Well, I’m going to continue with a topic you heard yesterday from my colleagues, Sherry Roland and Paul Crutzen.
But as you see I’m going to emphasize a bit more the aspects of the solution to the problem.
But I want to start by briefly reviewing where we left the theme yesterday.
First, just to remind you of a few of the things that we heard very briefly.
Paul Crutzen talked about this situation that we are now in, the anthropocene,
that we’re so many people on this planet that we’re actually affecting the way the planet functions.
And all I want to emphasize with this picture here is that our planet is really vulnerable from space,
the blue planet really looks vulnerable.
And in particular we are worried about the limited natural resources that it has and the fact
that with over six billion people on the planet we are really stressing, we’re putting pressure
on this limited amount of natural resources.
But in particular we’re focusing on the atmosphere.
The atmosphere from space as you see it, it’s very thin, you can only see the clouds.
But the atmosphere itself is like the skin of an apple.
It’s very thin and that’s why it’s feasible then, it’s understandable that human activities are really affecting it.
We also saw both Sherry and Paul, they indicated how the chemical composition, excuse me,
the chemical composition of the atmosphere is changing and it’s changing particularly in, in recent decades.
You can see very easily how it’s a consequence of human activities and in fact Paul showed this particular view graph
which comes from the Intergovernmental Panel on Climate Change.
You can see the sudden change.
And also the change in temperature.
Here what we’re showing is the consensus of,
from several different groups as to how the average temperature of the earth’s surface looks like.
Of course it was not easy to measure a thousand years ago because there were no thermometers
but you can look at the width of tree rings, coral rings,
there are any number of ways that you can infer what that average temperature was.
But in recent years there, of course millions of measurements,
thousands of measurements so you can take this proper average and clearly there is an increase.
And now the question is, are these two phenomena connected?
Sherry Rowland already pointed out that you can see the, there is a judge in the United States,
already he gave a quote that states, that the consensus of the scientific community is that these two observations,
change in the chemical composition and change in the temperature, are indeed connected.
And that’s the consensus.
But to make it even clearer.
This is what this group of scientists, close to two thousand scientists, working just on a voluntary fashion,
Intergovernmental Panel on Climate Change.
By the way, the chairman of this group is Rajendra Pachauri who will be, I believe with us,
this Friday and it’s this group that shared the Peace Nobel Prize with Al Gore just last year, okay.
But anyhow the point is that this group, in the fourth assessment report, I was in fact part of that group,
we concluded that indeed there is a connection between those two sets of observations,
change in composition, change in temperature.
But we’re not really absolutely certain, that’s a nature of science.
We only have ninety, ninety five percent probability that that’s the case.
So it already, is a number of years ago, we wanted this group to be more sort of,
to explain in clearer terms when there was scientific uncertainty, what we were talking about.
So that using language so that’s it’s very likely or likely.
In this case it’s very likely that it is indeed human activities that are causing the climate change,
but it’s not absolutely certain.
Also, just to continue one more, I’m just repeating as you see, a few slides.
One more that the, both Sherry and Paul again talked about is,
has to do with what was the composition of the atmosphere thousands of years ago,
in fact hundreds of thousands of years ago and it’s amazing that you can actually tell what the composition was,
at least in terms of the stable gases by analysing the air bubbles trapped in ice course.
But I want to show this again just to tackle the following question.
There are a number of people sceptics, not very well informed, that suggest that even among the scientific community but not,
not really the experts but they always wonder, well climate has always been changing,
has changed in the past so it’s not really a surprise that it’s changing again.
How do we know it’s in fact a consequence of human activities?
Well the point of this long break or is to indicate that there is a basic understanding of how climate change.
What drives the formation of ice ages and so on and so forth and in fact again as Paul mentioned it is the Milankovitch cycles,
it turns out that if you look in deeper at the parameters of the earth’s orbit
and that’s classical mechanics, Newtonian mechanics.
