I've been trying which kind of trendline fits best and my conclusion is that a trendline pointing at 2014 fits the data best (image left).
The respective data was produced by the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS, Zhang and Rothrock, 2003) developed at Polar Science Center, Applied Physics Laboratory, University of Washington.
As mentioned in the discussion, some ice may persist close to Greenland for a few years more, since Greenland constitutes a barrier that holds the sea ice in place. Similarly, it is suggested that natural variability could prolong the ice longer than expected.
However, such arguments offer no reason to rule out an imminent collapse of the sea ice, since natural variability works both ways, it could bring about such a collapse either earlier or later than models indicate.
In fact, the thinner the sea ice gets, the more likely an early collapse is to occur. It is accepted science that global warming will increase the intensity of extreme weather events, so more heavy winds and more intense storms can be expected to increasingly break up the remaining ice in future, driving the smaller parts out of the Arctic Ocean more easily. Much of the sea ice loss already occurs due to sea ice moving along the edges of Greenland into the Atlantic Ocean.
Looking at sea ice extent alone is deceptive, as volume has been decreasing even more dramatically. The thinner the sea ice gets, the bigger the chance that the increasingly intense and frequent storms will smash it to pieces, leaving only a small rim of ice along the edges of Greenland.
Indeed, there are different ways projections can be made from the existing data. Clearly, a linear trend would be inappropriate, given the increased impact of feedbacks such as albedo change. In fact, the above exponential projection is conservative compared to the logarithmic one, which actually appears to fit the data even better, and which points at 2013 as the most likely time when the September sea ice will disappear.
The trends are quite clear, as also illustrated by further charts at:
2. What makes Arctic sea ice retreat so rapidly?
Emissions result in global warming, as warmer water flows into the Arctic from ocean currents and rivers. Melting permafrost causes even more emissions, while there are further feedbacks such as wildfires raging in tundras and peatlands. The Arctic is especially vulnerable to soot, which darkens the ice, resulting in more sunlight being absorbed rather than reflected back into space. This albedo effect accelerates as sea ice retreats and amplifies warming in the Arctic. Without action to cool the Arctic, methane releases threaten to further amplify warming, triggering runaway warming.
3. Why is Arctic sea ice decline so important?
Permafrost and sea ice keep methane hydrates stable. Arctic sea ice and permafrost still reflect a lot of sunlight back into space while a lot of heat goes into the process of melting the ice. As the sea ice declines and permafrost melts, this light and heat is instead absorbed in the Arctic, further accelerating warming in the Arctic, which is already several times larger than elsewhere on Earth.
Such fires would cause huge amounts of soot that will in part settle down on the Himalayan Plateau, darkening the ice and snow, resulting in more heat absorption there and disruption of the flow of rivers that originate there. This can make that both the supply of food and water can be severely disrupted, threatening the extinction of many species.
Glaciers on the Himalayan Plateau act as a water storage tower for South and East Asia, releasing melt water in warm months to the Indus, Ganges, Brahmaputra and other river systems, providing fresh water to more than a billion people. In the dry season glacial melt provides half or more of the water in many rivers.
As the snow melts in the spring and summer, the impact of black soot on the glacier surface increases, since the soot particles do not escape in the melt water as efficiently as the water itself. As a consequence, the soot darkens the glacier surface even more during the melt season, increasing absorption of sunlight, and speeding up glacier disintegration.
Taking no action risks extinction for many species, including humans, possibly within one generation. With so much at stake, the cost of taking action is dwarfed by the price we pay when no action is taken. The longer we wait, the larger the risk becomes and the more difficult, expensive and risky it will become to take measures to try and reduce the risk.
6. What are methane hydrates?
Methane hydrates are crystal-like structures that hold methane. They are likely to remain intact as long as they are not disturbed (e.g. by landslides or earthquakes) and temperatures and pressures remain within certain bounderies.
7. Did methane hydrates ever release much methane in history?
They probably did, but the current situation looks much more dangerous than any previous periods. Current levels of greenhouse gases in the atmosphere are extremely high (and rising), which is the more dangerous given the presence of huge amounts of methane in the shallows of the ESAS. This situation and the dangers associated with this situation have no precedent in history.
8. What is “ESAS” and how did permafrost and methane hydrate get into the ESAS?
ESAS stands for East Siberian Arctic Shelf, an area of over 2 million square kilometers large on the edge of Siberia. ESAS is the largest continental shelf in the world, and 75% of the sea over the shelf is less than 50 meters deep.
