Showing posts with label EAC. Show all posts
Showing posts with label EAC. Show all posts

Monday, September 17, 2012

UK MET Office keeps downplaying significance of events in the Arctic

One of the most respected datasets on Arctic sea ice volume is produced by the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS, Zhang and Rothrock, 2003) developed at the Polar Science Center, Applied Physics Laboratory, University of Washington. The graph below shows PIOMAS data for annual minimum Arctic sea ice volume (black dots) with an exponential trend added (in red).

The Arctic Methane Emergency Group (AMEG), in a February 12, 2012, written submission to the U.K.  Environmental Audit Committee (EAC), pointed at the graph:
 . . summer volume [is] less than 30% of its value 20 years ago. The trend in volume is such that if one extrapolates the observed rate forward in time, by following an exponential trend line, one obtains a September near-disappearance of the ice by 2015.

The MET Office, in a March 8, 2012, written submission:
Climate models project the Arctic will become ice-free during summer at some point this century – though likely not before 2040. . . In September 2007, sea ice extent reached an all-time low, raising the question of whether the sea ice is likely to melt more quickly than has been projected. There is, however, no evidence to support claims that this represents an exponential acceleration in the decline. Indeed, modelling evidence suggests that Arctic sea ice loss would be broadly reversible if the underlying warming were reversed.

Professor Slingo, Chief Scientist, MET Office, elaborated on this in a March 14, 2012, oral submission:
Q114 Chair: . . when the Arctic will be ice free in summer. . .
Professor Slingo: . . Our own model would say between 2040 and 2060 . .

Q115 Chair: You would rule out an icefree summer by as early as 2015, for example?
Professor Slingo: Yes we would . . .

Q117 Chair: . . In terms of the modelling that you are using, does that cover . . . volume of ice?
Professor Slingo: We run quite a sophisticated sea ice model. . . and we are looking forward now to the new measurements from CryoSat-2.

Q118 Chair: . . evidence that we had suggested that the volume of ice had already declined by 75%, and that further decreases may cause an immediate collapse of ice cover.
Professor Slingo: I wouldn’t [give credence to that]. We don’t know what the thickness of ice is across the whole Arctic with any confidence. . . I probably would [rule it out altogether] . . . to say we have lost 75% of the volume is inconsistent with our assessments.

Professor Laxon, director of Centre for Polar Observation and Modelling, where CryoSat-2 data is being analysed, in an August 24, 2012, written submission:
. . [analysis of] CryoSat-2 and ICESat data . . suggest a decrease in ice volume over the period 2003–12 at least as large as that simulated by PIOMAS, and possibly higher.

The Met Office, in an August 31, 2012, supplementary written submission:
The changes in observed sea-ice volume only extends [sic] over a few years and cannot in isolation be interpreted as representative of a long term trend. . . . The extrapolation of short-term trends in ice volume is not a reliable way to predict when the Arctic will be seasonally ice free as negative feedbacks and changing weather patterns may slow the rate of ice loss. . . it is worth noting that climate models can show a period of recovery in ice volume following periods of large ice volume loss.

For some curious reason, some people seek to downplay the significance of the events taking place in the Arctic, as well as the risk of methane releases. Here's more on that.

AMEG added, in its above February 12, 2012 written submission:
The catastrophic risk of global warming leading to very large emissions of methane from large Arctic carbon pools, especially from subsea methane hydrate, is documented in the 2007 IPCC assessment.

By collaborating with others to protect the Arctic, a climate of cooperation can be engendered to protect the whole planet for the benefit of ourselves and future generations.

Professor Lenton, in a Feb 21, 2012, oral submission:
. . the Hadley Centre [has] permafrost in the latest state-of-the-art model . . . their best estimate is we may get 0.1°C of extra warming at the end of the century from the loss of methane from the northern high latitudes.

