This is the Powerpoint file from my presentation at AGU Fall Meeting in 2009 on quantifying the impacts of landslides on society, which is scheduled for Friday morning.
Please feel free to download it and to make use of it in presentations etc, but please acknowledge me. If you do use it please reference the presentation / abstract as follows:
Petley, D.N., Rosser, N.J and Parker, R. 2009. Quantifying the impacts of landslides on society. Eos Trans. AGU, 90(52), Fall Meet. Suppl., Abstract NH52A-04.
Showing posts with label AGU. Show all posts
Showing posts with label AGU. Show all posts
Thursday, December 17, 2009
AGU Day 4: landslide sessions
There were two landslide sessions at AGU today, both in the afternoon. This was the part of the meeting about which I was most excited, but sadly to be honest the reality did not meet my expectations. I won't write about all of the talks here, just a selected few.
First up was Bruce Malamud, who talked about the statistics of landslide clusters. This is great work, showing the remarkable similarity between landslide distributions for different multi-landslide events from different areas with different triggers. Helpfully he sumarised the ket implications of this work:
• It provides thae basis for a multi-landslide magnitude scale (like the Richter scale for earthquakes;
• The average landslide area in a multi-landslide event appears to be about 3000 square metres;
• It is at least theoretically possible to determine a volume of sediment production based on a volume area relationship;
• If large landslides arfe preserved in the landscape it shoukd be possible to determine the number of landslides that have been “lost” from erosion (turned out to be >99% in both Japan and Italy)
Interestingly, rockfalls have a very different statistical distribution - I wonder why.
Next up was Colin Stark, who tried to explain aspects of this distribution, and in particular the so-called "roll-over" component (basically there are fewer small slides than one would expect) but building a model of rupture propagation. This was interesting for two reasons. First, the model makes some assumptions about failure that cause concern (but this may have been misunderstanding; second, he came over as being exceptionally unsure of his own model, which was a little odd. The model appears to me to make some predictions that are very testable indeed - so this should evolve quickly.
Larsen, Montgomery and Korup gave a really interesting paper on the role of materials in controlling volume –area scaling for landslides. They challenged recent papers that have suggested that this scaling is independent of material, showing that in fact the scaling is very different from soil than for rock.
The final paper that I want to mention here was by Goren on the absolutely amazing Heart Mountain landslide. This will be the subject of a future post - but basically she was talked about the mechanics of this landslide - surely the largest terrestrial failure of all time! Wow!
First up was Bruce Malamud, who talked about the statistics of landslide clusters. This is great work, showing the remarkable similarity between landslide distributions for different multi-landslide events from different areas with different triggers. Helpfully he sumarised the ket implications of this work:
• It provides thae basis for a multi-landslide magnitude scale (like the Richter scale for earthquakes;
• The average landslide area in a multi-landslide event appears to be about 3000 square metres;
• It is at least theoretically possible to determine a volume of sediment production based on a volume area relationship;
• If large landslides arfe preserved in the landscape it shoukd be possible to determine the number of landslides that have been “lost” from erosion (turned out to be >99% in both Japan and Italy)
Interestingly, rockfalls have a very different statistical distribution - I wonder why.
Next up was Colin Stark, who tried to explain aspects of this distribution, and in particular the so-called "roll-over" component (basically there are fewer small slides than one would expect) but building a model of rupture propagation. This was interesting for two reasons. First, the model makes some assumptions about failure that cause concern (but this may have been misunderstanding; second, he came over as being exceptionally unsure of his own model, which was a little odd. The model appears to me to make some predictions that are very testable indeed - so this should evolve quickly.
Larsen, Montgomery and Korup gave a really interesting paper on the role of materials in controlling volume –area scaling for landslides. They challenged recent papers that have suggested that this scaling is independent of material, showing that in fact the scaling is very different from soil than for rock.
The final paper that I want to mention here was by Goren on the absolutely amazing Heart Mountain landslide. This will be the subject of a future post - but basically she was talked about the mechanics of this landslide - surely the largest terrestrial failure of all time! Wow!
AGU Day 4 - session on Scientists' Communication on Critical Global Environmental Issues
I am going to split my AGU Day 4 report into two posts. This one will cover the session this morning on the communication of the science of environmental change, whilst the second post will cover the landslide sessions.
The first session that I attended this morning was an excellent, experience-led examination of how to communicate environmental science to the public and to policy-makers. The central theme was, perhaps inevitably, aspects of climate change and its associated impacts, with a great array of speakers giving different perspectives on their experiences.
First up was the man the denialists love to hate (well, perhaps second to Al Gore and on a par with James Hanson), Michael Mann. His theme was on communicating temperature change, and he started with a quip that he has spent a fair amount of time on that theme of late, which raised something of a belly laugh from the audience. His central theme was that the science case is now clear (he noted that AGW is not controversial scientifically, only societally), and the case is not hard to make to an educated and rational audience. So why is there a problem? Well, the issue is that it is clear that there is a group that wish to do no more than sew doubt in the minds of the public, and so repeatedly stir up ill-founded controversies about climate change. He referred to the ongoing hockey stick discussion - noting that as a poster-child of the debate it was inevitable that it would be attacked - but also noting that the case for anthropogenic warming does not rely on this dataset in any way, even though it continues to withstand attacks by its detractors.
So what can we do? Mann argued that all scientists need to get out there to make the case. Basically with a few exceptions the mainstream media has proven incapable of understanding the science, or at least of presenting the argument in a rational way. It is essentially up to the science community to sort this out - something of a rallying call to us all. I hope that the science community will step up to the plate.
Second up was Richard Alley, talking about ice sheets and sea level. As with his Bjerknes lecture there was a sense of extraordinary enthusiasm for his science. It was sad to see that once again he put a disclaimer on the front of his talk, noting that he was not presenting the views of Penn State (it is deeply troubling that senior academics are driven to have to do that). He started by showing a map of the effects of a sea level rise of 6 m on the eastern seaboard of the USA to show why sea level rise matters.
Alley argued that scientists have the best job description going (essentially to find out about things), but that arguing is part of the job – we are required to continually challenge, chase and discuss. Although absolutely correct, this does not play well with policy makers or the public, who don't like to feel that there is uncertainty about science.
