To explain this properly, we need to do a bit of geology. The Permian Period is an interval of geological time which began 298.9 million years ago and ended 251.9 million years ago, so it lasted 47 million years1. At about the end of that time interval, occurred the greatest mass extinction event in the history of the planet. This extinction event wiped out an estimated 96% of all marine species, and an estimated 70% of all terrestrial species.2
For many years, scientists have been trying to understand the timing and duration of this extinction event to try to work out what caused it. To work out the time frame, Uranium-Lead dating of tiny zircon crystals, found in layers of volcanic ash, has shown that the extinction event occurred perhaps slightly before (about 100,000 years) the end of the Permian, at about 252 million years ago. Scientists also analyse the many fossils and microfossils entombed in the rock, to try to work out when extinctions occurred and at what rate they happened. They also analyse Oxygen isotopes which can tell them something about the temperature of the ocean, while analysing Carbon isotopes can tell them something about the state of the Carbon cycle. The carbon cycle is the series of processes by which carbon is exchanged between living organisms, soils, rocks, the oceans, rivers and lakes, and the atmosphere.
Recent work in Guangxi, in southern China, in a successions of rocks which were laid down around this time, was expected to show a gradual decline in the diversity of fossils, accompanied by changes in ocean temperature and chemistry. However, they did not. They did find that the ocean temperature in this part of the world rose from 30 degrees C to 35 degrees C a few tens of thousands of years before the main extinction event. The largest temperature rise occurred after most species had died out2. They also found that something happened to the Carbon cycle
This most favoured hypothesis is that this extinction event was caused by the massive volcanic eruptions of more than four million cubic kilometres of lava in Siberia, which occurred over an interval of about 400,000 years in the leadup to the extinction. These eruptions would have most likely released huge amounts of sulphur dioxide (SO2) and carbon dioxide (CO2) into the atmosphere, heating it and acidifying the ocean. However, the extinction was not a gradual event and it seems that the volcanism had little immediate effect for most of its duration. Indeed, the extinction was relatively abrupt and it is suspected that the environment reached a tipping point, and it was this which initiated the extinction.2
A recent paper by Uwe Brand and colleagues has suggested that a sudden release of methane (CH4) may be the tipping point in this extinction event. This has been determined by a shift in the carbon isotope content (a decrease in the relative abundance of the isotope Carbon 13 [i.e. 13C]) in sediments deposited at the time. While the emissions of large amounts of CO2 from the Siberian eruptions may have started the global heating, and it was this which led to the huge release of CH4, the latter was the ultimate cause for the extinction.3
Some months ago, I read a paper by Will Steffen (of the Australian National University) and colleagues, and wrote an essay about it. The paper was about feedbacks, both negative and positive, which may occur if the global average temperature rises by 2 degrees C or more. It warned that if some of the positive feedbacks come into play then we could see runaway temperature rises, leading to what they termed a ‘hothouse earth’4,5. One of the positive feedbacks was the release of methane from the melting of permafrost in the Arctic and the decomposition of methane hydrate* on the ocean floor. At the time, there was little indication that this was currently happening.