Professor Slingo, in the above March 14, 2012, oral submission:
Q126 Dr Whitehead:. . what sort of modelling factors may be accounted for by the possibility of tipping points or feedback attached to these? For example, the argument that follows very substantially from the extent of continental shelf that there is within the Arctic Basin and, therefore, the particular relationship that warming on that relatively shallow sea has on trapped methane-for example, the emergence of methane plumes in that continental shelf, apparently in quite an anomalous way-leading possibly to the idea that there may be either tipping points there or catastrophic feedback mechanisms there, which could then have other effects on things, such as more stabilised caps like the Greenland ice cap and so on. I rapidly collated all the possible catastrophe theories, but I mean how are those factored into the modelling process?

Professor Slingo: . . we are not looking at catastrophic releases of methane. . . We don’t see catastrophic change in the Arctic that would lead to catastrophic releases of methane, or very large changes in the thermohaline circulation, within the next century. Our understanding of the various feedbacks-and it is a very complex system-both through observations and modelling, suggests that we won’t see those catastrophic changes, in terms of the physical system.

Note that the above are excerpts, to make things easier to read. For the full text, click on the respective links.

Below an update of the image, produced earlier this month, with recent volume data for 2012 added. On September 2, 2012, PIOMAS recorded a volume of 3407 cubic km of ice, i.e. very close to what the exponential line projected. The volume is likely to continue to fall further before reaching its final 2012 minimum.
The image below shows Arctic sea ice extent (total area of at least 15% ice concentration) for the last 7 years, compared to the average 1972-2011, as calculated by the Polar View team at the University of Bremen, Germany.

Thursday, July 5, 2012

Supplementary evidence to the EAC from John Nissen on behalf of AMEG

Supplementary evidence to the Environmental Audit Committee (EAC) from John Nissen on behalf of AMEG

The Growing Crisis in the Arctic

I am writing on behalf of AMEG, the Arctic Methane Emergency Group, in regard to conflicting evidence you have received during your inquiry “Protecting the Arctic”.

The inquiry is both a highly commendable reaction to, and a highly authoritative confirmation of, the fact that for the last few decades the Arctic environment is being changed at a rate unprecedented in human history. The world’s scientific establishment is unequivocal that these changes to the Arctic environment, particularly the retreating sea ice, were initiated as a consequence of global greenhouse gas emissions arising from human activities. But, as the sea ice retreats, the open water absorbs more sunshine, warming the water and melting more ice in a vicious cycle known as “positive feedback”. Thus global warming from greenhouse gases is amplified in a process known as “Arctic amplification”. There is good evidence to suggest that the Arctic is currently warming several times faster than the average over the whole planet, see Appendix.

In the course of the EAC’s ongoing inquiry it has focused on the issue of the retreating sea ice because it is this feature of the changing environment that has attracted the interests of the oil, shipping and fishing industries and is also the critical disruptive element in the Arctic environment. AMEG representatives, Professor Peter Wadhams and I, have pointed out extreme dangers associated with the retreat, warranting the designation of a planetary emergency – a crisis of unprecedented magnitude to threaten all mankind – a matter of national and international security.

The EAC invited many organisations to give their evidence on how the near future of the Arctic would play out. AMEG provided compelling evidence that not only was the rate of reduction of sea ice extent and depth much higher than is currently being predicted by models (such as used by the Hadley Centre) but that the consequential release of entrapped methane, an extremely powerful greenhouse gas, was also accelerating, risking catastrophic exacerbation of global warming in coming decades. However the chain reaction of Arctic warming and further methane release could be stifled if the Arctic were cooled quickly by measures including geoengineering.

In her evidence, Professor Julia Slingo of the Meteorological Office flatly contradicted the AMEG evidence, particularly the evidence of rapid sea ice retreat given by Professor Wadhams. Especially, Professor Slingo said she did not find the PIOMAS volume data credible, and she was expecting to see “better data” fitting the Hadley Centre models soon. We wish to point out that it is quite extraordinary that Professor Wadhams, an acknowledged expert on sea ice who has spent many years studying sea ice thickness, should have his evidence thus repudiated. However, the committee might bear in mind that the reputation of the Hadley Centre, part of the Met Office, is largely based on their modelling expertise; and their models are still predicting the sea ice demise many decades in the future. Thus Professor Slingo was in effect attempting to defend the Hadley Centre reputation.

