You are currently browsing the monthly archive for March 2007.

RealClimate has a current piece on the IPCC sea level numbers, which includes amongst the many comments a range of responses relating to the ice sheets and sea ice levels:

Rabett Run has a piece on Prof. Hansen’s current work on the same subjects, including an extremely useful link to the (discussion version of the)  paper in press:

You’ll notice that there are links to both these important and useful blogs in the sidebar.

The main item under discussion, I suppose, is whether the IPCC estimates of 21st Century sea level rise are too conservative, giving a maximum without ice sheet variables, of 59cm. Apparently, Stephan Rahmsdorf has already produced a paper in which a simple linear projection forward from the most recent data produces a sea level rise of ~1M by 2100. Hansen cites several authors and recent papers, in which some evidence for dynamic changes in the sheets is apparent. In addition to these, there are three new papers in GRL worthy of note:

The 1979–2005 Greenland ice sheet melt extent from passive microwave data using an improved version of the melt retrieval XPGR algorithm

Analysis of passive microwave satellite observations over the Greenland ice sheet reveals a significant increase in surface melt over the period 1979–2005. Since 1979, the total melt area was found to have increased by +1.22 × 107 km2. An improved version of the cross-polarized gradient ratio (XPGR) technique is used to identify the melt from the brightness temperatures. The improvements in the melt retrieval XPGR algorithm as well as the surface melt acceleration are discussed with results from a coupled atmosphere-snow regional climate model. From 1979 to 2005, the ablation period has been increasing everywhere over the melt zone except in the regions where the model simulates an increased summer snowfall. Indeed, more snowfall in summer decreases the liquid water content of the snowpack, raises the albedo and therefore reduces the melt. Finally, the observed melt acceleration over the Greenland ice sheet is highly correlated with both Greenland and global warming suggesting a continuing surface melt increase in the future.

Rapid volume loss from two East Greenland outlet glaciers quantified using repeat stereo satellite imagery

The coastal portions of Kangerdlugssuaq and Helheim glaciers in southeast Greenland lost at least 51 ± 8 km3 yr−1 of ice between 2001–2006 due to thinning and retreat, according to an analysis of sequential digital elevation models (DEMs) derived from stereo ASTER satellite imagery. The dominant contribution to this ice loss was dynamic thinning caused by the acceleration in flow of both glaciers. Peak rates of change, including thinning rates of ∼90 m yr−1, coincided with the rapid increases in flow speed. Extrapolation of the measured data to the ice divides yields an estimated combined catchment volume loss of ∼122 ± 30 km3 yr−1, which accounts for half the total mass loss from the ice sheet reported in recent studies. These catchment-wide volume losses contributed ∼0.31 ± 0.07 mm yr−1 to global sea level rise over the 5-year observation period with the coastal regions alone contributing at least 0.1 ± 0.02 mm yr−1.

Effects of ice melting on GRACE observations of ocean mass trends

The Gravity Recovery and Climate Experiment (GRACE) was designed to measure variations in the Earth’s gravity field from space at monthly intervals. Researchers have used these data to measure changes in water mass over various regions, including the global oceans and continental ice sheets covering Greenland and Antarctica. However, GRACE data must be smoothed in these analyses and the effects of geocenter motions are not included. In this study, we examine what effect each of these has in the computation of ocean mass trends using a simulation of ice melting on Greenland, Antarctica, and mountain glaciers. We find that the recovered sea level change is systematically lower when coefficients are smoothed and geocenter terms are not included. Assuming current estimates of ice melting, the combined error can be as large as 30–50% of the simulated sea level rise. This is a significant portion of the long-term sea level change signal, and needs to be considered in any application of GRACE data to estimating long-term trends in sea level due to gain of water mass from melting ice.

 This is already a long post, so I won’t add much comment at the moment, except to say that there does appear to be a growing body of evidence supporting the idea that there are already processes at work in both Polar regions which should cause concern to policy makers, in particular because these have not been considered at all in the IPCC SPM.


It is not easy to discern the significant from the merely interesting in science journals, but papers often appear which are, to all intents and purposes, lost in the ether; they don’t see the light of day beyond the relatively narrow confines of their academic environment. Here are a few examples from recent journals. Links are to abstracts. Some of the journals, for example the ones published under the EGU/Copernicus system, are open access. Others may require a subscription or a chase through Google Scholar to find the authors and a copy of the main text.

The criteria for being offered here is that each may contain something which is illuminating to the ongoing discussions in climate science or policy. Their presence here is not to be read as support or endorsement, or as assumption of truth or accuracy. In all cases, attempts have been made to respect the copyright privileges of the publishers and authors.

The following examples all come from ‘Climates of the Past’.

  Clim. Past, 3, 77-87, 2007
© Author(s) 2007. This work is licensed
under a Creative Commons License.

