World-wide distribution of discovered or inferred gas hydrate deposits in sediments, USGS, 1996
Nature is not entirely defenseless against rising greenhouse gas (GHG) emissions. There is a class of elements called halogens (fluorine, chlorine, bromine, iodine, etc., often occurring in pairs) that are emitted into the atmosphere via ocean spray, where they destroy ozone (O3), a significant greenhouse gas and aerosol that promotes warming. But these same halogens release smaller reaction molecules that bind with methane (CH4, a potent GHG) and “pull” the gas back down into the ocean.
The removal or destruction of certain gases/chemicals in the atmosphere is referred to as “scrubbing”.
Ozone in the outer ionosphere actually protects the planet’s biosphere from harmful solar radiation. But in the troposphere (as tropospheric ozone) it bonds with other particles and acts to trap heat in the atmosphere. At ground level, O3 is a main constituent of smog. In a recent study by Read, K. A., et al, published on-line in Nature, the researchers found “extensive halogen-mediated ozone destruction” in the tropical Atlantic ocean.
The study also found that 50% more halogens were released by the open ocean than had been previously calculated. This might translate into more natural scrubbing too. However, the study also noted that the same process releases other small molecules known as hydroxyls (- OH) that are known to bond with methane (CH4), a pervasive and potent GHG. So, in theory, this bonding pulls the methane out of the lower atmosphere, and back down into the oceans (typically in the form of methane clathrate, or methane hydrate) where it eventually becomes a trapped gas.
Under great pressure and low temperature, the gas enters a more solid form (also called “methane ice” *). This activity is natural and no doubt ancient, and may be keeping the present methane emissions in our atmosphere in check, for now. More study of this effect will be needed. Whether or not this natural activity can compensate for ever-increasing GHG emissions is the big question. Ocean and atmospheric chemistry is complicated stuff (e.g., fluorine and chlorine in the upper atmosphere can combine with carbon [C] to form chlorofluorocarbons, CFCs, which destroy ionospheric ozone). At the least, this recently discovered process (and its estimated impacts) will now need to be incorporated into the next generation of computer simulated climate models. Still, most climate scientists think that these natural counter-balancing processes will be out-paced by current trends, unless major reductions are achieved in the next decade or so. * Note: the release of massive amounts of methane hydrate from the ocean floor, or from underneath thawing permafrost, has been the subject of several catastrophic predictions about human survival in recent TV documentaries). The chart at the top of the post refers indirectly to this topic by showing the known or suspected sources of buried hydrate gases (such as methane hydrate). chart source: USGS
About Michael Ricciardi
