In 2007, the Intergovernmental Panel on Climate Change (IPCC) and Al Gore, former US Vice President, received the Nobel Peace Prize in recognition of “their efforts to assemble and disseminate information on man-made climate change”. The IPCC was founded in 1988 by the World Meteorological Organization (WMO) and United Nations Environment Programme (UNEP) and includes 192 countries. It provides international authorities and political decision-makers with the scientific, technical and socio-economic data essential to implementing global actions. Every five years or so, over a thousand experts contribute to a substantial report which details the latest advances and research. The report is a unique reference tool which presents consensual results alongside areas where controversy exists.

The causes of global warming
The Earth’s average temperature depends essentially on the balance between the proportion of solar radiation it absorbs and the energy it sends back into space in the form of infrared rays. A number of natural factors affect this balance, including slight variations in the Earth’s orbit round the sun which are responsible for major and fully-identified climate cycles over the last million years. The industrial era gave birth to a new phenomenon: human activities are causing a change in the composition of the atmosphere and, more specifically, a significant rise in the concentration of gas that absorbs infrared rays. It is therefore harder for the Earth’s infrared rays to disperse in space, and energy balance can only be restored by warming. In the IPCC Fourth Assessment Report, scientists have succeeded in analysing the probability of the influence this process has on observed climate changes. The report provides a distribution of probabilities. “A better characterisation of uncertainties means a better understanding of climatic processes” explains Michel Petit, who is also Chairman of the Environment Committee at the Science Academy.
Global warming is now an unequivocal fact. “In all likelihood, this warming is linked to the rise in concentration of greenhouse gases in the atmosphere. This is widely recognised, with models of climate behaviour closely reproducing the observed patterns.” The report adds, “As long as emissions from humans continue to rise, the greenhouse effect will only get worse.” Observations highlight the simultaneous acceleration of the rise in average air temperatures at the surface, both on land and in water, and of concentrations of greenhouse gas in the atmosphere since the industrial era, particularly since the mid 20th century. The average speed of warming per decade seen over the last fifty years has thus almost doubled compared to that of the previous hundred years. At the same time, global emissions of greenhouse gas into the Earth’s atmosphere — mainly carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O) and chlorofluorocarbons (CFC) used as cooling gas or in aerosols — have continued to grow. They increased by 70% between 1970 and 2004. The concentration of CO₂ in the Earth’s atmosphere is much higher in 2005 (around 379 ppm(1)) than the natural variations of the last 800,000 years (between 180 and 300 ppm), reflecting the impact of human activities. The experts use the results of measurements to provide relatively accurate estimates of the annual quantities generated by human activities: the increasing consumption of fossil fuels (coal, oil and gas) throughout the world, changes in land use and deforestation.
 
Some uncertainties remain
The study of current and past climates is based on observations and digital simulations. Digital modelling is used to incorporate all phenomena, detect the probable causes of warming and draw up future projections. A climatic model is a digital simulation of air circulation in the atmosphere and of ocean water, and is a complex projection of all available information at a given moment. It is similar to the models used for weather forecasts. However, the way they are used is very different, since it is not the weather in a few decades’ time that is being simulated, but the climate; in other words, the average figures for seasonal variations over several years.
The most recent models incorporate an increasing number of phenomena, such as the influence of biosphere variations on the carbon cycle. As they become more complete, so they become more reliable. As Michel Petit notes, “In terms of digital projections, it would be difficult to do any better with the computers we currently have.” The decisive role played by human activities in climate change is described as “highly probable”. Indeed, the probability that this hypothesis is correct is estimated at 90%. But improvements in digital tools as well as observation instruments remain subject to ongoing research. As Jean-François Minster, Total’s Scientific Director, explains, “We are still missing data on key parameters, such as the three dimensional structure of clouds (crucial to assessing their influence on a planetary level), the thickness of sea ice, which would allow us to anticipate how fast it is melting, the dynamics of ice, a decisive factor in predicting the development of polar ice sheets, the humidity of the soil, and extreme phenomena, where we lack statistics and observations as they only rarely occur.”
What emerges from the possible projections is that, whereas it is highly probable that mountain glaciers will continue to melt, there is still uncertainty over how fast polar ice sheets are melting. Will the currently identified phenomena of accelerated melting of the ice sheets’ surface slow down, stabilise or speed up? “If the melting process speeds up, a new sword of Damocles will hang over all our heads. If the Greenland ice sheet shrinks, it will cause sea levels to rise by 6 to 7 metres. Scientist’s quantitative estimations take into account an average value, but no one knows what the situation will be in a century’s time” explains Michel Petit.

