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:

• 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.

One of the questions asked about how the Arctic Sea Ice looked for next year. His response was that it doesn't look good right now as the surface area is well below normal, and the ice is very thin and young. However, it will all depend upon the weather, which is unpredictable.

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.
  

Finally, Gleick from Oakland talked about scientific communication. This talk was a neat summary of the key themes that had emerged from the other talks, with one difference - he was unconvinced that it is really easy to separate science from policy, although there is a need to differentiate between science and opinion.

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.

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

Statement from the UK Science Community on climate change

In the aftermath of the UEA email hack, the UK science community have issued a statement regarding climate change. This is hosted by the UK Met Office web site:

http://www.metoffice.gov.uk/climatechange/news/latest/uk-science-statement.html

The statement, upon which I am proud to be listed, says:

"We, members of the UK science community, have the utmost confidence in the observational evidence for global warming and the scientific basis for concluding that it is due primarily to human activities. The evidence and the science are deep and extensive. They come from decades of painstaking and meticulous research, by many thousands of scientists across the world who adhere to the highest levels of professional integrity. That research has been subject to peer review and publication, providing traceability of the evidence and support for the scientific method.

The science of climate change draws on fundamental research from an increasing number of disciplines, many of which are represented here. As professional scientists, from students to senior professors, we uphold the findings of the IPCC Fourth Assessment Report, which concludes that ‘Warming of the climate system is unequivocal’ and that 'Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations'."

This statement has been signed by >1700 scientists from the UK.

The link between rainfall intensity and global temperature

The aftermath of a landslide in Taiwan caused by very heavy rainfall

One of the most interesting aspects of the global landslide database that we maintain at Durham is the way in which it has highlighted the importance of rainfall intensity in the triggering of fatal landslides. Generally speaking, to kill people a landslide needs to move quickly rapid, and rapid landslides appear to be primarily (but note not always) triggered by intense rainfall events (indeed in the reports the term "cloudburst" often crops up). So, a key component of trying to understand the impacts of human-induced global climate change on landslides is the likely nature of changes in rainfall intensity, rather than that of rainfall total. Put another way, it is possible that the average annual rainfall for an area might decrease but the occurrence of landslides increase if the rainfall arrives in more intense bursts.

There is of course a certain intuitive logic in the idea that rainfall intensity might increase with temperature. Warmer air is able to hold more moisture (as anyone who has been in the subtropics in the summer will know only too well!) and of course increased temperatures also drive greater convection, responsible for thunderstorm rainfall. Of course this is a very simplistic way to look at a highly complex system, so it is not enough to rely upon this chain of logical thought. However, until now there have been surprisingly few studies to actually quantify whether there is a relationship between global temperature and precipitation intensity, which has meant that for landslides understanding the likely impact of climate change has been quite difficult.

However, an important and rather useful paper examining exactly this issue has sneaked under the radar in the last few months. The paper, by Liu et al (2009) (see reference below), was published in Geophysical Research Letters a couple of months ago. The paper uses data from the Global Precipitation Climatology Project (GPCP). These data can be accessed online here (so no claims that climate scientists don't publish their data, please!) The dataset provides daily rainfall totals for 2.5 x 2.5 degree grid squares across the globe, extending back almost 50 years. Liu et al. (2009) looked at the data from 1979 to 2007, comparing precipitation density with global temperature in this time period.

Their results are both unsurprising and surprising. The unsurprising part is that they found that the occurrence of the most intense precipitation events does increase with temperature. The surprising part is the magnitude of the change - they found that a 1 degree Kelvin (Centigrade) increase in global temperature causes a 94% increase in the most intense rainfall events, with a decrease in the moderate to light rainfall events. Indeed the median rainfall increased from 4.3 mm day⁻¹ to 18 mm day⁻¹, which is a surprisingly high shift as well.