Linking glacial and future climates through an ensemble of GCM simulations

J. C. Hargreaves1, A. Abe-Ouchi1,2, and J. D. Annan1
1FRCGC/JAMSTEC, Yokohama, Japan
2CCSR, Tokyo, Japan

The MIROC3.2 model shows an asymmetry in climate sensitivity calculated by decreasing rather than increasing the greenhouse gases, with 80% of the ensemble having a weaker cooling than warming. This asymmetry, if confirmed by other studies would mean that direct estimates of climate sensitivity from the LGM are likely to be underestimated by the order of half a degree. Our suspicion is, however, that this result may be highly model dependent. Analysis of the parameters varied in the model suggest the asymmetrical response may be linked to the ice in the clouds, which is therefore indicated as an important area for future research.

Summer temperature trend over the past two millennia using air content in Himalayan ice

S. Hou1,2,3, J. Chappellaz1, J. Jouzel2, P. C. Chu4, V. Masson-Delmotte2, D. Qin3, D. Raynaud1, P. A. Mayewski5, V. Y. Lipenkov6, and S. Kang3

Abstract. Two Himalayan ice cores display a factor-two decreasing trend of air content over the past two millennia, in contrast to the relatively stable values in Greenland and Antarctica ice cores over the same period. Because the air content can be related with the relative frequency and intensity of melt phenomena, its variations along the Himalayan ice cores provide an indication of summer temperature trend. Our reconstruction point toward an unprecedented warming trend in the 20th century but does not depict the usual trends associated with “Medieval Warm Period” (MWP), or “Little Ice Age” (LIA).
  The DO-climate events are probably noise induced: statistical investigation of the claimed 1470 years cycle

P. D. Ditlevsen, K. K. Andersen, and A. Svensson
The Niels Bohr Institute, Department of Geophysics, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen O, Denmark

Abstract. The significance of the apparent 1470 years cycle in the recurrence of the Dansgaard-Oeschger (DO) events, observed in the Greenland ice cores, is debated. Here we present statistical significance tests of this periodicity. The detection of a periodicity relies strongly on the accuracy of the dating of the DO events. Here we use both the new NGRIP GICC05 time scale based on multi-parameter annual layer counting and the GISP2 time scale where the periodicity is most pronounced. For the NGRIP dating the recurrence times are indistinguishable from a random occurrence. This is also the case for the GISP2 dating, except in the case where the DO9 event is omitted from the record.

  Quasi-100 ky glacial-interglacial cycles triggered by subglacial burial carbon release

N. Zeng
1Department of Atmospheric and Oceanic Science, University of Maryland, College Park, MD 20742-2425, USA
2The Department of Geology and the Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD 20742-2425, USA

Abstract. A mechanism is proposed in which climate, carbon cycle and icesheets interact with each other to produce a feedback that can lead to quasi-100 ky glacial-interglacial cycles. A central process is the burial and preservation of organic carbon by icesheets which contributes to the observed glacial-interglacial CO2 change (the glacial burial hypothesis, Zeng, 2003). Allowing carbon cycle to interact with physical climate, here I further hypothesize that deglaciation can be triggered by the ejection of glacial burial carbon when a major icesheet grows to sufficiently large size after a prolonged glaciation so that subglacial transport becomes significant. Glacial inception may be initiated by CO2 drawdown due to a relaxation from a high but transient interglacial CO2 value as the land-originated CO2 invades into deep ocean via thermohaline circulation and CaCO3 compensation. Also important for glacial inception may be the CO2 uptake by vegetation and soil regrowth in the previously ice-covered regions. When tested in a fully coupled Earth system model with comprehensive carbon cycle components and semi-empirical physical climate components, it produced under certain parameter regimes self-sustaining glacial-interglacial cycles with durations of 93 ky, CO2 changes of 90 ppmv, temperature changes of 6°C. Since the 100 ky cycles can not be easily explained by the Milankovitch astronomical forcing alone, this carbon-climate-icesheet mechanism provides a strong feedback that could interact with external forcings to produce the major observed Quaternary climatic variations. It is speculated that some glacial terminations may be triggered by this internal feedback while others by orbital forcing. Some observable consequences are highlighted that may support or falsify the theory.

One of the central issues of concern in debates about climate science and policy should now be about how to manage the interfaces between science and policy, science and the public, and policy and the public. These interfaces are, of course, the various acts of communication in which people engage. As well as the problem of wilful misunderstanding and misrepresentation, there is also the problem of reaching a clear understanding of what is going on and what might yet happen, what can or cannot be done about it, who can or should act to deal with possible futures.