He then went on to look at the IPCC predictions from 2001 on CO2, warming and sea level rise. He noted that they were pretty good for the first two, but sea level was too uncertain to be able to predict. In 2007 a better prediction was made, with caveats for the unknown components, but the reality is that sea level is rising faster than expected. He then went on to talk about how melt on the large ice caps can lead to increased rates of collapse either from the loss of buttressing around the margins or from the movement of melt water from the surface to the base. The upshot was that he suggested that a sea level rise of a metre or so by 2100 is not unreasonable from a science perspective, but much higher rates look unlikely unless there is an unknown gorilla in the room.
Whilst he didn't spend a huge amount of time on issues of communication directly, the talk was an excellent summary – essentially a masterclass in how to communicate the science.
Third up was a talk by Serreze on Communicating Arctic Change - essentially focusing on sea ice loss. Again, the key observation was that the ice loss trend was more rapid than the scientific models had forecast. He then spent some time thinking through the key aspects of science communication, which included:
Next up was a great talk on changes in hurricane intensity by Elsner. He noted that his recent paper on the increasing strength of the most intense tropical cyclones had caused a storm (I bet he has never used that joke before...). He showed strong evidence to demonstrate that although the overall number of hurricanes had not really changed, the strength of the most intense ones had increased, especially in the N. Atlantic. He noted that arguments that this didn't matter as the most intense hurricanes occur out to sea do not stand up to scrutiny. However, he also noted that in the Caribbean it may well be that the number of hurricanes declines with warming, but that the strength of those that do occur increases.
From a science communication perspective he noted that they had put their data and their code on a website, providing open access to allow people to test their ideas. This has been very effective.
The penultimate talk was on the impacts of growing levels of hypoxia (oxygen deficits) in the ocean, given by Whitney. He noted that higher levels of nutrients from the land mass (mostly from fertilisers and human waste) is driving oxygen deficits in the oceans that are impacting their ecology. He noted in particular that there is a tendency to replace fish with jelly fish and that the squeeze that reduced oxygen levels are placing on the usable habitats is making species such as tuna and sailfish more susceptible to predation. Perhaps the most interesting part of the talk was the demonstration that warming in the seas off eastern N. Asia is affecting oxygen levels off the west coast of the USA, which is now seeing invasions of organisms that favour low oxygen conditions. He then went on to look at issues of communication with stakeholders, noting the need to:
I guess his key point was that policy makers need good scientists. There is only one thing worse than policies based on no science at all, and that is policy that is based on bad science. He noted that the fact is that we don’t communicate science well enough, or enough, or to the right audiences, or to the right audiences enough. He reminded the audience that the level of science education and awareness is low, which allows unnecessary controversies rage out of control. His final point was again that we all need to do our bit, and that we need better journalists!
In questions he made reference to the frustration of denialst blogs, and the need to respond to them, through reference to this cartoon - "someone is wrong on the internet":
Source of the cartoon: http://xkcd.com/386/
This raised quite a laugh.
Overall, it was a great session with good speakers and an audience was engaged and interested. The sense across the hall was of frustration that the strength of the science of environmental change, and the threat that this poses, just is not getting through. The lack of scientific controversy on all the key planks that underpin our understanding of anthropogenic climate change is a clear theme of the conference. We really do need to try to find ways to ensure that policy makers and the public at large understand this.
The first session that I attended this morning was an excellent, experience-led examination of how to communicate environmental science to the public and to policy-makers. The central theme was, perhaps inevitably, aspects of climate change and its associated impacts, with a great array of speakers giving different perspectives on their experiences.
First up was the man the denialists love to hate (well, perhaps second to Al Gore and on a par with James Hanson), Michael Mann. His theme was on communicating temperature change, and he started with a quip that he has spent a fair amount of time on that theme of late, which raised something of a belly laugh from the audience. His central theme was that the science case is now clear (he noted that AGW is not controversial scientifically, only societally), and the case is not hard to make to an educated and rational audience. So why is there a problem? Well, the issue is that it is clear that there is a group that wish to do no more than sew doubt in the minds of the public, and so repeatedly stir up ill-founded controversies about climate change. He referred to the ongoing hockey stick discussion - noting that as a poster-child of the debate it was inevitable that it would be attacked - but also noting that the case for anthropogenic warming does not rely on this dataset in any way, even though it continues to withstand attacks by its detractors.
So what can we do? Mann argued that all scientists need to get out there to make the case. Basically with a few exceptions the mainstream media has proven incapable of understanding the science, or at least of presenting the argument in a rational way. It is essentially up to the science community to sort this out - something of a rallying call to us all. I hope that the science community will step up to the plate.
Second up was Richard Alley, talking about ice sheets and sea level. As with his Bjerknes lecture there was a sense of extraordinary enthusiasm for his science. It was sad to see that once again he put a disclaimer on the front of his talk, noting that he was not presenting the views of Penn State (it is deeply troubling that senior academics are driven to have to do that). He started by showing a map of the effects of a sea level rise of 6 m on the eastern seaboard of the USA to show why sea level rise matters.
Alley argued that scientists have the best job description going (essentially to find out about things), but that arguing is part of the job – we are required to continually challenge, chase and discuss. Although absolutely correct, this does not play well with policy makers or the public, who don't like to feel that there is uncertainty about science.
He then went on to look at the IPCC predictions from 2001 on CO2, warming and sea level rise. He noted that they were pretty good for the first two, but sea level was too uncertain to be able to predict. In 2007 a better prediction was made, with caveats for the unknown components, but the reality is that sea level is rising faster than expected. He then went on to talk about how melt on the large ice caps can lead to increased rates of collapse either from the loss of buttressing around the margins or from the movement of melt water from the surface to the base. The upshot was that he suggested that a sea level rise of a metre or so by 2100 is not unreasonable from a science perspective, but much higher rates look unlikely unless there is an unknown gorilla in the room.
Whilst he didn't spend a huge amount of time on issues of communication directly, the talk was an excellent summary – essentially a masterclass in how to communicate the science.
