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trait

Livre "Climat, le temps d'agir"

Traduction par Lara Heledd Davies-Jones de l’Université de Cardiff au Pays de Galles

Preface

By Laurence Tubiana
France's Ambassador responsible for negotiations on climate change and Special Representative for the 2015 United Nations Climate Change Conference in Paris (COP21).

Climate, the Time to Act is a useful tool for all those wishing to understand the urgency of the climate change phenomenon and the need to take concrete action at every level: International, national, regional, but also individual.
It is essential that all citizens of the country hosting the 21st Conference of Parties (COP21) in December 2015 are able to understand and take ownership of the findings of international scientists presented in the latest report by the Intergovernmental Panel on Climate Change (IPCC). As the result of the huge carbon dioxide emissions into the atmosphere since the start of the industrial revolution, the climate of the entire planet is changing and will continue to change if nothing is done.
There is absolutely no reason to doubt the impact of human activity on climate change despite the fanciful notions of the climate change sceptics. Of course, the evolution and repercussions of climate change are very diverse in nature and vary depending on the region and the country, but our natural resources and our way of life will inevitably be affected. This book provides many concrete examples of the changes that could have consequences for the oceans, marine and terrestrial biodiversity, rising sea-levels, water resources, agriculture and health. Such changes could in turn trigger extreme weather events in the form of floods, storms and droughts.
Ultimately, any endeavour to transform the world and protect the climate must be the responsibility of society as a whole. That being, this book ends with a short chapter on the changing perceptions of ordinary citizens regarding climate change. Reading this chapter highlights how efforts to raise awareness across the world are still in very much in their infancy and that the work to educate and inform people must continue at every level.
It's the choice of our future development model that is at stake. We must make the change and head towards low-carbon economies by virtue of significantly reducing the use of fossil fuels in transport, construction and industry; reducing energy-usage full stop; being more efficient and, wherever possible, neutralising emissions across numerous spheres. This evolution in development models must be adapted to each developed or developing country in accordance with national choices, but such a reorientation is inevitable if we want to limit the effects of climate change.
Any international agreement struck in December 2015 in Paris must send a clear signal to all protagonists: It must, whilst establishing a set of regulations for all countries with a view to securing this century a significant reduction in global emissions, align the expectations of all parties and lay down clear ground rules.
To keep global warming below 2°C, 195 countries must reach an agreement and commit to reducing greenhouse gas emissions. The window of opportunity is very small but optimism must prevail. In France, several initiatives are emerging (1)Certain regions such as Aquitaine have set up a strategy unit to address the issue of reducing emissions and adapting to future changes. Territorial authorities play a central role in the formulation of strategies for sustainable regional development. Similarly, many companies are now increasingly convinced that a low-carbon economy represents the future and that fossil fuel resources constitute a risky investment. I am greatly heartened by all this.
You'll find in this book, written by recognised experts in language easy for everyone to understand, wide-ranging reflections to share"¦and to act upon.

Should we be worrying about a change in climate brought about by human activities?

Faut-il s'inquiéter d'une évolution du climat due aux activités humaines ?

Does the recent increase in temperature leave any room to doubt its anthropogenic (human caused) origin?

As far back as the 1970s, publication of the Keeling Curve(2) (illustrating the concentration of carbon dioxide CO2 in the atmosphere) was confirming what we then suspected. Namely that human activity, especially the huge use of fossil fuels, permanently changes the composition of the atmosphere. The seminal work of François Joseph from France, John Tyndall from Ireland and Svante Arrhénius from Sweden had already highlighted in the 19th century the inevitable global warming of the planet arising from this evolution in the concentration(s) of CO2. This is exactly what has been observed. However, after a rapid increase in temperatures over the period 1980-1990, this upward trend seems to have noticeably slowed down over the past fifteen years. Nevertheless, the ten-year average temperature has not stopped increasing.

Figure 1

The different curves correspond to the different sources of datasets (HadCRUT4, MLOST, GISS).
Figure 1: Change in average global temperature over ten years (Stocker, 2013, p.6).

This slow-down comes at a very bad time in the context of raising awareness about the climate emergency. But, it is in many respects representative of the behaviour of the climate-system and will serve as the baseline running throughout this chapter. Moreover, this pause or hiatus as it is sometimes called, changes nothing as regards long-term evolution of the climate. This we can say in all certainty because the phenomenon of warming arises from a basic principle of physics: Any system that gains more energy than it loses inevitably warms. It is this fundamental physics that we address here.
A body isolated in space, such as the Earth, gains and loses energy only via electromagnetic radiation (EMR). Solar radiation heats up earth which cools itself by emitting radiation of equal energy into space. Taking into account the respective temperatures of the sun and the earth, solar radiation corresponds to visible light and short near-infrared wavelengths, whereas radiation emitted by the earth corresponds to longer wavelengths in the form of infrared rays.

Figure 2

Figure 2: The radiation balance that determines the average temperature of the earth (Le Treut, 2007, p.115).

At thermal equilibrium, the earth emits as much radiation as it absorbs and we call this the radiation balance of the earth. When we use the term "earth" here, we are referring to earth as a system (ground, atmosphere, ocean) signifying that the radiation emitted is that which is released at the top of the earth's atmosphere and lost to space. Even in the absence of anthropogenic emissions, the atmosphere plays an essential role in the temperature of the earth's surface through the action of the greenhouse effect whereby the radiation leaving the atmosphere is significantly lower than that being emitted from the earth's surface. The atmosphere therefore acts as an insulating blanket with the insulating effect due to naturally-occurring greenhouse gases in the atmosphere like water vapour, carbon dioxide, methane and several other minor gases that absorb infrared radiation. This process of absorption is selective, it occurs only within certain frequency bands that are characteristic of greenhouses gases and within which the radiation coming from the surface of the earth is absorbed to various extents. The increase in the concentration of certain greenhouse gases enhances this insulating effect which in turn de-stabilizes the planet's radiation balance.

The anthropogenic contribution to the greenhouse effect.

From 1850 onwards and the start of the industrial era, the concentration of CO2 has increased more and more rapidly. As a consequence, the greenhouse effect has likewise increased leading to a rise of about 0.85°C in the earth's average temperature over this period. However, this increase has not been linear: The temperature rose sharply during two long periods of around thirty years each (close to 0.17°C per decade from 1910 to 1940 and again from 1970 to 1998), separated by a relatively stagnant period. Since 1998, this temperature has changed only slightly (from 0.05 to 0.06°C per decade) whereas emissions from greenhouse gases have not stopped increasing. What we are talking about here is a pause or hiatus in the warming process.

Figure 3

Figure 3 shows the current concentrations of the major greenhouse gases (carbon dioxide, methane, nitrous oxide) and their unprecedented rate of increase (Bernstein, 2007, p.38).

Such fluctuations are not surprising. The weather fluctuates from one year to the next and temperature records do not fall every year. Moreover, the climate is defined as the average weather pattern over a period of at least thirty years in order to eliminate chaotic fluctuations from one year to the next. Variations observed in the rate of temperature increase are recorded for the mid-point of the decade. Understanding and predicting these variations is a crucial factor in climate forecasting because it's all about the near-future.

Which greenhouse gases are the worst offenders?

Which anthropogenic emissions affect the climate?

Carbon dioxide and methane are top of the list.

The principal anthropogenic emissions affecting the climate are gas emissions which absorb infrared radiation and are eliminated only very slowly from the atmosphere. These gases remain in the atmosphere for several years or indeed several decades before the earth's natural processes remove them from the atmosphere. The absorption capacity of molecules is not the same for all gases. It is the product of this absorption capacity and the number of molecules that must be taken into account. A good illustration of this is methane. A methane molecule absorbs more infrared radiation than a molecule of carbon dioxide, but the number of molecules (per cm3) is 200 times lower than that of CO2. The net effect is that methane directly absorbs a slightly lower level of infrared radiation than CO2.
It follows therefore that carbon dioxide is the principal contributor to the greenhouse effect. It is produced largely from the use of fossil fuels (coal, oil and gas) which together supply 80% of the global energy market. It also produced from industrial processes such as cement production. Deforestation and other changes in land-use likewise contribute to 15% of total emissions.
Methane (CH4) is the second biggest contributor to the greenhouse effect and comes from a variety of sources. It is produced mainly by fermentation, in the absence of air, (anaerobic fermentation) which occurs during the cultivation of rice in soil that is naturally or artificially flooded. The same phenomenon is found during the rearing of ruminant livestock whose digestive systems produce methane which is then released via the upper and lower digestive tracts, i.e. by burping and passing wind. Manure, liquid manure and landfill sites also produce methane. Partial combustion of biomass is another source of methane which occurs during agricultural and forest fires. Lastly, the use of fossil fuels constitutes another principal source of methane emission. To begin with, the exploitation of "natural gas", (largely composed of methane) can give rise to fugitive emissions during well-drilling, extraction, transport, storage and distribution. Such emissions can also result from the malfunctioning of sluice gates or valves, or be linked to maintenance operations that lead to purging and emptying pipelines. Likewise, the oil industry produces methane as a by- product, of which only a small part is burned in the gas-flares of refineries, of oil fields or of offshore platforms.
Finally, we must mention the lesser contribution of fluorinated gases which were brought in to replace chlorofluorocarbons (CFCs) in order to mitigate damage to the ozone layer, but which have the same effect as CFCs in terms of the greenhouse effect. Another greenhouse gas with a marginal effect is nitrous oxide (N2O) which originates from the use of nitrogen fertilisers in agriculture.

Side effects that aren't….

