How extreme will it get?

The January-June period was the warmest first half of any year on record for the contiguous United States, reports NOAA in its June 2012 overview. The national temperature of 52.9°F was 4.5°F (2.5°C) above average. 

The United States Department of Agriculture has designated 1,016 primary counties in 26 states as natural disaster areas, making it the largest natural disaster in America ever.  

The U.S. Drought Monitor has declared 80% of the Contiguous U.S. to be abnormally dry or worse, with 61% experiencing drought conditions ranging from moderate to exceptional—the largest percentage in the 12-year history of the service.  

In the 18 primary corn-growing states, 30% of the crop is in poor or very poor condition. In addition, fully half of the nation’s pastures and ranges are in poor or very poor condition. The year-to-date acreage burned by wildfires has increased to 3.1 million. 

NOAA reports record temperatures in many places; in Mc Cook, Neb., it was 115°F (46°C) on June 26, while in Norton Dam, Kan., it was 118°F (48°C) on June 28. Meanwhile, it was 126°F (52°C) in Death Valley National Park on July 10, 2012.

Lake Michigan surface water temperatures recently reached temperatures of up to 83.9°F (29°C), as shown on the image right. Lake Michigan has a surface area of 22,400 square miles (58,000 square kilometers). The lake's average depth is 279 ft (85 m), while its greatest depth is 923 ft (281 m). The image below compares 2012 surface water temperature with the average for 1992-2011.

Earlier this year, in March 2012, another heatwave hit much the same area. A NOAA analysis of the heatwave notes the abrupt onset of the warmth at Minneapolis, Duluth, and International Falls on 10 March. On subsequent days, anomalies of well over 20°C (36°F) were recorded as shown on the image on the right.

Temperature anomalies of 27+°F (15+°C) were recorded in a large area from March 12th to March 23rd, 2012, as shown below. 

 

Global warming is responsible for much of the frequency and intensity of extreme weather events and this is linked to developments in the Arctic, where accelerated warming is changing the jet stream, concludes an analysis by Rutgers University professor Jennifer Francis.

Apart from the obvious impact that droughts and heatwaves have on food and fresh water supply, they also come with wildfires that cause additional emissions, constituting a further positive feedback that further contributes to global warming, while the additional soot makes things even worse in the Arctic.

All this combines to create a situation in the Arctic where extreme local warming events can trigger methane releases, causing further local warming and further releases of methane, in a vicious cycle that threatens to escalate into runaway global warming that feeds on itself.  

The above image pictures the three kinds of warming (red lines) and their main causes:

1. Emissions by people cause global warming, with temperatures rising around the globe, including the Arctic.
2. Soot, dust and volatile organic compounds settle down on snow and ice, causing albedo change. More heat is absorbed, rather than reflected as was previously the case. This causes accelerated warming in the Arctic.
3. Accelerated warming in the Arctic threatens to weaken methane stores in the Arctic with the danger that releases will cause runaway global warming.
   
   

In addition, there are at least three feedback effects (gold lines) that make things even worse:

• Fires feedback: Accelerated warming in the Arctic is changing the Jet Stream, contributing to increased frequency and intensity of droughts and heatwaves.
• Albedo feedback: Accelerated warming in the Arctic also speeds up the decline of ice and snow cover, further accelerating albedo change.
• Methane feedback: Methane releases in the Arctic further add to the acceleration of warming in the Arctic, further contributing to weaken Arctic methane stores, in a vicious cycle that threatens to escalate into runaway global warming.

Rapid warming periods in the past constitute an ominous warning. In a paper published about a year ago, Ruhl et al. conclude that the end-Triassic mass extinction, about 200 million years ago, started with global warming due to carbon dioxide from volcanoes. This also caused warming of oceans and melting of hydrates at the bottom of the sea, containing methane created by millions of years of decomposing sea life. The hydrates released some 12,000 gigatons of methane, causing global warming to accelerate and resulting in sudden extinction of about half the species on Earth at the time.