Beyond the language problem, there are other issues which will need to be dealt with at some time, such as the relationship between risk and responsibility. In the meantime, what needs to be understood (in the climate science community, above all), is that  by and large, important messages are not getting through to the public. Arguably, they are also not getting through to policy makers, either, but this is at least disputable, inasmuch as the responses of policy makers is not necessarily  obvious, due to alternative agendas and unseen pressures.

What is the basis for making the claim that the public is not ‘getting the right message’? In a recent survey on the forum, only about 50% of respondents ‘believed’ that AGW is ‘real’. 30% were unsure, but accepted the possibility of its reality; 20% simply did not ‘believe’ at all. (The use of the term ‘believe’ was embedded in the survey, so is reproduced here for accuracy; it isn’t a useful term to use, under the circumstances). As the forum is peopled by a broad social cross-section, with a small international element, it could be argued to be a reasonable representation of the more general perception of AGW.

There are many reasons why messages about climate change and AGW might not be effectively communicated to the public, amongst which the role of the media cannot be underestimated. But the media are not entirely to blame; at least a part (I would say a substantial part) of the problem lies in the relationship between the public and science, in the differences in the way science and the non-scientific are expressed, and in the language registers that are used in different spheres of human action.

Possibly the single most important message for scientists, though, is that the public does not understand you. And because it doesn’t understand, it struggles to trust you. When you add the common psychological reaction to bad news to the mix, it becomes easy to see why there is a communication gap. Once the mistrust is in place – a phenomenon which can have many sources – it is extremely hard to remove. But it is not easy to know how to deal with this problem; the effective communication of the scientific details of climate change and AGW to people, such that they are armed with an understanding which empowers them to make decisions and judgements based on sound reasoning and accurate information.

There is a great deal more to consider in the question of the language problem in climate change discussions, but for now, my suggestion is that science needs to seriously consider employing someone to do the communicating – a specialist in communication, who understands the science and the issues, but can also service the needs of the public audience. Such advocates do exist, but they are not often well-known; those who are tend to be scientists or politicians in the first place; Hansen, Gore, Pielke or Michaels come to mind.

Efforts are being made to bridge the gap between public understanding and scientific concerns about the consequences of AGW; the NERC, in the UK, have been running such a programme. There are a range of  websites and blogs, some of which have links on this page, which do an admirable job insofar as they can (though in most cases they are dealing with those with an active engagement in the subject, rather than a ‘passing interest’). For the moment, though, the climate science community needs to face up to a challenge nearly as great as the ones within its various disciplines; how to get the message across to the ‘general public’.

Be loved.

By Levinas’ definition, it appears that being can be good – or, good-beyond-being, that predisposition towards absolute acceptance which permits the facing of the other to be without appropriation. But it also seems that the will to action, intentionality, is fraught with difficulty. As soon as we choose to impose ourselves upon the world through willed action (I also imagine willed inaction would count, too) we place ourselves in a position of power in relation to others. We also place ourselves in a context for them, from which, whether we wish it or not, most people will appropriate a meaning for us of our being. In particular, they will create the sense of a power dynamic between us.

One imagines it would be possible to defuse the power dynamic in the face-to-face, but even if so, it still becomes a hurdle to overcome, given that, for the other, to face us with absolute acceptance is not presumed. In the lived experience of the day-to-day, it would be surprising to meet many people for the good-beyond-being is a natural state, therefore we must expect to be treated as a threat, a challenge to identity, a power relationship, whether or not this is our own predisposition.

If this is the case, then what we choose to do – our occupation or ‘defining’ activity –  makes a difference.  It is presumed that there exists a desire to  open to others the possibility of the good-beyond-being, but to do this, one would have to be in a position where this possibility exists. For most others, then, what we do is important as means to understand the first facing. After this, if the openness of the self to the meaning of the other persists and is authentic, the possibility of dialogue which is truthful and just becomes possible. But in most cases, the first facing is a precursor to saying, rather than the opportunity for the saying itself.

Whilst in principle we can wish to be open to the possibility of true being with all others, in effect, by consequence of our physical limitations, we can only ever be for a limited number of others. (Though, arguably, creativity in writing or art may transcend this limitation to some degree, whilst not replacing the original facing). So where does the choice enter the picture? Who chooses the others for whom we have the possibility of meaning and for whom through us the possibility of meaningfulness becomes real? To some extent, this will be defined by the world/society in which are are thrown – the state. To some extent it will be a function of the shared languages with which saying becomes possible. There is also, always, the family, for whom saying and being starts and within which its first definition comes to pass.

But, importantly, it is we who, by our choices of action, define the wider ‘family’ within which the good-beyond-being has potential. What we become, where we fit in the wider dynamic of the social state, (whether by choice or accident), determines for us the people with whom our lives are lived. Therefore, the ultimate responsibility for opening the possibility of the saying of the other and the self is ours. What we do, whether or not the intentionality is constricting or defining, is the context in which the possibility of being and of authentic meaning exists. Therefore, it has power.