The warming directly caused by these emissions can lead to phenomena that increase the atmospheric concentration of greenhouses gases. An example of this is the phenomenon whereby, when the temperature increases, the solubility of CO2 in water decreases; as we can experience for ourselves when we open a bottle of champagne that isn't sufficiently chilled. So, as the temperature of the ocean rises its capacity to absorb CO2 drops; thereby increasing the quantity of anthropogenic CO2 remaining in the atmosphere.
More worrying again is the presence of methane hydrates in the permanently frozen sub- soil of high latitude regions (permafrost) and in the sediments and alluvial deposits on the ocean floor. These molecules, called clathrates, comprise 6-to-8 water molecules enclosing a single molecule of CH4 and are stable only at low temperatures and high pressure. Global warming could therefore free the methane trapped within these molecules and create a sharp rise in temperature. Melting of the permafrost is accelerated by the disappearance of the covering of snow that reflects solar radiation. Meanwhile, in the deep ocean the increase in oceanic temperature is partially impeded by the increased pressure linked to rising sea-levels resulting from the melting of land-ice. Our current, insufficient knowledge around the quantities of methane that the permafrost and the deep ocean have the latent capability to release does not allow us to evaluate the magnitude of this risk - a risk that could have catastrophic consequences. In any case, these indirect emissions can be limited only by a reduction in direct emissions.
It is equally worth making mention of aerosol emissions (tiny atmospheric particles) which, with the exception of soot emissions, reduce the global warming caused by the greenhouse effect by virtue of reflecting solar radiation and an indirect effect on water vapour and clouds. Aerosols, however, in particular sulphur aerosols , are harmful to our health and this finding has given rise to increasingly strict regulations limiting their emissions. Immaterial of the justification for such regulation, they will lead to an acceleration in the rate of climate change.

Carbon dioxide – A persistent greenhouse gas?

The earth's climate system has an abundance of carbon. It is found principally in the form of carbonate (in combination with calcium) in many rocks and sediments as well as in the form of carbon dioxide (highly stable in combination with oxygen) which is found in the atmosphere and dissolved in the ocean. Carbon is likewise found totally or partially stripped of oxygen in wood, soil humus, living organisms, in gas and hydrocarbon deposits and in its pure state as coal.
Combustion of these reduced forms releases the solar energy captured over the geological timescale, energy to which humanity has become "addicted". Lighting a match or simply breathing suffices to re-oxidise this carbon and recover this energy. The total global uptake of CO2 via photosynthesis has for a long-time been of the same order of magnitude as the amount of CO2 produced by respiration and bacterial activity. This equilibrium is disturbed by humankind producing additional CO2 as the result of burning hydrocarbons and coal, making cement and changing land-use (particularly through deforestation).. This extra CO2 accumulates in the atmosphere, altering the planet's thermal balance via the greenhouse effect which in turn causes the climate to warm. Nevertheless, the atmosphere does not retain all of the CO2 produced by human activities, losing some of it to the oceans and to the terrestrial biosphere which act as "carbon sinks" (3) . Prior to the industrial era, these exchanges of CO2 between the atmosphere, the ocean and the biosphere were already taking place but human activity has modified them. The following question now arises: How exactly will the equilibrium be regained and what will this new equilibrium be?

The pre-industrial equilibrium

Before the industrial era, oceanic and terrestrial carbon sinks worked as a balancing regime with the result that the concentration of atmospheric CObarely changed from the end of the last glacial period right up to 1850, rising only slightly from 265 to 280 parts per million (ppm). The inter-exchange mechanisms governing this equilibrium are the same as those regulating the current evolution. Before examining the present-day disruption, it is worthwhile reminding ourselves how these mechanisms function.
Carbon dioxide is soluble in water. The exchanges between the ocean and the atmosphere are controlled by the difference in partial pressure of CO2 between these two environments (4). If this partial pressure is the same in the water and in the air, the balance of the exchange is zero. If the partial pressure is higher in the air, COwill enter the water. Likewise, if the partial pressure is higher in the ocean, CO2 will escape into the atmosphere. Two principal processes are at work here. Firstly, the partial pressure of CO2 (pCO2) increases (or decreases) by ~2.3% when the temperature of water increases (or decreases) by 1°C. Thus, over a large part of the ocean, winter cooling brings about a reduction in pCO2, the consequence of which is that atmospheric carbon dioxide penetrates the ocean. Conversely, summer warming brings about a "degassing" of the ocean. Over the cycle of a year, the two phenomena offset one another. The second process is brought into play by life cycles: Marine photosynthesis consumes CO2 which is then incorporated into living matter. The consequence is a reduction of pCO2 in the ocean. This living matter subsequently produces detrital particles of organic matter which descend into the depths where they are broken down by bacteria, thereby releasing CO2 in the deep ocean. When these CO2 enriched waters return to the surface by virtue of ocean circulation, they have a high pCO2 and expel CO2 into the atmosphere. Likewise in that sphere, photosynthesis and influxes of cold water rich in CO2 have opposing effects on the exchange of CO2 between the ocean and the atmosphere and tend to balance each other.
Across the continents before the industrial era, it was the photosynthesis-respiration balance-sheet of ecosystems which controlled CO2 exchanges with the atmosphere and this remained in balance via an alternating dominance of photosynthesis in the summer and respiration in winter. The summer-winter variations in these exchanges give a "zig-zag" appearance to the recordings of CO2 concentrations in the atmosphere, wherein the lowest measurement recorded is in August when photosynthesis in the northern hemisphere (the most terrestrial) is at its highest and when the oceans in the southern hemisphere (the most oceanic) are at their coldest and absorb CO2.

When humankind disrupts the equilibrium

Since 1850, widely regarded as the commencement of the industrial era, the concentration of CO2 in the atmosphere has increased from 280 to 400 ppm. We have added a total of 555 gigatons(5) of carbon (GtC) to the 589 gigatons of carbon present in the atmosphere around 1850 through activities such as the burning of hydrocarbons (375 gigatons) and the changing of land-use (180 gigatons).
As the concentration of atmospheric CO2 increases, the ocean reacts by absorbing CO2 to the point where the partial pressure in the atmosphere and that within the surface layer of the ocean balance each other. The solubility of CO2 alone plays a role here because the biological carbon-sink in the ocean remains unchanged, its intensity depending essentially on the supply of nutrients cycled around by the currents; a supply that up until the present - day appears to have remained consistent. Across the earth's land masses (solid surfaces of the earth not covered by water) we can see that the "photosynthesis minus respiration" balance-sheet has become positive. This is due to the fertilising effect of atmospheric CO2, higher concentrations of which stimulate photosynthesis.

What is the future for carbon dioxide?

Whether humanity uses a greater or lesser amount of fossil carbon over the coming decades will evidently determine our future climate. But, whatever our mode and rate of consumption, the fact is that we will not return to pre-industrial levels of CO2 for a very long time. On the contrary, it is to be feared that the concentration of CO2 in the atmosphere will increase rapidly in the years to come.

Will humankind be able to endure changes in climate

Can Mankind Adapt?

Will there be a lack of water?

The second volume (published 2014) of the IPCC's 5th report, focusing on impacts, vulnerability and adaptions relating to climate change, devotes significant coverage to issues around water. This is indeed a sphere wherein numerous impacts of climate change make themselves felt most powerfully in human societies, whether it be inland waters in general or, more specifically, freshwater that is affected. These impacts will be geographically and sociologically-speaking exceedingly diverse.
The impacts of climate change will be particularly severe in the regions already prone to recurring phenomena of droughts and/or flooding with the most vulnerable populations being the most affected, notably in the developing countries. Climate change will exacerbate conflicts amongst users, especially in the dry, Sub-tropical zones, due to its effect of reducing resources in globally renewable surface and ground-water. Around 80% of the population will be affected by water insecurity in one way or another (availability, demand, pollution).

"Around 80% of the population will be affected by water insecurity in one way or another (availability, demand, pollution)."

Depending on the region, changes in the intensity and frequency of precipitation (rainfall) will probably be associated with an increased incidence of extreme weather events, be they floods or droughts, or even with a heightening in the intensity of these events. There could be a tripling in the number of people at risk of floods by the end of the 21st century, potentially triggering significant economic losses along with social upheaval(s). As underlined by the IPCC however, this announcement comes with the caveat that there is an insufficient understanding of the observed effects of climate change on extreme weather events, given the lack of a sequence of measurements over the long-term.

Will there be a lack of food?

"When people are hungry that does not mean that there is not enough to eat, but that they do not have enough to eat." (Amartya Sen, 1981). This is indeed the current situation as regards food in the world. There is enough food in the world to feed the world but in some regions there is nonetheless a shortage, especially for certain people and food insecurity remains a significant issue.

Food insecurity: What exactly are we talking about?

Today's food situation is characterised using the term "triple burden": 842 million people suffer from malnutrition according to the United Nation's Food and Agriculture Organisation (FAO); 2 billion people are affected by serious nutritional deficiencies (iron, iodine, vitamins etc.), whereas 1.4 billion adults are overweight. These conditions sometimes occur in and one and the same family or village. That is why, from now on, food security can no longer be defined in terms of simply knowing that sufficient quantities of food will be available but also in terms of verifying that it will be of a suitable quality (non-contamination and nutritional composition), affordably priced for people and compliant with the regulations in force (price-volatility etc.). Thus it was that during the food riots of 2008, the price increase of cereal was the primary cause of hunger across poor, urban populations. Today, the produce of agriculture, fishing and aquaculture would be enough to feed the more than 7 billion people on the planet, yet poverty is the leading cause of hunger alongside wars and crises which destroy production as well as supply chains.

Climate change emphasises food vulnerabilities

March 2014 saw the publication of the IPCC report on the impacts of climate change. From then on the links between climate change and agricultural productivity were acknowledged. By way of illustration, the temperatures observed during the second half of the 20th century up to the start of the 21st century and the concomitant changes in precipitation have already had visible and measurable effects on agriculture. In 2011, the American scientist David Lobell described the impact of climates recorded between 1980 and 2008 on average yields of the major crops. Globally over this period, climate change caused average reductions in yields of 3.8% for maize and of 5.5% for wheat.

Figure 10

Figure 10: Change in average crop yields from 1980 to 2008. (Lobell, 2011, p.618).

