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A little speech given during the presentation of the movie "The Day After" to the french press

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What follows is a little address (6 minutes and 30 seconds exactely !) that I pronounced on May 3rd, 2004, during (just before, in fact) the presentation to the French press of the movie "The Day After". This movie features a couple of catastrophic climatic events, including a new ice age that brutally strikes the US and Europe, and the french distributors of the movie accepted to spare a little time during this event to clarify the link with the "true" climate change (excellent idea !).

I thus ended up giving the shortest speech of my life to a bunch of movie critics, that probably wondered for a while whether they were in the proper theater, and that I reproduced below (the speech, not the critics !). For those that would appreciate to learn more on some notions I had to evoke in the shortest possible amount of time, I loaded up the text with links in order to allow it.

If this text was to be quoted, I would to draw the attention of the reader/journalist that I carefully evaluated each word before writing it down, being cautious not to use any other word instead. Thanks a lot, therefore, not to put any other sentence in my mouth than what I actually wrote. The original speech is in french, and thus the english version may inclure a couple of translation errors.


Ladies and Gentlemen, and dear friends for those I know in the room,

I am truly happy that the distributor of the movie "The Day After", and the Fondation Nicolas Hulot, to whom I also partially own my presence here, granted me with a couple minutes before the show starts, to briefly evoke the climate change that goes on in the real world, before we discover together - because I did not benefit from a particular privilege - the climate change that is used as a background for the movie.

Nobody in this room has the slightest doubt, of course, that what we are about to see is a fiction, and I don't think that anyone - and particularly not its producers - claims that it gives a probable - or even merely possible - vision of the "real" climate change studied by science.

Still, it remains perfectly legitimate to wonder whether the movie that we are about to see is very far, just a little far, or not far at all from what could happen in the decades to come, for the existing inhabitants of the earth, or those that we will give birth to.

As I cannot answer this question right away, I will instead recall very briefly - a detailed description would require an hour at last - the main conclusions that can be found in the scientific file. For those that would whish it, I am sure that a number of people I recognize in the room - and your humble servant - will be delighted to answer to your questions when the show is over, knowing of course that I cannot guarantee an authorized opinion on the quality of the screenplay or the make-up of the main actress.


It has been now almost two centuries since physicists identified the main greenhouse gases present in the atmosphere, and that we know that their abundance influences the terrestrial climate.

It's been more than a century since Svante Arrhenius, a swedish scientist that will receive the Nobel Prize (in chemistry) in 1903, for other works, performed the first calculation - giving a roughly correct result - linking an increase of the CO2 in the air to a subsequent increase of the planetary temperature later on. From there, Arrhenius correctly deduced, but this thought did not disturb him then, that the industrial civilization would generate a global warming of a couple degrees (Celsius).

It's been almost a century and a half since the temperature records are numerous enough to allow a good vision of the evolution of the temperature average for the planet. At last, it's been more than 45 years since continuous measurements of the CO2 in the atmosphère began, and in this chronology I could have added that the first computer, built 60 years ago, was used to run the first weather prediction model ever designed. I should therefore not say that in this room, but the evolution of the earth's climate is a much older subject of interest for science than it is for the media.

A number of certainties can be drawn from the scientific file, even if many uncertainties remain otherwise :

Since 1850, humankind has increased the atmospheric CO2 concentration by 30%, by burning evergrowing quantities of coal, oil and gas, and by clearing forests. Mother Nature needs 10.000 years, at last, to generate "alone" the same variation of the CO2 concentration,

Once we have put this extra CO2 in the air, it requires centuries - if not millennia - to be evacuated, to the ocean or to the terrestrial ecosystems, with little hope that the rate of evacuation will increase in the future, our fears being rather that the "evacuation rate" will decrease in a modified climate,

Because of this longevity of the CO2 in the air, we - and our descendants - will witness increasing disruptions of the climate system for centuries or millennia, depending on the consequence we are talking of,

All estimates agree on an increase of the average temperature of 1 to 5 degrees Celsius (that is 2 to 9 ° F, roughly) during the 21st century, and the temperature will keep rising afterwards. The magnitude of the increase will essentially depend on our future CO2 emissions - CO2 being the main greenhouse gas emitted by man, but not the only one - during the century to come,

the only question raised by a couple of extra degrees for the world average is not whether Canada will replace Mexico for summer holidays. A couple of degrees extra for the world average is a change of climate age.