So why is this important in the context of landslides? Well, I think that there are probably two key implications:

1. It has long been speculated that anthropogenic warming will lead to an increase in landslides, but with little real quantitative evidence to confirm or deny this. The demonstration that higher global temperatures does lead to increased precipitation intensity starts to put some meat on the bones of this idea. Furthermore, if it is possible to directly link rainfall intensity to landslide occurrence (and there is some evidence both from my own work and from that of others that this may be possible), then it should be possible to start to examine the likely increase in landslides as warming proceeds.
2. The current global climate models assume a much lower increase overall in precipitation intensity with increasing temperature than Liu et al. (2009) suggest. Indeed most of the models assume about a 7% increase per degree Kelvin (Centigrade) warming. For the most intense precipitation events this means that the models predict about a 9% increase, which is an order of magnitude lower Liu et al. (2009) found. This suggests that the rainfall projections that are derived from the models are probably overly-conservative, and possibly very much so, which is a concern. If so, then forecasts of landslide occurrence that are derived from these models are likely to under-estimate the true impact.

Of course, this is only one study, and it should also be noted that the most intense rainfall events are usually associated with tropical areas and with those in the path of hurricanes and in particular typhoons. There is a great deal more work to do on this topic, but the initial results provide real cause for concern.

Reference
Liu, S., Fu, C., Shiu, C., Chen, J., & Wu, F. (2009). Temperature dependence of global precipitation extremes Geophysical Research Letters, 36 (17) DOI: 10.1029/2009GL040218

The Copenhagen Diagnosis

As a rule on this blog I try not to drift too far off-topic. Occasionally I will track a hurricane or a typhoon if there is the potential for them to trigger lots of slides. I never stray into the political domain on this blog - and I hope that I never will.

So, today for the probably the first time, I am going to drift into a different field. I am going to remain strictly within the science, but I am going to highlight a key document that is now available. Ahead of the Copenhagen climate discussions a group of key climatologists have released "The Copenhagen Diagnosis", which is an update to the most recent IPCC report on climate change.

Now, over the last week or so there has been some extraordinary garbage on both the internet and in the mainstream media in relation to the stolen emails and files from the University of East Anglia. I am appalled at the way in which comments within those emails have been manipulated and misrepresented, even by some who should know better, to undermine climate science. Meanwhile the physics of the atmosphere continues as before, and our knowledge of how it is behaving is unchanged, and the picture is not a good one. The strength of the Climate Diagnosis report is the fact that it relies upon good quality observational data. And lets be clear about what the data show:

• Greenhouse gas emissions are increasing;
• The climate is continuing to warm (and despite the guff that the denialists spout, tenperatures have increased over the last decade);
• Sea level is rising at the top end of the previous estimates;
• Arctice sea ice decline has accelerated

So why have I drifted into featuring climate science on this blog? Well, for two reasons. First, the denialists continue to peddle the myth that there is no consensus. This is not my experience, and so I think it is time for the silent majority of environmental scientists to stand up and be counted. Second, the CRU / Hadley Centre email hack was clearly designed to derail the science of climate ahead of Copenhagen. This is an outrageous attack on science and scientists that we should all oppose.

The document can be downloaded here. Please read it and try to understand what it is saying. This is so very, very important.

Coastal erosion and climate change: Implications for the shoreline over the next century

On Friday I gave a public lecture at the Badbury Centre in North Yorkshire (NE England), looking at the potential impacts of climate change on coastal erosion. The presentation was focused on the field site that we maintain at Boulby, close to the lecture venue. In the presentation I start by looking at our landslide database and then go on to talk about climate change. The main part of the presentation is an examination of the likely impact of climate change, looking at the ways in which potential erosion rates have been determined, and then using our own very high resolution work to examine how this can be done properly. I hope that in the presentation I show that in this area at least the impacts of climate change on erosion are not as great as some might fear, and that proper scientific analysis allows one to develop proper models of future impacts.