Climate change already affects livestock farming and crops, as it does natural habitats. Animals outside of their comfort zones, between 10 and 30°C, do not eat as much whilst higher temperatures affect their productivity and fertility. As regards crops, the effects of climate change are positive in the polar regions. But, 1°C of warming during the night of a dry season can reduce rice yields by 10% and every degree of warming above 30°C during the day in dry conditions can reduce maize yields by 1.7%. Increasing concentration of carbon dioxide in the atmosphere may, for its part, have a "fertilizing" effect on certain crops, whereas the modified rainfall patterns will generally be less favourable, largely because of the extreme weather events such as droughts and floods that will ensue. Equally, crop-quality is affected by new conditions: Protein and mineral content of seeds falls when the concentration of CO2 increases. Climate conditions affect animal and plant diseases. Competing demands on water increase in parts of the world where availability of water is already a limiting factor and the potential for crop irrigation is already reduced. It is the combined effect of all these factors on the world's different agricultural regions which we must study in order to begin to understand and prepare for the evolving agricultural supply and the adaptation it must, of necessity, make to new environmental conditions. Sub- Saharan Africa and South Asia are unfortunately amongst those regions most vulnerable to changes in temperature and rainfall. These are likewise the regions where malnutrition is the most rife.

Agriculture and food: Solutions for the climate

In the coming years, we need at one and the same time to ensure sustainable food security world-wide and contribute to the reduction of greenhouse gas emissions. We have already made mention of certain important measures to achieve this through reducing waste, moderating excessive eating habits and investing in regions where agricultural productivity is currently very low. Other complementary initiatives can also contribute to attenuating greenhouse gas emissions. Such initiatives generally carry a cost and an economic incentive should be put in place (carbon-trading, subsidy etc), thereby facilitating investment in those spheres wherein the price of the ton of carbon saved justifies this.
Avoiding losses and reducing waste, each of us in our own way, is part of this global effort.

Will health be affected?

From the time of Hippocrates, the idea that human health is largely dependent on the climate and on meteorological conditions has gradually gained ground. This being so, it follows that any change in climate will have multiple repercussions on our health - some proving to carry serious consequences. On account of climate change alone, the World Health Organisation (WHO) fears that between 2030 and 2050 there will be an average yearly excess mortality-rate of around 250,000. Foreseeable impacts will include both the direct effects of temperature on the human body (stresses linked to heat) and the indirect effects implicit in, malnutrition, water pollution, air pollution and new biological balances favouring the spread of infectious diseases. That said, the nature and extent of these potential impacts will vary greatly across the globe according to the nature of the climate, socio-economic conditions and the demographic structure.

The indirect effects of climate change: Emergence of disease

If we put to one side for a moment the repercussions for food security, the indirect health effects of climate change can be grouped under three main sections: 1) Diseases linked to food/water scarcity and to water pollution; 2) Diseases linked to air pollution; 3) Emergence or resurgence of infectious diseases or of vector-borne parasitic diseases(6). With the exception of damage to health caused by air pollution, it is the tropical and subtropical latitudes that would be the most affected, especially those economically poor countries wherein the health-care system remains precarious. However, neither the extratropical latitudes nor the economically rich countries will be totally spared.

Diseases linked to water/food scarcity and water pollution

The majority of experts are in agreement that in the 21st century climate change could exacerbate world-wide water poverty by around 20% even though the demand for water could increase drastically due to population growth and widespread poor wastewater- treatment. Rainfall patterns likewise being affected and causing, depending on location, more frequent flooding and more intense droughts. Disparities between regions would inevitably become more marked, touching all aspects of life, from the capacity of different countries to feed their people to their capacity to take care of their children. The shortage of water in particular represents a formidable factor as regards microbial infection and it can be a root-cause of dysentery or cholera epidemics as well as of an increased incidence of foodborne illnesses such as salmonellosis.

Diseases linked to air pollution

More and more arguments make us fearful that the warming of the climate will lead to a deterioration in air quality, in terms of both gas composition (i.e. higher concentrations of ozone) and particulate concentration (which decreases slightly in winter but increases significantly in summer). There could be a resultant increase in acute or chronic toxic effects, along with an exacerbation of cardiovascular and lung diseases. Furthermore, a hotter climate has a strong chance of bringing forward the flowering times, prolonging the pollen season, increasing the concentration of pollen grains in the air and enriching their allergenic content. These four trends will eventually combine to increase the prevalence and severity of respiratory allergies, rhinitis and asthma.

Vector-borne diseases

Serious concerns are advanced on a regular basis regarding a possible modification resulting from climate change in the spatial distribution of certain vectors of infectious diseases, whether it be insects (notably mosquitoes) or mites (ticks). The upshot of this could be the introduction into higher latitudes of pathogens which, up until this point, have been confined to tropical environments. These fears are not unfounded, but the complexity of the ecosystems at play makes any conclusion less reliable. In essence, the pathogenic micro- organism (virus, bacteria or parasite), its vector and the human being (not forgetting a possible animal reservoir) together constitute a system difficult to decipher which strives to re-establish equilibria and wherein interactions are numerous. The same rise in temperature can, in certain places, escalate the transmission of infectious agents whilst, in other places, it can reduce the viability of the vector.
Either way, it is undeniable that climate change will have repercussions on our health and all the evidence suggests that it is the negative effects that will prevail over the positive. We must not forget however that the links between climate and health are complex, multiform and largely modulated by how a particular society is organised.

Can the concentration of carbon dioxide be controlled?

Fossil Fuels - the number one producer of carbon dioxide

Fossil fuels currently provide a little over 80% of worldwide primary energy. The major fossil fuels are coal, oil, natural gas and their derivatives. All of them originate from the very slow transformation, over geological time, of organic debris (kerogen) contained in certain sediments. Rich in carbon and hydrogen, their combustion produces heat, of which a small portion is used as such with the rest converted into mechanical energy or electricity. Combustion of fossil fuels produces carbon dioxide and is the number one contributor to the anthropogenic greenhouse effect.

Will our use of fossil fuels decrease?

Having, by dint of their very nature, taken such a long time to form, fossil fuels are limited in quantity. Humankind's current developmental trajectory, which is largely based on use of fossil fuels, is inherently unsustainable. As regards availability of fossil fuels, the view most widely-held rests on the following idea: Accessing the reserves will certainly cost more and more, but the abundance of resources (in particular those of coal) along with on-going technological advancement will lead to the reserves continuing to grow, at least for the remainder of this century. The stock of recoverable materials is, however, inevitably finite and it is taking longer and longer to discover and exploit them. Indeed the global production of "conventional" oil started to decline in 2005. This decline is, for the moment, being compensated for, even being put slightly into reverse, by an increase in the production of "non-conventional" oil, in particular shale oil from the United States and bitumen from Canada. The question is, how long can this last? We should expect, before the end of the century, a progressive decline in the production of fossil fuels - firstly oil, then coal, then gas; despite a growing demand coming from large emerging countries such as, China, India and Brazil. Notwithstanding this projected decline, such is the extent of the coal reserves that emissions of CO2 to the atmosphere resulting from utilisation of the available fossil fuels will have grave repercussions for the climate and acidification of the ocean.

Reduce emissions linked to the production of electricity?

Electricity is an easy-to-use energy vector which inhabitants of the developed countries access through the intermediary of a reliable energy-distribution network and for whom a several hour-long power-cut would seem very difficult to manage. At the other extreme, more than a billion people have no access to electricity and they can only hope to have electricity for just several hours per day in order to improve their standard of living.
Fossil fuel emissions resulting from the production of electricity have spiralled upwards over the course of the last decade to reach 14 gigatonnes (Gt) of CO2 in 2010; this stems predominantly from the growing share of coal. According to the latest IPCC report, these emissions could double or even triple between now and 2050. Improving the output of power-plants, swapping coal for oil or, even better, for natural gas can reduce CO2 emissions. Moreover, the capture and storage of CO2 avoids it being emitted into the atmosphere. This raises another question: Can we produce electricity from something other than fossil fuels that would have zero or minimal greenhouse gases emissions?

Advantages and disadvantages of Hydropower

At this moment in time, hydropower is the only source of renewable energy to have proven its capacity to produce large amounts of energy profitably and on an industrial scale. It provides around 17% of the world's electricity. Hydropower is a concentrated form of solar energy insofar as it is the evaporation of water under the action of solar radiation which produces clouds; clouds which themselves feed precipitations in regions at high altitude. The force of earth's gravity gives water stored at height a potential energy that is transformed into kinetic energy as this water flows downwards - kinetic energy which is capable of driving turbines that turn the electricity-generating alternators.
Electricity generated from hydropower has significant advantages. It is renewable, emits only small amounts of greenhouse gases (apart from during the construction phase of dams and factories) and in suitable sites it is very economical. Above all hydroelectric energy is very versatile: It takes only several minutes to produce maximum power, making an ideal complement to intermittent sources of renewable energy such as wind and certain other forms of solar energy. In terms of as disadvantages, the large dams alter the landscape (although not always in a bad way) and necessitate the flooding of large areas of sometimes fertile land and the consequent evacuation of communities living there.

Wind energy - From the land to the sea

Windmills have been used since the Middle Ages for milling grains, pressing olives and driving pumps. Today, materials developed for aeronautics allow for the construction of long blades, several tens of metres in length, rotating around a horizontal axis (described here is only the most classic of commercial wind turbines). This axis is located on the upper section of a tower which can reach up to 150 metres (m) in height. The wind makes the rotor blades turn, thereby driving an electricity generator, likewise to be found in the nacelle at the top of the tower and capable of producing a peak power in the range of 1 to 7 megawatts (MW).
Except for the wind turbine construction-phase, the generation of electrical energy from wind turbines emits no greenhouse gases and each wind turbine takes up only 2% of the area of the agricultural land on which it is installed. However, the establishment of "large wind farms" does not meet with unanimous support. Some residents complain about degradation of the landscape, noise, harm caused to birds and of electromagnetic interference which can interfere with television reception.
Since 1995, these devices have nevertheless been extensively deployed, particularly during these last few years. The most recent global statistics indicate that at the end of 2013, the total peak power capacity of installed devices was 320,000 MW (320 gigawatts, GW). The development of offshore "wind farms" is currently underway and presents two big advantages: On the one hand, reduced pollution and other environmental nuisances for residents and on the other, the chance to benefit from often strong, more regular offshore winds. However, their installation and maintenance is difficult.