The above image pictures how a similar thing could happen in our times, with global warming leading to accelerated warming in the Arctic, triggering hydrate destabilization and abrupt release of, say, 1 Gt of methane, which would further accelerate Arctic warming and lead to subsequent releases of methane from hydrates.

For more details on above two graphs, see the page How much time is there left to act?

Could extreme weather, like the U.S. is now experiencing, also occur in the Arctic?

Well, it actually did, not too long ago. Above image on the right, from the Cryosphere Today, shows air temperature anomalies in the Arctic of up to 6°C (10.8°F) for the month September 2007.

By how much will the sea warm up during such extreme local warming events?

The image on the right, produced with NOAA data, shows mean coastal sea surface temperatures of over 10°C (50°F) in some areas in the Arctic on August 22, 2007.

How extreme was this?

The image below, from NOAA, shows that sea surface temperature anomalies of over 5.5 were recorded for August 2007 in some areas in the Arctic.



Could such warming reach the bottom of the sea?

Again, this did happen in 2007, when strong polynya activity caused more summertime open water in the Laptev Sea, in turn causing more vertical mixing of the water column during storms in late 2007, according to one study, and bottom water temperatures on the mid-shelf increased by more than 3°C (5.4°F) compared to the long-term mean.

Another study finds that drastic sea ice shrinkage causes increase in storm activities and deepening of the wind-wave-mixing layer down to depth ~50 m (164 ft) that enhance methane release from the water column to the atmosphere. Indeed, the danger is that heat will warm up sediments under the sea, containing methane in hydrates and as free gas, causing large amounts of this methane to escape rather abruptly into the atmosphere.

Would this heat be able to penetrate sediments?

The image on the right, from a study by Hovland et al., shows that 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, which can result in huge abrupt releases of methane.

Since waters can be very shallow in the Arctic, much of the methane can rise up through these waters without getting oxidized.

Shakova and Semiletov warn, in a 2010 presentation, that some 75% of the East Siberian Arctic Shelf (ESAS) is shallower than 50 m, as shown on the image below. Furthermore, the ESAS region alone has an accumulated methane potential of some 1700 Gt in the form of free gas and hydrates under the sediment, in addition to organic carbon in its permafrost.

As the methane causes further warming in the atmosphere, this will contribute to the danger of even further methane escaping, further accelerating local warming, in a vicious cycle that can lead to catastrophic conditions well beyond the Arctic.

Above image shows the carbon in the melting permafrost, estimated by Schuur et al. at 1700 Gt. Much of this carbon could also be released as methane under warmer and wetter conditions.

Under warmer and dry conditions, things wouldn't be much better. The 2010 heatwave in Russia provides a gloomy preview of what could happen as temperatures rise at high latitudes. Firestorms in the peat-lands, tundras and forests in Siberia could release huge amounts of emissions, including soot, much of which could settle on the ice in the Himalaya Tibetan plateau, melting the glaciers there and causing short-term flooding, followed by rapid decline of the flow of ten of Asia's largest river systems that originate there, with more than a billion people's livelihoods depending on the continued flow of this water.

Proposal to extract, store and sell Arctic methane

A Proposal for the Prevention of

Arctic Methane Induced Catastrophic

Global Climate Change by Extraction

of Methane from beneath the Permafrost/

Arctic Methane Hydrates and its Storage and

Sale as a Subsidized "Green Gas"

Energy Source

By Malcolm P.R. Light

PhD. UCL
May 27th, 2012

DEDICATION

This proposal is dedicated to my Father and Mother, Ivan and Avril Light,

both meteorologists and farmers who knew about the vagaries of the weather;

and to all our grandchildren whose entire future depends on its successful outcome.

EXECUTIVE SUMMARY

Methane hydrates (clathrates) exist on the Arctic submarine shelf and slope where they are stabilized by the low temperatures and they have a continuous cap of frozen permafrost which normally prevents methane escape (Figure 1 below).