The concentration of CH4 in the atmosphere increased slowly in the years up to 2014, averaging less than one part per billion per annum, but in 2014 and 2015 this increased dramatically up to 10 parts per billion6. This seems to be at odds with what was suspected to be the rate at which much methane would be released, which was thought likely to be over centuries rather than in a decade or so. A recent study has shown that waterlogged permafrost can produce significant amounts of CH4 within a few years7,8. In some parts of the Arctic, there has been some thawing of the permafrost and this thawing forms small lakes, called thermokarst lakes. These lakes are actually forming their own local feedback cycles and they increase the rate of thawing of the permafrost underneath themselves, and thereby the rate of release of CH4 and CO2. This has not been accounted for in climate projections.9
Shakhova and colleagues published a study in 2010 warning how the rapid warming of the Arctic could lead to the release of CH4 from methane hydrates on a massive and catastrophic scale8,10. However, this suggested catastrophic release has been debated by Ruppel & Kessler, who in part based their argument on the absence of data showing any increases in atmospheric CH4 at the surface of the Arctic8,11. Most of the sensors used to measure atmospheric CH4 are land based, and Bendell8 wonders if that may be why the recent unusual increases in atmospheric CH4 (see above) cannot be explained from these land based data sets. He suggests that a better way to ascertain how much CH4 is coming from the oceans is to measure upper atmosphere CH48. Recent work by scientists on Arctic News has shown that CH4 levels at mid-altitudes were at around 1865 parts per billion in early 2018, which represents an increase of 35 parts per billion (i.e. 1.8%) over the previous year8,12. Surface measurements over the same time interval only increased about 15 parts per billion8. This indicates that the oceans are already starting to release CH4 into the atmosphere. This may not be a catastrophe yet, but it might be the beginning of one. This is because a calculation of the effect of methane hydrate on global heating may be as much as 1.1 degrees C with the next decade. Coupled with all other feedbacks such as the decline of snow and ice (decreasing albedo), increased water vapour in a warmer atmosphere, and others, it is possible that in the next decade we could already see the beginning of runaway climate change, with estimates as high as another 8 degrees C increase beyond the current 1.0 degree above pre-industrial levels12. The Paris Accord’s target of a rise of 1.5 degrees C, now looks to be a forlorn hope.
As I have said before, we have known there was a threat to the planet and to humans for three decades, ever since the first Intergovernmental Panel on Climate Change report came out in 199013. The malevolence of the denialism industry and its paid mouthpieces in the political class need to pay, not for their inaction, but for their active obstruction of action. If these prognostications above come to pass, millions of humans are likely to die and many more become climate refugees. These deniers may have doomed those who survive this catastrophe to live on a planet large parts of which may be uninhabitable. This is a crime against humanity far worse than those committed by Hitler, Stalin, Mao or Pol Pot or any other rabid psychopath. Deniers need to be referred to the International Criminal Court, if indeed there is still one by the time the climate gets bad enough for people to realise what has been done to them.
*Methane hydrate, also called methane clathrate, is essentially the trapping of molecules of methane (from decaying organic matter) within a crystal structure of water, forming a solid similar to ice. Its chemical formula is (CH4)4(H20)23, and it has been discovered in huge quantities within sediments on the ocean floor where temperatures are low (about 2 degrees C). Methane hydrate looks like ice, but can be made to burn, with a flame above and water dripping off below4. It is very odd stuff. If the ocean heats up much more it will become unstable and release its methane into the ocean and into the atmosphere.
- Brand, U., Blamey, N., Garbelli, C., Posenato, R., Angiolini, L., Azmy, K, Farabegoli, E. & Came, R., 2016. Methane Hydrate: Killer cause of Earth’s greatest mass extinction. Palaeoworld 25, 496-507.
- Steffen, W., Rockström, J., Richardson, K., Lenton, T.M., Folke, C., Liverman, D., Summerhayes, C.P., Barnosky, A.D., Cornell, S.E., Crucifix, M., Donges, J.F., Fetzer, I., Lade, S.J., Scheffer, M., Winkelmann, R. & Schellnhuber, H.J., 2018. Trajectories of the Earth System in the Anthropocene. Proceedings of the National Academy of Sciences. https://doi.org/10.1073/pnas.1810141115
- Saunois et al., 2016. The global methane budget 2000–2012. Earth System Scientific Data 8, 697–751.
- Knoblauch, C., Beer, C., Liebner, S., Grigoriev, M.N. & Pfeiffer, E.-M., 2018. Methane production as key to the Greenhouse Gas Budget of thawing permafrost. Nature Climate Change, 19 March.
- Shakhova et. al., 2010. Extensive methane venting to the atmosphere from sediments of the East Siberian Arctic Shelf. Science 327, 1246-1250
- Ruppel, C.D. & Kessler, J.D., 2017. The interaction of climate change and methane hydrates. Review of Geophysics 55 (1),126-168.