At the last glacial maximum (LGM), at the height of the ice age about 20,000 years ago, the sea level was approximately 120 metres lower than it is today. The ESAS was well above sea level and the cold air temperature would have cooled the land surface to considerable depth, freezing water around organic matter into permafrost. Then the sea level rose, and the land and permafrost were inundated. Some of the organic matter would have decomposed, producing methane which could, at certain pressures and temperatures, combine with groundwater to form methane hydrate (a "lattice" of ice and gas). Thus, below the permafrost is now a mixture of hydrate and free methane gas.
Methane release from the East Siberian Arctic Shelf and the Potential for Abrupt Climate Change
On carbon transport and fate in the East Siberian Arctic land–shelf–atmosphere system
Semiletov et al. (2012)
9. How much methane could be released from the East Siberian Arctic Shelf (ESAS)?
Selected parts from:
Recent geochemical and geophysical evidence demonstrates that the ESAS subsea permafrost has been showing signs of destabilization (Shakhova et al., 2010a, b). If this permafrost further destabilizes, emissions could be significantly larger than teragram-sized.
The amount of CH4 that could theoretically be released in the future is enormous. The volume of gas hydrates that underlie the Arctic Ocean seabed is estimated to be 2,000 Gt of CH4 (Makogon et al., 2007). About 85% of the Arctic Ocean sedimentary basins occur within the continental shelf; therefore, within the ESAS alone, which comprises ~30% of the area of the Arctic shelf, hydrate deposits could contain ~500 Gt of CH4. An additional two-thirds of that amount (~300 Gt) is stored in the form of free gas (Ginsburg and Soloviev, 1994). Because submarine permafrost is identical to on-land permafrost, the carbon pool held within submarine permafrost can be estimated to include not less than 500 Gt of carbon within a 25-m-thick permafrost body (Zimov et al., 2006). Thus the total amount of carbon preserved within the Arctic continental shelf could total ~1300 Gt of carbon, of which 800 Gt is previously formed CH4 ready to be suddenly released when appropriate pathways develop (Shakhova and Semiletov, 2009; Shakhova et al., 2010b). Release of only 1% of this reservoir would more than triple the atmospheric mixing ratio of CH4, probably triggering abrupt climate change, as predicted by modeling results (Archer and Buffett, 2005).
A new model of subsea permafrost degradation
The Arctic Ocean is surrounded by offshore and onshore permafrost, which is being degraded at increasing rates under warming conditions. This warming is most pronounced in the East Siberian part of the Arctic, where surface air temperature increased by about 5°C during 2000–2005 compared to 20th century temperature patterns (Figure 4). In response to this anomalous warming, shrinkage of onshore permafrost is projected to double by 2090 (ACIA, 2004).
At the same time, no attention has been paid to that part of the onshore permafrost that is the most sensitive to warming. This sensitive permafrost was inundated during the last 10–15 Kyr, when the ocean level rose by ≤ 100 m. The thermal regime of the surrounding environment changed drastically as the sea intruded, warming by as much as 12–17°C; gradually, the temperature of the submerged permafrost responded.
ACIA. 2004. Impacts of a warming Arctic: Arctic Climate Impact Assessment. Cambridge University Press, Cambridge, 139 pp.
Archer, D.E. and B. Buffett. 2005. Time-dependent response of the global ocean clathrate reservoir to climatic and anthropogenic forcing. Geochem., Geophys., Geosys., 6(3), doi: 10.1029/2004GC000854.
Ginsburg, G.D. and V.A. Soloviev. 1994. Submarine Hydrates. VNIIOkeangeologia, Sankt- Peterburg, 1999.
Makogon, Y.F., S.A. Holditch, and T.Y. Makogon. 2007. Natural gas-hydrates – A potential energy source for the 21st Century. J. Petrol. Sci. Engineering, 56, 14-31.
Shakhova, N.E. and I.P. Semiletov. 2009. Methane Hydrate Feedbacks. In Martin Sommerkorn & Susan Joy Hassol, eds., Arctic Climate Feedbacks: Global Implications, Published by WWF International Arctic Programme August, 2009, ISBN: 978-2-88085-305-1, p. 81-92.
Shakhova, N., I. Semiletov, A. Salyuk, V. Joussupov, D. Kosmach, and O. Gustafsson. 2010a. Extensive methane venting to the atmosphere from sediments of the East Siberian Arctic Shelf. Science 327, 1246-1250.
Shakhova, N., I. Semiletov, I. Leifer, P. Rekant, A. Salyuk, and D. Kosmach. 2010b. Geochemical and geophysical evidence of methane release from the inner East Siberian Shelf. J. Geophys. Res. -Oceans, in press
Zimov, S.A., E.A.G. Schuur, and F.S. Chapin III. 2006. Permafrost and global carbon budget. Science, 312, 1612-1613.