You can calculate with great accuracy how these parameters change with time, the frequency,
the eccentricity the ellipticity and so on and with those types of changes,
you can explain basically the occurrence of ice ages.
They have to be amplified this, this, different stages.
The temperature changes are amplified by the presence of this greenhouse gases.
Again as we heard yesterday they have the ones that affect the thermal balance of the planet absorbing infra-red radiation.
But the point is the following.
With that basic understanding it’s clear that what we’re seeing just in this last century is not expected.
We don’t expect temperature or climate to have changed as we observe it from natural causes.
There’s, the parameters of the earth’s orbit again, that is all well established that that is not the cause this time.
It’s something unexpected.
Furthermore, I won’t have time to do it in great detail but what this group, the IPCC, by the way they don’t do research.
But they survey the scientific literature in great detail.
And so what they assess is so-called attribution, is this temperature change consistent with the cause being,
this increase in greenhouse gases.
Consistent from the point of view of the way temperature changes with altitude and with latitude the so-called fingerprints.
And indeed that’s, that’s a case.
It’s not consistent with the changes being attributable just to a change in solar intensity for example.
It’s all, you also do, but not exclusively but it’s an important part of the proof has to do with computer models.
You model an entire climate system.
It’s very complicated that’s why you’re not absolutely certain.
But the consistency is all there.
So the conclusion again, just to emphasize it, is that the, it is human activities that are changing the climate,
that’s a consensus of the well informed scientific community which has also very well documented in the literature
and there were remarkably few if any, scientific papers I would call them, through the scientific papers
that really put a serious question on these conclusions and meaning again that yes there is some probability
that it might have happened naturally.
Also we recall that we’re not talking about weather or temperature in any one given year.
This is climate which is an average over what the weather is over a number of years.
So having established all that, what do, why should we worry about this?
If you look at the temperature change I show it’s less than one degree Celsius.
Like one seven point eight so that looks very small.
On the other hand if we consider that ice ages, the temperature change between an ice age
and an inter glacial was again relatively small, maybe four to eight degrees Celsius.
That’s because we’re talking about the global average.
But the consequences are already clear.
It’s not that we’re predicting climate change for the end of the century.
We are already seeing it very clearly.
Most glaciers are melting, not all of them but for example in the,
Himalayas these are very important events because the glaciers feed the rivers
that in turn feed literally hundreds of millions of people in Asia.
And so there is a significant change of servable already glaciers in California for example are also clearly melting.
What about events such as Katrina?
These are very costly damaging events.
This is what we are, call extreme weather events.
And here is the situation.
We cannot really tell for certain that Katrina is a consequence of climate change.
We’re again not sure.
But we can use statistics.
It’s very clear that floods as well as intense hurricanes, two symptoms of extreme weather events,
the frequency has increased quite clearly in all continents.
So coming back to Katrina all we can say that statistically it fits the pattern very well.
Again we cannot choose any one particular event and be certain
that it’s caused by climate change but statistically the number of such events are very clearly increasing.
We also have events such as wildfires in California.
We had that many where I work so it’s clearly increasing, with time.
And so are droughts.
So the, what’s happening is that the amount of rain falling on the planet is not, hasn’t really changed
that much but it’s changed the way it’s distributed.
It comes in events that give rise to floods or droughts and droughts are particularly costly.
You can see that, how the very dry land in just the last thirty, forty years has actually, the amount has actually doubled.
Let’s go now to the point, to the question so what should we do about it first and then is it possible?
And one way to discuss this is, with this diagram that I’m borrowing from, the story from Nicolas Stern,
an economist in the United Kingdom where we talk, he talks, we know in the community we,
they have done that before but he summarizes it very neatly.
What are the impacts of climate change, as a function of the expected average temperature change at the earth’s surface,
reminding you that so far we’re less than one degree.
And we have all sorts of possible impacts, agriculture, health and so on, which I won’t discuss in any detail,
just mention two of them just for completeness.
The second arrow means that some impacts actually are beneficial, positive,
perhaps in some northern countries the growing seasons will be longer.
