COP26: “The warming of the last century is unprecedented in more than 2,000 years” | Climate change | Climate and Environment

One of the consequences of postponing the Glasgow World Climate Summit (COP26) for one year is that the added time has allowed us to reach this new United Nations conference, having previously carried out the largest scientific review on global warming: the last report of group I of the main panel of experts on climate change, the IPCC, co-chaired by Valérie Masson-Delmotte (50 years old, Nancy). This French climatologist, who has had to learn to separate her emotions from scientific data in order not to get carried away by anguish or helplessness, explains that climate change has not accelerated, but it is intensifying, with more intense meteorological events and frequent. As he emphasizes, the scale and speed of the current disturbances in the climate are unprecedented in the last millennia.

Question. What stands out from your scientific report on climate change from the IPCC?

Answer. Advances in scientific knowledge show the intensification of climate change, its widespread effect in all regions of the world, and the human influence on global climate and extreme events, such as heat waves, heavy rains or droughts. We have a finer understanding of the effect of our emissions of carbon dioxide, and also of methane, to understand how we disturb the climate.

P. Is global warming today faster than scientists anticipated?

R. The evolution of warming is as expected, the trends we observe were anticipated in the late eighties. In fact, this year’s Nobel Prize in Physics has been awarded to pioneers of climate modeling. [los climatólogos Syukuro Manabe y Klaus Hasselmann, junto a Giorgio Parisi]. The only point where there has really been an acceleration, an increase in pace, is at the rise in sea level.

P. What, then, does it mean that an intensification of climate change is taking place?

R. This means, in particular, more intense and frequent extreme events. In addition, there is also an intensification in the sense that it touches the limits of the ecosystems or the infrastructures that exist. We run after the weather; We see that our current agricultural practices or infrastructures are not adapted to today’s climate. This finer diagnosis and this intensification of decision-making must be taken into account to prepare. Many of today’s actions, such as construction, are carried out taking into account the climate of the last 100 years. They are done looking at the past, backwards, it is like looking through the rear-view mirror.

P. To what extent is the climate being disturbed?

R. Across the planet, the scale and speed of current changes represent a break with respect to the natural climatic variations of the last millennia. The warming of the last century is unprecedented in more than 2,000 years, the rise in sea level in more than 3,000 years, the atmosphere’s own CO₂ content in several million years. We are really disrupting the climate system in depth. The ocean has accumulated about 90% of the supplemental heat, but the mixing time of the ocean is several centuries, so the change that has already taken place is irreversible in the long term. When CO₂ is emitted, one part enters the ocean, acidifying it, another goes to the vegetation, and about half remains in the atmosphere: between 15% and 40% of the emissions put into the atmosphere annually will continue to act. about the climate on a thousand-year scale.

P. The report emphasizes that some of these changes are already irreversible for hundreds or thousands of years.

R. A rise in sea level is irreversible on time scales from centuries to thousands of years, but we also show how the future evolution of the climate depends on choices we can make. If we were to reduce emissions in a really strong way around the world, we would see many benefits: for air quality they would be very fast, in a few years, for the evolution of the temperature on the surface of the Earth, after twenty years, not much on the scale of a human life.

P. How do you psychologically manage to work all the time with such alarming information?

R. I have been working on these issues for 30 years and it is really important to put aside the emotions that can be paralyzed, such as anguish, the feeling of helplessness or, sometimes, anger, due to a reaction that is too slow. In my case, I prefer to underline how the progress of scientific knowledge makes it possible to better understand what is going to happen in each region. If we do not have knowledge, we advance in the dark. Now I hope that this knowledge, this diagnosis, will lead to more ambitious and effective actions.

P. This IPCC report uses much harsher language than previous ones: is it because more is known about the phenomenon now or is it due to the decision of this body?

R. Scientific knowledge has advanced, but we have also made an effort not to be tougher, but clearer. Often in previous IPCC reports, when people read them they drowned in overly technical vocabulary and terms about confidence levels that were incomprehensible to a normal citizen.

P. The pandemic forced this report to be carried out by working remotely, over the internet, with several hundred scientists from around the world. How was the experience?

R. Yes, since February 2020. The dedication of the authors was extraordinary, since it has required to work in different time slots and outside the usual hours, which greatly interferes with family life. In order to allow 234 researchers from 65 countries to participate remotely, in the different time slots, each meeting was held twice, one very early in the morning and another in the afternoon.

P. Should this be an example for other climate meetings, such as the summit now starting in Glasgow?

R. I am very attentive to limiting my greenhouse gas emissions and my travel, particularly by plane. In the IPCC, until 2020 the norm was to have meetings in the four corners of the world, but many climate scientists had shown their reservations, because for them it was contradictory. I had asked to do virtual meetings and they told me it was not possible. What was not possible before 2020 has now become the norm. We have learned lessons. Is not easy. The final approval of the report was made during two weeks: in the first week the working hours for us in Europe were from noon to midnight and in the second, from five in the morning to two in the afternoon, but in South America they he had to work in the middle of the night for 15 days in a row.

P. How do you see the Glasgow summit? Are we in time to stop the worst of climate change?

R. In our report we see five major scenarios with emissions: large increase, increase, stagnation, decline or very sharp decline. The scenario of large increase is less possible today, due to the climate policies in place and due to the technological break with low-carbon electricity. If the updated commitments for the reduction of emissions of the countries for 2025 and 2030 are fulfilled, that is, the promises, not the actions put in place, what comes out is something similar to our stagnation scenario and this means two degrees more in 2050 and three degrees at the beginning of the next century. Right now there is a very shocking gap between the commitments made by countries and the objectives of the Paris Agreement on climate.

P. Contrary to what many people think, the IPCC does not conduct its own studies.

R. Yes, the IPCC does not produce new knowledge, it reviews existing knowledge in a methodical, objective, rigorous and neutral way. Participate in what I call the maturation of knowledge.

P. What do you think of the allegations of pressure to influence other IPCC reports?

R. In reality, the IPCC is also a co-production and works with an open rereading system. Each report is the result of several successive reviews that are carried out by those who want to from the scientific community, thousands of scientists, and then by representatives of the different countries, who may also have, of course, geopolitical perspectives. These comments are taken into account, but it is not the opinion expressed by the representative of a country that will decide a scientific analysis. We rely on studies, data, and knowledge that are robust, and that ultimately prevail, even if they clash with the agendas of some countries. When an IPCC report is published in its final version, the set of comments received in the re-readings are also published.

P. So you don’t consider it pressure?

R. The report you are talking about is a draft of the Group III report and some comments have been made by some governments in rereading, which is one of the stages of preparation. In the Group I report that we published this summer, this stage of rereading by governments has helped us to be clearer in our conclusions, without ambiguity. I see an opportunity in being able to have that collective production.

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