Shakhova et al. estimate the accumulated methane potential for the Eastern Siberian Arctic Shelf alone as follows:
- organic carbon in permafrost of about 500 Gt;
- about 1000 Gt in hydrate deposits; and
- about 700 Gt in free gas beneath the gas hydrate stability zone.
Methane release from the East Siberian Arctic Shelf and the Potential for Abrupt Climate Change
10. How much methane could be released, say, within a few years?
". . . we consider release of up to 50 Gt of predicted amount of hydrate storage as highly possible for abrupt release at any time."
Shakhova, Semiletov, Salyuk and Kosmach (2008)
11. Is it possible for heat to reach hydrates deep down in the sediment underneath the ESAS?
It is possible for heat to reach hydrates in a short period. Waters in the Arctic can be very shallow, which makes that they can heat up quite rapidly, especially in summer when the sun hardly sets in the Arctic.
As above image shows, sea surface temperature anomalies of over 5 degrees Celsius were recorded in 2007. Strong polynya activity in 2007 caused more summertime open water in the Laptev Sea, in turn causing more vertical mixing of the water column during storms in late 2007 -- bottom water temperatures on the mid-shelf increased by more than 3 degrees Celsius compared to the long-term mean.
Drastic sea ice shrinkage causes increase in storm activities and deepening of the wind-wave-mixing layer down to depth ~50 m that enhance methane release from the water column to the atmosphere.
Hydrates can exist at the end of conduits in the sediment, formed when methane did escape from such hydrates in the past. Heat can travel down such conduits relatively fast, warming up the hydrates and destabilizing them in the process, resulting in huge abrupt releases of methane.
Submarine pingoes: Indicators of shallow gas hydrates in a pockmark at Nyegga, Norwegian Sea
Hovland et al., Marine Geology 228 (2006) 15–23
The danger is that heat will warm up permafrost and reach hydrates. Because the waters are so shallow, much of the methane that rises up through these waters will not get oxidized. As the methane causes further warming in the atmosphere, this will causing further release of methane that further accelerates warming, in a vicious cycle leading to runaway global warming.
12. How much methane is/was there in the atmosphere, how much is added annually?
The above figure for radiative forcing (RF of about 0.5 W per square meter) does not include indirect effects of methane, such as water vapor. These effects are included in the images below.
According to the IPCC, methane has a global warming potential (GWP) over 20 years of 72 times that of carbon dioxide. Shindell pointed out in 2009 that this IPCC figure didn't include some important direct and indirect effects, which increase the GWP of methane to 105 over 20 years. Over shorter periods, the GWP is even higher. Unlike carbon dioxide, methane's GWP does rise as more of it is released.
Global Warming Potential, Intergovernmental Panel on Climate Change (IPCC, 2007)
Improved Attribution of Climate Forcing to Emissions, Drew Shindell (2009)
14. What is the lifetime of methane?
Methane can persist in the atmosphere for as little as 8 years, but its lifetime can be extended to decades.
Methane's GWP and lifetime depend on variables such as the size of emissions and the location of emissions (hydroxyl depletion already is a big problem in the Arctic atmosphere), the wind, the time of year (when it's winter, there's less hydroxyl), etc. Another variable is the indirect effect of large emissions and what's often overlooked is that large emissions will trigger further emissions of methane, thus further extending the lifetime of both the new and the earlier-emitted methane, which can make the methane persist locally for decades.
15. Is methane already venting in the Arctic from hydrates?
Evidently, it is, given the high levels of methane in the Arctic. Above NASA image shows methane levels of 1870+ in the Arctic for January 2012.
From: Sam Carana, Methane venting in the Arctic
The two images below, produced with NASA GES DISC Giovanni data system, show methane levels for early April 2012.
The top image below shows where methane levels exceed 1.9 parts per million.
The image below is a polar projection; note the different scale on the right, which is the one automatically calculated as the default one and exceeds 2 parts per million.
High methane levels in Arctic - April 2012
More monitoring should take place to verify all venting. Furthermore, data should be more easily available online, while more should be done to interpret the data and assess the risks.
To some extent, the question how much methane is already venting in the Arctic is irrelevant. Action can no longer be postponed. It is necessary to start reducing the risk that large amounts of methane will be released abruptly in future. We need to reduce this risk while we still can do so.
Methane in the Arctic is monitored through flask and in situ measurements at only three sites, i.e. Barrow (Alaska), Alert (Nunavut, Canada) and Svalbard (Norway), as discussed at:
At times, balloons and aircraft also take measurements at higher altitudes, e.g. HIPPO.