Disparity between current  and future impacts
The most recent observations show that the years 1995-2006 were the hottest ever recorded over the last century (with the exception of 1996) and that the average speed of warming has practically doubled. Analyses using balloons and satellites also reveal warming of the troposphere (2). There is an increase in the average content in the atmosphere of water vapour on the earth’s surface and in the troposphere, and an increase in the average temperature of the oceans down to depths of over 3,000 metres, causing seawater to expand and sea levels to rise. The melting of mountain glaciers and the reduction in snow cover in the two hemispheres as well as the ice-cap(3) in Greenland and the Antarctic most probably contributed to the rise in sea levels between 1993 and 2003 (around 3.1 mm a year). Permafrost(4) is already shrinking in Siberia and Canada. In these areas, the soil is becoming increasingly unstable and mountain rock fall is becoming more frequent.
These changes seem to be affecting living organisms. “We are detecting a great many modifica-tions in land and sea ecosystems. Satellite observations of the land reveal that vegetation is becoming green earlier; we can also observe changes affecting bird migration and egg-laying, as well as the seasonal cycle of insect life in many regions. Observation of the oceans also shows that coral reefs and other sea organisms are being weakened and that the migration of some species  of fish is being affected,” explains Jean-François Minster. The warming effect on Atlantic waters thus causes species and organisms to move to more northerly waters. The additional carbon dioxide generated by human activities since 1850 has led not only to climate change but also to acidification of the oceans.
“The most catastrophic effect of climate change is on water,” asserts Michel Petit. In subtropical areas already suffering from water stress (numerous African countries, the Mediterranean region, Brazil, Southern Australia, the Caribbean and Southeast Asia), rainfall is diminishing. On the other hand, violent storms and flash floods could become more frequent in higher latitudes (Northern Europe, eastern North and South America, and Northern and Central Asia). “Even in regions affected by drought, rainfall is becoming more intense,” explains Michel Petit. “These events damage crops and therefore adversely affect food supplies. Water quality is also affected, something which could cause serious health problems.”
Projections of future impacts show the effects they are likely to have. The average global temperature is set to rise, despite efforts to reduce greenhouse gas emissions. Even if the polar ice sheets do not change, sea levels should rise by between 18 and 59 cm by 2100. Coastal regions would come under threat, especially Bangladesh and island states, as well as the major deltas of Africa and Asia. If seawater continues to infiltrate the land, soil salinity will increase, affecting the crop quality, which will concern between 600 million and 1.2 billion people.
Water-related problems are likely to worsen in different areas of Africa and Asia. In arid tropical regions, models predict a drop of 10% to 30% in water availability. In Africa, between 75 and 250 million people are expected to suffer the effects of drought. By 2030, some parts of Australia and New Zealand are set to suffer from rarer rainfall and increased evaporation. “This drop in water availability and rise in temperatures in regions that are already very hot may well lead to a drop in agricultural production provoking food shortages. In short, it may cause hardship for many people that will only worsen as the planet’s population increases,” stresses Michel Petit. A sixth of the world’s population would be affected and this is likely to lead to population migrations. From this point of view, “the real problem is the increase in the number of future climate refugees.” In terms of ecosystems, climate change would cause irreversible damage, possibly even the extinction of 20% to 30% of species if temperatures rise by 1.5°C to 2.5°C. If they rise by over 3.5°C, 40% to 70% of species could be affected.

The need to strengthen North-South solidarity
“It is true that there are a great many predictable impacts,” adds Jean-François Minster, “and we have to prioritise them according to their local importance.” This is where the capacity for management and adaptation comes in, since there is no denying that a given impact depends not only on related climatological, biological and/or physical phenomena, but also on how the society that is subject to them is organised.
It is clear that not every area of the planet has the same capacity for adaptation. The less countries are equipped to face the challenges, the more vulnerable they will be. Local policies are already in place in northern countries.“Preventive measures to combat heat waves taken in France and the heightening of dams in the Netherlands are signs of an adaptation to climate warming and the rise in sea levels,” points out Michel Petit. “Southern Europe will tackle drought by desalinating seawater, for example. But what will become of non-industrialised countries?” The poorest countries lack funding and appropriate technologies and IPCC experts are encouraging decision-makers to think in terms of long-term solutions such as co-development, transfer of technology and sustainable development, as well as technologies that do not generate large amounts of CO₂. Michel Petit is convinced this is the way forward. “North-South solidarity is a priority. It goes hand in hand with global political stability and balance. Helping the countries most affected by global warming to tackle the issue is crucial.”

Limiting climate change: an impossible challenge?
According to the IPCC, to ensure that the rise in average temperatures does not exceed 2°C to 3°C in a century, the concentration of CO₂ in the atmosphere must not exceed 490 to 550 ppm (the figure for 2005 is 380 ppm). This means cutting greenhouse gas emissions by half by 2050, requiring a considerable effort, or even, according to the International Energy Agency (IEA), a “heroic” effort. “It is very interesting to see how the need to take preventive measures is now understood worldwide,” underlines Jean-François Minster. The most effective way to reduce the effect of human activities on the climate is to tackle the problem of how greenhouse gas emissions are generated and to focus on sustainable development. Naturally enough, this particularly concerns the energy sector. New investments in energy production in developing countries and the improvement of energy infrastructures in industrialised countries would be valuable. As a hydrocarbon producer, Total has been taking the IPCC reports into account for several years and taking action in response to them. “The Group is committed both to research into greater energy efficiency for its industrial sites and products (fuel oils, lubricants, polymers, etc.) and to developing new energies and ways of harnessing and storing carbon dioxide,” points out Jean-François Minster.
In the short and medium term, changes in lifestyle and behaviour are likely to contribute to limiting climate change in all sectors. Measures aimed at redesigning homes and means of transport to limit the use of fossil fuels are already in place. Governments can use various measures to encourage populations to improve management of their energy needs and modify their consumption patterns. Changes in farming methods, such as reducing water wastage and the use of fertilizers, and improving waste management are two other possible means. Above and beyond economic and tax incentives, new choices will spring from a dramatic change in the scale of values. “I often insist on the importance of urging the public to consider the good of the planet over the period of a century,” explains Michel Petit. “Then, ideally, everyone will have the inner conviction needed to choose an ecological car rather than a four-wheel drive, and politicians will be encouraged to take useful measures.”
Poor countries can also take similar action on a lower scale, without undermining their legitimate desire for growth. “Ultimately, education will be the driving force behind a change in attitudes,” asserts Jean-François Minster with conviction. It is plain to see that everybody needs to make an effort.

1- ppm: one part per million, i.e. 1 molecule per million; ppb: one part per billion.
2- The layer of the atmosphere between the Earth and the stratosphere, which is situated at an altitude of between 18 and 50 kilometres.
3- Continental glaciers in the polar regions.
4- Totally impermeable and permanently frozen soil in Arctic regions.