Solar Energy - Abundant but impossible to harness?

The sun brings a very large amount of heat to our planet, around seven thousand times more than the energy consumed globally. This resource would therefore be "sufficient" to meet all of humanity's needs.

The Sun - A source of heat

Solar radiation is, for example, directly absorbed by the fabric of buildings. Its energy is stored there in the form of heat and released at night. The sun can be used to heat domestic water via heat exchanges which can then be stored in suitably insulated water tanks that keep the water warm for around twenty-four hours.
Provided that this solar thermal energy can be concentrated by virtue of various suitable devices, we can use it to heat a fluid to a high temperature and produce electricity.

The Sun - A source of electricity

The transformation of solar radiation into electrical energy can be done directly through photoelectric cells that are now commonplace, in particular for charging small devices and machines in everyday use. For heavier duty usage, solar panels can be practically used in installations destined for isolated sites which do not have access to a national electricity grid. They produce direct current and are most often associated with storage batteries. Deploying them is an effective means of improving the living standards of populations cruelly suffering energy shortages. There is currently underway in the world a significant extension in usage with numerous medium-sized surfaces being equipped with these panels: Roofs of agricultural buildings, stadium stands, undercover car-parks in retail, centres or industrial premises. Most recently, moreover, large-scale projects have emerged, particularly in desert regions.
In sum, there are many ways of producing electricity without using fossil fuels and there is no reason to think that any of these alone will be the panacea. The choice between these solutions will depend on the local conditions and the political decisions peculiar to each country.

Store energy to improve usage?

Storing energy in the form of electricity or heat for use as and when needed is necessary and can lead to savings in terms of both costs and greenhouse gas emissions. Storage allows for smoothing in the supply of electricity: The the excess from off-peak periods is stored for use during subsequent peak periods. For intermittent energy sources such as wind and solar photovoltaic (PV), production of which does not always match demand, storage is vital if we want to avoid use of greenhouse gas-emitting complementary sources of energy to produce the extra electricity needed.

Reduce emissions linked to transport?

Transport of passengers and freight plays an important role in trade, the economy, the supply of food and our quality of life. According to the IPCC's fifth report (2013), transport emissions were 6.7 Gt of CO2 in 2010 and without taking effective action, these emissions could double between now and 2050 due to population growth and global economic development. Several complementary approaches allow us to curb this unfortunate trend: Reducing vehicle emissions for a given service, improving infrastructures, avoiding siting production far from the place of consumption, changing our behaviour and putting in place political measures that are coherent.

Imprisoning "industrial" carbon dioxide underground?

The capture and geological storage of CO2 is a powerful way of combatting climate change. It's a case of capturing the CO2 emitted from fixed industrial facilities and burying it in deep geological layers so that it can remain there for several centuries, even several millennia - the time-span needed to secure the transition towards a future wherein energy will be entirely decarbonised. CO2 of this origin represents nearly half of all CO2 emitted at ground- level. Acting on these sources will have a significant impact in terms of controlling the atmospheric CO2 concentration.

Mitigation(7) and Adaptation

International political discussions have led to our setting ourselves on the following objective: Limit the increase in average global temperature to 2°C as compared with its average value between 1860 and 1880. Based on numerical simulations of the climate, to achieve this target we must make sure that the post-1870 cumulative emissions of CO2 stay within the range of 2550 to 3150 Gt of CO2. This range takes into account various hypothesises regarding other relevant factors, notably the other greenhouse gases and aerosols. Given the fact that total cumulative emissions up to 2011 have already been estimated to be 1900 Gt of CO2, it follows that we would have to limit emissions to between 650 and 1250 Gt of CO2, in other words twenty to forty years-worth of emissions at the current rate.

What to do in the face of climate change?

Two responses, non-exclusive and often complementary, must be adopted to reduce the climate change-related risks subject to varying deadlines: Adaptation and mitigation (or reduction of emissions).
Adaptation to the effects of climate change, such as the choice of different cultivars or the construction of a dam in certain places, can be beneficial in confronting current and future risks. Adaptation planning and execution can be improved by complementary initiatives such as raising the awareness of populations to risks of flooding. These need to be led at every level, from that of the individual to that of the government.
Mitigation in the short-term and continuing over the course of this century can substantially reduce the future effects of climate change, that is to say in the last decades of the 21st century and beyond. It can bring further benefits such as reduced pollution via decreasing the fuel consumption of vehicles. Mitigation can likewise entail risks, if only in terms of deploying technologies inconvenient to use and that carry a cost not properly assessed at the outset. Notwithstanding this, such risks are not as severe, not as wide-spread and easier to reverse than those of climate change.
All of these actions are dependent on societal values, objectives and perceptions of risk. Analysis of diverse interests, of circumstances, socio-cultural contexts and expectations can help to make good decisions. Possible options for mitigation and adaptation are myriad but no single one will suffice on its own. Political choices and co-operation at every level will determine the range of measures to be adopted and the efficacy of their implementation. Such a process can benefit from a co-ordinated response linking adaptation and mitigation with other societal objectives.

The Climate - A global problem?

Globally, what have been the main features of evolving public opinion vis-à-vis climate change?

Public opinion on climate change represents a major indicator as to how readily actions to reduce emissions will be accepted at both the individual and the collective level. Within this arena it is generally recognised that any change in collective behaviour stems from: 1) individual recognition of the reality of the change; 2) acceptance of its anthropogenic origin; 3) concern about negative impacts and 4) belief that it is essentially a personal and social responsibility.

Doubt as to the part played by human beings

Since the end of the last millennium, studies often show that in certain countries levels of doubt and scepticism regarding climate change have risen. Despite this trend, in many countries a large majority of the population continued to express a high level of concern and clear recognition of the problem.
The Global Trends study led by Ipsos-Mori in 2014 shows that of 20 countries studied, the lowest percentages of people convinced of the anthropogenic origin of climate change are in the United States, the United Kingdom and Australia (64%, 64% and 54% respectively). Seven countries (China, Argentina, India, Italy, Spain, Turkey and France) show high percentages over 80%, whereas in Russia and Poland the percentages are low and climate- scepticism is widespread. Another international study carried out in 2014 across twelve countries confirms these results. However, inter-country comparison is littered with obstacles. Use of the internet as a method of conducting the majority of these studies means that the participants are not necessarily representative of the population as a whole, particularly as regards developing countries.

Fears that fade

Longitudinal studies conducted in the same country and by the same organisation are more reliable. In the United Kingdom, Ipsos-Mori and the University of Cardiff compiled the results of studies from 2005 onwards which show a continuing rise in the proportion of British people who doubt that the earth's climate is in the process of changing (these are doubts about the reality of climate change as opposed to its cause). Results show that these doubts rose from 4% in 2005 to 15% in 2010 and to 19% in 2013. According to serval studies in the rest of the world, the level of concern vis-à-vis environmental questions (including climate change) has plummeted over the last few years.

Highly influential media

The level of concern can be influenced by the intensity and the type of media coverage vis- à-vis these issues but equally by competing concerns about the economy, first-hand experience of extreme weather events, communication campaigns organised by lobbying groups as well as by the discourse of political figures demanding action. Two European studies concluded that the economic context and in particular the recessions at the end of the last millennium played a crucial role in the decline of concerns about the environment. This finding is consistent with the paradigm whereby individuals have a finite "pool of worry", meaning that urgent concerns such as those around employment or the cost of living take precedence.
By way of a conclusion, additional research efforts are needed in order to understand the mechanisms at the origin of the evolution in public opinion on climate change over time, whether that be within one country or between different countries. A multiplicity of factors - socioeconomical, political, geographical and psychological - determine public opinion. The varying level of influence of each of these, across the different parts of the world, are not fully known. It is crucial that we understand these aspects given that international agreement between extremely diverse countries is at the heart of concluding an effective treaty to reduce greenhouse gas emissions.

Traduction de quelques chapitres du livre "Climat, le temps d'agir"

par Lara Heledd Davies-Jones de l’Université de Cardiff au Pays de Galles

Preface

By Laurence Tubiana
France's Ambassador responsible for negotiations on climate change and Special Representative for the 2015 United Nations Climate Change Conference in Paris (COP21).