Third up was a talk by Serreze on Communicating Arctic Change - essentially focusing on sea ice loss. Again, the key observation was that the ice loss trend was more rapid than the scientific models had forecast. He then spent some time thinking through the key aspects of science communication, which included:
- The use of analogy – for example he showed some great maps from Donald Perovich showing areas of seasonal ice loss as a proportion of the land mass of Europe or N. America
- The need to find themes that resonate for the community in question
- The need to be open and transparent, and to use opportunities to explain properly the scientific process
- The need to respond to misinformation and challenges quickly, but to do so in a thoughtful manner.
Next up was a great talk on changes in hurricane intensity by Elsner. He noted that his recent paper on the increasing strength of the most intense tropical cyclones had caused a storm (I bet he has never used that joke before...). He showed strong evidence to demonstrate that although the overall number of hurricanes had not really changed, the strength of the most intense ones had increased, especially in the N. Atlantic. He noted that arguments that this didn't matter as the most intense hurricanes occur out to sea do not stand up to scrutiny. However, he also noted that in the Caribbean it may well be that the number of hurricanes declines with warming, but that the strength of those that do occur increases.
From a science communication perspective he noted that they had put their data and their code on a website, providing open access to allow people to test their ideas. This has been very effective.
The penultimate talk was on the impacts of growing levels of hypoxia (oxygen deficits) in the ocean, given by Whitney. He noted that higher levels of nutrients from the land mass (mostly from fertilisers and human waste) is driving oxygen deficits in the oceans that are impacting their ecology. He noted in particular that there is a tendency to replace fish with jelly fish and that the squeeze that reduced oxygen levels are placing on the usable habitats is making species such as tuna and sailfish more susceptible to predation. Perhaps the most interesting part of the talk was the demonstration that warming in the seas off eastern N. Asia is affecting oxygen levels off the west coast of the USA, which is now seeing invasions of organisms that favour low oxygen conditions. He then went on to look at issues of communication with stakeholders, noting the need to:
- Identify issues to which the local community can relate;
- Make story understandable;
- Use case studies that the people can relate to;
- Separate scientific analysis from advice on policy;
- Prepare for resistance to the scientific message.
I guess his key point was that policy makers need good scientists. There is only one thing worse than policies based on no science at all, and that is policy that is based on bad science. He noted that the fact is that we don’t communicate science well enough, or enough, or to the right audiences, or to the right audiences enough. He reminded the audience that the level of science education and awareness is low, which allows unnecessary controversies rage out of control. His final point was again that we all need to do our bit, and that we need better journalists!
In questions he made reference to the frustration of denialst blogs, and the need to respond to them, through reference to this cartoon - "someone is wrong on the internet":
Source of the cartoon: http://xkcd.com/386/This raised quite a laugh.
Overall, it was a great session with good speakers and an audience was engaged and interested. The sense across the hall was of frustration that the strength of the science of environmental change, and the threat that this poses, just is not getting through. The lack of scientific controversy on all the key planks that underpin our understanding of anthropogenic climate change is a clear theme of the conference. We really do need to try to find ways to ensure that policy makers and the public at large understand this.
Wednesday, December 16, 2009
AGU Day 3
There were two highlights of day 3 for me, which to be honest did not have much of interest on landslides. The first was the Geobloggers lunch, which was attended by about 30 bloggers. It was interesting to put names to faces and also to learn about some new blogs. I was struck by two things: 1. the range of ages of bloggers - far less oriented towards the young than I had expected; and 2. the diversity of reasons for blogging. All were pretty sure that they got a lot out of it and were enthusiastic about the role that they play. I sense that organisations like AGU have a sense that blogs and bloggers need to be a part of their future, but don't know what that role would be. I am not sure that this session will have helped though!
The second was a session on coastal processes, mostly focused on erosion. In most cases erosion is a mass movement (landslides or rockfalls) process of course, so this was of direct relevance. I presented the work of my PhD student Emma Norman, and a post-doc in my team, Mike Lim, presented his work too. There was one other hard rock talk, a presentation from Limber and colleagues on the development of a model for coastal erosion, with an emphasis on how bays and headlands form. The headline message was interesting - that headlands can only be preserved if erosion is enhanced in bays by small pocket beaches, which provide sediment that increases the rate of abrasion on the cliffs. This is all very well, but the model appeared to over-simplify to the point of irrelevance. I sensed that the audience was pretty frustrated too, with a quite pointed question about the assumption that the geology is homogeneous.
After that attention turned to erosion in the Arctic. This session was started with a quite surreal presentation. Jesse Walker is one of the gods of Arctic geomorphology, so the convenors asked him to attend to give a presentation on this theme as background. Unfortunately he was unwell - I hope he recovers quickly - so one of the session chairs gave it on his behalf. A presentation of over 50 slides in 15 minutes by someone who did not put together the talk was not a great experience, although the presenter did the very best he could in the circumstances.
Afterwards there were four rather mixed presentations on the processes and rate of coastal erosion in Alaska. The underlying message is startling - erosion rates of 10-15 m per year are common at these latitudes. Given that most of the erosion occurs in a very short summer season, this gives retreat rates of 10 to 15 cm per day!!! One of the speakers, Cameron Wobus, presented some fabulous time-lapse photography over a full summer season to show this erosion. Just to give you an idea of how fast this erosion occurs, the image below is from his website, showing just a few years of retreat:
The real concern must be the response of this system to the rapid and massive changes in temperature and summer ice cover at these high latitudes. The eroding bluffs primarily consist of ice (dirty icebergs was one description of them). The warming is causing increases in erosion because:
1. The temperatures are warmer so the bluffs are thawing;
2. Under normal conditions at the start and end of the warm season the shore is protected by ice berms - basically marine ice that has blown onshore. These berms are smaller and are melting faster;
3. The loss of sea ice in the summer means that the waves have a larger fetch, so that they are larger and more powerful;
4. The melting season has become longer;
5. Sea level is rising;
6. The time period of ice free marine conditions each year is longer, so the sea erodes for more time;
7. The sea is warmer so can erode more quickly (much of the erosion is caused by the warm sea melting a notch in the bluff).