But most impacts are negative particularly as you get to the higher temperature changes.
They become clearly very damaging effects of climate change.
There is also an arrow somewhere towards the bottom which I’ll come back to
which has to do with abrupt changes or almost irreversible changes that are indeed very worrisome.
But if you examine then these potential impacts and you examine the cost in human induced,
it’s possible to reach a consensus as, as has the European Union and most experts.
Not just scientists now but economists and politicians and so on.
The consensus being that it would be wise to attempt for the temperature the surface temperature
not to rise above two degrees Celsius and that’s because it begins to be very dangerous, very worrisome.
Here however, I need to make a point very clear.
Sometimes you hear that the science tells us that we should not let the temperature go above two degrees.
It’s not really the science.
The scientists are very careful about it, this panel, the IPCC, Intergovernmental Panel on Climate Change,
makes a point about not making policy judgments.
What scientists do is simply say okay if the temperature goes up this much this is what is likely to happen,
if it goes this much more, that’s what is likely to happen.
But the judgment, what is a reasonable goal to shoot for involves not just science, it also involves economics,
policy issues and value judgments, so scientists do not have a particular right or expertise
to talk about that type of risk assessment.
So when we talk about this consensus, I can be giving an opinion but it’s then more as an individual
not as a scientist but that consensus clearly among informed people, scientists and other experts is
that indeed we should shoot for less than a two degree hopefully certainly less than two and a half
or three degrees temperature change because we’re getting into very dangerous terrain if we let that happen.
And then the next question is, is it possible?
How do we manage for the temperature not to go above two or three, if in fact the projections are
that if we do nothing it will go much higher than that.
What we have here is a graph of emissions.
Emissions versus time of the main greenhouse gas, carbon dioxide, you will recall there are others.
I will refer to that also in a minute, and you heard that already from Paul and Sherry yesterday.
But the trend is for the emissions to continue increasing quite dramatically and you can see where they come from,
in fact China is emitting at the moment about as much as the United States in terms of carbon dioxide.
Although the cumulative amounts mean that of course, that are still significantly larger for the United States.
But it’s clear that both developed and developing countries need to do something about it.
What needs to be done?
Well here again is a graph of these emissions versus time for the future and what we would have to do,
if we don’t want to go above two degrees is to change from where we are, which is the upper red curve
to somewhere in the green or yellow curves.
And that is a very big change considering that all this has to do with the way society uses energy,
mostly coming from fossil fuels.
So we really need a revolution in the way society functions to be able to switch so that we, we achieve that goal
which by the way is equivalent to not letting the carbon dioxide amount in the atmosphere raise about certain concentration,
three fifty, four fifty parts per medium.
We could also talk about CO2 equivalents, if we add, not just carbon dioxide but methane nitrous oxide and so on,
we could talk about the equivalent total amount.
But CO2 is perhaps the most challenging one.
And the question is can this be done?
Is it possible to switch in this very drastic way?
And the answer is basically yes.
We do have existing technologies.
With existing technologies in this decade and possibly next one, we can already achieve very major changes
but it’s imperative that we also start developing aggressively better and newer technologies
so that this can be done, not just in the next decade for, but during the rest of the century.
What I have here is again a graph of emissions versus time and it’s a graph borrowed from my Princeton colleagues,
Steve Pacala and Rob Socolow.
And here is a summary if you want in terms of what the solution is.
First of all there is no silver bullet.
There is no simple solution such as ah, let’s just switch to nuclear energy.
Unfortunately if you look at the details we cannot do that fast enough.
So the simple answer is, we need to take many measures.
At least the ten that are indicated here and each of them is contributing just a wedge,
a small decrease in the total amount of emissions so we have to do them all basically.
An important number, the top ones, the ones that are already beneficial for society
even if the climate change were not an issue have to do with using energy much more efficiently than we’re doing it today.
That can be done with, with the transportation sector, with cars for example,
United States just very recently passed a law that, of certain efficiency standards Europe had that law already some time ago.