Climate, the Time to Act is a useful tool for all those wishing to understand the urgency of the climate change phenomenon and the need to take concrete action at every level: International, national, regional, but also individual.
It is essential that all citizens of the country hosting the 21st Conference of Parties (COP21) in December 2015 are able to understand and take ownership of the findings of international scientists presented in the latest report by the Intergovernmental Panel on Climate Change (IPCC). As the result of the huge carbon dioxide emissions into the atmosphere since the start of the industrial revolution, the climate of the entire planet is changing and will continue to change if nothing is done.
There is absolutely no reason to doubt the impact of human activity on climate change despite the fanciful notions of the climate change sceptics. Of course, the evolution and repercussions of climate change are very diverse in nature and vary depending on the region and the country, but our natural resources and our way of life will inevitably be affected. This book provides many concrete examples of the changes that could have consequences for the oceans, marine and terrestrial biodiversity, rising sea-levels, water resources, agriculture and health. Such changes could in turn trigger extreme weather events in the form of floods, storms and droughts.
Ultimately, any endeavour to transform the world and protect the climate must be the responsibility of society as a whole. That being, this book ends with a short chapter on the changing perceptions of ordinary citizens regarding climate change. Reading this chapter highlights how efforts to raise awareness across the world are still in very much in their infancy and that the work to educate and inform people must continue at every level.
It's the choice of our future development model that is at stake. We must make the change and head towards low-carbon economies by virtue of significantly reducing the use of fossil fuels in transport, construction and industry; reducing energy-usage full stop; being more efficient and, wherever possible, neutralising emissions across numerous spheres. This evolution in development models must be adapted to each developed or developing country in accordance with national choices, but such a reorientation is inevitable if we want to limit the effects of climate change.
Any international agreement struck in December 2015 in Paris must send a clear signal to all protagonists: It must, whilst establishing a set of regulations for all countries with a view to securing this century a significant reduction in global emissions, align the expectations of all parties and lay down clear ground rules.
To keep global warming below 2°C, 195 countries must reach an agreement and commit to reducing greenhouse gas emissions. The window of opportunity is very small but optimism must prevail. In France, several initiatives are emerging (1)Certain regions such as Aquitaine have set up a strategy unit to address the issue of reducing emissions and adapting to future changes. Territorial authorities play a central role in the formulation of strategies for sustainable regional development. Similarly, many companies are now increasingly convinced that a low-carbon economy represents the future and that fossil fuel resources constitute a risky investment. I am greatly heartened by all this.
You'll find in this book, written by recognised experts in language easy for everyone to understand, wide-ranging reflections to share"¦and to act upon.

Should we be worrying about a change in climate brought about by human activities?

Faut-il s'inquiéter d'une évolution du climat due aux activités humaines ?

Does the recent increase in temperature leave any room to doubt its anthropogenic (human caused) origin?

As far back as the 1970s, publication of the Keeling Curve(2) (illustrating the concentration of carbon dioxide CO2 in the atmosphere) was confirming what we then suspected. Namely that human activity, especially the huge use of fossil fuels, permanently changes the composition of the atmosphere. The seminal work of François Joseph from France, John Tyndall from Ireland and Svante Arrhénius from Sweden had already highlighted in the 19th century the inevitable global warming of the planet arising from this evolution in the concentration(s) of CO2. This is exactly what has been observed. However, after a rapid increase in temperatures over the period 1980-1990, this upward trend seems to have noticeably slowed down over the past fifteen years. Nevertheless, the ten-year average temperature has not stopped increasing.

Figure 1

The different curves correspond to the different sources of datasets (HadCRUT4, MLOST, GISS).
Figure 1: Change in average global temperature over ten years (Stocker, 2013, p.6).

This slow-down comes at a very bad time in the context of raising awareness about the climate emergency. But, it is in many respects representative of the behaviour of the climate-system and will serve as the baseline running throughout this chapter. Moreover, this pause or hiatus as it is sometimes called, changes nothing as regards long-term evolution of the climate. This we can say in all certainty because the phenomenon of warming arises from a basic principle of physics: Any system that gains more energy than it loses inevitably warms. It is this fundamental physics that we address here.
A body isolated in space, such as the Earth, gains and loses energy only via electromagnetic radiation (EMR). Solar radiation heats up earth which cools itself by emitting radiation of equal energy into space. Taking into account the respective temperatures of the sun and the earth, solar radiation corresponds to visible light and short near-infrared wavelengths, whereas radiation emitted by the earth corresponds to longer wavelengths in the form of infrared rays.

Figure 2

Figure 2: The radiation balance that determines the average temperature of the earth (Le Treut, 2007, p.115).

At thermal equilibrium, the earth emits as much radiation as it absorbs and we call this the radiation balance of the earth. When we use the term "earth" here, we are referring to earth as a system (ground, atmosphere, ocean) signifying that the radiation emitted is that which is released at the top of the earth's atmosphere and lost to space. Even in the absence of anthropogenic emissions, the atmosphere plays an essential role in the temperature of the earth's surface through the action of the greenhouse effect whereby the radiation leaving the atmosphere is significantly lower than that being emitted from the earth's surface. The atmosphere therefore acts as an insulating blanket with the insulating effect due to naturally-occurring greenhouse gases in the atmosphere like water vapour, carbon dioxide, methane and several other minor gases that absorb infrared radiation. This process of absorption is selective, it occurs only within certain frequency bands that are characteristic of greenhouses gases and within which the radiation coming from the surface of the earth is absorbed to various extents. The increase in the concentration of certain greenhouse gases enhances this insulating effect which in turn de-stabilizes the planet's radiation balance.

The anthropogenic contribution to the greenhouse effect.

From 1850 onwards and the start of the industrial era, the concentration of CO2 has increased more and more rapidly. As a consequence, the greenhouse effect has likewise increased leading to a rise of about 0.85°C in the earth's average temperature over this period. However, this increase has not been linear: The temperature rose sharply during two long periods of around thirty years each (close to 0.17°C per decade from 1910 to 1940 and again from 1970 to 1998), separated by a relatively stagnant period. Since 1998, this temperature has changed only slightly (from 0.05 to 0.06°C per decade) whereas emissions from greenhouse gases have not stopped increasing. What we are talking about here is a pause or hiatus in the warming process.

Figure 3

Figure 3 shows the current concentrations of the major greenhouse gases (carbon dioxide, methane, nitrous oxide) and their unprecedented rate of increase (Bernstein, 2007, p.38).

Such fluctuations are not surprising. The weather fluctuates from one year to the next and temperature records do not fall every year. Moreover, the climate is defined as the average weather pattern over a period of at least thirty years in order to eliminate chaotic fluctuations from one year to the next. Variations observed in the rate of temperature increase are recorded for the mid-point of the decade. Understanding and predicting these variations is a crucial factor in climate forecasting because it's all about the near-future.

Which greenhouse gases are the worst offenders?

Which anthropogenic emissions affect the climate?

Carbon dioxide and methane are top of the list.

The principal anthropogenic emissions affecting the climate are gas emissions which absorb infrared radiation and are eliminated only very slowly from the atmosphere. These gases remain in the atmosphere for several years or indeed several decades before the earth's natural processes remove them from the atmosphere. The absorption capacity of molecules is not the same for all gases. It is the product of this absorption capacity and the number of molecules that must be taken into account. A good illustration of this is methane. A methane molecule absorbs more infrared radiation than a molecule of carbon dioxide, but the number of molecules (per cm3) is 200 times lower than that of CO2. The net effect is that methane directly absorbs a slightly lower level of infrared radiation than CO2.
It follows therefore that carbon dioxide is the principal contributor to the greenhouse effect. It is produced largely from the use of fossil fuels (coal, oil and gas) which together supply 80% of the global energy market. It also produced from industrial processes such as cement production. Deforestation and other changes in land-use likewise contribute to 15% of total emissions.
Methane (CH4) is the second biggest contributor to the greenhouse effect and comes from a variety of sources. It is produced mainly by fermentation, in the absence of air, (anaerobic fermentation) which occurs during the cultivation of rice in soil that is naturally or artificially flooded. The same phenomenon is found during the rearing of ruminant livestock whose digestive systems produce methane which is then released via the upper and lower digestive tracts, i.e. by burping and passing wind. Manure, liquid manure and landfill sites also produce methane. Partial combustion of biomass is another source of methane which occurs during agricultural and forest fires. Lastly, the use of fossil fuels constitutes another principal source of methane emission. To begin with, the exploitation of "natural gas", (largely composed of methane) can give rise to fugitive emissions during well-drilling, extraction, transport, storage and distribution. Such emissions can also result from the malfunctioning of sluice gates or valves, or be linked to maintenance operations that lead to purging and emptying pipelines. Likewise, the oil industry produces methane as a by- product, of which only a small part is burned in the gas-flares of refineries, of oil fields or of offshore platforms.
Finally, we must mention the lesser contribution of fluorinated gases which were brought in to replace chlorofluorocarbons (CFCs) in order to mitigate damage to the ozone layer, but which have the same effect as CFCs in terms of the greenhouse effect. Another greenhouse gas with a marginal effect is nitrous oxide (N2O) which originates from the use of nitrogen fertilisers in agriculture.

Side effects that aren't….

The warming directly caused by these emissions can lead to phenomena that increase the atmospheric concentration of greenhouses gases. An example of this is the phenomenon whereby, when the temperature increases, the solubility of CO2 in water decreases; as we can experience for ourselves when we open a bottle of champagne that isn't sufficiently chilled. So, as the temperature of the ocean rises its capacity to absorb CO2 drops; thereby increasing the quantity of anthropogenic CO2 remaining in the atmosphere.
More worrying again is the presence of methane hydrates in the permanently frozen sub- soil of high latitude regions (permafrost) and in the sediments and alluvial deposits on the ocean floor. These molecules, called clathrates, comprise 6-to-8 water molecules enclosing a single molecule of CH4 and are stable only at low temperatures and high pressure. Global warming could therefore free the methane trapped within these molecules and create a sharp rise in temperature. Melting of the permafrost is accelerated by the disappearance of the covering of snow that reflects solar radiation. Meanwhile, in the deep ocean the increase in oceanic temperature is partially impeded by the increased pressure linked to rising sea-levels resulting from the melting of land-ice. Our current, insufficient knowledge around the quantities of methane that the permafrost and the deep ocean have the latent capability to release does not allow us to evaluate the magnitude of this risk - a risk that could have catastrophic consequences. In any case, these indirect emissions can be limited only by a reduction in direct emissions.
It is equally worth making mention of aerosol emissions (tiny atmospheric particles) which, with the exception of soot emissions, reduce the global warming caused by the greenhouse effect by virtue of reflecting solar radiation and an indirect effect on water vapour and clouds. Aerosols, however, in particular sulphur aerosols , are harmful to our health and this finding has given rise to increasingly strict regulations limiting their emissions. Immaterial of the justification for such regulation, they will lead to an acceleration in the rate of climate change.

Carbon dioxide – A persistent greenhouse gas?