However, recent research has shown that millions of tons of methane are already being released in the Siberian Arctic through perforated zones in the subsea permafrost cap with the concentrations reaching up to 100 times the normal, such as in the discharge region of the Lena River and the junction of the Laptev and East Siberian Seas (Shakova et al. 2010).

Mean methane concentrations in the Arctic atmosphere showed a striking anomalous buildup between November 1-10, 2008 and November 1-10, 2011 (Figure 2 above)(Yurganov 2012 in Carana, 2012a).

The surface temperature hotspots in the Arctic caused by global warming correlate well with the anomalous buildups of atmospheric methane in the Arctic (Figure 3 right, in Arctic feedbacks in Carana, 2012a).

This indicates that there is a strong correlation between the dissociation of Arctic subsea methane hydrates from the effects of globally warmed seawater and the increasing size and rate of eruptions of methane into the Arctic atmosphere.

• Methane eruption zones (torches) occur widely in the East Siberian Arctic Shelf (ESAS) (Shakova et al., 2008; 2010), but the largest and most extreme are confined to the region outside the ESAS where the Gakkel "mid ocean" ridge system intersects at right angles the methane hydrate rich shelf slope region (Figure 9 above and Figure 17 right). 
  
  The wedge-like opening and spreading of the Gakkel Ridge is putting the formations and overlying methane hydrate sediments under torsional stress and in the process activating the major strike slip faults that fan away and thrust faults that radiate from this region (Figure 16 below). 
  
  Light and Solana (2002) predicted that the north slope of the Barents - Laptev - East Siberian seas at the intersection of the slowly opening Gakkel Ridge. This region would be especially vulnerable to slope failures where unstable methane hydrate would be affected by seismicity from earthquakes with magnitudes greater then 3.5 Richter and at depths of less than 30 km. Many earthquakes occur along the Gakkel Ridge often with magnitudes greater than 4 to 6 and at depths shallower than 10 km (Avetisov, 2008) continuously destabilizing the already unstable methane hydrates there (Figure 16 below). 

• Major and minor strike slip and normal faults form a continuous subterranean network around the Gakkel Ridge and are clearly charged with overpressured methane because methane gas is escaping from these fault lines many hundreds of km up dip and away from the subsea methane hydrate zones through which these fault zones pass (Figures 9 above and Figure 18 right).
   
• One small methane eruption zone occurs directly over the centre of the Gakkel Ridge and probably represents thermogenic deep seated methane being released by the magmatic heating of adjacent oil/gas fields by rising (pyroclastic) magma (Figure 9 above)(Edwards et al. 2001). This surface gas eruption appears to only represent a tiny percentage of the total gas released from other sources such as methane hydrates, as do methane eruptions around Cenozoic volcanics offshore Tiksi on the East Siberian shelf (Figure 11 right and Figure 16 above).
  
  
• An elongated set of methane eruption zones occur on the submarine slope north of Svalbard flanking the Gakkel Ridge and result from methane hydrate decomposition caused by sudden changes in pressure and temperature conditions due to submarine slides/slumps (Figure 9 above). These submarine slides/slumps were evidently set off by seismic activity along the Gakkel Ridge which lies a short distance to the north in an area where the ridge opening is the widest (Figure 16 above). This may be similar to the Storegga slide (Light and Solana, 2002; NGI, 2012). Light and Solana (2002) predicted that the western slopes of Norway and along the Barents Sea to Svalbard, would be especially vulnerable to slope failures in regions of unstable methane hydrate. Here the slowly spreading Gakkel Ridge runs as close as 30 km to the slope. Earthquake activity along the Gakkel Ridge often has magnitudes greater than 4 to 6 at depths shallower than 10 km (Avetisov, 2008) and will also be destabilizing the already unstable methane hydrates here leading to eruptions of methane into the atmosphere (Figure 9 above and Figure 16 above).

