and those who run into the cognitive dissonance of believing they are fully capable of doing the calculation but dismiss the result anyway because it doesn’t fit their desired result.

      • If it’s not a Poe, I invite nobodySpecial to submit calculations showing how much CO2 will be released by a 0.1°C warming, 2 km beneath the ocean’s surface.

  6. Radical Rodent says:

    I am sorry, but you seem to be giving the impression that to be sceptical in science is not a good thing. Admittedly, I am not a scientist, but I have long held the understanding that scepticism was inherent in science, and was to be encouraged at all times – most especially of your own work! When did this idea change?

    • Ned says:

      It didn’t change. Nobody is arguing against skepticism.

      • Ned says:

        To elaborate, what is being criticized is the opposite of skepticism. RT and others are criticizing people who call themselves “skeptics” for being extraordinarily credulous and unskeptical of various laughably bad arguments on their “side”.

        Calling yourself “a skeptic” doesn’t actually make you skeptical.

  7. chipstero7 says:

    @MARCO What is the increase in atmospheric CO2 you get from a 1C increase in the mean water temperature? Just out of curiosity.

  8. Latimer Alder says:

    H’mm

    Grassland burning? Maybe in Southern Africa.

    But what about Brazil? And NE China? And the southern tip of Greenland? Or the high concentrations above the ocean to the north of New Zealand and to the east of Japan?

    • Eli Rabett says:

      Slash and burn is a huge contributor to CO2 and black carbon emissions across Brazil and most of the southern hemisphere. The best way of seeing this is to look at CO, NOx and ozone emissions as a group, esp CO.

      The other problem with underwater volcanoes as sources of CO2 are the implications wrt pH depth profiles. Just ain’t there.

      Give it up

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