The earth's climate system has an abundance of carbon. It is found principally in the form of carbonate (in combination with calcium) in many rocks and sediments as well as in the form of carbon dioxide (highly stable in combination with oxygen) which is found in the atmosphere and dissolved in the ocean. Carbon is likewise found totally or partially stripped of oxygen in wood, soil humus, living organisms, in gas and hydrocarbon deposits and in its pure state as coal.
Combustion of these reduced forms releases the solar energy captured over the geological timescale, energy to which humanity has become "addicted". Lighting a match or simply breathing suffices to re-oxidise this carbon and recover this energy. The total global uptake of CO2 via photosynthesis has for a long-time been of the same order of magnitude as the amount of CO2 produced by respiration and bacterial activity. This equilibrium is disturbed by humankind producing additional CO2 as the result of burning hydrocarbons and coal, making cement and changing land-use (particularly through deforestation).. This extra CO2 accumulates in the atmosphere, altering the planet's thermal balance via the greenhouse effect which in turn causes the climate to warm. Nevertheless, the atmosphere does not retain all of the CO2 produced by human activities, losing some of it to the oceans and to the terrestrial biosphere which act as "carbon sinks" (3) . Prior to the industrial era, these exchanges of CO2 between the atmosphere, the ocean and the biosphere were already taking place but human activity has modified them. The following question now arises: How exactly will the equilibrium be regained and what will this new equilibrium be?

The pre-industrial equilibrium

Before the industrial era, oceanic and terrestrial carbon sinks worked as a balancing regime with the result that the concentration of atmospheric CObarely changed from the end of the last glacial period right up to 1850, rising only slightly from 265 to 280 parts per million (ppm). The inter-exchange mechanisms governing this equilibrium are the same as those regulating the current evolution. Before examining the present-day disruption, it is worthwhile reminding ourselves how these mechanisms function.
Carbon dioxide is soluble in water. The exchanges between the ocean and the atmosphere are controlled by the difference in partial pressure of CO2 between these two environments (4). If this partial pressure is the same in the water and in the air, the balance of the exchange is zero. If the partial pressure is higher in the air, COwill enter the water. Likewise, if the partial pressure is higher in the ocean, CO2 will escape into the atmosphere. Two principal processes are at work here. Firstly, the partial pressure of CO2 (pCO2) increases (or decreases) by ~2.3% when the temperature of water increases (or decreases) by 1°C. Thus, over a large part of the ocean, winter cooling brings about a reduction in pCO2, the consequence of which is that atmospheric carbon dioxide penetrates the ocean. Conversely, summer warming brings about a "degassing" of the ocean. Over the cycle of a year, the two phenomena offset one another. The second process is brought into play by life cycles: Marine photosynthesis consumes CO2 which is then incorporated into living matter. The consequence is a reduction of pCO2 in the ocean. This living matter subsequently produces detrital particles of organic matter which descend into the depths where they are broken down by bacteria, thereby releasing CO2 in the deep ocean. When these CO2 enriched waters return to the surface by virtue of ocean circulation, they have a high pCO2 and expel CO2 into the atmosphere. Likewise in that sphere, photosynthesis and influxes of cold water rich in CO2 have opposing effects on the exchange of CO2 between the ocean and the atmosphere and tend to balance each other.
Across the continents before the industrial era, it was the photosynthesis-respiration balance-sheet of ecosystems which controlled CO2 exchanges with the atmosphere and this remained in balance via an alternating dominance of photosynthesis in the summer and respiration in winter. The summer-winter variations in these exchanges give a "zig-zag" appearance to the recordings of CO2 concentrations in the atmosphere, wherein the lowest measurement recorded is in August when photosynthesis in the northern hemisphere (the most terrestrial) is at its highest and when the oceans in the southern hemisphere (the most oceanic) are at their coldest and absorb CO2.

When humankind disrupts the equilibrium

Since 1850, widely regarded as the commencement of the industrial era, the concentration of CO2 in the atmosphere has increased from 280 to 400 ppm. We have added a total of 555 gigatons(5) of carbon (GtC) to the 589 gigatons of carbon present in the atmosphere around 1850 through activities such as the burning of hydrocarbons (375 gigatons) and the changing of land-use (180 gigatons).
As the concentration of atmospheric CO2 increases, the ocean reacts by absorbing CO2 to the point where the partial pressure in the atmosphere and that within the surface layer of the ocean balance each other. The solubility of CO2 alone plays a role here because the biological carbon-sink in the ocean remains unchanged, its intensity depending essentially on the supply of nutrients cycled around by the currents; a supply that up until the present - day appears to have remained consistent. Across the earth's land masses (solid surfaces of the earth not covered by water) we can see that the "photosynthesis minus respiration" balance-sheet has become positive. This is due to the fertilising effect of atmospheric CO2, higher concentrations of which stimulate photosynthesis.

What is the future for carbon dioxide?

Whether humanity uses a greater or lesser amount of fossil carbon over the coming decades will evidently determine our future climate. But, whatever our mode and rate of consumption, the fact is that we will not return to pre-industrial levels of CO2 for a very long time. On the contrary, it is to be feared that the concentration of CO2 in the atmosphere will increase rapidly in the years to come.

Will humankind be able to endure changes in climate

Can Mankind Adapt?

Will there be a lack of water?

The second volume (published 2014) of the IPCC's 5th report, focusing on impacts, vulnerability and adaptions relating to climate change, devotes significant coverage to issues around water. This is indeed a sphere wherein numerous impacts of climate change make themselves felt most powerfully in human societies, whether it be inland waters in general or, more specifically, freshwater that is affected. These impacts will be geographically and sociologically-speaking exceedingly diverse.
The impacts of climate change will be particularly severe in the regions already prone to recurring phenomena of droughts and/or flooding with the most vulnerable populations being the most affected, notably in the developing countries. Climate change will exacerbate conflicts amongst users, especially in the dry, Sub-tropical zones, due to its effect of reducing resources in globally renewable surface and ground-water. Around 80% of the population will be affected by water insecurity in one way or another (availability, demand, pollution).

"Around 80% of the population will be affected by water insecurity in one way or another (availability, demand, pollution)."

Depending on the region, changes in the intensity and frequency of precipitation (rainfall) will probably be associated with an increased incidence of extreme weather events, be they floods or droughts, or even with a heightening in the intensity of these events. There could be a tripling in the number of people at risk of floods by the end of the 21st century, potentially triggering significant economic losses along with social upheaval(s). As underlined by the IPCC however, this announcement comes with the caveat that there is an insufficient understanding of the observed effects of climate change on extreme weather events, given the lack of a sequence of measurements over the long-term.

Will there be a lack of food?

"When people are hungry that does not mean that there is not enough to eat, but that they do not have enough to eat." (Amartya Sen, 1981). This is indeed the current situation as regards food in the world. There is enough food in the world to feed the world but in some regions there is nonetheless a shortage, especially for certain people and food insecurity remains a significant issue.

Food insecurity: What exactly are we talking about?

Today's food situation is characterised using the term "triple burden": 842 million people suffer from malnutrition according to the United Nation's Food and Agriculture Organisation (FAO); 2 billion people are affected by serious nutritional deficiencies (iron, iodine, vitamins etc.), whereas 1.4 billion adults are overweight. These conditions sometimes occur in and one and the same family or village. That is why, from now on, food security can no longer be defined in terms of simply knowing that sufficient quantities of food will be available but also in terms of verifying that it will be of a suitable quality (non-contamination and nutritional composition), affordably priced for people and compliant with the regulations in force (price-volatility etc.). Thus it was that during the food riots of 2008, the price increase of cereal was the primary cause of hunger across poor, urban populations. Today, the produce of agriculture, fishing and aquaculture would be enough to feed the more than 7 billion people on the planet, yet poverty is the leading cause of hunger alongside wars and crises which destroy production as well as supply chains.

Climate change emphasises food vulnerabilities

March 2014 saw the publication of the IPCC report on the impacts of climate change. From then on the links between climate change and agricultural productivity were acknowledged. By way of illustration, the temperatures observed during the second half of the 20th century up to the start of the 21st century and the concomitant changes in precipitation have already had visible and measurable effects on agriculture. In 2011, the American scientist David Lobell described the impact of climates recorded between 1980 and 2008 on average yields of the major crops. Globally over this period, climate change caused average reductions in yields of 3.8% for maize and of 5.5% for wheat.

Figure 10

Figure 10: Change in average crop yields from 1980 to 2008. (Lobell, 2011, p.618).

Climate change already affects livestock farming and crops, as it does natural habitats. Animals outside of their comfort zones, between 10 and 30°C, do not eat as much whilst higher temperatures affect their productivity and fertility. As regards crops, the effects of climate change are positive in the polar regions. But, 1°C of warming during the night of a dry season can reduce rice yields by 10% and every degree of warming above 30°C during the day in dry conditions can reduce maize yields by 1.7%. Increasing concentration of carbon dioxide in the atmosphere may, for its part, have a "fertilizing" effect on certain crops, whereas the modified rainfall patterns will generally be less favourable, largely because of the extreme weather events such as droughts and floods that will ensue. Equally, crop-quality is affected by new conditions: Protein and mineral content of seeds falls when the concentration of CO2 increases. Climate conditions affect animal and plant diseases. Competing demands on water increase in parts of the world where availability of water is already a limiting factor and the potential for crop irrigation is already reduced. It is the combined effect of all these factors on the world's different agricultural regions which we must study in order to begin to understand and prepare for the evolving agricultural supply and the adaptation it must, of necessity, make to new environmental conditions. Sub- Saharan Africa and South Asia are unfortunately amongst those regions most vulnerable to changes in temperature and rainfall. These are likewise the regions where malnutrition is the most rife.

Agriculture and food: Solutions for the climate

In the coming years, we need at one and the same time to ensure sustainable food security world-wide and contribute to the reduction of greenhouse gas emissions. We have already made mention of certain important measures to achieve this through reducing waste, moderating excessive eating habits and investing in regions where agricultural productivity is currently very low. Other complementary initiatives can also contribute to attenuating greenhouse gas emissions. Such initiatives generally carry a cost and an economic incentive should be put in place (carbon-trading, subsidy etc), thereby facilitating investment in those spheres wherein the price of the ton of carbon saved justifies this.
Avoiding losses and reducing waste, each of us in our own way, is part of this global effort.