Overall the picture painted was alarming. As Tom Ravens said, most coastal erosion in the US is undertaken in the south where rates are generally small. The reality is that the serious problems are in the high latitudes, so there is a desperate need to reorient coastal research.
Tomorrow is the main landslide day. This appears to have a mass of stuff of interest. I can't wait. Tonight I have to work on a research grant proposal - what joy!
The second was a session on coastal processes, mostly focused on erosion. In most cases erosion is a mass movement (landslides or rockfalls) process of course, so this was of direct relevance. I presented the work of my PhD student Emma Norman, and a post-doc in my team, Mike Lim, presented his work too. There was one other hard rock talk, a presentation from Limber and colleagues on the development of a model for coastal erosion, with an emphasis on how bays and headlands form. The headline message was interesting - that headlands can only be preserved if erosion is enhanced in bays by small pocket beaches, which provide sediment that increases the rate of abrasion on the cliffs. This is all very well, but the model appeared to over-simplify to the point of irrelevance. I sensed that the audience was pretty frustrated too, with a quite pointed question about the assumption that the geology is homogeneous.
After that attention turned to erosion in the Arctic. This session was started with a quite surreal presentation. Jesse Walker is one of the gods of Arctic geomorphology, so the convenors asked him to attend to give a presentation on this theme as background. Unfortunately he was unwell - I hope he recovers quickly - so one of the session chairs gave it on his behalf. A presentation of over 50 slides in 15 minutes by someone who did not put together the talk was not a great experience, although the presenter did the very best he could in the circumstances.
Afterwards there were four rather mixed presentations on the processes and rate of coastal erosion in Alaska. The underlying message is startling - erosion rates of 10-15 m per year are common at these latitudes. Given that most of the erosion occurs in a very short summer season, this gives retreat rates of 10 to 15 cm per day!!! One of the speakers, Cameron Wobus, presented some fabulous time-lapse photography over a full summer season to show this erosion. Just to give you an idea of how fast this erosion occurs, the image below is from his website, showing just a few years of retreat:
The real concern must be the response of this system to the rapid and massive changes in temperature and summer ice cover at these high latitudes. The eroding bluffs primarily consist of ice (dirty icebergs was one description of them). The warming is causing increases in erosion because:1. The temperatures are warmer so the bluffs are thawing;
2. Under normal conditions at the start and end of the warm season the shore is protected by ice berms - basically marine ice that has blown onshore. These berms are smaller and are melting faster;
3. The loss of sea ice in the summer means that the waves have a larger fetch, so that they are larger and more powerful;
4. The melting season has become longer;
5. Sea level is rising;
6. The time period of ice free marine conditions each year is longer, so the sea erodes for more time;
7. The sea is warmer so can erode more quickly (much of the erosion is caused by the warm sea melting a notch in the bluff).
Overall the picture painted was alarming. As Tom Ravens said, most coastal erosion in the US is undertaken in the south where rates are generally small. The reality is that the serious problems are in the high latitudes, so there is a desperate need to reorient coastal research.
Tomorrow is the main landslide day. This appears to have a mass of stuff of interest. I can't wait. Tonight I have to work on a research grant proposal - what joy!
Tuesday, December 15, 2009
AGU Day 2
NB: I have posted a review of the session on Scientists' communication of critical global environmental change issues, in which both Michael Mann and Richard Alley spoke here:
Communication of critical global environmental change issues
There wasn't much in the Natural Hazards area of interest to me on Day 1, so I decided not to blog yesterday. There was a little more today - and lots later in the week - so here goes.
I spent the first part of the morning in the underground geoscience session, for which I gave the first (8 am) invited paper on our Boulby Geoscience project. The rest of the papers were pretty good, but beyond the scope of this blog. After coffee I went to a paper by Karnawati and her colleagues from Gadjah Mada University, the topic being the landslides triggered by the recent earthquake in West Sumatra. This was pretty interesting, although I was a little frustrated by the lack of detail. She noted that the area around Maninjau lake, to the north of the epicentre, was most seriously affected by landslides. The lake is the remains of a volcanic crater, so I guess the materials may well be pretty susceptible to failure, but she noted that the main landslides all lay close to faults or lineaments, which is an ingteresting observation in this setting (I wonder whether essentially everything is close to a lineament in such a dynamic setting?). There is now a serious threat from post-seismic re-activation of the slides - not a surprise - and the author gave some examples showing that this has already started to happen. The rainy season starts about now. Dr Karnawati noted that a key task is therefore identifying safe areas for relocation of affected villages - it appears that this is going well - and community engagement with disaster risk reduction.
I then moved sessions to a presentation on the Slumgullion landslide by Schulz from USGS (see my earlier post on this work here). The first part of this talk reiterated the extraordinary observation that the daily movement of the slide is correlated with atmospheric tides, as per their recent paper. In the second half Schulz noted that the processes and morphology of large landslides and faults are similar, but that it is much easier to study landslides. To gain a better understanding of movement processes (presumably relating to both systems) they had positioned an array of seismometers on the landslide for week in the summer. Although they had power problems early on (so often the case with seismometers in my experience), the later data showed that the seismic events also correlated with the movement events and thus the atmospheric tides. The initial analysis has focused on the harmonic events that they recorded - which are likely to be related to fluid flow. As these occurred during periods of low atmospheric pressure it may be that their hypothesis about atmospheric tides inducing pore water movements is on the right lines.
This was followed by an entertaining talk by Dick Iverson, also from the USGS, who sought to explain stick-slip movements on landslides. These movements - in which the slide appears to move and then stop repeatedly - are something of a conundrum. The problem is that stick-slip in faults is usually explained by the storage of energy in elastic deformation, but in a slope with no cohesion it is hard to do this. Iverson demonstrated mathematically that the behaviour is related to the relationship between pore pressure and movement - basically when the slide starts to move diffusion allows the pore pressure to drop, which slowly reduces movement. When the slide stops pore pressure builds again until movement restarts. I think that the idea that this is the key mechanism has been around for a while, but this was the first time I have seen it modelled properly.
