Causes, consequences, solutions… The French climatologist, figure of the international group of experts on the climate, takes stock of scientific knowledge, on the occasion of the release of a new report.
It is the culmination of eight years of scientific work on global warming. The Intergovernmental Panel on Climate Change (IPCC) published on Monday March 20 a summary of the reports produced by its scientists since 2015. The opportunity for franceinfo to meet with climatologist Valérie Masson-Delmotte, co-chair of one of the institution’s working groups.
>> What to remember from the summary of the work of the IPCC
At the end of a marathon weekend in the Swiss city of Interlaken, the researcher, whose mandate at the IPCC is ending, takes stock of the causes and consequences of global warming, but also of the tools to limit the damage. .
Franceinfo: Few today dispute the reality of global warming. On the other hand, many people continue to doubt the man’s responsibility. What does the IPCC say on this question?
Valerie Masson-Delmotte: Human influence on global climate is unequivocal. The scientists compared the observations to climate models. They have replayed the history of the climate since 1850, taking into account natural factors (such as the activity of the sun, that of volcanoes, etc.) and nothing explains this accumulation of heat. Conversely, when we take our influence into account, we see that the simulations correspond to what we observe. The warming observed over the period 2010-2019 reaches +1.1°C. Our best estimate of human influence is +1.07°C. The numbers converge. A second approach, which consists of drawing up the energy balance of human and natural factors, leads to the same result.
Without human influence, the heat accumulation cannot be explained.
Valérie Masson-Delmotte, climatologistat franceinfo
What human activities are causing this warming?
The first factor is the release of CO2, a greenhouse gas emitted especially when burning coal, oil and gas. Then there is deforestation and methane emissions. This other greenhouse gas is released by leaks in the fossil fuel sector, but also by ruminant farms.
The Earth’s climate has already varied. Why is this climate change so worrying?
In the past, there have been slow variations in climate, with glacial and interglacial periods. These are changes that our species has experienced over tens or hundreds of thousands of years. When you look at the difference between a mild climate and a glacial climate on a planetary scale, there is only a five degree difference. And the most rapid of these changes occurred at a rate of about one degree per millennium.
>> Our answers to your questions about global warming
Today, we are already in a mild period. The observed rate of warming is just over one degree in 100 years. It is therefore exceptional on a planetary scale compared to these past variations. Of course, there are adaptive capacities: the history of humanity and living things shows it. But the faster the warming, the more we reach the limits of adaptation.
This synthesis also returns to the already observed effects of climate change. What are they ?
With +1.1°C of global warming, we are already seeing widespread and severe impacts. For example, there is a drop in agricultural yields in certain regions of Africa, with hotter and drier conditions. There are the difficulties of water supply, with the drought, but also the intensification of extreme rains which increase the severity of the floods, in particular in the city where urbanization promotes runoff.
There are of course heat waves, which affect human health. We saw it during the summer of 2022 in Western Europe, with significant excess mortality. There are effects on ecosystems, with coral bleaching or sea heat waves killing gorgonians [des colonies de coraux] in Mediterranean. The rise in sea level will also increase chronic flooding at high tide, records during storms and erosion for example for sandy coasts.
The year 2022, marked by heat, fires and drought, was the hottest ever recorded in France. Is this a glimpse of what awaits us in the coming decades?
The year 2022 is fairly representative of what an average year around 2050 could be, if current public policies continue and if there is no leap in the world to reduce greenhouse gas emissions. Greenhouse.
Global warming is hitting the countries of the South even harder. What does the IPCC say about climate inequalities?
This report highlights how critical consideration of equity and justice issues is to climate action. Those living in the most fragile contexts, around 3 billion people, have greater vulnerability and are facing loss and damage today. What is also striking is that it is these people who contribute the least to the accumulation of heat in the climate system. Their historical and current greenhouse gas emissions are lower than the global average. Conversely, in countries where greenhouse gas emissions are higher than the planetary average, there is a greater capacity to act.