I must stress here that this does not suggest that climate change is not a real and urgent problem - it is - and in the talk and in the questions afterwards I stressed the vital importance of a successful outcome to the Copenhagen talks.

The presentation is available via Authorstream below:

Coastal erosion and climate change

See more presentations by Dr_Dave | Upload your own PowerPoint presentations

My personal Authorstream page, which contains a selection of my recent presentations, is available here:

www.authorstream.com/user-presentations/Dr_Dave/

Oh dear, more scientific hyperbole about climate change and natural disasters

My Alma Mater, University College London, is this week hosting an interesting colloquium on the theme of "Climate Forcing of Geological and Geomorphological Hazards". This is a really interesting topic and the organisers should be applauded for attracting some really interesting talks. If it wasn't for the fact that I am heading out to Asia on Wednesday I would attend for sure. However, the Observer, which is the Sunday version of the UK broadsheet newspaper The Guardian, has today run a two page story about the conference. Again, this is not unwelcome - it is important that articles are run about the multi-faceted implications of climate change - but unfortunately the tone of the headline and lead material is an example of scientific hyperbole has left me speechless:

Climate change: melting ice will trigger wave of natural disasters
Scientists at a London conference next week will warn of earthquakes, avalanches and volcanic eruptions as the atmosphere heats up and geology is altered. Even Britain could face being struck by tsunamis.

Scientists are to outline dramatic evidence that global warming threatens the planet in a new and unexpected way – by triggering earthquakes, tsunamis, avalanches and volcanic eruptions.

Reports by international groups of researchers – to be presented at a London conference next week – will show that climate change, caused by rising outputs of carbon dioxide from vehicles, factories and power stations, will not only affect the atmosphere and the sea but will alter the geology of the Earth.

Melting glaciers will set off avalanches, floods and mud flows in the Alps and other mountain ranges; torrential rainfall in the UK is likely to cause widespread erosion; while disappearing Greenland and Antarctic ice sheets threaten to let loose underwater landslides, triggering tsunamis that could even strike the seas around Britain.

At the same time the disappearance of ice caps will change the pressures acting on the Earth's crust and set off volcanic eruptions across the globe. Life on Earth faces a warm future – and a fiery one.

Now, there is little doubt that there is a possible link between climate change and geophysical hazards, and that this is a topic that requires study. But to present the topic in this way is ridiculous given our current state of knowledge. Some elements of the quote above are probably untrue (melting glaciers will set of avalanches for example), and some of the remainder is speculative at best (e.g. widespread erosion in the UK, underwater landslides from the loss of ice sheets). Much of the rest has sensationalised climate impacts by presenting end member (i.e. large but unlikely) events as having a far great likelihood than is the reality - e.g. the UK being affected by tsunamis generated by underwater landslides caused by Arctic melting. This is possible, but is very, very unlikely, and there is little if any evidence that such events have occurred in the past.

But, unfortunately it gets worse. Bill McGuire, the Director of the Benfield Hazards Research Centre at UCL, is quoted as saying the following:

'"Not only are the oceans and atmosphere conspiring against us, bringing baking temperatures, more powerful storms and floods, but the crust beneath our feet seems likely to join in too," said Professor Bill McGuire, director of the Benfield Hazard Research Centre, at University College London (UCL)."Maybe the Earth is trying to tell us something,"'.

Now I like and admire Bill, I consider to be a friend, and I think that he has done a lot of good stuff. But this type of quote is really unhelpful. In my view there is no place for scientists to state things sthat the the oceans and atmosphere are "conspiring against us" - they are responding to the forcing that we are causing. And what can one say about a scientist stating that "Maybe the Earth is trying to tell us something"?

The remainder of the article is rather more measured, with some not unreasonable quotes from some good scientists. However, the damage is done in the first part of the article, and of course in the headline.