Furthermore, there are satellite measurements, such as discussed at:
Methane in the sea is monitored by buoys, by submarines (Peter Wadhams) and by ships, e.g. at expeditions as discussed at:
16. What should be done to reduce the risk that methane hydrates will trigger runaway warming?
Large-scale geo-engineering, afforestation and dramatic reduction of emissions are necessary to bring the atmosphere and oceans back to their pre-industrial state as soon as possible. Additionally, further geo-engineering is necessary to reflect more sunlight back into space, break down or capture methane, etc.
"[Measures identified to reduce black carbon and tropospheric ozone] could reduce warming in the Arctic in the next 30 years by about two-thirds . . ."
Dr. Drew T. Shindell et al. in: Summary for Policy Makers, UNEP/WMO 2011
"Increases in global methane emissions have caused a 26% decrease in hydroxyl; global carbon monoxide emissions have caused a 13% decrease in hydroxyl."
Dr. Drew T. Shindell et al. in: NASA Research News, from: Science, October 30, 2009
PART B. The atmosphere and oceans need to be brought back to their pre-industrial state.
This will take many years and will require the help of a range of geo-engineering methods including large-scale afforestation, biochar and enhanced weathering.
PART C. Geo-engineering methods must also be deployed as part of emergency measures to avoid runaway warming, for starters to replace the cooling effect of aerosols now released through combustion. Further geo-engineering will be necessary, particularly ways to capture or break down methane in the Arctic.
17. What are the costs of this proposed action (to reduce the risk of runaway warming)?
Again, we cannot afford not to act. Each policy that seeks to accomplish the necessary shifts comes with costs and benefits, and they will be greater for some than for others, but generally we will all be much better off. To get the atmosphere and oceans back to their pre-industrial state, feebates are the most effective policy instruments, they can be budget-neutral, have the least leakage and are best implemented locally. Such local implementation means that one doesn't have to wait for policy implementations elsewhere. While a global commitment to act is imperative, the exact shape of such policies is best decided and implemented locally. In many cases, this increases health, job and investment opportunities, while prices of products will come down over time.
Furthermore, geo-engineering methods must be deployed to reflect more sunlight back into space, break down or capture methane, etc. The direct cost of this are estimated to be under $1 billion per year. Additionally, there may be some undesirable side effects of geo-engineering, but - again - the cost of that would be dwarfed by the cost of taking no action.
There are risks associated with any chosen policy; a business-as-usual scenario carries the highest risk of extinction of many species, including humans. With so much at stake, the cost of taking no action is incalculable. The longer we wait, the larger the risk becomes and the more difficult, expensive and risky it will become to take measures in efforts to reduce the risk.
Of course, research should continue, but there's enough evidence that decisive action is necessary now, and there are many measures that can be taken that are beneficial in many ways. There are sufficient technologies and resources available to start acting now. The one thing we don't have enough is time. We are rapidly running out of time. We cannot afford not to act.
20. Why should drilling be banned in the Arctic? Why is a spill or blow-out particularly bad in the Arctic?
Given the risk of oil spills and disturbing methane hydrates, drilling in the Arctic should be banned. Since a rapid shift to clean energy is necessary globally, there's no need to drill for fossil fuel in the Arctic in the first place. Rather than drilling for oil and natural gas, oil companies should use their experience with drilling and with hydrates to help out in dealing with the problems.
Circumstances in the Arctic are different from most other places in the world. There is hardly any response capacity ready for launch in the Arctic, while arrival of winter ice would make it even harder to reach many places. Standard responses such as drilling relief wells or using booms are hard to apply when the ice thickens. An oil spill in the Arctic would risk that oil gets underneath the sea ice, from where it will be very hard to recover. Low temperatures mean there are less bacteria to break down the oil. In other places, currents may bring bacteria back to the location of the spill repeatedly. Currents in the Arctic are long, so once bacteria flow away from the location of the spill, it may take a long time for them to return, too long to survive in the cold water and often with little or no sunshine.
Methane won't get broken down easily in the Arctic, as this requires oxygen, which isn't quickly replenished in the Arctic, once depleted. Furthermore, hydroxyl levels in the Arctic are very low, so methane that reaches the atmosphere won't get broken down there easily either.
"It seems clear that in a warming world (for whatever reason), methane will be released in increasing quantities, e.g. from warming permafrost, thus augmenting global warming. Disturbances on the sea bed may also cause the decomposition of methane-hydrate. It is known that drilling into methane hydrate poses a hazard to oil prospecting operations, and it is also thought that decomposition of methane hydrate with an eruption of methane could trigger a tsunami."
Professor Chris Rhodes in: Methane Gas Hydrates. . Feb 1, 2012
Peter Wadhams - written evidence submitted to UK Environmental Audit Committee
Greenpeace - written evidence submitted to UK Environmental Audit Committee