Be loved.

I’m definitely not a ‘catastrophist’ in the sense that it is normally understood. One problem lies with defining what counts as ‘dangerous’ climate change – a problem brought in the Hadley report (COP10?) a couple of years ago. The media want ‘dangerous’ to mean the same as ‘disastrous’, or ‘catastrophic, e.g., causing a big, picturesque and pitiable human disaster on a grand scale, like the 2004 tsunami. Politicians seem to want to play on our common misunderstanding of the idea of ‘dangerous’ to play on our fears, thus justifying the changes they are bringing in now. But for climate scientists, ‘dangerous’ can mean something different to either of these.

With the state of our understanding of climate as it is, with some things well understood but others still not well-modelled, not well explained, and responding to unknown causal agencies, there is a genuine concern that, at some given point in the future (which ‘point’ could be a decade or two long), the climate will have been committed to warming by the increase of CO2, to such an extent that the feedback effects become both increasingly unclear and increasingly risky, as well as being unstoppable. This is why there is research in the ice sheets, the arctic, the ocean circulation and heat content, etc.

First, it is clear that these areas need to be better understood and better modelled in the climate simulations under certain forcings, so as to reduce the uncertainty involved. Second, it is clear that, if the assumption that CO2 is the dominant forcing at the moment is correct, the longer it takes to actively reduce the increases in emissions, the more likely it is that we wiil reach a point beyond which the climate is ‘committed’ to some more permanent changes, for example, increased drought in some regions, the loss of the Amazon rain forest, the loss of Summer Arctic sea ice cover, the unstoppable decline of the Greenland Ice Sheet, a collapse of the WAIS…

As to whether such changes, most of which are likely to have impacts decades or further away, are ‘dangerous’; that depends on what counts as ‘danger’. If you live in a marginal society in subsistence conditions, any change which reduces the already perilous state of agriculture and water supply is likely to be rapid and fatal. If you live in marginal coastal areas where flood risk already exists, that risk increases persistently, until a point is reached when it is no longer sensible to preserve the hard-won property you own. If you live in the UK, ‘danger’ is more like to come from secondary effects rather than primary ones, for example, economic recession or hyper-inflation.

The assumption also exists that, where resources and climate are unstable, so political and lawful structures become vulnerable; the greater the hardship, the greater the change of destabilisation.

How do I see things panning out over the next decade? The USA will do nothing until Bush is replaced. Depending on the make-up of the two houses in Washington, it will take at least two years beyond that time before a policy becomes likely, and a further ten years beyond that for the effects of the policy to kick in (allowing businesses to adapt, where needed, to the changes). So, active US emissions reductions are unlikely before 2012 at the earliest, and meaningful reductions, probably not before 2018-20.

China will continue to expand its engergy producing capability, based on coal, for the next ten years, whilst paying lip-service to changes, and making some high-profile but ultimately ineffectual ‘compromises’ to its emissions. India will do likewise, but seems more likely to respond to the challenge of sustainable energy, for a variety of reasons.

Because the balance of world trade and power still resides in oil (and to a lesser extent, gas) production, distribution and consumption, and the power of the various leaders is more or less dependent on this, it seems likely that oil will continue to be extracted, processsed and used until it becomes no longer viable, which will be in 40 years at the least. Therefore, whilst some CO2 output may well be slowed, the amount of CO2 in the atmosphere by 2050 is very likely to equal or exceed 550ppm. How much it goes up beyond that in the following 50 years is harder to tell.

Biofuels will continue to be developed, but it is clear that, as they stand, they will never be able to replace fossil fuels; there isn’t anough land available in the world to grow enough biofuel crops and enough food for 6-9 billion people. For biofuels to become a viable major energy source, there will need to be a breakthrough in this field. Of course, the assumption that biofuels are necessary at all is based on the idea that, in the absence of fossil fuels, we will need something like fossil fuels to replace them (an assumption based on far to many other assumptions to be considered correct).

Nuclear power would seem to be a possible longer-term solution to energy needs, but as Iran shows, there is enough difficulty in working out who controls the worlds nuclear output to make this solution politically challenging. I suspect there may be some ground made in this area in the next decade, but there is still too much politicial self-interest involved in the process to be comfortable with the notion that this will be easy. Once you move away from a mutual dependence on oil-trade to autonomy based on nuclear capability, the entire balance of power between states changes. This is not a comfortable state of affairs for those who currently hold that balance of power.

There is a good chance that there will be a breakthrough in hydrogen-based vehicle fuel technology. Whilst this will reduce demand, eventually, for petrol, it will not prevent the burning of fossil fuels, as these resources will be diverted to other uses.

That’s probably enough of my opinion for the time being.


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