After lunch I went to the Bjerknes Lecture - one of the big set pieces - which was given by Richard Alley from Penn State. He brought a geological perspective to the link between atmospheric carbon dioxide and temperature. He started the lecture by noting the ongoing harassment of climate scientists by the denialist camp - giving an example of a demand made to his university that he be fired for continuing to claim that carbon dioxide causes temperature change. He presented this with great humour and grace, but the underlying message about the way that scientists are being treated was clear, and was a great concern. At a time when the denialist scientist de jour, Iam Plimer, has been embarrassed in a debate with a journalist, and the high profile campaigner Christopher Monckton has been caught on video calling campaigners "The Hitler Youth", and then has brazenly denied it, the sense that the science community is under siege is clear.
Anyway, back to the lecture. Alley reviewed climate changes in the geological record, going back 4.5 billion years. His central point was that in almost every case carbon dioxide has emerged as the smoking gun in terms of causation, and indeed that it is essentially impossible to explain the observed changes without carbon dioxide acting as the key forcing. This is true for the "faint young sun paradox" (4.6 billion years ago), the snowball earth period, the late Permian extinction period, the mid-Cretaceous "Saurian sauna" period and the Palaeocene-Eocene thermal maximum for example.
Alley did note that although his own data shows that for the last 500,000 years carbon dioxide and temperature have moved in lockstep together, sometimes that CO2 lags behind temperature. He observed with great amusement that this has led some denialists to claim that CO2 is a thermometer not a cause of temperature change. Of course the glacial - interglacial cycle is driven by the cyclicity in the orbit, but Alley noted that the magnitude of the temperature changes can only be explained using a carbon dioxide feedback mechanism. He ridiculed the idea that because CO2 sometimes lags temperature it cannot be the cause of warming. He compared this to debt associated with credit cards, saying that if he went out and spent a modest amount on his card he would end up owing the credit card company money. If he didn't pay this off then punitive interest rates would mean that his debt rapidly spiralled out of control. In the end his bankruptcy would be the result of the debt increasing due to the interest rates. The application of the interest rates lagged behind the spend, but still caused the insolvency. He likened the orbital cycle to the initial spend but the carbon dioxide to the interest. So, clearly carbon dioxide can drive the temperature, even if it didn't act as the initiator of the process. Of course you need an explanation as to why this would be the case - but that explanation is simple as its is an application of straightforward radiative physics, as demonstrated two centuries ago.
Next he noted the huge progress that has been made in understanding the link between temperature and CO2 in recent years. He noted that when he was a young scientist there were several examples in the geological record in which there was global warmth but no apparent corresponding high CO2 level in the atmosphere. As sampling and measurements have improved it has been shown that almost all of these cases do in fact have high carbon dioxide concentrations. Just a few anomalies remain - most notably the warm period in the Miocene. However, very recent (peer reviewed) research is now showing that CO2 levels were high, although more work is needed.
Finally, he took a few minutes to show that arguments for other causal factors for global temperature change in the geological record just don't hold water, He used the example of cosmic ray flux, a favourite of the denialist blogosphere a year or two ago. He showed that the geological record globally demonstrated a huge spike in cosmic ray flux at 40,000 years BP, but that temperature did not respond at all.
He finished with a very simple message - the geological record shows that carbon dioxide is the key factor that controls temperature. Other factors do operate, but the CO2 signal consistently dominates. He noted that the geological record shows that over a timescale of few centuries timescale a doubling of CO2 results in a warming of about 2.8 C, which is consistent with the IPCC figure for climate sensitivity. He made a very bold statement that if the key factor that explains the temperature record in the geological record is CO2 - without carbon dioxide concentration changes it is impossible to explain the observed behaviour.
Overall it was a great lecture - highly entertaining, informative, challenging and coherent. The audience for the talk was huge, and greatly appreciative of the quality of the presentation.
The lecture should be available as a podcast in due course here:
http://www.agu.org/meetings/fm09/lectures/
Do take a look - you won't regret it (not least for the amusing first five minutes).
NB: I have posted a review of the session on Scientists' communication of critical global environmental change issues, in which both Michael Mann and Richard Alley spoke here:
Communication of critical global environmental change issues
Communication of critical global environmental change issues
There wasn't much in the Natural Hazards area of interest to me on Day 1, so I decided not to blog yesterday. There was a little more today - and lots later in the week - so here goes.
I spent the first part of the morning in the underground geoscience session, for which I gave the first (8 am) invited paper on our Boulby Geoscience project. The rest of the papers were pretty good, but beyond the scope of this blog. After coffee I went to a paper by Karnawati and her colleagues from Gadjah Mada University, the topic being the landslides triggered by the recent earthquake in West Sumatra. This was pretty interesting, although I was a little frustrated by the lack of detail. She noted that the area around Maninjau lake, to the north of the epicentre, was most seriously affected by landslides. The lake is the remains of a volcanic crater, so I guess the materials may well be pretty susceptible to failure, but she noted that the main landslides all lay close to faults or lineaments, which is an ingteresting observation in this setting (I wonder whether essentially everything is close to a lineament in such a dynamic setting?). There is now a serious threat from post-seismic re-activation of the slides - not a surprise - and the author gave some examples showing that this has already started to happen. The rainy season starts about now. Dr Karnawati noted that a key task is therefore identifying safe areas for relocation of affected villages - it appears that this is going well - and community engagement with disaster risk reduction.
I then moved sessions to a presentation on the Slumgullion landslide by Schulz from USGS (see my earlier post on this work here). The first part of this talk reiterated the extraordinary observation that the daily movement of the slide is correlated with atmospheric tides, as per their recent paper. In the second half Schulz noted that the processes and morphology of large landslides and faults are similar, but that it is much easier to study landslides. To gain a better understanding of movement processes (presumably relating to both systems) they had positioned an array of seismometers on the landslide for week in the summer. Although they had power problems early on (so often the case with seismometers in my experience), the later data showed that the seismic events also correlated with the movement events and thus the atmospheric tides. The initial analysis has focused on the harmonic events that they recorded - which are likely to be related to fluid flow. As these occurred during periods of low atmospheric pressure it may be that their hypothesis about atmospheric tides inducing pore water movements is on the right lines.