During the last ice age termination, the earth's average temperature increased from 10 °C - its value 20.000 years ago ; Germany was then covered by a glacier 3 km thick, and the Channel [NDR : the sea between Great Britain and France, for those who do not know !] was dried up - to 15 °C, its value 10.000 years ago, and, since then, it has not changed much. But our ancestors had to adapt to a 5 °C increase in 10.000 years, whereas we are now talking of a couple degrees increase in one or two centuries, which would be 50 to 100 times faster ! This situation is unprecedented in the history of humankind, and will be considerably more risky than all we have known in the past. I might try to illustrate my purpose by saying that's it's just like the difference between hitting a wall at 1 mile per hour, or hitting it at 50 or 100 miles per hour...

As this situation will be unprecedented, it is - and will remain - strictly impossible for scientists to describe precisely in advance all the possible consequences of this evolution. Turning to the past is without any doubt of great help to better figure out what the future will be made of, but is not sufficient, alas, to make very detailled projections for the centuries to come. We should nevertheless take care not to believe, as we are commonly inclined to, that ignorance is a warranty that everything will be fine, and we should remember that the major extinction crisis in the past were most likely associated to brutal climate transitions, such as the one that led to the vanishing of dinosaurs, 65 millions years ago. My feeling - but I insist that it is only my feeling, and nothing else - is that it is not possible, today, to rule out a couple of billion deaths as the ultimate consequence of a climate change that would be in the higher part of the bracket of the available projections.

One of the possible consequences of the present evolution on which there is some visibility, however, is often a major source of surprise for who discovers it : it is the possibility of a brutal cooling on all the Northern Atlantic, in a world that would otherwise heat up. Brutal means here "in a couple decades", and not, as it is the case in the film (this is the only revelation I was given), in a week. Such a brutal cooling of the Northern Atlantic could happen if the Gulf Stream collapsed in the future, as it did several times during the last 100.000 years, for reasons that are now pretty well known.

The before the last stop of the Gulf Stream, 12.000 years ago, also resulted, beyond a sharp temperature decrease, in a division by 2 to 4 of the precipitations for the places in Western Europe where data is available. If such a stop of the Gulf Stream occurred in the future, the question of the evolution of the precipitations would be raised, without any definite answer available today.

If it is beyond my possibilities to say right now whether this movie depicts a plausible world or not - and my guess is that it should not be (plausible), because any moviemaker is entitled to his share of imagination ! -, the possibility of a cooling hitting Europe and the eastern part of Northern America with massive consequences, happening in a couple decades in a globally warming world, is not totally fanciful. Science cannot conclude today on the probability of occurrence (we just know that it is possible), the date if it happens, and the exact magnitude of the process if it happens.

What can nevetheless say science, it is that as long as we will emit increasing amounts of greenhouse gases, the risk that such a halt of the Gulf Stream happens, in a future ranging from decades to centuries, will increase with time.

After these words of hope, I leave the audience to the projectionist, and wish you to enjoy the movie !


And once I have seen the movie, what do I think about it ?