China has one and so on, so that’s one example.
In the, the building, say the construction of housing and so again it’s possible to have much more efficient buildings,
houses and so on so we don’t need to use more energy and so on.
So I could go along the list, in fact we would have a panel discussion I believe after the break
where the topic will be this, some of these energies.
But clearly you need renewable energy sources, wind solar and so on.
And which are now just barely beginning to be developed.
Perhaps I’ll just make two brief points.
Nuclear is a very interesting question but it would take too much time to discuss in any detail
but it is a solution we should have on the table,
particularly for the new generation of nuclear power plants if they’re safer and have less problems in terms of accidents.
Nuclear proliferation is still a very big worry in terms of the availability of material for bombs and so on, but it’s possible.
It’s an option that many agree, now agree in contrast with what the situation was a number of years ago
that it’s an option society should have.
It’s still regrettably costly but if you consider the investment as a long term investment,
it turns out it does pay for itself.
Anyhow nuclear is the subject of discussion.
Bio fuels is also, can be discussed a lot for example using ethanol from corn as is the case in the United States.
It’s only justifiable in terms of an energy supply in the United States, not to depend so much from a fall in oil,
but it doesn’t have net environmental benefits because too much fossil fuel energy is used to generate that ethanol.
So there are ways to generate bio fuels perhaps, from sugar cane in Brazil is a better example where
it’s more favourable environmentally.
But here again the bottom line is that there are second and third generation bio fuels
that we should have that will indeed be much better for the environment and just continue using fossil fuels.
And if we want to continue using fossil fuels there is only one way to do it safely in the future
which is to capture and store the carbon dioxide that is emitted, and store it in for example,
saline domes, on the one, not to let it go to the, to the atmosphere.
Perhaps I should mention here briefly again that there is also the general idea in, in the community
and particularly in the business community that we have a very serious problem
that we will run out of oil in the next few decades.
Two points.
We’re not running out of fossil fuels because there is a lot of coal, okay, the United States and China again
are examples of countries that generate a lot of electricity from coal and that is going to last a long time.
Second indeed, we are going to run out of oil and that’s why it’s imperative to develop new sources of energy.
But long before we run out of oil, we’re going to run out of atmosphere,
or rather the capacity of the atmosphere to clean the emissions.
So that cannot be the solution to the climate change program.
We need to act much before that’s really the problem.
Okay so the summary here is that there are ways to solve the problem, to address the problem,
to reduce emissions with existing technologies, although we aggressively need to develop the newer and better technologies.
But now I want to turn on to another point which is, which has to do with, again I want to review,
why is it that it’s reasonable to sort of have a goal of two degrees or around there abouts
in terms of a maximum temperature change.
First of all what I want to show you is that we’re talking about statistics.
This graph climate sensitivity talks about predicted temperature changes for,
in this case for a particular model in the United Kingdom.
And you can see that you have a distribution curve, depending on how much greenhouse gas you will end up in the atmosphere.
So you’ll have to deal with statistics and one way to look at it is, I’m borrowing this now from my colleagues at the MIT,
I spent many years at MIT, so my colleagues Ron Prinn, an atmospheric scientist and J.J. Cullen an economist,
have been working together with a very complete model of climate and the economy of the planet.
And this is one way to represent this idea in terms of risk, particular to the larger community,
to the community of decision makers or politicians if you want.
So imagine for a moment you are a politician and not a student.
And I am explaining to you what is going on.
I say we’re actually playing a game which is almost like a roulette game
and if we look at the roulette into the left that’s where we are now.
We’re gambling, we could put a number there, let’s say we play a game of a hundred thousand dollars.
And I tell you if you win, you, to win the hundred thousand dollars the temperature has to increase less and to decrease.
So you know you have some chances according to this roulette, better than twenty five percent or so, but not very big chances.
If you really want to win you would be better off with the other roulette because we increase the chances that you will get.
And the question is what will it cost, what does it cost to change roulette?