There are some 1000 Gt to 1400 Gt (10^9 tonnes) of carbon contained in the methane hydrates on the East Siberian Arctic Shelf and 700 Gt of free methane is trapped under the Arctic submarine permafrost (Shakova et al. 2008, 2010). Shakova et al. estimate that between 5% to 10% of the subsea permafrost (methane hydrates) in that region is now punctured allowing methane to escape at a rate of about 0.5 Mt (500,000 tonnes) a year and that up to 50 Gt (10^9 tonnes) could be released abruptly at any time soon. Release of this subsea Arctic methane would increase the worldwide atmospheric methane content about 12 times equivalent to doubling the carbon dioxide content of the atmosphere. This "methane hydrate gun", which is cocked and ready to fire at any moment, is an extremely serious scenario that will cause abrupt climate change (CCSP, 2008; IMPACTS 2008). Even if this subsea volume of Arctic methane is released over a longer interval of some ten to twenty years it will still result in a massive feedback on global warming and drive the Earth on an irretrievable plunge into total extinction.

Figure 5. From: Carana 2012b, originally from: arctische pinguin - click to enlarge

After 2015, when the Arctic Ocean becomes navigable (Figure 5 above, Carana 2012b) it will be possible to set up a whole series of drilling platforms adjacent to, but at least 1 km away from the high volume methane eruption zones and to directionally drill inclined wells down to intersect the free methane below the sealing methane hydrate permafrost cap within the underlying fault network (Figure 18 above).

High volume methane extraction from below the subsea methane hydrates using directional drilling from platforms situated in the stable areas between the talik/fault zones will reverse the methane and seawater flow in the taliks and shut down the uncontrolled methane sea water eruptions (Figure18 above). The controlled access of globally warmed sea water drawn down through the taliks to the base of the methane hydrate - permafrost cap will gradually destabilize the underlying methane hydrate and allows complete extraction of all the gas from the methane hydrate reserve (Figure18 above). The methane extraction boreholes can be progressively opened at shallower and shallower levels as the subterranean methane hydrate decomposes allowing the complete extraction of the sub permafrost reserve (Figure18 above).

The methane and seawater will be produced to the surface where the separated methane will be processed in Floating Liquefied Natural Gas (FLNG) facilities and stored in LNG tankers for sale to customers as a subsidised green alternative to coal and oil for power generation, air and ground transport, for home heating and cooking and the manufacture of hydrogen, fertilizers, fabrics, glass, steel, plastics, paint and other products.

Where the trapped methane is sufficiently geopressured within the fault system network underlying the Arctic subsea permafrost and is partially dissolved in the water (Light, 1985; Tyler, Light and Ewing, 1984; Ewing, Light and Tyler, 1984) it may be possible to coproduce it with the seawater which would then be disposed of after the methane had be separated from it for storage (Jackson, Light and Ayers, 1987; Anderson et al., 1984; Randolph and Rogers, 1984; Chesney et al., 1982).

Many methane eruption zones occur along the narrow fault bound channels separating the complex island archipelago of Arctic Canada (Figure 6 and 9). In these regions drilling rigs could be located on shore or offshore and drill inclined wells to intersect the free methane zones at depth beneath the methane hydrates, while the atmospheric methane clouds could be partly eliminated by using a beamed interfering radio transmission system (Lucy Project) (Light 2011a). A similar set of onshore drilling rigs could tap subpermafrost methane along the east coast of Novaya Zemlya (Figure 6 below and 9 above).

Methane is a high energy fuel, with more energy than other comparable fossil fuels (Wales 2012). As a liquid natural gas it can be used for aircraft and road transport and rocket fuel and produces little pollution compared to coal, gasoline and other hydrocarbon fuels.