Will health be affected?

From the time of Hippocrates, the idea that human health is largely dependent on the climate and on meteorological conditions has gradually gained ground. This being so, it follows that any change in climate will have multiple repercussions on our health - some proving to carry serious consequences. On account of climate change alone, the World Health Organisation (WHO) fears that between 2030 and 2050 there will be an average yearly excess mortality-rate of around 250,000. Foreseeable impacts will include both the direct effects of temperature on the human body (stresses linked to heat) and the indirect effects implicit in, malnutrition, water pollution, air pollution and new biological balances favouring the spread of infectious diseases. That said, the nature and extent of these potential impacts will vary greatly across the globe according to the nature of the climate, socio-economic conditions and the demographic structure.

The indirect effects of climate change: Emergence of disease

If we put to one side for a moment the repercussions for food security, the indirect health effects of climate change can be grouped under three main sections: 1) Diseases linked to food/water scarcity and to water pollution; 2) Diseases linked to air pollution; 3) Emergence or resurgence of infectious diseases or of vector-borne parasitic diseases(6). With the exception of damage to health caused by air pollution, it is the tropical and subtropical latitudes that would be the most affected, especially those economically poor countries wherein the health-care system remains precarious. However, neither the extratropical latitudes nor the economically rich countries will be totally spared.

Diseases linked to water/food scarcity and water pollution

The majority of experts are in agreement that in the 21st century climate change could exacerbate world-wide water poverty by around 20% even though the demand for water could increase drastically due to population growth and widespread poor wastewater- treatment. Rainfall patterns likewise being affected and causing, depending on location, more frequent flooding and more intense droughts. Disparities between regions would inevitably become more marked, touching all aspects of life, from the capacity of different countries to feed their people to their capacity to take care of their children. The shortage of water in particular represents a formidable factor as regards microbial infection and it can be a root-cause of dysentery or cholera epidemics as well as of an increased incidence of foodborne illnesses such as salmonellosis.

Diseases linked to air pollution

More and more arguments make us fearful that the warming of the climate will lead to a deterioration in air quality, in terms of both gas composition (i.e. higher concentrations of ozone) and particulate concentration (which decreases slightly in winter but increases significantly in summer). There could be a resultant increase in acute or chronic toxic effects, along with an exacerbation of cardiovascular and lung diseases. Furthermore, a hotter climate has a strong chance of bringing forward the flowering times, prolonging the pollen season, increasing the concentration of pollen grains in the air and enriching their allergenic content. These four trends will eventually combine to increase the prevalence and severity of respiratory allergies, rhinitis and asthma.

Vector-borne diseases

Serious concerns are advanced on a regular basis regarding a possible modification resulting from climate change in the spatial distribution of certain vectors of infectious diseases, whether it be insects (notably mosquitoes) or mites (ticks). The upshot of this could be the introduction into higher latitudes of pathogens which, up until this point, have been confined to tropical environments. These fears are not unfounded, but the complexity of the ecosystems at play makes any conclusion less reliable. In essence, the pathogenic micro- organism (virus, bacteria or parasite), its vector and the human being (not forgetting a possible animal reservoir) together constitute a system difficult to decipher which strives to re-establish equilibria and wherein interactions are numerous. The same rise in temperature can, in certain places, escalate the transmission of infectious agents whilst, in other places, it can reduce the viability of the vector.
Either way, it is undeniable that climate change will have repercussions on our health and all the evidence suggests that it is the negative effects that will prevail over the positive. We must not forget however that the links between climate and health are complex, multiform and largely modulated by how a particular society is organised.

Can the concentration of carbon dioxide be controlled?

Fossil Fuels - the number one producer of carbon dioxide

Fossil fuels currently provide a little over 80% of worldwide primary energy. The major fossil fuels are coal, oil, natural gas and their derivatives. All of them originate from the very slow transformation, over geological time, of organic debris (kerogen) contained in certain sediments. Rich in carbon and hydrogen, their combustion produces heat, of which a small portion is used as such with the rest converted into mechanical energy or electricity. Combustion of fossil fuels produces carbon dioxide and is the number one contributor to the anthropogenic greenhouse effect.

Will our use of fossil fuels decrease?

Having, by dint of their very nature, taken such a long time to form, fossil fuels are limited in quantity. Humankind's current developmental trajectory, which is largely based on use of fossil fuels, is inherently unsustainable. As regards availability of fossil fuels, the view most widely-held rests on the following idea: Accessing the reserves will certainly cost more and more, but the abundance of resources (in particular those of coal) along with on-going technological advancement will lead to the reserves continuing to grow, at least for the remainder of this century. The stock of recoverable materials is, however, inevitably finite and it is taking longer and longer to discover and exploit them. Indeed the global production of "conventional" oil started to decline in 2005. This decline is, for the moment, being compensated for, even being put slightly into reverse, by an increase in the production of "non-conventional" oil, in particular shale oil from the United States and bitumen from Canada. The question is, how long can this last? We should expect, before the end of the century, a progressive decline in the production of fossil fuels - firstly oil, then coal, then gas; despite a growing demand coming from large emerging countries such as, China, India and Brazil. Notwithstanding this projected decline, such is the extent of the coal reserves that emissions of CO2 to the atmosphere resulting from utilisation of the available fossil fuels will have grave repercussions for the climate and acidification of the ocean.

Reduce emissions linked to the production of electricity?

Electricity is an easy-to-use energy vector which inhabitants of the developed countries access through the intermediary of a reliable energy-distribution network and for whom a several hour-long power-cut would seem very difficult to manage. At the other extreme, more than a billion people have no access to electricity and they can only hope to have electricity for just several hours per day in order to improve their standard of living.
Fossil fuel emissions resulting from the production of electricity have spiralled upwards over the course of the last decade to reach 14 gigatonnes (Gt) of CO2 in 2010; this stems predominantly from the growing share of coal. According to the latest IPCC report, these emissions could double or even triple between now and 2050. Improving the output of power-plants, swapping coal for oil or, even better, for natural gas can reduce CO2 emissions. Moreover, the capture and storage of CO2 avoids it being emitted into the atmosphere. This raises another question: Can we produce electricity from something other than fossil fuels that would have zero or minimal greenhouse gases emissions?

Advantages and disadvantages of Hydropower

At this moment in time, hydropower is the only source of renewable energy to have proven its capacity to produce large amounts of energy profitably and on an industrial scale. It provides around 17% of the world's electricity. Hydropower is a concentrated form of solar energy insofar as it is the evaporation of water under the action of solar radiation which produces clouds; clouds which themselves feed precipitations in regions at high altitude. The force of earth's gravity gives water stored at height a potential energy that is transformed into kinetic energy as this water flows downwards - kinetic energy which is capable of driving turbines that turn the electricity-generating alternators.
Electricity generated from hydropower has significant advantages. It is renewable, emits only small amounts of greenhouse gases (apart from during the construction phase of dams and factories) and in suitable sites it is very economical. Above all hydroelectric energy is very versatile: It takes only several minutes to produce maximum power, making an ideal complement to intermittent sources of renewable energy such as wind and certain other forms of solar energy. In terms of as disadvantages, the large dams alter the landscape (although not always in a bad way) and necessitate the flooding of large areas of sometimes fertile land and the consequent evacuation of communities living there.

Wind energy - From the land to the sea

Windmills have been used since the Middle Ages for milling grains, pressing olives and driving pumps. Today, materials developed for aeronautics allow for the construction of long blades, several tens of metres in length, rotating around a horizontal axis (described here is only the most classic of commercial wind turbines). This axis is located on the upper section of a tower which can reach up to 150 metres (m) in height. The wind makes the rotor blades turn, thereby driving an electricity generator, likewise to be found in the nacelle at the top of the tower and capable of producing a peak power in the range of 1 to 7 megawatts (MW).
Except for the wind turbine construction-phase, the generation of electrical energy from wind turbines emits no greenhouse gases and each wind turbine takes up only 2% of the area of the agricultural land on which it is installed. However, the establishment of "large wind farms" does not meet with unanimous support. Some residents complain about degradation of the landscape, noise, harm caused to birds and of electromagnetic interference which can interfere with television reception.
Since 1995, these devices have nevertheless been extensively deployed, particularly during these last few years. The most recent global statistics indicate that at the end of 2013, the total peak power capacity of installed devices was 320,000 MW (320 gigawatts, GW). The development of offshore "wind farms" is currently underway and presents two big advantages: On the one hand, reduced pollution and other environmental nuisances for residents and on the other, the chance to benefit from often strong, more regular offshore winds. However, their installation and maintenance is difficult.

Solar Energy - Abundant but impossible to harness?

The sun brings a very large amount of heat to our planet, around seven thousand times more than the energy consumed globally. This resource would therefore be "sufficient" to meet all of humanity's needs.

The Sun - A source of heat

Solar radiation is, for example, directly absorbed by the fabric of buildings. Its energy is stored there in the form of heat and released at night. The sun can be used to heat domestic water via heat exchanges which can then be stored in suitably insulated water tanks that keep the water warm for around twenty-four hours.
Provided that this solar thermal energy can be concentrated by virtue of various suitable devices, we can use it to heat a fluid to a high temperature and produce electricity.

The Sun - A source of electricity

The transformation of solar radiation into electrical energy can be done directly through photoelectric cells that are now commonplace, in particular for charging small devices and machines in everyday use. For heavier duty usage, solar panels can be practically used in installations destined for isolated sites which do not have access to a national electricity grid. They produce direct current and are most often associated with storage batteries. Deploying them is an effective means of improving the living standards of populations cruelly suffering energy shortages. There is currently underway in the world a significant extension in usage with numerous medium-sized surfaces being equipped with these panels: Roofs of agricultural buildings, stadium stands, undercover car-parks in retail, centres or industrial premises. Most recently, moreover, large-scale projects have emerged, particularly in desert regions.
In sum, there are many ways of producing electricity without using fossil fuels and there is no reason to think that any of these alone will be the panacea. The choice between these solutions will depend on the local conditions and the political decisions peculiar to each country.