This was followed by an entertaining talk by Dick Iverson, also from the USGS, who sought to explain stick-slip movements on landslides. These movements - in which the slide appears to move and then stop repeatedly - are something of a conundrum. The problem is that stick-slip in faults is usually explained by the storage of energy in elastic deformation, but in a slope with no cohesion it is hard to do this. Iverson demonstrated mathematically that the behaviour is related to the relationship between pore pressure and movement - basically when the slide starts to move diffusion allows the pore pressure to drop, which slowly reduces movement. When the slide stops pore pressure builds again until movement restarts. I think that the idea that this is the key mechanism has been around for a while, but this was the first time I have seen it modelled properly.
After lunch I went to the Bjerknes Lecture - one of the big set pieces - which was given by Richard Alley from Penn State. He brought a geological perspective to the link between atmospheric carbon dioxide and temperature. He started the lecture by noting the ongoing harassment of climate scientists by the denialist camp - giving an example of a demand made to his university that he be fired for continuing to claim that carbon dioxide causes temperature change. He presented this with great humour and grace, but the underlying message about the way that scientists are being treated was clear, and was a great concern. At a time when the denialist scientist de jour, Iam Plimer, has been embarrassed in a debate with a journalist, and the high profile campaigner Christopher Monckton has been caught on video calling campaigners "The Hitler Youth", and then has brazenly denied it, the sense that the science community is under siege is clear.
Anyway, back to the lecture. Alley reviewed climate changes in the geological record, going back 4.5 billion years. His central point was that in almost every case carbon dioxide has emerged as the smoking gun in terms of causation, and indeed that it is essentially impossible to explain the observed changes without carbon dioxide acting as the key forcing. This is true for the "faint young sun paradox" (4.6 billion years ago), the snowball earth period, the late Permian extinction period, the mid-Cretaceous "Saurian sauna" period and the Palaeocene-Eocene thermal maximum for example.
Alley did note that although his own data shows that for the last 500,000 years carbon dioxide and temperature have moved in lockstep together, sometimes that CO2 lags behind temperature. He observed with great amusement that this has led some denialists to claim that CO2 is a thermometer not a cause of temperature change. Of course the glacial - interglacial cycle is driven by the cyclicity in the orbit, but Alley noted that the magnitude of the temperature changes can only be explained using a carbon dioxide feedback mechanism. He ridiculed the idea that because CO2 sometimes lags temperature it cannot be the cause of warming. He compared this to debt associated with credit cards, saying that if he went out and spent a modest amount on his card he would end up owing the credit card company money. If he didn't pay this off then punitive interest rates would mean that his debt rapidly spiralled out of control. In the end his bankruptcy would be the result of the debt increasing due to the interest rates. The application of the interest rates lagged behind the spend, but still caused the insolvency. He likened the orbital cycle to the initial spend but the carbon dioxide to the interest. So, clearly carbon dioxide can drive the temperature, even if it didn't act as the initiator of the process. Of course you need an explanation as to why this would be the case - but that explanation is simple as its is an application of straightforward radiative physics, as demonstrated two centuries ago.
Next he noted the huge progress that has been made in understanding the link between temperature and CO2 in recent years. He noted that when he was a young scientist there were several examples in the geological record in which there was global warmth but no apparent corresponding high CO2 level in the atmosphere. As sampling and measurements have improved it has been shown that almost all of these cases do in fact have high carbon dioxide concentrations. Just a few anomalies remain - most notably the warm period in the Miocene. However, very recent (peer reviewed) research is now showing that CO2 levels were high, although more work is needed.
Finally, he took a few minutes to show that arguments for other causal factors for global temperature change in the geological record just don't hold water, He used the example of cosmic ray flux, a favourite of the denialist blogosphere a year or two ago. He showed that the geological record globally demonstrated a huge spike in cosmic ray flux at 40,000 years BP, but that temperature did not respond at all.
He finished with a very simple message - the geological record shows that carbon dioxide is the key factor that controls temperature. Other factors do operate, but the CO2 signal consistently dominates. He noted that the geological record shows that over a timescale of few centuries timescale a doubling of CO2 results in a warming of about 2.8 C, which is consistent with the IPCC figure for climate sensitivity. He made a very bold statement that if the key factor that explains the temperature record in the geological record is CO2 - without carbon dioxide concentration changes it is impossible to explain the observed behaviour.
Overall it was a great lecture - highly entertaining, informative, challenging and coherent. The audience for the talk was huge, and greatly appreciative of the quality of the presentation.
The lecture should be available as a podcast in due course here:
http://www.agu.org/meetings/fm09/lectures/
Do take a look - you won't regret it (not least for the amusing first five minutes).
NB: I have posted a review of the session on Scientists' communication of critical global environmental change issues, in which both Michael Mann and Richard Alley spoke here:
Communication of critical global environmental change issues
Saturday, December 12, 2009
The annual cycle of fatal rainfall-induced landslides
On the flight to San Francisco yesterday I spent some time preparing for one of my AGU presentations - the one on Friday on the impact of landslides on society. I have been looking at my landslide fatality database, which now stretches back for over seven years. There is still some way to go with this to really understand long term trends in fatal landslides, but the dataset is now big enough to do some quite interesting things.
I have divided each year into five-day blocks (we often call one of these blocks a bin), and then taken the average number of recorded fatal landslides within that bin over the seven year period. So, bin number one is 1st to 5th January, the second is 6th to 10th, etc. I have then looked at the cycle through time by plotting a graph in which I have smoothed the data using a 25 day filter - this is a noisy dataset, so this is needed given the comparatively short window:
The resulting graph is pretty interesting I think. First, the peak in aggregate recorded fatal landslides (the black line) clearly occurs in the northern hemisphere summer, the minimum is around about now. The peak is actually on about 25th July. This is coincident with the peak of the SW Monsoon over the Indian subcontinent. Notice though that the graph is asymmetric - i.e. it rises to a peak more quickly (about 100 days) than it then declines (about 150 days). I assume that this is because in this post-SW monsoon peak the influence of the monsoon in East Asia and of tropical cyclone landfalls becomes significant.