I mean how much are you willing to give me from your hundred thousand dollars should you win it to change the roulette?
And that’s of course what the economic studies are all about.
So I think for a second what, how much would you willing to, to give up from a hundred thousand and I went to a survey here
but it’s possible that it’s a reasonable amount to say okay well ten thousand, maybe twenty thousand
or even thirty thousand dollars is what I would be willing to pay to move from the left to the right because I,
I increase my chances.
What is surprising is that what the economic stories indicate is that it only costs about one or two percent of global GDP.
So it’s really only a thousand or two thousand dollars what you have to pay to change roulette.
It’s a bargain.
Why don’t we do it, that’s what the planet really should do.
There is a worry though, this roulette, this, what my colleagues at MIT have calculated several years ago,
in fact since the IPCC report came out, the more current findings all indicate that the problem is more urgent.
Quite a bit more urgent than we had anticipated so the more recent roulettes that my colleagues just published
look a lot worse and in particular I want to point out what’s happening with the red points there.
You, you see there is a certain chance, maybe only ten percent, twenty percent that the temperature of the planet
will increase more than five degrees.
But that would be almost catastrophic, if you look at the details, that’s extremely dangerous.
With a new roulette, that’s now a lot more likely.
Twenty five percent probability that we’re really in trouble and again changing roulette,
paying that amount that we’re talking about really makes a lot of sense, okay.
And why?
So let me briefly explain what has happened, why have things changed in these recent years in terms of assessing
what has happened?
You saw again yesterday this, this graph representing the contributions from the different forcing agents,
CO2, all the greenhouse gases and then atmospheric particles.
It turns out that particular sulphate particles from burning coal, counteract climate change.
They make the planet more hazy and reflect part of solar radiation.
So what the community of experts have done, they have their papers and so on, have under estimated this compensating effect,
and so the more recent studies, I’ve looked at it very closely,
indicate that actually the sensitivity of the planet to these increases in greenhouse gases is larger.
So if we reduce the number of those sulphate particles as we should for public health reasons,
and in order to have a cleaner planet, we’re making climate change, forcing worse.
But we have to deal with that and the point is that it, anyhow that we’re expecting because of this,
that the risk of these almost catastrophic events to increase.
So that’s the main reason but there are others.
Another important reason is the realization that carbon dioxide remains in the atmosphere,
in the environment much longer than really have been anticipated.
It’s not just a hundred years but a recent paper by Susan Solomon and colleagues and so on,
it’s practically millennium.
So we’re making almost irreversible changes to the environment to the extent that we let this CO2 accumulate.
And here is one additional big worry.
What we call tipping points, okay.
These are instabilities of the system, since time is short I’ll just let you read about it.
But here is, let me graphically indicate what is happening.
If we represent temperature of climate by the position of this little ball, in this diagram and we start from the front,
we’re pushing the climate system, changing the shape of the stability diagram
in such a way that the ball is moving slightly to the left.
It’s getting warmer.
But what we’re worried is that at some point, there is a tipping point.
The ball will move quite significantly with very little additional forcing
and that’s what we call either the tipping point, an abrupt climate change or something like that
and the big worry is that we have a risk.
This is now a paper from my colleagues, Ramanathan and Feng at Scripps.
If you look at the temperature distribution that something we’re already committed to,
and you look at various possibilities of the so-called tipping points.
Arctic summer ice is already melting so that’s a tipping point we already achieved practically irreversible
because once it melts it will take at least a millennium even if we clean the atmosphere for things to recover.
But then there are other issues.
The glaciers that I mentioned before, Greenland ice sheet, the Amazon rainforest could,
could be in big trouble if you push the climate system far enough.
Or the ocean circulation and so on.
If the west Antarctic sheet were to melt you, you would have many meters of a sea level rise.
Some of this, this has been analysed, I want to detail some of these tipping points will occur relatively soon
and others will take many decades.
