Climate change: interviews with BRGM scientists at COP21

I am Gonéri Le Cozannet. I work at the BRGM, the French Geological Survey, in the Coastal Risk and Climate Change unit, Risk & Prevention department. Among the risks of climate change, the rising sea level is a major concern. We expect it to bring about major risks of marine submersion, and maybe coastal erosion. Precise examples: what's happening today, we're working on...The team I work in is modelling marine submersion phenomena. Notably, we work on sites such as Gâvres, in Brittany, Hyères, in Provence-Alpes-Côte d'Azur and Palavas-les-Flots in Languedoc-Roussillon. We almost invariably see that in low-lying zones, such as sandy beds, very low-lying zones, just a few metres above sea level, the risk of marine submersion greatly increases when the sea level rises by 50 cm. The sea level has already risen by 20 cm since 1870. The problem is that it will keep rising. We're sure of this. Even if all emissions stopped today, it would rise a few millimetres a year. We can't stop sea level rising, however, what we can do is limit the speed at which it rises by limiting greenhouse gas emissions. This is what we hope for in reducing emissions. But, some effects cannot be avoided: at least a few dozen centimetres of sea level rise by the end of the century. A few dozen centimetres of sea level rise significantly increases the frequency and intensity of marine submersions. This first subject...  This phenomenon is a priority we have to deal with. We know the risk zones, but it isn't only the BRGM that does this. In France, for example, there are several regulatory mechanisms and it means that we define the zones that are the most... ... the most vulnerable to a rise in sea level. For instance, for high-flood risk areas, we have risk-prevention plans. Once the sites are identified, the problem is: how do we adapt these sites? And so, there's... The idea is to... We can't forbid building in all low-lying zones. That would be impossible because people have development priorities. We try to model marine submersions very precisely, taking into account the inevitable consequences of the rising sea level. So, for example, there's a mechanism called "Coastal risk prevention plan". In this mechanism, we model a storm, we look at its maximum spatial extent and add in 60 cm of sea level rise. A 60 cm rise in sea level is what we'll be looking at, in any case, in 2100. The areas that are flooded by this modelling define a zone in which to forbid new buildings. This is one of our main mechanisms. Since 2011, we include sea level rise in Coastal risk prevention plans. This is a first step towards adapting coastlines to rising sea level. We've worked on coastal erosion on islands in Polynesia, and my colleagues on hurricane risk. So, the questions that arise... Hurricane risks are extremely practical. This zone doesn't get many Hurricanes, but they can happen. There was a series in 1983, which caused major marine submersions, notably in the Tuamotu atolls. My colleagues model marine submersions due to hurricanes. I worked specifically on the coastal erosion of the atolls. The question was that, for various reasons, over 60 years, Polynesia has had a sea level rise faster than average, at around 30%. Instead of 1.7 mm a year for 50 years, it was 2-3 mm, 2-2.5 mm a year, depending on the atolls. We asked ourselves whether the atolls... We'd already observed the impacts of sea level rise on these atolls, already hit by a faster-than-average rise. In fact, we see that, today, the mobility of the atolls' coastline is mainly governed by the effects of human actions, waves, hurricanes, etc. This somehow reinforces the idea that we can avoid a general retreat of the coastline in many low-lying zones. That is, if sea level doesn't rise too fast. And this is only possible given a scenario where we greatly lower CO2 emissions. However, emitting a lot of CO2, in 2100 we'll have a 70% risk of being between 0.5 and 1 m, and 30% of being above. In that event, we have a 1 cm rise in sea level a year, meaning 20 cm of sea level rise every 20 years. 20 cm is the overall rise since 1870. We must avoid this situation. In the event of a rapid rise in sea level, we'd have generalised coastline retreat. We might avoid it if we greatly reduce greenhouse gas emissions.

I'm Laurent Rouvreau, research engineer at the BRGM. My field of research is recycling and waste management, in public building & works. Recycling in a circular economy, we work on two levels. The traditional level: the process. Here we look at how to recycle this material, dismantle buildings, separate the various components, and reintroduce each of these components in a new product,a new material, a new building. That's the approach on the level of process. There's another approach: the global or systemic approach. Here, before starting on a process or on recycling a material or product, we try to understand how it fits in with the economy, how it fits in with the national economy, the economy of a region, a town, so as to see how our actions can be as efficient as possible. Should we... For example, with site waste, we'll say that this waste comes from a quarry. We used material from a quarry which we then transformed industrially, to build, construct. One day, we'll demolish this building or renovate it, thus generating waste material. Our aim will be to reuse or put back into the cycle as much as possible of this waste, called secondary raw material. We consider this circular economy because, if we recycle more material when demolishing buildings, we reduce energy needs. Materials won't come from so far away, so there'll be less trucks, less energy needed to get the material, less energy needed to use the material. Of course, some energy is used in recycling processes, but we'll still have a more virtuous system in that we'll do better using a little less energy. This contributes indirectly to climactic needs, since the system helps preserve raw materials, which are non-renewable. Quarry material is not infinitely available, contrary to what people often think. Also, with a proximity economy, since you recycle material near to where it will be used, you need less energy. The main direction of research is as I said, along two major lines. First, how things fit together globally, since looking at material flow, at organising it and the energy consumption involved, you have to break down all these elements, to see how this works. Then you can act on the processes, on using the material better. That's one approach. Then, there's the use of more efficient material. For example, can I build as many square metres, or more, using less materials? Are these materials more efficient, that you need less of, and which require less energy? Another approach is the use of more renewable materials, like wood, for example. In construction now, we see the use of straw, a variety of fibres, all renewable materials, which can bring, to a degree, reduced consumption and better energy balance.

I'm Serge Lallier. I am a hydrogeological engineer at the French Geological Survey in charge of studying the behaviour of groundwater resources. The instrument you see here is a simple one. It simulates a boring made in the ground going down to the level of the groundwater table. It simply measures the water level in the underground reservoir. Just like a device for measuring the level of liquid in any tank. Here, our reservoir is called an "aquifer", a subsurface layer containing water. The state of water tables in France varies, but globally, France has no water problem, except on occasion and regionally. You probably heard in the media of periods of concern about water resources, with usage restrictions. But once again, these are more regional, local episodes. Generally speaking, in France, we don't have a water resource problem. We at the BRGM study and monitor these resources and we are also an official state operator providing instruments to a network that is composed, in France, of over 3,000 of these devices, to get an overview of the general state of our reservoirs in real time, and give the information to the government, in terms of quantity, with these devices, but also, through this network, in terms of quality. BRGM and climate change has various aspects. Clearly, since it's our subject, the issue of water resources, and their management, because, once again, there's no basic problem. Climate change also impacts the entire coastline. As you know, the problem of the rising sea level has consequences for the erosion and stability of the coast, as well as its retreating. Another subject related to climate change, of course, is everything concerning renewable energy. Notably, geothermal energy, taking heat from deep underground layers and using it.