“Advances in scientific knowledge show the intensification of climate change”

One of the consequences of postponing the world climate summit in Glasgow (COP26) for a 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 latest report from the 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 the scientific data so as not to be carried away by anguish or impotence, explains that climate change has not accelerated, but it is intensifying, with more intense weather events and frequent. As he emphasizes, the scale and speed of current disturbances in the climate are unprecedented in recent millennia.

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

Response. 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 carbon dioxide emissions, and also of methane, to understand how we disturb the climate.

Q. Is global warming today faster than scientists predict?

A. The evolution of warming is as expected, the trends we observed were anticipated in the late 1980s. In fact, this year’s Nobel Prize in Physics has been awarded to pioneers in climate modeling [climatologists Syukuro Manabe and Klaus Hasselmann, together with Giorgio Parisi]. The only place where there has really been an acceleration, an increase in pace, is in sea level rise.

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

A. 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 infrastructures that exist. We run after the weather; we see that our infrastructures or our current agricultural practices are not adapted to today’s climate. You have to take into account this finer diagnosis and this intensification in decision making 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 made looking at the past, backwards, it is like looking through the rear-view mirror.

Q. To what extent is the climate being disturbed?

A. On the planet as a whole, the scale and speed of the 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 CO₂ content of the atmosphere itself in several million years. We are really deeply disturbing the climate system. The ocean has stored 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, a part enters the ocean, acidifying it, another part 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 on climate on a thousand-year scale.

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

A. A rise in sea level is irreversible on time scales of centuries to thousands of years, but we also show to what extent future climate change depends on choices we can make. If we cut emissions really hard all over the world we would see a lot of benefits: for air quality it would be very fast, in a few years; for the evolution of the temperature on the surface of the Earth, after about twenty years; It’s not much on the scale of a human life.

P. How do you do psychologically 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 remove the emotions that can paralyze, 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 allows us 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 the previous ones: is it because more is known about the phenomenon now or by its own decision?

R. There has been progress in scientific knowledge, but we have also made an effort not to be harsher, but more clear. Often in previous IPCC reports, when people read them they were drowned in too technical vocabulary and confidence level terms that were incomprehensible to the average citizen.

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

A. Yes, since February 2020. The dedication of the authors was extraordinary, since it has required working in different time slots and outside the usual schedules, which greatly interferes with family life. To allow 234 researchers from 65 countries to participate remotely, in different time slots, we held each meeting twice, once in the early morning and once in the afternoon.

Q. Should this be an example for other climate meetings, like the summit that starts now in Glasgow?

R. I am very careful to limit 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 for virtual meetings and was told that 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 took two weeks: in the first week the work schedule for us in Europe was 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 15 days in a row.

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

A. In our report we see five major scenarios with emissions: large increase, increase, stagnation, decrease or very strong decrease. The scenario of a 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 scenario of stagnation and this means two degrees of 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 the countries and the objectives of the Paris Agreement on climate.

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

R. That’s right, the IPCC does not produce new knowledge, it reviews existing knowledge in a methodical, objective, rigorous and neutral manner. Participate in what I call the maturation of knowledge.

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

R. Actually, the IPCC is also a co-production and works with an open review system. Each report is the result of several successive revisions that are carried out by those who want to from the scientific community, thousands of scientists, and then by the 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, knowledge that are robust, and that in the end are imposed, 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 rereadings are also published.

Q. 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 the governments has helped us to be clearer in our conclusions, without ambiguities. I see an opportunity in being able to have this collective production.

Source: The Country