Let me introduce myself, here I am, more than 70 years ago, in the lap of my grandmother,
she had a tough life, she came from Poland and just the year before my grandfather had died, so she was not very happy.
She was only 59 years old and had a very tough life.
But I am smiling and I was more lucky than she.
I’ve changed a lot, but many other things have changed.
So during the past three centuries the human population has 10 folded and in the last century alone it has more than 4 folded.
And cattle population grew with the humans and we have about 1,400 million cattle in the world,
that means per family on average a cow, which is producing milk and cheese and also steaks for us.
It also influences the chemistry of the atmosphere to which I will speak.
Urbanisation grew more than a factor of 10 fold in the past century and almost half of the people now live in cities.
And increasingly also in megacities, especially in the developing countries.
Industrial output increased 40 times in the past century and energy use 16 times.
Almost 50% of the land surface has been changed by human activities.
Then water use has increased.
So we are now using per capita per year about 800 cubic metre of water,
mostly for irrigation, 25% for industry and only 10% for households.
Human appropriation of net primary productivity is as high as about 30%.
Fish catch increased 40 times.
And if you go to the atmosphere, the release of SO2 to the atmosphere by coal and oil burning is now,
it’s about twice the sum of all natural emissions.
And if you look at the land, it’s even much more than that.
And that has caused acid rain, it causes bad visibility, health effects,
it also influences the climate and I’ll come back to that.
Then the release of NO to the atmosphere has also more than doubled
and that has influences on ozone formation in troposphere, photo chemicals, smog.
And also it adds to acid rain.
Then we have several climatically important gases like CO2 which has grown by a factor of 30% since pre-industrial times,
and also especially methane has grown today to more than double the values of industrial times.
That has a contribution by the cattle.
Humanity is also responsible for the presence of many toxic substances in the environment.
But even some which are not toxic at all, like the CFC gases, but they of course, as we all know,
have played a large role in destroying ozone in the stratosphere and no doubt Sherry Rowland will speak more about it.
Which has consequences for UV radiation and for instance skin cancer.
Nitrogen fixation, at about 1980 the anthropogenic nitrogen fixation became equal to that by natural processes,
that’s where the Haber-Bosch mechanism to produce ammonia, which is then converted into nitrogen fertilizer.
We are now putting in more nitrogen fertilizer in the soils of the world to feed the people than natural processes.
And it’s interesting and disturbing to know that this is of course done for a good reason, to feed the people in the world.
But actually what ends up in the mouths of people is less than 10% of the nitrogen we put into the soils
and we don’t really know where it is accumulating, what it is doing.
We know one thing and that is that nitrous oxide, and that will always be produced,
which is a greenhouse gas with a kilogram of emission, 300 times larger effect than carbon dioxide.
So all of that has to be considered.
Man is destroying the surface layer of the earth
and we can say that man-made erosion around the world is about a factor of 15 times larger than natural erosion.
We have species extinction, the normal rate of species extinction is about one species per million per year,
actually it is now 100 to 10,000 times larger, as estimated by E.O. Wilson of Harvard.
So the many changes which have occurred, and I only gave you a few examples,
but generally we can say we have played increasingly a larger role in effecting natural process in the atmosphere.
And for that reason I have dubbed a new geological era and that’s called the anthropocene, it’s the human geology,
the geological period which is now, since about the beginning of the last century,
has dominated the biological cycles and also climate and atmospheric composition.
The two most famous examples of things which have happened in the environment, in the atmosphere,
is the rise of carbon dioxide in the atmosphere and carbon dioxide is a greenhouse gas.
And you see here the famous curves derived by Dave Keeling who unfortunately died last year, the pioneer of these measurements.
You see also the wiggles, the up-and-downs, and they are the seasonal variations, the photosynthesis process is reflected there.
We also see the ozone hole in the lowest two pictures.
Since about the middle of the’70s, there is no doubt that ozone has gone down,
the total amount of ozone is shown in the lower left hand picture and it doesn’t need a statistical analysis,
you see with your own eyes that, and this is over Antarctica in Halley Bay, the station of the British Antarctic survey.
You see a very rapid decline.
So we have now about 2 to 3 times less ozone over Antarctica during spring time in the atmosphere.
And this was not predicted, this came about because we hit the chemical system of the stratosphere in very sensitive ways.
And that leads to depletions of ozone and interesting enough and shocking enough you see that normally,
and that is shown in the right part of the picture,
you see that normally when we have a maximum in ozone distribution in the stratosphere, just during the spring time,
you see we have gone down from a maximum to a minimum.
Who could have predicted that?
Nobody, it was not predicted, the measurements were out, initially the measurements were not believed,
the observers were not believed but the data came back, this is what is happening.
And I leave it to Sherry to say more about it, and instead concentrate a little more on climate.