Store energy to improve usage?

Storing energy in the form of electricity or heat for use as and when needed is necessary and can lead to savings in terms of both costs and greenhouse gas emissions. Storage allows for smoothing in the supply of electricity: The the excess from off-peak periods is stored for use during subsequent peak periods. For intermittent energy sources such as wind and solar photovoltaic (PV), production of which does not always match demand, storage is vital if we want to avoid use of greenhouse gas-emitting complementary sources of energy to produce the extra electricity needed.

Reduce emissions linked to transport?

Transport of passengers and freight plays an important role in trade, the economy, the supply of food and our quality of life. According to the IPCC's fifth report (2013), transport emissions were 6.7 Gt of CO2 in 2010 and without taking effective action, these emissions could double between now and 2050 due to population growth and global economic development. Several complementary approaches allow us to curb this unfortunate trend: Reducing vehicle emissions for a given service, improving infrastructures, avoiding siting production far from the place of consumption, changing our behaviour and putting in place political measures that are coherent.

Imprisoning "industrial" carbon dioxide underground?

The capture and geological storage of CO2 is a powerful way of combatting climate change. It's a case of capturing the CO2 emitted from fixed industrial facilities and burying it in deep geological layers so that it can remain there for several centuries, even several millennia - the time-span needed to secure the transition towards a future wherein energy will be entirely decarbonised. CO2 of this origin represents nearly half of all CO2 emitted at ground- level. Acting on these sources will have a significant impact in terms of controlling the atmospheric CO2 concentration.

Mitigation(7) and Adaptation

International political discussions have led to our setting ourselves on the following objective: Limit the increase in average global temperature to 2°C as compared with its average value between 1860 and 1880. Based on numerical simulations of the climate, to achieve this target we must make sure that the post-1870 cumulative emissions of CO2 stay within the range of 2550 to 3150 Gt of CO2. This range takes into account various hypothesises regarding other relevant factors, notably the other greenhouse gases and aerosols. Given the fact that total cumulative emissions up to 2011 have already been estimated to be 1900 Gt of CO2, it follows that we would have to limit emissions to between 650 and 1250 Gt of CO2, in other words twenty to forty years-worth of emissions at the current rate.

What to do in the face of climate change?

Two responses, non-exclusive and often complementary, must be adopted to reduce the climate change-related risks subject to varying deadlines: Adaptation and mitigation (or reduction of emissions).
Adaptation to the effects of climate change, such as the choice of different cultivars or the construction of a dam in certain places, can be beneficial in confronting current and future risks. Adaptation planning and execution can be improved by complementary initiatives such as raising the awareness of populations to risks of flooding. These need to be led at every level, from that of the individual to that of the government.
Mitigation in the short-term and continuing over the course of this century can substantially reduce the future effects of climate change, that is to say in the last decades of the 21st century and beyond. It can bring further benefits such as reduced pollution via decreasing the fuel consumption of vehicles. Mitigation can likewise entail risks, if only in terms of deploying technologies inconvenient to use and that carry a cost not properly assessed at the outset. Notwithstanding this, such risks are not as severe, not as wide-spread and easier to reverse than those of climate change.
All of these actions are dependent on societal values, objectives and perceptions of risk. Analysis of diverse interests, of circumstances, socio-cultural contexts and expectations can help to make good decisions. Possible options for mitigation and adaptation are myriad but no single one will suffice on its own. Political choices and co-operation at every level will determine the range of measures to be adopted and the efficacy of their implementation. Such a process can benefit from a co-ordinated response linking adaptation and mitigation with other societal objectives.

The Climate - A global problem?

Globally, what have been the main features of evolving public opinion vis-à-vis climate change?

Public opinion on climate change represents a major indicator as to how readily actions to reduce emissions will be accepted at both the individual and the collective level. Within this arena it is generally recognised that any change in collective behaviour stems from: 1) individual recognition of the reality of the change; 2) acceptance of its anthropogenic origin; 3) concern about negative impacts and 4) belief that it is essentially a personal and social responsibility.

Doubt as to the part played by human beings

Since the end of the last millennium, studies often show that in certain countries levels of doubt and scepticism regarding climate change have risen. Despite this trend, in many countries a large majority of the population continued to express a high level of concern and clear recognition of the problem.
The Global Trends study led by Ipsos-Mori in 2014 shows that of 20 countries studied, the lowest percentages of people convinced of the anthropogenic origin of climate change are in the United States, the United Kingdom and Australia (64%, 64% and 54% respectively). Seven countries (China, Argentina, India, Italy, Spain, Turkey and France) show high percentages over 80%, whereas in Russia and Poland the percentages are low and climate- scepticism is widespread. Another international study carried out in 2014 across twelve countries confirms these results. However, inter-country comparison is littered with obstacles. Use of the internet as a method of conducting the majority of these studies means that the participants are not necessarily representative of the population as a whole, particularly as regards developing countries.

Fears that fade

Longitudinal studies conducted in the same country and by the same organisation are more reliable. In the United Kingdom, Ipsos-Mori and the University of Cardiff compiled the results of studies from 2005 onwards which show a continuing rise in the proportion of British people who doubt that the earth's climate is in the process of changing (these are doubts about the reality of climate change as opposed to its cause). Results show that these doubts rose from 4% in 2005 to 15% in 2010 and to 19% in 2013. According to serval studies in the rest of the world, the level of concern vis-à-vis environmental questions (including climate change) has plummeted over the last few years.

Highly influential media

The level of concern can be influenced by the intensity and the type of media coverage vis- à-vis these issues but equally by competing concerns about the economy, first-hand experience of extreme weather events, communication campaigns organised by lobbying groups as well as by the discourse of political figures demanding action. Two European studies concluded that the economic context and in particular the recessions at the end of the last millennium played a crucial role in the decline of concerns about the environment. This finding is consistent with the paradigm whereby individuals have a finite "pool of worry", meaning that urgent concerns such as those around employment or the cost of living take precedence.
By way of a conclusion, additional research efforts are needed in order to understand the mechanisms at the origin of the evolution in public opinion on climate change over time, whether that be within one country or between different countries. A multiplicity of factors - socioeconomical, political, geographical and psychological - determine public opinion. The varying level of influence of each of these, across the different parts of the world, are not fully known. It is crucial that we understand these aspects given that international agreement between extremely diverse countries is at the heart of concluding an effective treaty to reduce greenhouse gas emissions.

Postface

By Érik Orsenna from the Académie française.

Four years have gone by since a very useful book (Climate, A Planet and Human Beings) explained the workings of these complex phenomena and proved, indisputably, that our species plays the major role in causing our "skies to fall" and the ensuing, inevitable catastrophes.

What progress have we made since 2011?

No progress has been made in global control of the greenhouse effect - more and more carbon is being emitted into the atmosphere. Nevertheless, there is, at the same time, a growing awareness. We are like those smokers who know very well they are facing inevitable death from lung cancer yet continue to smoke like never before.

This new book, Climate, The Time to Act, written by the same impressive team of "Argonauts", comes at just the right time. Its clarity and clearness is unprecedented. You who (like me) are not scientists must dive in - you will understand everything. First and foremost the urgency to act. And you who, like me, hate "throwing in the towel" must understand that we can act. Taking different action according to one's country, whether it be rich or poor, democratic or dictatorial. And at every level: Regions, towns, neighbourhoods, our homes, us as individuals. Yes, act, straightaway. Don't wait for the unlikely agreement of the State which is under too many constraints to fully commit. What government will sacrifice current growth and employment for the future health of our development? Time that passes is the enemy of time to come. The sheer originality of this book lies in its realism as opposed to incantatory chants and its detailed rather than general analysis. And in its suggestions everyone can follow.
Such a "practical" approach does not flinch from addressing the major taboo: Demographics. One minute we condemn the economy and modern technology, holding them responsible for our ills; the next, we trust them to get us out of this tight spot. But no longer does anyone dare ask themselves whether the presence of nine or ten billion human beings allows for any control whatsoever to be exerted.

I say thank you to this book. It brings us back to ourselves. This climate issue is the mirror of our contradictions and of our lack of courage.

But let's go into battle with full knowledge of the facts! And each of us with our action plan.


(1) Represented here are purely France-based initiatives aimed at reducing greenhouse gas emissions. Consultation of the following links will provide information regarding similar initiatives in the United Kingdom:
Government Publishes Updated Plan to Tackle Climate Change. [Accessed: 14 August 2019].
Reducing Carbon Emissions. [Accessed: 14 August 2019].
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(2) The Keeling Curve is a graph showing seasonal and annual changes in atmospheric carbon dioxide (CO2) concentrations from 1958 onwards. The data is collected from the Mauna Loa Observatory in Hawaii. The graph, devised by American climate scientist Charles David Keeling, charts the build-up of CO2 in the atmosphere. It is the longest uninterrupted instrumental record of atmospheric CO2 in the world (NASA, 2009).
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(3) A carbon sink is a "a reservoir (natural or human, in soil, oceans and plants) where a greenhouse gas is stored. Carbon sinks suck up and store carbon dioxide from the atmosphere" (Thompson, 2012; IPCC, 2018).
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(4)The partial pressure of an individual gas mixed with other gases is equal to the total pressure of the mixture of gases multiplied by the mole fraction of that gas (Chemistry, 2019).
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(5)A gigaton is one billion tons (Hanania, 2018).
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(6) A vector is a living organism that transmits an infectious agent from an infected animal to a human or another animal.
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(7) Mitigation: Action aimed at reducing the scale of climate change
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