“There is no conclusive proof that hydrate-derived methane is reaching the atmosphere now”
There is concrete evidence from Shakhova and Semiletov that methane emanating from the Arctic Ocean seabed is rising in huge plumes, with significant quantities reaching the atmosphere
Although it is not proven that this methane originates from methane hydrate, the quantities would seem to indicate hydrate as the most probably source.
The level of methane in the Arctic reaches occasional peaks of well over 2000 ppb, commensurate with seabed emissions reaching the surface in large quantities.
The source of the excursions of methane level in the Arctic atmosphere is most likely from methane hydrate beneath the seabed, since no other possible explanation is given.
The statement suggests that proof is required. This is perhaps the most challenging philosophical aspect of this report – it is fundamentally trying to prove a negative which is impossible. It is equivalent to the conundrum of trying to prove that there are no white black birds anywhere in the world. In the same way that it is not possible to validate that every black bird in the world is not white, then it is not possible to prove that a large scale methane emission will not occur by critiquing those arguments and pieces of evidence that have been offered as warnings that it can as it will never be known if others exist.
The only way in which it could be categorically demonstrated that methane emissions will not accelerate and rise beyond a critical level is to calculate the critical level at which this would occur. This fundamental question remains unconsidered and unanswered by the paper.
The statement suggests to the reader that the situation is less serious than actual observations would suggest.
2. Incorrect and misleading values for GWP
“In the most recent assessment of the Intergovernmental Panel on Climate Change [Intergovernmental Panel on Climate Change (IPCC), 2013], methane (CH4) was deemed 84 times more potent than carbon dioxide (CO2) as a greenhouse gas over a 20-year time frame and 25 times more potent over a century on a per unit mass basis.”
To correct a minor point, the hundred year global warming potential of methane is used by the IPCC AR5 report is 34 (not 25) over 100 years and 86 (not 84) over 20 years, see WG1 Chapter 8, Table 8.7.
More seriously, the report is repeating the mistake of the past where the estimate of methane’s global warming potential was primarily based on its 100 year equivalence to CO2. However, if the level of atmospheric methane is increasing steadily as it is today, the global warming potential must be based on the shortest timescale, perhaps over 1 year. This error is bought into focus given the estimated half-life of methane in the atmosphere of around 12.4 years. It is on these much shorter timescales (circa 1 year) that the global warming potential of methane is estimated at 120 that of CO2 (see Intergovernmental Panel on Climate Change (IPCC), 2013, Figure 8.29) thus the factor of 84 as the global warming potential is a dangerous under estimate.
The report has also omitted any consideration of the Global Temperature change Potential (GTP; Shine et al., 2005a). IPCC acknowledges that “this goes one step further down the cause–effect chain and is defined as the change in global mean surface temperature at a chosen point in time in response to an emission pulse—relative to that of CO2.” It is defined by the relationship GTP(t)i = AGTP(t)i / AGTP(t)CO2 = ∆T((t)i /∆T(t)CO2. Over a 20 year time period, this is quoted at 67, i.e. the temperature increase for a pulse of methane will be 67 times that of CO2. However, IPCC does not give an estimate of the GTP over a much shorter time period and against a scenario of steadily increasing methane emissions.
The necessity to focus on the short term heating impact of methane makes the exceptionally rapid rises in temperature that are now being experienced in the Arctic regions a critical issue as a fast temperature rise is much more likely to lead to the trapped methane escaping its various reservoirs in a short period of time which will lead to the maximum global warming potential of the methane being experienced. By contrast, if a slow warming in the Arctic was to occur where the methane can be decomposed as quickly as it is released, then no significant increase in atmospheric methane will be experienced. The paper makes (i) no consideration of the exceptional rate of temperature increase in the Arctic, (ii) no nor any prediction of how this anomalous trend will continue in the coming years, (iii) no prediction of nor how this increased rate of temperature change will influence the stability of reservoirs.
3. Misleading statement on permafrost as a barrier
“As in marine sediments, CH4 released from gas hydrate dissociation at depth has to overcome numerous physical and chemical sinks to reach the tundra surface, and ice-bearing permafrost can be an effective permeability cap for upward migration of CH4 liberated during dissociation.”
The rapid heating that is occurring today in the Arctic is melting the permafrost or weakening what remains. This loss allows a more rapid methane release to the atmosphere.
4. Dismissing genuine concerns
“Even under a possible future scenario of rising arctic CH4 emissions, which are expected to lag warming, discerning the component related to gas hydrate dissociation may always remain more challenging at high northern latitudes due to the number of methane sources in these settings and their overlapping depths of origin (Figure 10).”
This statement is dismissing the concern without any justification that once the rate of methane emissions exceeds a certain level, they will not lag global heating, but lead it. There is no consideration in the text of the critical rate of methane emissions to the atmosphere that are needed to trigger the transition from lagging to leading.
We would contend that the methane release is governed by the solution of non-linear differential equations which relate the (1) acceleration of the rate of methane emissions to the actual rate of methane release to the atmosphere and (2) the rate of methane emissions with the cumulated heat build up from the methane in the atmosphere. The solution to these equations would give an indication of critical rates of release that would trigger uncontrollable dissociation.