Support should be sought from the United nations, World Bank, national governments and other interested parties for a subsidy (such as a tax rebate) of some 5% to 15% of the market price on Arctic permafrost methane and its derivatives to make it the most attractive LNG for sale compared to LNG from other sources. This will guarantee that all the Arctic gas recovered from the Arctic methane hydrate reservoirs and stockpiled, will immediately be sold to consumers and converted into safer byproducts. This will also act as an incentive to oil companies to produce methane in large quantities from the Arctic methane hydrate reserves. In this way the Arctic methane hydrate reservoirs will be continuously reduced in a safe controlled way over the next 200 to 300 years supplying an abundant "Green LNG" energy source to humanity.

Video and poster - methane in the Arctic

Methane in the Arctic threatens to escalate into runaway global warming.

The poster shown in the video is added below. 

Click on the poster to view a higher-resolution version, for printing out and hanging it on the wall.

Methane in the Arctic

Methane is often said to have a Global Warming Potential (GWP) of 21 times as strong as carbon dioxide, a figure based on IPCC assessment reports that date back to the 1990s. However, the IPCC has updated methane's GWP several times since, as illustrated in Table 1. below.

In its Fourth Assessment Report (AR4, 2007), the IPCC gives methane a GWP of 25 as much as carbon dioxide over 100 years and 72 as much as carbon dioxide over 20 years.

Furthermore, a 2009 study, by Drew Shindell et al., points out that the IPCC figures do not include direct+indirect radiative effects of aerosol responses to methane releases that increase methane's GWP to 105 over 20 years when included

Moreover, in the context of tipping points, which seems appropriate regarding methane releases in the Arctic, it makes sense to focus on a short time horizon, possibly as short as a few years.

Accordingly, methane's GWP can best be visualized as in the image below, which is also displayed mid-right on the poster above.

The image on the left shows methane's global warming potential (GWP) for different time horizons, pointing out that methane's GWP is more than 130 times that of carbon dioxide over a period of ten years.

IPCC¹ figures were used to create the blue line. The red line is based on figures in a study by Shindell et al.², which are higher as they include more effects. This study concludes that methane's GWP would likely be further increased by including ecosystem responses.

The ecosystem response can be particularly strong in the Arctic, where the seabed contains huge amounts of methane. Continued warming in the Arctic can cause large abrupt methane releases which in turn can trigger further methane releases from sediments under the sea.

This is particularly worrying, not only because of the presence of huge amounts of methane, but also because the sea is quite shallow in areas such as the East Siberian Arctic Shelf (ESAS), which in the case of large abrupt releases can soon lead to oxygen depletion in the water and make that much of the methane will enter the atmosphere without being oxidized in the water.

Additionally, low water temperatures and long sea currents in the Arctic Ocean are not very friendly toward bacteria that might otherwise break down methane in the water.

For further background, also see the post The potential impact of large abrupt release of methane in the Arctic at the Arctic Methane blog³, and the FAQ page at that blog.

References:

1. IPCC, Climate Change 2007: Working Group I: The Physical Science Basis, Table 2.14 (2007)
http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch2s2-10-2.html

2. D.T. Shindell et al., "Improved Attribution of Climate Forcing to Emissions". Science vol 326: pp. 716-718 (2009)
http://www.sciencemag.org/content/326/5953/716.abstract

3. Sam Carana, The potential impact of large abrupt release of methane in the Arctic (2012)
http://arcticmethane.blogspot.com/2012/05/potential-impact-of-large-abrupt.html

Supplementary evidence by Prof. Peter Wadhams

Supplementary written evidence 
submitted by Professor Peter Wadhams 
to the Environmental Audit Committee (EAC)

http://www.publications.parliament.uk/pa/cm201012/cmselect/cmenvaud/writev/1739/arc26.htm

I am writing in response to information provided recently by Professor Julia Slingo OBE, Chief Scientist, Meteorological Office, firstly in the report 'Possibility and Impact of Rapid Climate Change in the Arctic' to the Environmental Audit Committee and subsequently in answering questions from the Committee on Wednesday 14 March 2012. In the responses, the Meteorological Office refers to an earlier presentation to the Committee by myself, made on 21 February 2012.