Take a look at the comments on the Guardian web page. Unsurprisingly, the denialist community has jumped on this to undermine the research that is being undertaken on climate change. This is a great shame - anthropogenic climate change is a huge issue based on good science. Unfortunately, articles like this, based on speculation and exaggeration, are really unhelpful to those trying to do good science and to persuade society of the importance of this issue. If there is one thing that I have learnt in the last couple of years is that as scientists we need to be measured and realistic about what we write and say. The organisers of this conference would be wise to remember this.

The role of landslides in global warming

A rather extraordinary paper has just been published in Geophysical Research Letters about landslides triggered by the Wenchuan (Sichuan) earthquake. Why is it extraordinary - well, let me quote from the abstract. The paper suggests that the landslides caused destruction of vegetation such that "the cumulative CO₂ release to the atmosphere over the coming decades is comparable to that caused by hurricane Katrina 2005 (~105 Tg) and equivalent to ~2% of current annual carbon emissions from global fossil fuel combustion."

Wow! In case you are struggling to decode the above, this suggests that the landslides triggered by the earthquake caused a massive loss of vegetation that will now decay. In decaying it will release CO2, which will add to the effects of global warming. This is a pretty interesting result - and it has already been picked up by the mainstream media.

So, how do the authors reach these remarkable conclusions, and are they valid? Well, I am afraid that I have some serious doubts about this study, which seem to be based on some misunderstandings of earthquake-induced landslides. Lets base the analysis on Fig 2 of the paper, reproduced below, in which the authors highlight one of the landslides that blocked the valley on the river upstream of Beichuan:


So why do I object so strongly to the paper? Well first, the use of terminology is inexcusably weak. For example, the authors describe the landslides thus (referring to Fig 2a): " (a) Living carbon scars left by mudslides, which indicates the geographical locations of the landslides for this region." NO - these are not mudslides - these are clearly shallow rockslides - a very different beast. Of Figure 2b they say "A quake surface wave triggered basal sliding that initiated the movement through liquefying the top ~2 m slab." NO. Failure was not due to liquefaction, and even the most cursory view of the image shows that more than 2 m of material was displaced. Finally, they say of Fig. 2d "An aerial photo taken on May 26, 2008, showing the landslide mud that formed the Tangjiashan quake lake". No again - this is most definitely not mud (see image below) - it is bouldery / fragmented debris (if it was mud then the problems would have been far less serious). They say that there model suggests that "The material reaches a maximum speed of 5 m s⁻¹ but only briefly because the resistance stress is strong for the still coherent sliding material. " Again, this is poppycock. 5 m/sec is 18 km/hour - there is no way that this failure was as slow as that - look at how the debris fragmented and at how it spread across the valley (see image of the landslide deposit being excavated for the drainage channel below):

This is not a deposit that was emplaced at 5 m/sec, and nor is it mud. Pretty poor stuff, frankly. Note finally that figs 2b and 2d are supposed to represent the same area. However, in 2d the debris is clearly in the valley floor, with the source being the slopes above. In 2d the debris is above the 1155 m contour line. There is no debris between 1100 m and 1155 m - so the deposit areas are completely different.

So now lets turn to the modelling. The paper is ridiculously short of proper detail of what they have actually done - I cannot understand how the editors/referees let this through. It states that they have used an "advanced modeling tool—a scalable and extensible geo-fluid model—that explicitly accounts for soil mechanics, vegetation transpiration and root mechanical reinforcement, and relevant hydrological processes. The model considers non-local dynamic balance of the three dimensional topography, soil thickness profile, basal conditions, and vegetation coverage ... in determining the prognostic fields of the driving and resistive forces, and describes the flow fields and the dynamic evolution of thickness profiles of the medium considered, be it granular or plastic."

Hmmm! Not sure what this means really. However, they do state that "we need to use the finest possible digital elevation model (DEM) and soil profile data". However, they have actually used the SRTM data-set, which has a spatial resolution of 30 metres at best, and possibly 90 metres (!). I cannot believe that this is anything like good enough. Where velocity exceeded 1m/s in their model they assume that vegetation is destroyed. They have used this to determine the total amount of vegetation lost, and then calculated the contribution of the CO2 to the atmosphere.