5. Missing the point
“In recent years the discovery of deep, rapidly developed Yamal Peninsula craters that emit CH4 has been attributed by some to thawing gas hydrates, although recent analyses of high-resolution satellite imagery implies pingo collapse as a more likely cause [Kizyakov et al., 2015]”
The paper referred to here talks about pingo collapse, but does not give a specific cause despite referring to it as “gas emission crater.” Furthermore, research specifically links pingo structures with methane dissociation, (see https://pubs.er.usgs.gov/publication/70031775).
Contrary to the report’s assertions, the exploding pingos provide a pathway for large scale methane releases to bypass the anaerobic oxidation sinks in the ocean sea floor sediments referred to in the paper. The pingo formations that are now being observed across the Arctic, both on the surface and subsea will lead to rapid and sustained blow outs of methane. These pingos develop as the pressure increases from beneath the surface due to the temperature rises. The stress from this focuses on weak spots. Once these weak spots fail in the form of pingos, arterial routes from the main reservoir to the atmosphere are established which due to their highly localised nature will overwhelm the sinks referred to in the paper. The localisation of methane emissions and its potential to overwhelm the sinks has been given no consideration in the paper, yet it is the speculated strength of the sinks that forms a major element of the argument presented.
6. Disregarding huge temperature increases
“Even if deep ocean temperatures were to increase by several degrees, which is larger than anticipated in any global warming scenario over the multicentury scale and comparable to the difference between the LGM and the present [Adkins et al., 2002], the ambient hydrostatic pressure regime means that gas hydrates in the shallow part of the sedimentary section at these locations would generally remain stable.”
Atmospheric and ocean temperatures have already increased in the Arctic region by more than the several degrees that the Adkins paper refers to. Furthermore, the Adkins 2002 paper is 15 years out of date in relation to the changes of today. In fact, it is quite simply preposterous to claim that a several degree temperature rise will occur over a multi-century period and that this is larger than any global warming scenario when measurements show this is already happening in the Arctic. To put this in perspective, February 9, 2017, the water at a spot near Svalbard was 13°C or 55.3°F, i.e. 12.1°C or 21.7°F warmer than 1981-2011.
A further complication is that as the heat energy increases in the planet, the variance in the weather will increase with the current example of the extreme El Nino being but one example. Thus with a significantly higher temperature, then the risk increases of extremely hot spikes occurring in localised areas such as the current temperature increases around Spitzbergen. These short term spikes will accelerate the rate of change over and above that which would normally occur if the temperature rise was to be smooth and homogenous through an action similar to that of a thermal jack hammer.
7. Invalid argument
“Methane emissions at deepwater seeps are sometimes driven from below, meaning that climate-related perturbations are not the causal process”
Evidence already exists of heat flow through the seabed. Again we cite the emergence in recent years of pingos and new seabed methane releases, such as those observed on the Washington coast and which were triggered by a sea temperature rise of only 0.30C.
8. Unbalanced arguments
"The final CH4 sink sometimes missing from more geologically focused climate-hydrates models is the atmospheric one. Failure to include this sink can lead to overestimation of the radiative warming of the atmosphere owing to the stronger greenhouse potential of CH4 relative to CO2."
"Coupled with the emergence of better data on CH4 emissions to the atmosphere, a fuller treatment of atmospheric chemistry processes in models could provide more reliable insights into the direct, as well as indirect, effects of CH4 on climate over the full range of the timescales of interest for unravelling climate-hydrate interactions"
Again, there is no mention of the extreme global warming potential of methane on a short 1 to 2 year time frame which is the critical issue if atmospheric methane levels are rising.
The point regarding the lack of knowledge on the atmospheric chemistry illustrates the fundamental problem of trying to prove a negative.
9. Missing argument
"About two-thirds of the increased heat content of the oceans since the midtwentieth century resides in the upper 700 m of the water column [Levitus et al., 2012], meaning that upper continental slopes are most affected (section 6.4)."
This is exactly the depths at which at the hydrates that are most at risk exist.
This paper has ignored the fundamental evidence that the Arctic is already in a vicious cycle of warming and melting, hurtling towards a state with seasonal sea ice, which will affect catastrophically the rest of the planet as regards ocean circulation, climate, sea level, and temperature (especially with the methane).
Unless immediate intervention is made to cool the planet and reduce heat flow into the Arctic regions, then the methane releases that are already occurring will accelerate so quickly that no effective intervention will be possible. This forms an immutable timeframe against which climate restoration strategies must be developed and deployed. Intellectual thought should thus be focused on determining this timeframe and the consequences of delay.
 Johnson, H. P., U. K. Miller, M. S. Salmi, and E. A. Solomon (2015), Analysis of bubble plume distributions to evaluate methane hydrate decomposition on the continental slope, Geochem. Geophys. Geosyst., 16, doi:10.1002/ 2015GC005955.
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