What the committee may not know is that there was a whole assemblage of models used by the IPCC in 2007 for their AR4 report. Most of these models predicted the sea ice survival beyond the end of the century. None of the models showed the positive feedback from sea ice retreat that we refer to above. An excuse could be made that this feedback is difficult to quantify and to model, so was omitted on procedural grounds. However the resultant predictions bore no relation to reality. Even in the 1990s, the observations of sea ice extent were deviating from the most pessimistic of the models. Then in September 2007 the sea ice extent plummeted to a record low, about 40% below the level at start of satellite measurement. Nevertheless, IPCC, supported by models from the Hadley Centre, continued on the assumption that global warming predictions could be made for the whole century without taking into account possible sea ice disappearance and massive methane release. Even with the “wake-up call” of sea ice retreat in 2007, the Hadley Centre would not admit that their models were fundamentally flawed and they continue to ignore the evidence of sea ice volume, which is showing an exponential downward trend.

Note that in their written evidence to EAC, the Met Office says: “In September 2007, sea ice extent reached an all-time low, raising the question of whether the sea ice is likely to melt more quickly than has been projected. There is, however, no evidence to support claims that this represents an exponential acceleration in the decline.” They also assure the EAC to trust models giving 2040 as the earliest date for the Arctic to become ice-free during summer. However the PIOMAS volume data clearly shows acceleration in decline, a close fit to the exponential trend curve, and a likely date for an ice-free September around 2015. (Note that as the volume approaches zero, so must the extent, implying a collapse in extent before 2015.)

And they are even now ignoring the evidence of the growing methane emissions from the East Siberian Arctic Shelf (ESAS) where “vast plumes of methane bubbles, many over a kilometre across” have been reported arising from the seabed by the Russian scientists, Shakhova and Semiletov. In her oral evidence, Professor Slingo shows apparent ignorance of the Arctic methane situation, which may have misled the committee. She ignores the vast area of ESAS (over 2 million square kilometres) and claims that only a small fraction of methane from hydrates reaches the surface. That may be true for methane from the shelf margins at several hundred meters depth; but the shelf itself is mostly less than 40 metres deep, so the methane has little time to be oxidised and most of it reaches the surface. Furthermore she suggests only a small rise in temperature at the seabed, but in ESAS temperature rises of up to 6 degrees have been recorded. Far from the stratification of the water, which Professor Slingo suggests, there has been a growing turbulence as the sea ice cover is removed, resulting in this seabed warming.

This denial of the true situation might mislead the committee into thinking that there is no significant amount of methane entering the atmosphere, let alone a growth. But methane detection stations show recent spikes in methane levels which can only be easily explained by seabed origin. Furthermore satellite measurements have shown a growing anomaly of excess methane over the Arctic Ocean, again suggesting a seabed origin. All this evidence was available to the Met Office but they chose to ignore it.

Thus the Met Office (and Hadley Centre within it) is party to a complete denial of what is actually happening in the Arctic with accelerated warming, precipitous decline in sea ice and ominous rise in methane emissions.

Margaret Thatcher, in her opening of the Hadley Centre, 25th May 1990 said: “Today, with the publication of the Report of the Inter-Governmental Panel on Climate Change, we have an authoritative early warning system… [This] Report confirms that greenhouse gases are increasing substantially as a result of Man's activities; that this will warm the Earth's surface, with serious consequences for us all, and that these consequences are capable of prediction. We want to predict them more accurately and that is why we are opening this Centre today.”

We wish to hold the Met Office and its chief scientist to account for putting out scientifically unfounded and incorrect information to delude the government and public that no possible Arctic planetary emergency exists.

The importance of the sea ice for the planet is not in dispute; it provides a reflective mirror to reflect solar energy back into space, thus cooling the planet. James Lovelock has made his own estimate that loss of sea ice would be equivalent to the warming of all the CO2 that has accumulated in the atmosphere as a result of mankind’s emissions over the past century. In any event, recent research has confirmed that retreat of sea ice to date is a major cause of Arctic amplification. Therefore, if the Arctic Ocean were to become free of sea ice for several months of the year, as possible by 2020 according to the PIOMAS data, there would necessarily be a spurt in Arctic warming. This would be serious in terms of mounting disruption of the Northern Hemisphere climate system (see below). But it would also lead to an inevitable increase in the rate of methane release, risking the onset of an unstoppable methane feedback, whereby the methane causes further Arctic warming and in turn further methane emission in a positive feedback loop. A warning of the danger to all humanity from such methane feedback has been made by top scientists, such as US Energy Secretary and Nobel Laureate, Steven Chu, and NASA climate scientist, Jim Hansen. The likelihood of runaway methane feedback as the sea ice disappears cannot be easily estimated from current evidence, but, even if small, it has to be considered seriously because of the extraordinary devastation were it to get going.