There are several problems with this. First, the landslide model appears to be erroneous, as described above. Second, they seem to omit to include the uptake of CO2 by vegetation as it re-establishes on the slide scars, which will in the long term balance that emitted. Finally, note that they say 2% of CO2 emitted by burning fossil fuels, not 2% of all anthropogenic sources. This makes the contribution sound larger than it actually is. Indeed, 2% of annual anthropogenic emissions spread over a substantial period (it doesn't say how long) indicates a comparatively minor annual total.

In my view the basis of the paper is iffy, although it would have helped if the methodology had been properly outlined. Unfortunately, the work is already being picked up the climate change denier community. Read this and weep. The logic used by Paul Fuhr in this opinion piece makes no sense at all to me, but the fact that he can use this paper in this way is deeply unfortunate, providing yet more ammunition for the pseudo-science community of climate change deniers.

Reference
Diandong Ren, Jiahu Wang, Rong Fu, David J. Karoly, Yang Hong, Lance M. Leslie, Congbin Fu, Gang Huang (2009). Mudslide-caused ecosystem degradation following Wenchuan earthquake 2008 Geophysical Research Letters, 36 (5) DOI: 10.1029/2008GL036702

Future British seasonal precipitation extremes - implications for landslides

One of the great questions of the age is of course the ways in which climate change will affect the weather patterns that we are likely to see in the future. In the case of landslides the key issue is the ways in which precipitation patterns will alter, especially the most intensive rainfall events that are responsible for many of the most damaging landslides. One of the most significant steps forward over the last few years has been the ability of global climate models to handle these extreme events, meaning that at last we are starting to develop some capability.

This week an important paper has been published by Fowler and Ekstrom (2009), which seeks to look at the likely changes to very intense rainfall events in the UK. Helen Fowler, is based just up the road from me at Newcastle (the city with the chronically under-performing football team), and her co-author have used modelling ensembles to examine how UK precipitation regimes are likely to change in the time period 2070 to 2100 under the SRES A2 emissions scenario, which is currently effectively our best estimate as to how carbon dioxide emissions will change with time (Fig. 1).

Fig 1: SRES Emissions Scenarios. A2, as used in this study, is shown in Fig. (b). Source: http://www.grida.no/publications/other/ipcc_sr/?src=/Climate/ipcc/emission/014.htm

Ensemble modelling looks at the results of a series of different climate models to examine the range of outputs. Each model operates in a slightly different way, meaning that there will always be a range of results. Therefore, papers presenting ensemble model outcomes always present a range. One of the key issues of interest is whether there is some consistency between them. In this study. Of course the results of such modelling runs are highly complex - in this paper the authors have looked at the 1 day and 10 day precipitation events with a current return period of 25 years. The 1 day event can be thought of as the impact of an intense storm; the 10 day probably simulates a series of low pressure systems tracking across the country, as has happened several times in the last few of years. In landslide terms the 1 day storms might trigger the catastrophic debris flow and sallow failure events, whilst the 10 day events might trigger deeper seated and large slope failures.

First the model is run for the a control period (1961-1990) to check that they can realistically simulate observed conditions. They can. The models are then run to look at what would happen in the period between 2070 and 2100, and the results are then pooled using a fairly interesting approach. Well, the first thing to say is that the Global Climate Models (GCMs) do predict a much warmer climate - global mean temperatures are predicted to be 3.1 to 3.56 degrees warmer than at present. Interestingly though the occurrence of these intense rainfall events also greatly increases for three of the four seasons:
Winter: Increases in occurrence of extreme precipitation of 5 to 30%
Spring: Increases in occurrence of extreme precipitation of 10 to 25%
Summer: Very varied results, with some models suggesting decreases and other increases. More work is needed
Autumn (Fall): Increases in occurrence of extreme precipitation of 5 to 25%