Of course, just after this short address I had the privilege to discover the movie, what definitely allows a better opinion on the scientific "likelihood" of the scenario. I was not mistaken when I supposed that the movie writer called more on his imagination than on the IPCC reports :

If a halt of the Gulf Stream, in a future which is at least a matter of decades (and more probably a matter of centuries) is possible, that it could happen in a week is strictly impossible. Such a process would take a couple decades at least between its beginning and its end,

Such a halt could in no way generate a new ice age over Europe and the US, as in the film. A drop of 4 to 5 degrees (Celsius) of the average temperature compared to today (what the halt of the Gulf Stream produced over the Northern Atlantic in the past), it is not enough to trigger a new ice age, what requires a temperature drop of at least 10 degrees (Celsius) over Europe.

if a tidal wave was to submerge New York during a hurricane, the water would of course withdraw once the hurricane is over, and go back to the ocean (it would be different if there were dams or sea walls and water went over, the dams then preventing the water to go back to the ocean, but in New-York it is not really the case). For New York to remain permanently under 30 feet of water afterwards, it would require that the ocean level rose by 30 feet in a matter of days : this is not for tomorrow ! (and is strictly impossible in a couple days : the time scale for a rise of such a magnitude would rather be several centuries to a millenium)

If the catastrophas descrived in the movie are not possible in our world (but this is normal : it is a fiction, not a documentary), still, there are two elements enclosed in this movie that are somewhat close to what happens in the real world :

There is "something" in the interaction between some of the main characters which is conform to reality :

the incredulity that the scientific world meets when explaining to its audiences (politicians, journalists, economic "leaders", and more generally each one of us, because we vote !) that the world of tomorrow might well be very different from the one we have always known, and the spontaneous "refusal" of such an hypothesis by all these audiences, correspond pretty well to what I see around, even if the real dangers we should fear are not at all those of the film.

In particular, though it is exaggerated in the movie, I am ready to believe that the absence of dialogue between the handsome professor, and the nasty and stubborn vice-president (that is not without reminding the real one ; probably an explicit allusion !) is not far from what really goes on in the US, but also in our country, even if it is done in a softer way, and not directly between the president and the researchers (see just below). I experienced this situation on several occasions (what wouldn't I do to try to ressemble the handsome professor) : when trying to expose the contents of the scientific file to someone in the political world (a congressperson, a minister...), and why a logical consequence would be to start without delay a soft revolution, because the changes to be made are as huge as the possible consequences, one is considered as a lunatic, or a dangerous monomaniac, whatever.

There is, still, an essential profession that the movie forgets to show, and that changes everything in the real dialogue in the real world : the media. Contrary to what happens on the screen during one of the first scenes, where the professor speaks in front of a carefully listening Vice-President, I doubt very much that the scientists that investigate the man-made climate change frequently have the opportunity to explain directly to M. Cheney (or M. Bush, or M. Blair, or M. Putin, or M. Chirac) how the world we live in could evolve ! As far as I am concerned, I do not know a single researcher to whom a president or prime minister granted a couple hours of his time, accepting to return to the student's desk to well understand what all this is about. In the real world, all the dialogue between science and politics is done through the media, with very important side effects, that are not only due to the incompetence or the bad faith of journalists. A scene more realistic would have been the apparition of a skeptical expression on the face of the Vice-President after he had read, in 5 minutes, the interview of a scientist in the paper, or a short note prepared by one of his advisors from the interview of a scientist in the paper...... In the real world, prime hand and detailed information getting to the political world is the exception, not the rule.

Though the events that occur in the film are, I do insist, totally impossible, the idea that the current evolution of the climate will yield some surprises, probably much more unpleasant than pleasant, that science will not be able to predict long before they happen, if not predict at all, is correct. The movie has at least the merit to recall that ignorance is not a warranty against major bad surprises, what too many people implicitely consider when explaining that we should act only when the vision of the future becomes crisp clear (what science will never allow, as explained in the "speech" above).

If I summarize, on the basis of events that are factually impossible, but that definitely allow to show numerous special effects, the movie draws one's attention on a true issue of the true file of the true climate change : how can it be made possible to allow the decision makers, that are not familiar with climate processes (which is normal), and more generally each one of us, to interpret correctly, and "in time", the danger signals emitted by the scientific community, and react in an appropriate way to them ?


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