UPDATED ON AUGUST 3 DUE TO NEW INFORMATION
This week, the scientific journal Nature issued a bombshell article in which Peter Wadhams and a number of Arctic specialists warned that very large methane pulses, on the order of 1-50 gigatons in a single year, are likely to begin to appear soon in the Arctic. Other specialists, including Gavin Schmidt, a climate scientist at NASA’s GISS division, have noted that such an event is very unlikely.
Schmidt, in his argument, points toward past periods — 8,000 and 125,000 years ago — when the summer Arctic was mostly ice free and notes that there is no geological evidence of rapid release during these times. Wadhams, on the other hand, points toward large methane plumes that are already rising from a region of the East Siberian Arctic Shelf — a region vulnerable to rapid warming. Joining the mix is a NASA scientist, Ed Dlugokencky, who claimed in a recent Live Science article, that there has been no detectable change in Arctic methane emissions over the past two decades.
Critics of Wadhams have also made an interesting claim that, for the methane to have a ‘significant impact’ most of it would need to release rapidly. David Archer, a climate scientist at the University of Chicago noted in the Live Science interview:
“It [methane] has to be released within a few years to have much impact on climate, but the mechanisms for release operate on time scales of centuries and longer.”
There’s no indication what Archer is referring to, the ESAS stores (composing about 500 gigatons) or the much larger Arctic tundra and hydrate stores, composing hundreds to thousands of gigatons or global methane stores which are about double that of the Arctic (I’ll respond to this more in my assessment below).
What these arguments present is a veritable scientific fur-ball. One that will be very difficult for the casual observer to unravel and one we had better damn well get right soon as the Arctic begins to enter a new ice-free state not seen in over 800,000 years.
It’s basically accepted science that release from the vast Arctic methane stores will increase as the planet warms, and sea ice, ice sheets, and tundra continue to melt. The argument, right now, basically hinges over how fast this process will occur — years, decades, centuries or millennia. As to whether the amount of methane coming from the Arctic is increasing or not, I’d like to see the data Ed Dlugokencky is looking at. Because, to my knowledge there is no complete survey of annual Arctic methane emissions. If he would like to provide them, they would be very helpful. And if we don’t have means to provide such information, then I think it is urgent we develop it.
What is available, at least in open source data, shows that atmospheric methane levels in the Arctic are higher than the global average, which would indicate a local emission of large volume (melting tundra, peat bogs, ocean emissions, thawing ESAS stores, environmental fire releases etc). And numerous studies — CARVE, the ESAS study, and others — have found very large local emissions sources in the Arctic in the megaton range and at levels far higher than previously anticipated. Wadhams joins a group of experts who believe a more rapid emission is possible (on the order of 1-50 gigatons per year in the case of the ESAS). Schmidt seems to believe there is no possibility for a release on a scale of anything less than 1,000 years or more.
My own opinion is that there is no possible means by which the Arctic’s methane stores can remain locked in their various traps so long as human greenhouse gas emissions continue along a business as usual path. In my view, it is entirely likely, that along this path, nearly all these stores will have released within a 500-1000 year time-frame, with Arctic methane emissions beginning to steadily increase now. The human greenhouse gas forcing will be enough to render the Arctic Ocean ice free during summer within the next few decades at the longest. And, without a major interrupting melt pulse from Greenland, this ice free state will continue to advance until winters show no ice as well. The last time this happened was likely in the Pliocene, around 2.5 million years ago. But the Pliocene oceans were settling down into a glacial period and not emerging from one. Such a set of rather disturbing circumstances will almost certainly result in large methane releases from the Arctic that are significant and contribute markedly to warming — even if such events don’t happen as fast as Wadhams warns.
Yet the gap between the two estimates from professional scientists is wide and no-one (except, apparently, me) seems to be occupying any middle ground in this particular discussion. Schmidt uses past interglacials where sea ice mostly vanished during summer time as a flimsy reassurance. But Schmidt does not acknowledge that we are out of reckoning of these time periods due to the clear and obvious fact that the current CO2 levels of 400 ppm puts us in the context of the Pliocene, nearly 2.5 million years ago, when the Arctic Ocean likely saw no sea ice and, as mentioned above, the newly emerging Arctic Ocean is one charged with carbon stores. So the situation may well be worse than the Pliocene. Sadly, this imperfect corollary is a moving target because the human emission that is currently nearly 32 gigatons drives CO2 levels higher by 2-3 ppm each year. Such an emission is at least ten times faster than any comparable emission in geological history — even that seen from the massive Siberian flood basalts during the Permian. This rate of emission, unless rapidly halted, will hit the Earth System like a 10 kilometer boloid — only potentially locking in catastrophic conditions that last for tens of thousands of years, not decades.