The minimum period coincides I think with the onset of winter in the northern hemisphere (which is a dry period for many of the most landslide prone areas) but is before the rainy season really gets going in SE Asia. By early January the rains in for example Indonesia are really under way, and the occurrence of landslides increases.
The standard deviation is a measure of variability between years. So, if for a specific bin the number of fatal landslides was always three then the standard deviation would be low. If however one year there were none, the next six, the next ten and the next two then the standard deviation would be much higher. It is interesting that as the average number of fatal landslides increases in the N. Hemisphere summer so does the standard deviation - this is to be expected. However, in the post-peak period the standard deviation remains high for a while before declining. I think that this probably reflects the influence of tropical cyclones in this period, which tend to landfall rather sporadically but then to cause many landslides over a small area. Over the seven year period many of the bins in this period have been affected by a tropical cyclone.
I hope to see you at the session!
I have divided each year into five-day blocks (we often call one of these blocks a bin), and then taken the average number of recorded fatal landslides within that bin over the seven year period. So, bin number one is 1st to 5th January, the second is 6th to 10th, etc. I have then looked at the cycle through time by plotting a graph in which I have smoothed the data using a 25 day filter - this is a noisy dataset, so this is needed given the comparatively short window:
The resulting graph is pretty interesting I think. First, the peak in aggregate recorded fatal landslides (the black line) clearly occurs in the northern hemisphere summer, the minimum is around about now. The peak is actually on about 25th July. This is coincident with the peak of the SW Monsoon over the Indian subcontinent. Notice though that the graph is asymmetric - i.e. it rises to a peak more quickly (about 100 days) than it then declines (about 150 days). I assume that this is because in this post-SW monsoon peak the influence of the monsoon in East Asia and of tropical cyclone landfalls becomes significant.The minimum period coincides I think with the onset of winter in the northern hemisphere (which is a dry period for many of the most landslide prone areas) but is before the rainy season really gets going in SE Asia. By early January the rains in for example Indonesia are really under way, and the occurrence of landslides increases.
The standard deviation is a measure of variability between years. So, if for a specific bin the number of fatal landslides was always three then the standard deviation would be low. If however one year there were none, the next six, the next ten and the next two then the standard deviation would be much higher. It is interesting that as the average number of fatal landslides increases in the N. Hemisphere summer so does the standard deviation - this is to be expected. However, in the post-peak period the standard deviation remains high for a while before declining. I think that this probably reflects the influence of tropical cyclones in this period, which tend to landfall rather sporadically but then to cause many landslides over a small area. Over the seven year period many of the bins in this period have been affected by a tropical cyclone.
I hope to see you at the session!
Thursday, December 3, 2009
Landslides at the AGU Fall meeting
Like 16,000 other Earth and environmental scientists, I am heading off next week to the Fall Meeting of the American Geophysical Union, which is held in San Francisco. I have attended several times before - it is an amazing meeting - but this year there is added spice provided by the new Natural Hazards grouping, which means that there is far more of interest for me. The landslide specific session is entitled "Landslide Prediction and Assessment: Mechanisms and Controls on Size Distribution", wich consists of two oral sessions and a large poster session, all on Thursday 17th December. The oral sessions have a great line-up, including:
I am giving three papers at the meeting. These are:
Session Title: EP33C. Coastal Geomorphology and Morphodynamics III
Location: 2004 (Moscone West)
Start time: Wed, Dec 16 - 1:40 PM
EP33C-01. Energy Delivery to Cliffs from Waves, Tides and Storms. E. C. Norman; N. J. Rosser; M. Lim; D. N. Petley
Another paper in the same session will be delivered by a researcher from my team, Mike Lim:
EP33C-03. A quantitative analysis of rock cliff erosion environments. M. Lim; N. Rosser; D. N. Petley; E. C. Norman; J. Barlow
Session Title: H21J. Rocks, Fractures, Fluids, and Life: Insights From Subsurface Observatories I
Location: 3005 (Moscone West)
Start time: Tue, Dec 15 - 8:00 AM
H21J-01. On the development of an underground geoscience laboratory at Boulby in NE England (Invited). D. N. Petley; N. Rosser; J. Barlow; M. J. Brain; M. Lim; M. Sapsford; D. Pybus View Pres.
Session Title: NH52A. Extreme Natural Hazards: Risk Assessment, Forecasting, and Decision Support III
Location: 2006 (Moscone West)
Start time: Fri, Dec 18 - 10:20 AM
NH52A-04. Quantifying the impacts of landslides on society. D. N. Petley; N. Rosser; R. Parker View Pres.
And I am involved in a series of posters too:
Session Title: EP43A. Coastal Geomorphology and Morphodynamics IV Posters
Location: Poster Hall (Moscone South)
Start time: Thu, Dec 17 - 1:40 PM
EP43A-0635. GEOLOGICAL AND ENVIRONMENTAL CONSTRAINTS ON THE NEGATIVE POWER LAW SCALING OF ROCKFALLS, YORKSHIRE, UK.. J. Barlow; N. Rosser; D. N. Petley View Pres.
Session Title: H23E. Rocks, Fractures, Fluids, and Life: Insights From Subsurface Observatories II Posters
Location: Poster Hall (Moscone South)
Start time: Tue, Dec 15 - 1:40 PM
H23E-0997. The Boulby Geoscience Project Underground Research Laboratory: Initial Results of a Rock Mechanics Laboratory Testing Programme. M. J. Brain; D. N. Petley; N. Rosser; M. Lim; M. Sapsford; J. Barlow; E. Norman; A. Williams; D. Pybus View Pres.
Session Title: NH43C. Remote Sensing of Natural Hazards III Posters
Location: Poster Hall (Moscone South)
Start time: Thu, Dec 17 - 1:40 PM
NH43C-1350. Controls on the spatial distribution of landslide hazards triggered by the 2008 Wenchuan Earthquake, Sichuan Province, China . R. N. Parker; N. J. Rosser; D. N. Petley; A. L. Densmore View Pres.
See you there I hope!
