The Paris Accord, adopted by COP21, set even more ambitious targets than the 2-degree Celsius cap on global average temperature increases set in Copenhagen in 2009. Indeed, its 196 signatories agreed to maintain this ceiling by 2100 and to continue their efforts to try to limit this rise to less than 1.5 degrees Celsius. Given that the temperature rise already recorded since 1750 amounts to 0.89 degrees Celsius, this leaves the international community with only a very limited carbon emission credit and requires it to engage in a major energy transition if it is to meet its commitments. Is it feasible, technically, financially, economically, socially and at what cost?
The IPCC has been asked to answer this series of questions by 2018, mainly to quantify the emissions trajectory that must be respected if the objective of limiting temperatures to 1.5 degrees Celsius is to be achieved.
What emissions credit do we have?
In the meantime, we already have a series of studies and books that allow a broad non-specialist public to familiarise themselves with these questions, which concern them in various ways. As a citizen - how can we reduce our carbon footprint and consume energy more efficiently? -As a taxpayer - which carbon tax, direct or indirect, should be set? -As a homeowner - what insulation, what source of heat, what direction to choose? -, these questions open up broad fields of investigation for a branch of energy geo-economics.
In Fossil Zero. Désinvestir du charbon, du gaz et du pétrole pour sauver le climat, Nicolas Haeringer argues outright for a massive disinvestment of coal, gas and oil (here listed in alphabetical order and not by priority) to save the climate (Éditions Les Petits Matins, 2015, 108 pages). Based on information provided by the Carbon Tracker Initiative, he puts forward key figures that the mainstream press has taken up several times. On the one hand, fossil fuel reserves, which, it should be remembered, represent 80% of the world's energy balance in 2014: 1,816 gigatons of coal, 614 gigatons of oil and 363 gigatons of gas, for a rounded total of 2,795 gigatons of fossil fuels with as many potential greenhouse gas (GHG) emissions. However, knowing that since 1750, the world has already emitted 2,000 gigatons of CO2 equivalent, it has only one emission credit left: 565 gigatons to limit warming to 2 degrees Celsius and only 400 gigatons to limit it to 1.5 degrees Celsius. We can see that these are very tight numbers, because at an annual rate of almost 40 gigatonnes of global GHG emissions, there would only be 14 years or 10 years of emissions left. This means that the targets set in Paris would be impossible to achieve. Other estimates put our emissions credit at 1,000-1,200 gigatonnes, which would leave an adaptation margin of around 30 years. Hence the dilemma facing the international community. If all fossil fuel reserves were extracted, used and burned, the result would be an average temperature increase of 9 degrees Celsius by 2100. Hence the author's conclusion: more than 80% of coal reserves, 50% of gas reserves and 30% of oil reserves must remain in the ground!
It is curious that Nicolas Haeringer, in charge of the campaign for 350 organizations in France, did not address the thesis of CCS (Carbon capture and sequestration), which would make it possible to capture CO2 from thermal power plants and cement factories and reinject it into disused gas reservoirs. Admittedly, there are currently only 14 experimental units in the world dedicated to this process, which reduces the efficiency of power plants by 30%. Aside from as yet unresolved technical problems such as the efficiency of capture, the stability of CO2, which is expected to be stored for thousands of years, is mainly a question of the cost of the operation ($80 to $100 per tonne). But this amount is fairly close to the carbon tax that many economists would like to introduce, including Jean Tirole, who has been awarded the Nobel Prize in Economics in 2014.