The current disruption of the Northern Hemisphere climate system, with an ever increasing incidence of severe heat waves on the one hand and severe flooding on the other, is likely due to the warming of the Arctic in relation to the tropics, thus reducing the temperature differential that has a stabilising effect on the jet stream and weather system patterns. There is evidence that the jet stream is now getting “stuck” such as to cause the unusual and unpredictable weather which is of considerable concern to farmers. Allowing the Arctic to continue warming is thus a very real danger to food security – which is a strong argument for cooling the Arctic, regardless of other considerations.

The evidence given by Professor Tim Lenton suggesting that the global warming produced by Arctic methane would only amount to 0.1 degree or less, by the end of the century, can be dismissed if you accept that the sea ice cover will be removed as quickly as the PIOMAS data suggests. Even climatologist Professor David Archer of the University of Chicago, who recently claimed that AMEG concerns on methane were “much ado about nothing”, admits that a release of only one fifth of the 50 Gt of methane, which researchers Shakhova and Semiletov say could be released “at any time”, would take global warming over the 2°C limit established by IPCC as “dangerous anthropogenic interference” with the climate system.

But Professors Slingo and Lenton are not alone in their misleading analysis of the situation. We are appalled that there appears to be no recognition within any part of the scientific establishment, whether Government Departments, Research Councils, Institutes or Universities, of the imminence of extremely dangerous developments that would flow from allowing the present incipient runaway situation to develop in the Arctic. This amounts to a collective denial of danger – a collective burial of heads in the sand.

Similarly there appears to be little or no willingness to consider possible actions that could be taken immediately and within the next few years, as necessary in view of the rapidity with which the position in the Arctic is deteriorating.

So, what is to be done? Clearly a major effort has to be made immediately to cool the Arctic otherwise the whole of humanity is put at risk. Even if you, as a committee, concluded that the danger is overstated by AMEG, we would argue that the effort is worthwhile as an insurance policy. Suppose that this effort is made and proves to have been unnecessary, what has been lost? The technology for cooling the Arctic will have been developed for use at a later date or for a different circumstance.

Contrast the anti-precautionary approach espoused by Professor Slingo, Professor Lenton and the people from the modelling community who submitted evidence against geoengineering just before our hearing. They would prefer to see nothing done immediately to cool the Arctic on the grounds that there is uncertainty in the situation, and it is not yet proven whether (i) the Arctic sea ice is disappearing as rapidly as AMEG warns, and (ii) the methane threat is as great as AMEG warns. This is extraordinary for people who one would expect to espouse a precautionary principle in government, as surely they would in any other situation where there is a risk to millions of lives. Unless these people can prove that there is no risk arising from collapse of sea ice and escalation of methane emissions, which clearly they cannot, the committee has a responsibility to advise government that measures to cool the Arctic need to be taken on a precautionary principle.

Governments are expected to protect their own citizens on this principle, even if the danger is not proven. We would like to quote Article 3, paragraph 3, from the UNFCCC Convention, article 3, paragraph 3:
"3. The Parties should take precautionary measures to anticipate, prevent or minimize the causes of climate change and mitigate its adverse effects. Where there are threats of serious or irreversible damage, lack of full scientific certainty should not be used as a reason for postponing such measures, taking into account that policies and measures to deal with climate change should be cost-effective so as to ensure global benefits at the lowest possible cost. To achieve this, such policies and measures should take into account different socio-economic contexts, be comprehensive, cover all relevant sources, sinks and reservoirs of greenhouse gases and adaptation, and comprise all economic sectors. Efforts to address climate change may be carried out cooperatively by interested Parties." (Our underlining)
Note that AMEG considers that the cooling of the Arctic should be seen as one of many efforts to bring the atmosphere and oceans back towards their pre-industrial state, especially since such efforts reduce both immediate and longer-term risks arising from Arctic warming, sea ice retreat and methane release. AMEG is fully supportive of these efforts.