The following comments are based on the uncorrected transcript of Professor Slingo’s presentation to the EAC, 14 March 2012 session, as at: 
http://www.publications.parliament.uk/pa/cm201012/cmselect/cmenvaud/uc1739-iv/uc173901.htm

1. Speed of ice loss

In response to questions from the Chair, Prof. Slingo ruled out an ice-free summer by as early as 2015. Furthermore, Prof. Slingo rejected data which shows a decline in Arctic sea ice volume of 75% and also rejected the possibility that further decreases may cause an immediate collapse of ice cover.

The data that Prof. Slingo rejected are part of PIOMAS, which is held in high regard, not only by me, but also by many experts in the field. From my position of somebody who has studied the Arctic for many years and has been actively participating in submarine measurements of the Arctic ice thickness since 1976, it seems extraordinary to me that for Prof. Slingo can effectively rule out these PIOMAS data in her consideration of the evidence for decreasing ice volume, when one considers the vast effort and diligence that has been invested over such an extended period in collecting data under the ice by both British and US scientists. Prof. Slingo offers no reason whatsoever for dismissing this extremely pertinent set of measurements and their associated interpretation, arguing that "the observational estimates are still very uncertain". This is not the case. I expand on this in an Appendix to my letter.

It has to be said that it is very poor scientific practice to reject in such a cavalier fashion any source of data that has been gathered according to accepted high scientific standards and published in numerous papers in high-profile journals such as Nature and Journal of Geophysical Research, the more so when the sole reason for this rejection appears to be perceived uncertainty. If other data are in conflict with one’s own data, then caution should be given to the validity of one’s own data, while this should immediately set in train further research and measurement in efforts to resolve possible conflicts. In this case, however, the crucial point is that there is currently no rival set of data to compare with the scale and comprehensiveness of the PIOMAS data; Prof. Slingo sets against the clear observational database only the Met. Office’s models. These models (and in fact all the models used by IPCC) have already shown themselves to be inadequate in that they failed to predict the rapid decline in sea ice area which has occurred in recent years. It is absurd in such a case to prefer the predictions of failed models to an obvious near-term extrapolation based on observed and measured trends.

Regarding the possibility of an imminent collapse of sea ice, Prof. Slingo ignores a point raised earlier by herself, i.e. that, apart from melting, strong winds can also influence sea ice extent, as happened in 2007 when much ice was driven across the Arctic Ocean by southerly winds (not northerly, as she stated). The fact that this occurred can only lead us to conclude that this could happen again. Natural variability offers no reason to rule out such a collapse, 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, both mechanically and by enhancing ocean heat transfer to the under-ice surface.

The concluding observation I have to make on this first point is that Prof. Slingo has not provided any justification for ignoring the measurements that we have of ice volume changes and the clear trend towards imminent ice-free summers that they indicate.

2. Methane – potential emissions and escalation

My second point of contention is Prof. Slingo’s position on the possibility of imminent large releases of methane in the Arctic, which is consistent with her sanguine attitude to the rate of loss of ice cover. She states "Our estimates of those (large releases of methane) are that we are not looking at catastrophic releases of methane." Prof Slingo suggests that there was "a lack of clarity in thinking about how that heating at the upper level of the ocean can get down, and how rapidly it can get down into the deeper layers of the ocean". This appears to show a lack of understanding of the well-known process of ocean mixing. As Prof. Slingo earlier brought up herself, strong winds can cause mixing of the vertical water column, bringing heat down to the seabed, especially so in the shallow waters of the East Siberian Arctic Shelf. A recent paper shows that "data obtained in the ESAS during the drilling expedition of 2011 showed no frozen sediments at all within the 53 m long drilling core" (Dr. Natalia Shakhova et al. in: EGU General Assembly 2012;
http://meetingorganizer.copernicus.org/EGU2012/EGU2012-3877-1.pdf ).

