Hervé Le Treut discusses the details and consequences of global warming


The climatologist and former member of the Joint Scientific Committee of the world climate research programme, currently a member of the Academy of Sciences and Director of the Pierre Simon Laplace Institute who regularly participates in the evaluation reports of Intergovernmental Panel on climate change (IPCC) has expressed its views on global warming, as well as changes that are more “difficult to predict in their details and consequences”.

Hervé Le Treut was invited by the friends of the University for a series of lectures on global warming. In an interview with zinfos974.com, the digital climate simulation specialist, whose studies focus on the impacts of climate change and the associated environmental risk analysis, Mr. Le Treut explained “inexorable” changes related to climate change.

When you started your PhD a few years ago, could you have imagined holding lectures with such alarmist subjects of study in our time?

I started a postgraduate thesis in 1978, on modelling the atmosphere. The idea of global warming did not exist for me at that time, it was primarily a matter of understanding the workings of a complex system. Nevertheless, there was a very serious drought situation in West Africa, and the idea that our science could be useful, that it could help to understand crisis situations was nonetheless present-and provided a definite motivation.

What motivated a young student like you at the time to target his thesis on climatology?

I was a student in mathematics, then in physics, at the ENS (Ecole Normale Superieure, ed.), with exceptional professors, but without imagining being able to make my life around too abstract Sciences, or turned to the study of the infinitely large or of the infinitely small. I wanted to stay on a human scale, I loved history, geography. I was thinking of turning to geology, geophysics, but when I discovered the existence, in an ENS corridor of a laboratory dedicated to the climate, to the planet, it immediately tempted me. The modeling work was technical, but it referred to extremely motivating issues.

What was the event, the year and/or the Summit between States that was actually a turning point in the realization?

It depends very much on the actors involved in this problem. There have been successive awareness-raising. I started working on the role of CO2 in 1986, with English partners, and with the first PhD student I framed, who is still a close colleague. But with regard to the political world the most important period for me is 1988, year of an exceptional drought in the United States, at 1992, or instead the Summit of the Earth of Rio that gathers high-level politicians (Al Gore), and sets up the first international agreements.

When was the word “climate warming” used for the first time?

I will not know! Perhaps by the Swedish chemist and Nobel Laureate Svante Arrhenius, at the end of the 19th century or at the beginning of the 20th. But he imagined that this warming would protect us from the next glaciation. The first real alerts date back to the years 1955 or 1957.

To what scenario do your research and those of your colleagues around the world agree for the 50 or 100 years to come?

There is no doubt today about the reality of warming resulting from greenhouse gas emissions, with inexorable consequences: canicules, droughts, melting of the ice floes, melting of the great continental glaciers and raising of the level of the sea, rapid impact on the fauna and flora… This is accompanied by changes that are also inexorable, but more difficult to predict in their details and their consequences.

Last year, in reunion, a meteoric storm (Fakir) surprised a lot of people in April, although officially the cyclonic season runs until May. Are we already experiencing this change?

Climate is a matter of statistics. The statistics on cyclones are difficult to do because they concern rare events. They will ask for decades or more. But the risks of serious events are sufficiently important for the need to take precautionary and adaptation measures to be strengthened, in anticipation of a future that will necessarily be different.

How will the meeting and more globally the tropical islands have to do (erosion, rising water, flooding,…) in the face of climate change?

There are many things to consider and of course these are initiatives that belong to the reunion or other ilians concerned. However, I think it is important to have in each island a collective view of these problems, ranging from physical problems to social problems: they cannot be considered independently of each other. It must also be borne in mind that the changes to come will be more numerous, and/or more intense, we must prepare, protect ourselves, anticipating these evolutions, that one can at least not be prevented from doing so.


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