Why do these intelligent people from the modelling community seem to view all geoengineering as intrinsically dangerous? That may be the view in the media and among many environmentalists, but these scientists should be capable of a more rational assessment of each technique on its merits, on the limited scale as required for cooling the Arctic.

The candidate techniques AMEG proposes are all based on natural phenomena that can be observed. They can be switched off if and when any dangerous side-effects become apparent. There is nothing intrinsically dangerous about geoengineering – mankind has been doing it for millennia by altering the environment, albeit inadvertently.

Let’s look on the positive side. Cooling the Arctic and saving the sea ice has the obvious benefit of saving an entire ecosystem. Furthermore common sense suggests that geoengineering will tend to make things better because it is reversing the trends resulting from regional warming. One of the main effects of Arctic warming has been to cause disruption of regional weather patterns in the Northern Hemisphere, with more weather extremes and less long-term predictability of the weather. This has can only have had an adverse effect for farmers who rely on annual cycles like the monsoons. Thus cooling the Arctic should improve this situation. Yet Professor Slingo, in her oral evidence, states that, like the climate forcing from CO2 emissions, geoengineering will have "huge ramifications" implying that it is likely have serious side effects. Of course the very modelling that can be used to anticipate such side effects can also be used to avoid them, by adjusting the parameters of the techniques to be used (see note below). Thus modelling has an important part to play in the successful deployment of geoengineering.
Note: Each geoengineering technique has adjustable parameters, to allow the technique to be tailored to a particular situation. In the case of stratospheric aerosols, the height, latitude and time-of-year for the release of aerosol (or aerosol precursor) can be adjusted for maximum positive effect and minimum negative effect, using models to estimate these effects in advance. In the case of techniques to brighten or remove tropospheric clouds, more localised effects can be obtained; and parameters can be adjusted for different locations of deployment giving a great deal of flexibility as well as control.
Now we have no option other than to employ our best technology and expertise to get out of the crisis situation we have got ourselves into.

We respectfully suggest that modellers should turn their attention to modelling the effects of different geoengineering techniques, showing how unwanted side-effects can be minimised and working out how best to use various techniques in combination. This would be a useful contribution to the enormous challenge now faced to cool the Arctic. They must stop lulling the climate change community, and hence governments, into a false sense of security with their obsolete models which don't take account of reality.

In the light of the above we are writing to plead that you immediately alert the Prime Minister and his cabinet to the above conclusions: how the deteriorating situation in the Arctic has extremely threatening implications for all mankind if measures are not immediately adopted to cool the Arctic in order to reverse the current trends of retreating sea ice, escalating methane release and disruption of Northern Hemisphere climate. We realise that, under normal circumstance, we should wait for your report; but this is no ordinary situation. The sooner measures to cool the Arctic can be taken, the better. This is a daunting challenge, perhaps the biggest ever faced by humanity, but it can be met if there is a determined and concerted effort over the coming weeks and months by top scientists, engineers and yes modellers, tasked specifically to deal with the problems in the Arctic.

Only a directive from the highest levels of government is capable of initiating the programme of action required. The UN and all world governments must be alerted to the perilous situation now exposed.

Traditionally governments have tended to react to events rather than forestall them. But in this case we risk sliding irreversibly into ultimate climate catastrophe. We are close to a point of no return. Not to act as quickly as possible to halt the slide would be an abject failure of the most primary responsibilities of government. And, because such a catastrophe would threaten the life of every person on the planet, not to act would also be suicidal.

We implore the committee to give its full and serious attention to the challenge that this inquiry has thrown up, a challenge that whilst embracing the Arctic environment in its essence goes far beyond that in its enormously far-reaching implications for the rest of the planet. The committee has a unique opportunity to change the course of history.