The East Siberian Arctic Shelf (ESAS), where the intensive seabed methane emissions have been recorded, is only about 50 m deep. Throughout the world ocean, the Mixed Layer (the near-surface layer where wind-induced mixing of water occurs) is typically 100-200 m deep. It is shallower only in areas where the water is extremely calm. This used to be the case for the Arctic Ocean because of its ice cover, but it is no longer the case, because of the large-scale summer sea ice retreat which has created a wide-open Beaufort Sea where storms can create waves as high as in any other ocean, which exert their full mixing effect on the waters. It is certain that a 50 m deep open shelf sea is mixed to the bottom, so I am at a loss to understand Prof. Slingo’s remarks, unless she is thinking of the deep ocean or deeper shelves elsewhere than the East Siberian Sea.

Furthermore, Prof. Slingo states that "where there is methane coming out of the continental shelf there it is not reaching the surface either, because again the methane is oxidised during its passage through the sea water and none of those plumes made it to the surface. So there is a general consensus that only a small fraction of methane, when it is released through this gradual process of warming of the continental shelf, actually reaches the surface." This statement is also incomprehensible as far as the East Siberian Arctic Shelf is concerned. With such a shallow water depth the methane plume reaches the surface within a few seconds of release, giving little opportunity for oxidation on the way up. She may be confusing this situation with that of the much deeper waters off Svalbard where methane plumes are indeed observed to peter out before reaching the surface, due to oxidation within the water column.

To illustrate the reality of this warming of ESAS shelf water, I reproduce (fig. 1) a satellite sea surface temperature data (SST) map from September 2011, provided by Dr James Overland of Pacific Marine Environmental Laboratory (PMEL), Seattle. This shows that in summer 2011 the surface water temperature in the open part of the Beaufort and Chukchi seas reached a massive 6-7°C over most of the region and up to 9°C along the Arctic coast of Alaska. This is warmer than the temperature of the North Sea at Scarborough yesterday. This extraordinary warming is due to absorption of solar radiation by the open water. These are not the temperatures of a very thin skin as suggested by Prof. Slingo. The NOAA data apply to the uppermost 7 m of the ocean, while PMEL has backup data from Wave Gliders (automatic vehicles that run oceanographic surveys at preprogrammed depths) to show that this warming extends to at least 20 m. We can conclude from fig.1 that an extraordinary seabed warming is taking place, certainly sufficient to cause rapid melt of offshore permafrost, and this must cause serious concern with respect to the danger of a large methane outbreak.

Once the methane reaches the surface, one should note that there is very little hydroxyl in the Arctic atmosphere to break down the methane, a situation that again becomes even worse with large releases of methane.

3. The choice of pursuing geo-engineering or not.

Finally, I would like to address Prof. Slingo’s closing remarks on geo-engineering.

Both Professor Slingo and Professor Lenton repeat a point made by many critics of geo-engineering that once you start geoengineering you have to continue. On this point, I like to draw attention to evidence earlier provided to the Environmental Audit Committee by Professor Stephen Salter, as can be found at
http://www.publications.parliament.uk/pa/cm201012/cmselect/cmenvaud/writev/1739/arc22.htm

Prof. Salter responds: "I must disagree. You have to continue only until emissions have fallen sufficiently or CO2 removal methods have proved effective or there is a collective world view that abrupt global warming is a good thing after all. No action by the geo-engineering community is impeding these. Indeed everyone working in the field hopes that geoengineering will never be needed but fears that it might be needed with the greatest urgency. This is like the view of people who hope and pray that houses will not catch fire and cars will not crash but still want emergency services to be well trained and well equipped with ambulances and fires engines." Basically he is talking about the precautionary principle.