The Paris agreement plans to limit global warming to well below +2°C and ideally to +1.5°C. Where are we today?
This is one of the IPCC’s key messages. Current trends are not at all compatible with stabilizing global warming, which would ensure a livable and equitable world. Efforts have been made, but they are not on a sufficient scale for a fast enough reduction in greenhouse gas emissions.
If we want to limit global warming to around +1.5°C, we would have to almost halve global CO2 emissions by 2030. However, emissions have continued to increase and the promises put on the table by the various countries, if they were held, could allow a slight decrease between 2020 and 2030.
Massive reductions in greenhouse gas emissions are needed in all sectors of activity, at an unprecedented pace, in all directions.
Valérie Masson-Delmotte, climatologistat franceinfo
With the public policies in place, global warming would be around 1.5°C at the beginning of the 2030s, around +2°C around 2050 and, in 2100, around 3°C.
Even if it does not make political recommendations, the IPCC assesses solutions to limit global warming. What are they ?
On energy, the priority is to get out of coal and to deploy as much as possible everything that makes it possible to produce low-carbon electricity. Of the options assessed, photovoltaics and wind power have the highest potential for avoided greenhouse gas emissions, at an affordable cost. But there are of course many other levers of action, such as nuclear or hydroelectricity, which however have the disadvantage of not being accessible everywhere in the world.
On the issue of food and land use, there is the fight against deforestation, the optimized use of nitrogen fertilizers [des engrais fabriqués à partir d’ammoniac qui entraînent des pollutions de l’eau, de l’air et des sols, ainsi que de fortes émissions de gaz à effet de serre] or efforts to reduce methane emissions from ruminants. Finally, there is the change in dietary practices and the fact of having a diet with more vegetable proteins and less animal proteins.
In public debate, individual “small gestures” and collective “big gestures” are often opposed. Has the IPCC looked into this question?
It is public policies that allow everyone to adopt changes in daily practices. It’s not the injunction to individual morality, it’s more structuring actions. For example, in the city, the fact of setting up public transport or cycling infrastructures is a condition for not depending on the private car.
It is always interesting to try to measure your own carbon footprint, for example on the Ademe site. This gives an idea of our habits that weigh the most on the climate, because there are sometimes misconceptions in this area. We often think, for example, that digital and sending emails weigh heavily on our carbon footprint, while their impact is negligible compared to that of the car or heating.
Despite this observation, the major oil companies, such as TotalEnergies, continue to invest massively in fossil fuels. Is this compatible with our climate objectives?
The IPCC reports do not comment on a particular project. But each investment in the fossil fuel sector leads to an additional accumulation of CO2 emissions, and therefore to global warming. The question is not to deprive oneself of fossil fuels tomorrow. It is to redirect investments in order to get out of it as quickly as possible.
To appear virtuous, these companies tend to hide their investment in fossil fuels behind a very small component of investment in renewable energies, shown in advertising. Finally, there have been many recent announcements that show a big step back from the climate commitments made by these oil and gas companies. It is very worrying.
IPCC reports are increasingly read in the business world. I think that is also our role: it is not a question of posing as a judge, but of providing a framework which allows civil society to examine its actions and to question whether they are compatible with the limitation climate risks.
Despite all your knowledge of the magnitude of the problem, you remain optimistic. How do you do ?
We do not have the choice. We are all inhabitants of this planet and there are not so many alternatives. We are in a difficult situation, which could get worse. The question is not to be optimistic, but to understand that we have our backs to the wall, and that solutions exist. They must be put in place as quickly as possible and in the most intelligent way possible.
I am a scientist. My role has been to produce knowledge, evaluate it and transmit it in the most rigorous way possible. It is not for scientists to bear the responsibility for climate action around the world. It’s up to everyone to do it. And the more we have high capacity to act, the higher we have a high level of responsibility, the greater this mental load should be.