Dave
- A General Landslide Distribution for Triggered Event Landslide Inventories from 100-10,000 Landslides (Invited). B. D. Malamud; F. Guzzetti; D. L. Turcotte
- Landslide scaling and magnitude-frequency distribution (Invited). C. P. Stark; F. Guzzetti
Material Matters in Landslide Volume-Area Scaling . I. J. Larsen; D. R. Montgomery; O. Korup - Erosion effects on the size and mobility of granular avalanches and landslides. A. Mangeney; O. Roche; O. Hungr; N. Mangold; A. Lucas
- Acoustic Emissions During Progressive Failure of Earth Materials – Can we “Hear” The Onset of a Landslide?. G. K. Michlmayr; D. O. Cohen;
- A framework for spatial and temporal prediction of shallow landslides induced by rainfall (Invited). J. W. Godt; N. Lu; B. Sener-Kaya; R. L. Baum
- The early warning system of landslides and sediment runoffs using meteorological condition including rainfall-soil moisture index (Invited). T. Kubota; I. C. Silva; H. Hasnawir
- New techniques for landslide hazard assessments: opportunities, methodology, and uncertainty. D. B. Kirschbaum; C. D. Peters-Lidard; R. F. Adler; Y. Hong
- Prediction of Rainfall-Induced Landslides . F. Nadim; F. Sandersen
I am giving three papers at the meeting. These are:
Session Title: EP33C. Coastal Geomorphology and Morphodynamics III
Location: 2004 (Moscone West)
Start time: Wed, Dec 16 - 1:40 PM
EP33C-01. Energy Delivery to Cliffs from Waves, Tides and Storms. E. C. Norman; N. J. Rosser; M. Lim; D. N. Petley
Another paper in the same session will be delivered by a researcher from my team, Mike Lim:
EP33C-03. A quantitative analysis of rock cliff erosion environments. M. Lim; N. Rosser; D. N. Petley; E. C. Norman; J. Barlow
Session Title: H21J. Rocks, Fractures, Fluids, and Life: Insights From Subsurface Observatories I
Location: 3005 (Moscone West)
Start time: Tue, Dec 15 - 8:00 AM
H21J-01. On the development of an underground geoscience laboratory at Boulby in NE England (Invited). D. N. Petley; N. Rosser; J. Barlow; M. J. Brain; M. Lim; M. Sapsford; D. Pybus View Pres.
Session Title: NH52A. Extreme Natural Hazards: Risk Assessment, Forecasting, and Decision Support III
Location: 2006 (Moscone West)
Start time: Fri, Dec 18 - 10:20 AM
NH52A-04. Quantifying the impacts of landslides on society. D. N. Petley; N. Rosser; R. Parker View Pres.
And I am involved in a series of posters too:
Session Title: EP43A. Coastal Geomorphology and Morphodynamics IV Posters
Location: Poster Hall (Moscone South)
Start time: Thu, Dec 17 - 1:40 PM
EP43A-0635. GEOLOGICAL AND ENVIRONMENTAL CONSTRAINTS ON THE NEGATIVE POWER LAW SCALING OF ROCKFALLS, YORKSHIRE, UK.. J. Barlow; N. Rosser; D. N. Petley View Pres.
Session Title: H23E. Rocks, Fractures, Fluids, and Life: Insights From Subsurface Observatories II Posters
Location: Poster Hall (Moscone South)
Start time: Tue, Dec 15 - 1:40 PM
H23E-0997. The Boulby Geoscience Project Underground Research Laboratory: Initial Results of a Rock Mechanics Laboratory Testing Programme. M. J. Brain; D. N. Petley; N. Rosser; M. Lim; M. Sapsford; J. Barlow; E. Norman; A. Williams; D. Pybus View Pres.
Session Title: NH43C. Remote Sensing of Natural Hazards III Posters
Location: Poster Hall (Moscone South)
Start time: Thu, Dec 17 - 1:40 PM
NH43C-1350. Controls on the spatial distribution of landslide hazards triggered by the 2008 Wenchuan Earthquake, Sichuan Province, China . R. N. Parker; N. J. Rosser; D. N. Petley; A. L. Densmore View Pres.
See you there I hope!
Dave
Monday, July 27, 2009
Landslide sessions as the AGU Fall meeting in San Francisco
The annual Fall Meeting of the American Geophysical Union (AGU) has long been the meeting of choice of the geoscience community, although these days it is being challenged by its European equivalent (the European Geosciences Union). The meeting this year is expected to attract about 16,000 earth and environmental scientists (I bet you didn't realise there were that many...).A frustration for the surface process and natural hazards communities has been the lack of representation at this meeting, but this year AGU has put this right.
Abstracts are due in early September, but I thought it would be helpful to pull together a list of the sessions potentially of interest to landslide scientists:
H56: Hydrometeorological Hazards in a Changing World
NH01: Natural Hazards General Contributions
NH03: Remote Sensing of Natural Hazards
NH04: The Development and Characterization of Natural Hazard Catalogs
NH06: Reducing Human Losses to Natural Hazards
NH14: Controls on Landslide Sizes and Size Distribution
NH18: Rainfall Induced Landslides: Prediction and Assessment
NH20: The Science of High-Probability, Unpredictable Hazards: From Theory to Practice
NH22: Extreme Natural Hazards: Risk Assessment and Forecasting
NH25: Energy in Natural Disaster Systems
EP02: Sediment Supply, Storage, and Delivery as Controlled by Hillslope-Channel Coupling
See you there!
Abstracts are due in early September, but I thought it would be helpful to pull together a list of the sessions potentially of interest to landslide scientists:
H56: Hydrometeorological Hazards in a Changing World
NH01: Natural Hazards General Contributions
NH03: Remote Sensing of Natural Hazards
NH04: The Development and Characterization of Natural Hazard Catalogs
NH06: Reducing Human Losses to Natural Hazards
NH14: Controls on Landslide Sizes and Size Distribution
NH18: Rainfall Induced Landslides: Prediction and Assessment
NH20: The Science of High-Probability, Unpredictable Hazards: From Theory to Practice
NH22: Extreme Natural Hazards: Risk Assessment and Forecasting
NH25: Energy in Natural Disaster Systems
EP02: Sediment Supply, Storage, and Delivery as Controlled by Hillslope-Channel Coupling
See you there!
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