I fully agree with Prof. Salter on this point, and I also fully share with Prof. Salter the anxieties of the Arctic Methane Emergency Group. A highly proactive geo-engineering research programme aimed at mitigating global warming is more rational than expecting the worst but not taking any action to avert it.

Peter Wadhams,
Professor of Ocean Physics,
Department of Applied Mathematics and Theoretical Physics (DAMTP),
University of Cambridge
Member of Arctic Methane Emergency Group; Review Editor for Intergovernmental Panel on Climate Change 5th Assessment (chapter 1).

FIG.1. September 12-13 2011. NOAA-6 and-7 imagery of sea surface temperature in Beaufort Sea (courtesy of J. Overland). Alaska is brown land mass in bottom half. Note 6-7°C temperatures (green) in west, over East Siberian Shelf, and up to 9°C (orange) along Alaskan coast.

Appendix. The scientific database for sea ice loss.

On a previous occasion (21 February) I testified to the Committee and showed them the results of submarine measurements of ic thickness combined with satellite observations of ice retreat. When these two datasets are combined , they demonstrate beyond doubt that the volume of sea ice in the Arctic has seriously diminished over the past 40 years, by about 75% in the case of the late summer volume. If this decline is extrapolated, then without the need for models (which have demonstrably failed to predict the rapid retreat of sea ice in the last few years) it can be easily seen that the summer sea ice will disappear by about 2016 (plus or minus about 3 years). It might be useful to summarise the history of research in this subject.

In her testimony Prof Slingo placed her faith in model predictions and in future data to come from satellites on thickness (presumably Cryosat-2, which has not yet produced any usable data on ice thickness). Yet since the 1950s US and British submarines have been regularly sailing to the Arctic (I have been doing it since 1976) and accurately measuring ice thickness in transects across that ocean. Her statement that "we do not know the ice thickness in the Arctic" is false. In 1990 I published the first evidence of ice thinning in the Arctic in Nature (Wadhams, 1990). At that stage it was a 15% thinning over the Eurasian Basin. Incorporating later data my group was able to demonstrate a 43% thinning by the late 1990s (Wadhams and Davis, 2000, 2001), and this was in exact agreement with observations made by Dr Drew Rothrock of the University of Washington, who has had the main responsibility for analyzing data from US submarines (Rothrock et al., 1999, 2003; Kwok and Rothrock, 2009) and who examined all the other sectors of the Arctic Ocean. In fact in his 2003 paper Rothrock showed that in every sector of the Arctic Ocean a substantial hickness loss had occurred in the preceding 20 years. Further thinning has since been demonstrated, e.g. see my latest paper on this (Wadhams et al., 2011). Among the foremost US researchers at present active on sea ice volume decline are Dr Ron Kwok of the NASA Jet Propulsion Laboratory and Dr Axel Schweiger of University of Washington (leader of the PIOMAS project), and these have both been moved to write to Prof Slingo expressing their surprise at her remarks deriding the scientific database.

Even if we only consider a 43% loss of mean thickness (which was documented as occurring up to 1999), the accompanying loss of area (30-40%) gives a volume loss of some 75%. Summer melt measurements made in 2007 in the Beaufort Sea by Perovich et al. (2008) showed 2 m of bottom melt. If these enhanced melt rates are applied to ice which is mainly first-year and which has itself suffered thinning through global warming, then it is clear that very soon we will be facing a collapse of the ice cover through summer melt being greater than winter growth. These observations do not just come from me but also from the PIOMAS project at the University of Washington (a programme to map volume change of sea ice led by Dr Rothrock himself and Dr Schweiger), the satellite-based work of Ron Kwok, and the high-resolution modelling work of Dr Wieslaw Maslowsky at the Naval Postgraduate School, Monterey (e.g. Maslowsky et al 2011).

References

Kwok, R., and D. A. Rothrock ( 2009 ), Decline in Arctic sea ice thickness from submarine and ICESat records: 1958- 2008,Geophys. Res. Lett ., 36, L15501.

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