A coal power station in operation on November 19, 2015 in Datong, China. Achieving carbon neutrality by 2050 will require this energy to be passed off as quickly as possible. – GREG BAKER / AFP
The Giec reiterated in its latest report: limiting global warming to 1.5 ° C will require reaching a "carbon neutrality" in 2050, a point of equilibrium between the amount of greenhouse gas emissions in the world and the ability of the Earth to capture and store carbon dioxide.
In this equation, preserving natural carbon sinks (oceans, forests, grasslands) is crucial. Another way would be to create artificial carbon sinks. But the projects are still in the research phase and show limits.
Then emerges a certainty, reaffirmed again in the last report of the Giec: we will drastically reduce our greenhouse gas emissions. And well before 2050.
Declining yields of staple foods such as wheat, maize and rice in many parts of the globe. Less water available. More than 40 cm of sea level rise by 2100 compared to 2000. 90% of affected corals and increased number of climate refugees … Global warming of 1.5 degrees by 2100 – compared to the pre-industrial period – will have impacts on life on Earth.
Less than a 2-degree warming, says the Intergovernmental Panel of Experts on Climate (Giec) in its latest
report published in the night from Sunday to Monday at
Incheon (South Korea). And much less than a leap to more than 3 or even 4 degrees, trajectory to which we are moving at the rate of current emissions of greenhouse gases.
The Giec is not an instance of decisions. It is usually content to give the state of scientific knowledge on global warming. Policy makers then decide. This last report, however, leaves little room for maneuver. To limit global warming to 1.5 ° by 2100, the world will have to undertake "rapid" and "unprecedented" transformations.
Towards a total emission of 70 million tonnes of CO2 equivalent
More than a transformation, achieving carbon neutrality in 2050 is the general direction set by the IPCC on Monday. This is an equilibrium point at which the world generates fewer emissions of greenhouse gases into the atmosphere than the Earth is able to remove.
It is not possible to limit global warming to 1.5ºC, according to the new @IPCC_ch report. But it will require urgent, unprecedented & collective #ClimateAction in all areas. There is no time to waste. https://t.co/m3HQkSmAHY- António Guterres (@antonioguterres) October 8, 2018
We are far from that goal today. Take the case of France. "In our scenario, we will have to reach a total of 70 million tonnes of CO2 equivalent emissions in 2050 to achieve carbon neutrality," says Stéphane Chatelain, director of négaWatt, an association of energy experts. We are issuing 470 million today. More worrying, after three years of stagnation,
global emissions of CO2 are distributed again in 2017 with a total of 41 billion tonnes issued. So we are moving away from this carbon neutrality goal more than we are getting closer to it.
Towards a natural capture of carbon?
So how to reverse the trend? The first idea, attractive on paper, would be to increase the Earth's capacity to capture and store carbon. This is the crucial role played by the natural carbon sinks of our oceans, our forests, our grasslands or our mangroves. "On the continental surfaces, this natural carbon capture is essentially linked to the
photosynthesis, explains Roland Séférian, climatologist at
National Center for Meteorological Research and co-author of one of the chapters of the last IPCC report. Plants absorb carbon dioxide into sugar to create new tissues or organic matter for growth. For the oceans, the mechanism is twofold. This principle of "photosynthesis" is found with microplankton, unicellular organisms that absorb CO2 to grow. In addition, there is a physicochemical process that makes the carbon soluble in water and thus remains there. "
It is difficult to precisely quantify the volumes of CO2 that these natural wells can capture and store. "It is estimated that they absorb 50% of the CO2 emitted each year in the world," says Roland Séférian. To achieve carbon neutrality in 2050, we must at least ensure not to degrade this current storage capacity of our natural wells … "What is not won in advance, warns Lola Vallejo, director of the climate program at l Iddri (Institute for Sustainable Development and International Relations), which published a report at the end of September
on the issues of carbon neutrality. These carbon sinks are themselves affected by global warming and some of our behaviors. We will have to change our agricultural practices, ensure the conservation of forests, fight against the urbanization of our coastlines … "
Create artificial wells … a very risky bet?
Others go further and work on technological solutions that will create artificial carbon sinks. Several techniques are under study. Some may seem ubiquitous, at least to this day. "One of them would be to fertilize the oceans by injecting iron to stimulate the photosynthesis reaction of phytoplankton and allow it to store carbon," says Lola Vallejo. Another way would be to recover the carbon output of factory chimneys and coal power plants and then reinject it into the ground, in underground cavities. Old oil wells for example.
The #GIEC report proves it scientifically: we have all the cards in hand to fight against global warming. But everyone has to act now! #OnePlanetSummit #IPCC @ COP24 @CCNUCC https://t.co/4QIinW61Px- Emmanuel Macron (@EmmanuelMacron) October 8, 2018
These technologies are discussed, tests have been made … "But there is a real danger to date to rely on them, continues Lola Vallejo. Not only are these solutions not mature but they are unlikely to be scaled up to the scale needed to meet the challenge of climate change. "
Drastically lower our emissions as early as 2030
There is little choice then: limiting global warming to 1.5 ° C will mean drastically reducing our greenhouse gas emissions. Long before 2050. The Giec sets the course to lower our global CO2 emissions by 45% by 2030 compared to 2100. "The goal is not unachievable but it requires now to change the software of our policies current, "says Stéphane Chatelain.
To reduce these emissions will be difficult in some sectors. That of agriculture, for example, in which part of the greenhouse gases emitted by livestock comes from the enteric fermentation of animals [leur digestion rejette du méthane, puissant gaz à effet de serre]. "On the other hand, no more fossil fuel combustion is needed in 2050 in the transport, construction, industry and energy sectors," says NegwaWatt's manager. That means no more oil in our cars and trucks, more fuel-heated buildings, more coal-fired power plants … "
The report of the IPCC recommends to increase significantly the share of renewable energy in electricity production, from 20 to 70% by 2050. "Again, that will not be enough, completes Stéphane Chatelain. It will also work to reduce our consumption by actions of sobriety and energy efficiency. "