Our climate is also effected by human activities.
What is shown here is the radiation and energy budget of the atmosphere.
At the top of the atmosphere on average we receive about 340 W/m2, and let's call that 100 units.
Of these 100 units about almost 30 units are reflected back to space
and that is by reflection from clouds and also by particles in the atmosphere.
In the atmosphere we have further some absorption of solar radiation and finally what comes down to the earth surface is 47 units.
The earth has to get rid of these 47 units because if not the earth will be cooking
and the oceans will be cooking in a question of 1,000 years.
Now, of the 47 units, and we’re now looking at the right hand part of the figure,
of these 47 units, 29 units are given off from the earth surface into the atmosphere by sensible heat conduction
and also by convected processes releasing latent heat that is condensation of heat into the atmosphere.
There are 18 units left which the earth has to get rid of, if that would be all,
we would have a temperature at the earth surface of the order of –25°C.
But the earth does this in a very efficient way.
There’s an enormous recycling of energy taking place.
So in fact of just giving off 18 units, the earth gives up 114 units and 98 units come back to the earth surface.
This is what we call the greenhouse effect.
It’s caused by a number of gases in the atmosphere like water vapour, carbon dioxide, methane, ozone, N2O and also the CFC gases.
And we are disturbing this, I mean this is the basis of science of climatic change.
But that’s not the whole story.
We warm the atmosphere by the greenhouse gases, that’s shown here,
that’s the increase in the warming of the atmosphere and the earth surface.
And it adds up to about 2.7 W/m2.
And then we have some tropospheric ozone, also contributing to that.
So say almost 3 W/m2 is given off, what is in netto captured by the earth, infrared radiation.
There are also factors which cool the atmosphere and those are the particles in the atmosphere.
We have examples here like black carbon and sulphur dioxide emissions, they form particles in the atmosphere,
sulphate particles for instance, biomass burning and also the erosion processes,
wind erosion is adding to the particulate load in the atmosphere.
And they have a cooling effect because they reflect these particles, reflect solar radiation,
they also act as condensation nuclei in the atmosphere.
So all of that leads to a cooling, how much we don’t know because all these individual terms are very uncertain.
And that’s a big problem.
I have tried, together with a colleague, Ramanathan, to summarise in a very simple picture what might be happening.
I just mentioned that on average the energy which is trapped by the earth since preindustrial times, is only average 2.7 W/m2.
Let’s look where this 2.7 W/m2 is going.
It’s going to heat the ocean, 0.3 W/m2, maybe a little more.
Then we have, because the earth is warming up by about 0.6°C since preindustrial times, mainly over the last century,
if we assume that the relative humidity of the atmosphere stays constant,
that means, if temperatures go up, also the amount of water vapour which the atmosphere can trap goes up.
Then that can be calculated, that cooling term, increased upwards infrared radiation, can be estimated to be about 1 W/m2.
So we have two terms here which don’t balance the 2.7 W/m2,
and that is what might be the increased albedo effect of the order of 1.4 W/m2,
being half of the initial heating of the atmosphere, the energy balance.
So of the potential to increase warming of the atmosphere,
only half of that is actually factuated by the reflection of solar radiation at particles,
these particles will increase cloudiness in the world, the clouds will also stay around longer and have a cooling effect.
Now, it’s very interesting to compare the 2.7 W/m2 with the heat released to the atmosphere.
We just take the heat supply to the atmosphere by burning, that’s only 0.025 W/m2,
in fact the greenhouse warming is 2.7, it’s 100 times more.
And that is due to the fact that we get our energy from the burning of fossil fuels.
Also compare this 2.7 W/m2 or the 0.025 W/m2 with the original input of solar radiation to the earth system, which is 340 W/m2.
So there’s a lot of energy, which is supplied by the sun to the earth and only a very small fraction of that is used.
Climate models is the only way to get some idea of potential increases of temperatures,
climate warming in the future, they are very complicated.
And especially they are very complicated because we don’t very well understand the hydrological cycle,
the water cycle of the atmosphere, cloud formation, cloud decay,
that’s a major problem causing many uncertainties in prediction of the future.
So I just mentioned that climate has always been very important in the history of mankind,
people have been moving from places because of climate changes.
We are now in a very quiet period, climatologically seen, we had the ice age about 18.000 years before,
and then we have come into the holocene with rather constant temperatures around the globe.
But there were also variations and especially people have been very sensitive to the supply of water.
So it is quite likely that the Inca civilisation broke down
because of a long period of few hundred years of very low water availability.
So what are the current statements?
The very latest report by the Intergovernmental Panel on Climate Change, I haven’t seen yet,
it’s on the review and I will be pleased to read it.
But let’s look at the Intergovernmental Panel on Climate Change, this is an international organisation,
part of the United Nations system, which brings together the best scientists around the world to look at the problem.