A few of the models do predict larger (and smaller) increases - look at the paper for the full detail. Overall, the authors conclude that "Nevertheless, importantly for policy makers, the multi-model ensembles of change project increases in extreme precipitation for most UK regions in winter, spring and autumn. This change is physically consistent with warmer air in the future climate being able to hold more moisture. The use of multi-day extremes and return periods also showed that short-duration extreme precipitation is projected to increase more than longer-duration extreme precipitation, where the latter is associated with narrower uncertainty ranges."

The implications for landslides are stark. Increases on this level of the occurrence of extreme precipitation events will inevitably increase the occurrence of slope failures. Therefore, we should expect to see an increase in the occurrence of slope failures. Unfortunately, as landslides are triggered by just a small proportion of our existing rainstorm events, increases in this range are likely to have a disproportionate impact.

Of course the next thing to do will be to build the outputs of these models into slope stability models. This will be a fascinating exercise.

Reference:
H. J. Fowler, M. Ekström (2009). Multi-model ensemble estimates of climate change impacts on UK seasonal precipitation extremes International Journal of Climatology DOI: 10.1002/joc.1827

Article in the New Strait Times Malaysia

Shield your eyes from the photograph though...

People pressure on land has a telling effect

Malaysia talk

The following is my presentation at the International Symposium on Slopes in Kuala Lumpur, Malaysia. It is an invited paper on the topic of landslides in Asia in relation to climate change and other environmental pressures. I hope you find it of interest.

The file should appear below:


Uploaded on authorSTREAM by Dr_Dave

If you cannot see the file then click on the highlighted Dr_Dave link above. The full Powerpoint file can be downloaded from that location too. I will post a report on the most interesting parts of Day One tomorrow.

The influence of the summer monsoon on fatal landslides in Asia

I am currently putting together a keynote paper for the forthcoming International Conference on Slopes, which is being held in Malaysia in November. I have been looking at the occurrence of fatal landslides in Asia, using the Durham Landslide Database as the source of data. I have plotted the number of fatal landslides by month for 2002-2007 for three areas - South Asia (i.e. the Indian subcontinent), East Asia (which includes China, Taiwan, Korea and Japan) and SE. Asia (which should be self evident). The graphs are shown below (note the different magnitudes of the y-axis scales by the way).

First, South Asia shows a very strong monsoon signal. Look in particular at the mean trend for the five years. The level of fatal landsliding in the winter months is very low, with most of the events occurring in June to September. It is also clear that the number of landslides increases rapidly at the start of the monsoon as the rain bands push northwards, but then decline slowly as the monsoon disperses. There is also considerable year-on-year variation; in particular the very strong and prolonged monsoon rainfall across parts of India is very clear for 2007.

East Asia (below) also shows a strong monsoon signal, of course slightly modified by the impact of typhoons too. Here though the pattern is quite different - again look at the graph of the mean of the other data. In this case the monsoon signal is far more symmetrical, again reaching a peak in July but rising and declining at about the same rate. Again there is considerable year-one-year variation both in terms of number of events and the variation through the year. The big spike in July 2006 is particularly clear.

SE. Asia present a completely different picture (below). As much of SE. Asia is tropical there is far less monthly variation. Unsurprisingly no monsoon spike is seen. The occurrence of landslides is slightly higher in the latter part of the year as the rainy season affects Indonesia for example. Of particular note are the variations in the distribution between years - this really does reflect the occurrence of extreme tropical cloud bursts.


So the impact of the really large scale climate systems on Asian landslides is absolutely clear. This is particularly interesting in the context of climate change - exactly how the Asian monsoon in particular will change will partially determine the landslide impact. Unfortunately the models are not resolving this issue too well at the moment, but most do suggest an increase in the occurrence of the most intense rainfall events. The implications for landslides of this are stark.