Wadhams, in contrast to Schmidt uses the Shakhova study and his own observations to support a claim that rapid methane release on the order of 1-50 gigatons is likely over the next 30 years. It is worth noting that a study conducted by Carolyn Ruppel refuted Shakhova’s findings for rapid methane hydrate release. This refutation may or may not stand as disproof. It’s too early in the scientific process, at this point, to be certain. So, though I agree with Schmidt and Archer that a slower release is more likely, I’m not assured enough by a single refutation to agree with them in their complete dismissal of Wadhams concerns.
The assertion that a slower rate of methane release would have little effect is also incorrect. Global methane stores are on the order of thousands of gigatons. And there are many ways by which such stores could hit the atmosphere — action by bacteria on thawing tundra, direct warming of anoxic carbon stores in shallow sea beds, heat forcing directly to hydrate locations, and potential for slope collapse and large release during destabilization. Some of these mechanisms remain unproven in the science. But all remain on the table. Should just 500 megatons of this vast store release each year (less than 1/10000th the total amount), global methane emissions will have doubled, putting at risk sinks and creating a very strong additional forcing to add to CO2 emissions. Global methane levels are increasing at a rate of around 4 ppb each year, some of this increase comes from the approximately 350-400 megaton human release, the rest comes from an Earth Systems release totaling around 130 megatons of which the Arctic is a portion. Yet the sinks are limited and there is good reason to believe that they will be saturated soon if current methane emissions double or more.
As I’ve noted before, I think that methane release is a part of a total Earth Systems response to a given forcing, in this case, human warming. And that total, given our best views of paleoclimate, is somewhere between 4-7 degrees Celsius of warming for each doubling of CO2 once all the ‘slow feedbacks’ come in. A 50 gigaton release in a single year would be far outside this usual range — a truly catastrophic event. So, in this case, Schmidt is probably right. But, as during the Permian, we sit at the end of a rather long glacial period in which global carbon stocks represent a very large charge and, potential, though unproven, larger than expected climate response. This is a disturbing circumstance and, in addition to the still accepted in broader scientific literature, Shakhova study, provides a strong reason to not entirely dismiss Wadhams concerns. In addition to these risks and considerations, lower levels of still significant methane release are likely still a significant and non-dismissible part of the total Earth System response. Responses we may start to see now and of which we have point source, though not broader, evidence for at this time.
The controversy, therefore, is in no small part caused by a lack of clarity and context. It is also due to the transient and amplifying nature of our current climate crisis. This is not an attack on the science, but a direct call for more effort, study, and proofs — from both sides of the argument. We need more context, not broad claims and flat dismissals. Such effort, I believe, would make the science stronger and provide a better tool for human resilience. So this is also an appeal for more direct support from policy makers — for all those who investigate Earth Systems responses to climate change.
To this point, I’d like to add Charles Miller’s own statement regarding the NASA CARVE mission with which he is involved:
“Permafrost soils are warming even faster than Arctic air temperatures — as much as 2.7 to 4.5 degrees Fahrenheit (1.5 to 2.5 degrees Celsius) in just the past 30 years. As heat from Earth’s surface penetrates into permafrost, it threatens to mobilize these organic carbon reservoirs and release them into the atmosphere as carbon dioxide and methane, upsetting the Arctic’s carbon balance and greatly exacerbating global warming.”
To this last point made by a scientist outside of the current controversy, I continue to believe that a rapid reduction in greenhouse gas emissions is a necessary and urgent response. To Schmidt and others who would cite past interglacials, I would add that unless human carbon emissions stop soon, the only set of geological events that will be worth looking at for long-term corollaries are the PETM and the P-T, especially after the ice goes. And it will surely go unless said soon human emissions halting actually happens.