But the bottom line here is that we have to think of what we’re doing to the, to the planet in this risk assessment point of view,
giving a lot of weight to the risk of reaching these tipping points, even if it’s not the most likely thing.
This has been analysed formally by economists, well particularly Martin Weitzman in, at Harvard with the following conclusion.
I mentioned just a little while ago that the economic models suggest that it’s reasonable to make the changes I suggested.
To shoot for two degrees as a maximum change because it’s something that will not cost very much.
If you wanted to do that same change very fast, the cost might increase quite dramatically.
So you need to give the economy some time to move.
But according to Weitzman in these formal ways but according to just simple judgment that we have,
we should not play roulette with the planet.
If there is a ten percent risk for each of those tipping points,
the cumulative risk that something drastic will happen begins to be very worrisome.
Who would climb in an airplane if they tell you that there’s a ten percent risk that both engines will fail.
You have the choice of waiting a few hours and taking the next one.
You might have to pay ten percent more for the tickets.
Well very few people I think would want to go into the first plane just to be there a few hours earlier, okay.
So that’s what we’re talking about.
We’re talking about what is dominance from the point of view of the economic issue is the fact
that you have this fat tails as we call it, the distribution is really not just a Gaussian
but there’s a significant probability that these red areas in the roulette that I mentioned will materialize.
It’s a risk that is not wise to take.
But now I summarise it not just from, for economic reasons but really it’s a matter of ethics.
Our generation has the responsibility to protect the planet for future generations who will be highly responsible
knowing that there is such a risk, just to gamble and say well it’s possible that not much will happen.
But to let the planet sort of deteriorate so that it would be much harder for future generations to,
to achieve the same standards of living that we have.
I see that my time is basically running out so I just want to summarise briefly that it’s very important for the planet
to reach a consensus and essentially for these actions to take place there has to be a price signal into the economy.
The price of emissions has to be incorporated to the economy.
You cannot achieve all this just through voluntary actions.
Furthermore there has to be more to research, there has to be collaboration with, with developing countries,
it’s imperative that developed and developing countries work together.
The existing Kyoto Protocol really doesn’t work very well but the expectation is that in Copenhagen at the end of this year,
something will happen so that developed and developing countries will really collaborate to solve this problem.
And let me just finish seeing that my time is really up although I didn’t mention,
I didn’t mention it very accurately but I want to finish with this story of the Montreal Protocol
that again you already heard it yesterday from Paul and Sherry.
To show an example that it is indeed possible for the planet to reach an agreement.
Most nations on the planet or more than a hundred and ninety two, agreed already
to phase out completely the CFCs and this is in connection with protecting the ozone layer,
by the way because the CFCs are also the greenhouse gases, the Montreal Protocol has done a lot more,
at least five or six times more for the climate change than the Kyoto Protocol so far.
But the point is that it is possible, it is possible to reach an agreement and of course much more difficult
if it involves energy because it’s important for the economy but let me just go to the, I’m going to skip things,
I no longer have time to which is that we can do the economic studies much more carefully
and show that it’s certainly beneficial but let me just end with this graph again that you, that shows the sudden explosions.
And I will leave you with this final thought.
The planet has been mostly affected, contaminated if you want with just a fraction of this population we have at the moment,
one fourth maybe, which is the developed countries because of the way the economies have grown.
Three fourths of that population is striving to reach the same standards of living to have rapid economic growth
and they suddenly have the right to do that, developing countries.
But the huge challenge, particularly for the younger generations, for you students, is somehow or other to allow that to happen,
standards of living to increase, poverty to be eradicated.
It’s an enormous challenge on its own but in a very different way we cannot possibly do it the same way
that the developed countries have done it so far in terms of using energy, contaminating the planet and so on.
The planet is just too small to do that, so we need to develop new ways to use energy.
New ways to function much more efficiently, because of course we can in no way deny the right of all these people to have a huge,
to increase in their standard of living and it is not just economics which makes a lot of sense but it’s a very strong
responsibility from an ethical point of view.
Thank you for your attention.