John Nissen, Chair of AMEG
29th June, 2012

Appendix – “Life in 2032”

One of the questions raised at our hearing on 21st February concerned what life would be like in 20 years’ time, i.e. by 2032. We have considered this in respect of different scenarios, depending on methane emissions. We estimate that the Arctic is warming at about 1 degree per decade, around five times faster than the rest of the planet, and this is mainly because of sea ice retreat and more open water to absorb solar energy. In 10 years, i.e. by 2022, PIOMAS volume data suggests that the Arctic Ocean will be essentially free of ice for 6 months of the year, and the Arctic will then be warming at about 4 degrees per decade. The Arctic temperature will be 5 or 6 degrees hotter than today. The disruptive effect on Northern Hemisphere weather systems will be traumatic, leading to severe food shortages for all and starvation for millions if not billions of people.

If in addition there were an early release of the 50 Gt of methane that Shakhova and Semiletov say could be released from the East Siberian Arctic Shelf “at any time” (due to seabed warming and the instability of methane-holding structures), then we could expect over 3 degrees of global warming by 2032, liable to start runaway methane feedback. Not only would we be facing world-wide starvation but probably global conflict as well.

On the other hand if geoengineering and other measures were successful in cooling the Arctic sufficiently to bring back the sea ice to its pre-2007 volume and extent, then growth of methane emissions into the atmosphere would almost certainly be curtailed and the dreaded methane feedback avoided. The weather systems in the Northern Hemisphere weather systems would be stabilised, allowing the world farming community to plan for providing a growing world population with food. The spread of insect-born disease would be slowed. Conflicts arising from degraded environments would be reduced. And we would have more time to solve the underlying problems to ultimately remove the requirement to use geoengineering technology.

Tolerability of life in 2032 will thus depend on whether governments act quickly in response to today’s rapidly deteriorating situation by taking measures to cool the Arctic.

Editor's note: Above is a copy of the 31st submission to the Protecting the Arctic inquiry of the U.K. Environmental Audit Committee.  Submissions to date are listed below, with links to videos and submissions highlighted in yellow that are particularly relevant to points brought up by the Arctic Methane Emergency Group (AMEG)

Sunday, April 29, 2012

Supplementary evidence by Prof. Peter Wadhams

Supplementary written evidence 
submitted by Professor Peter Wadhams 
to the Environmental Audit Committee (EAC)
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:
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; ).
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
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).
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.
Maslowsky, W., J. Haynes, R. Osinski, W Shaw (2011). The importance of oceanic forcing on Arctic sea ice melting. European Geophysical Union congress paper XY556. See also Proceedings, State of the Arctic 2010, NSIDC.
Perovich, D.K., J.A. Richter-Menge, K.F. Jones, and B. Light (2008). Sunlight, water, ice: Extreme Arctic sea ice melt during the summer of 2007. Geophysical Research Letters 35: L11501. doi: 10.1029/2008GL034007 .
Rothrock, D.A., Y. Yu, and G.A. Maykut. (1999). Thinning of the Arctic sea-ice cover . Geophysical Research Letters 26: 3469–3472.
Rothrock, D.A., J. Zhang, and Y. Yu. (2003). The arctic ice thickness anomaly of the 1990s: A consistent view from observations and models. Journal of Geophysical Research 108: 3083. doi: 10.1029/2001JC001208 .
Shakhova, N. and I. Semiletov (2012). Methane release from the East-Siberian Arctic Shelf and its connection with permafrost and hydrate destabilization: First results and potential future development. Geophys. Res., Vol. 14, EGU2012-3877-1.
Wadhams, P. (1990). Evidence for thinning of the Arctic ice cover north of Greenland. Nature 345: 795–797.
Wadhams, P., and N.R. Davis. (2000). Further evidence of ice thinning in the Arctic Ocean. Geophysical Research Letters 27: 3973–3975.
Wadhams, P., and N.R. Davis (2001). Arctic sea-ice morphological characteristics in summer 1996. Annals of Glaciology 33: 165–170.
Wadhams, P., N Hughes and J Rodrigues (2011). Arctic sea ice thickness characteristics in winter 2004 and 2007 from submarine sonar transects. J. Geophys. Res., 116, C00E02.