And they said in already 1995 that the balance of evidence suggests a discernible human influence on global climate.
And then six years later, the report comes out in this intervals of six years,
they said there’s new and stronger evidence that most of the warming observed over the last 50 years
is attributable to human activities.
And what are the projections for the future, for this century?
An increase in temperatures, on the average of 1.4 to 5.8°C.
Very uncertain, the uncertainty coming from science but also human behaviour.
If we continue business as usual, as we do now, we certainly may approach the upper end of these temperature rises,
so we have to get away from fossil fuel burning as soon as that is economically possible.
That will lead to sea level rise, redistribution of precipitation, the effects will not be uniformly distributed around the globe.
Extreme risk and extreme weather, like we had in 2003,
and to rapid climate change so that the ecosystems cannot keep up with it.
What should we do?
Fossil fuels have to be replaced, we can’t go on with business as usual.
But the task is enormous.
To stabilise the amount of CO2 in the atmosphere, we have to reduce the emissions of carbon dioxide by more than 60%.
And that does not include the justified hunger of developing nations to also eat from the cake of fossil fuel burning.
Methane, there we have a little bit of a success story because methane at the moment is hardly increasing in the atmosphere,
there is an equilibrium at the moment between methane input and output in the atmosphere.
But that doesn’t mean that this will be forever, because if the earth’s surface
and especially the permafrost regions of Siberia and Canada, if they heat up, they may release methane, CO2, in the atmosphere.
Nitrous oxide is a gas which is a by-product of nitrogen fertilisation,
70 to 80% reduction is needed in order to just stabilise the amount in the atmosphere.
And then we had some other success stories, the CFC gases are no longer produced,
so the picture is not totally gloomy but is definitely very serious.
And where is the CO2 put in the atmosphere, by which nations?
Well, North America is leading, Oceania, Europe is also contributing substantially, and then we have basically the countries,
the poor countries in Asia and Africa, who emit much less CO2 in the atmosphere.
We should not believe that nature in some way will help us out,
by if temperatures go up that then the biosphere will react by lowering the temperature.
No, if you look in the geological records, in the ice course,
which traps atmospheric gases in the atmosphere and analyse them, you see any time that temperatures went up,
also the amount of CO2 went up, the amount of methane went up.
Reinforcing the initial drive in temperature change, mostly by the Milankovitch orbital theory,
can be explained by that, but enhancing it.
Where will be the future? How stable is climate?
Well, it can’t be that unstable as indicated in the upper graphs here in caricature,
because we would already have fallen down, the climate had collapsed.
It can’t be as stable as pictured here, because we have had ice ages.
So we are somewhere in between, but we really don’t know very well what the future has in stake for us.
The most sensitive parts of the earth are probably the high latitudes, especially the northern hemisphere.
By doubling of carbon dioxide in the atmosphere, and that can be reached by the end of this century,
if we don’t do anything about it, is leading to temperature increases of the order of 5°C or more,
less in the equatorial region and also we see a maximum warming increase in temperature of the Antarctic region.
But especially the northern latitudes are very sensitive.
So new studies indicate that the Arctic Ocean ice cover is about 40% thinner than 20 to 40 years ago
and that with that we get a positive feedback, because that means that less radiation is reflected into space.
And the earth at high latitudes will warm.
There is dramatic climate change happening in the Arctic, about 2 to 3 times the pace for the whole globe.
Next year will be the polar year, international polar year, where we look in much more detail at this process,
because the earth is most sensitive to human activities in the high latitude regions of the north.
There may be effects on the gulf stream which has been discussed,
that maybe because of changes in the salinity and temperatures of the ocean waters,
the hydrological cycle is slowing down and maybe we get a less warm water going to the north, this was a few years ago,
it was a very strong indication, but in the meanwhile, research has shown that probably this is not going to happen too easily.
We should not believe that only people in the developed world are polluting the atmosphere,
because we have also very primitive activities in the tropics.
Deforestation, which adds to the carbon dioxide amounts in the atmosphere and which also has large regional effects,
we see here a picture taken more than 20 years ago in Brazil, when we did experiments there.
We see here two parts, we see the Himalayas and Mount Everest over here,
we made a tourist flight to have a look at the mountain but very soon we were much more interested as scientists
in what we see here, looking away from the Himalayas, namely air pollution, I hope you can see that very well.
Also you go 1.000 kilometres south and south-west of India and you see an atoll in the Maldives and you see also,
it’s maybe not so well visible, you see here air pollution, we call it Asian brown cloud.
It has a major effect on the radiation balance of the atmosphere in those regions.
And it’s especially important because many components in these particles which catalyse and many components,
chemical components in there, especially important is the loading with black carbon.
Black carbon, as the name says, absorbs lots of energy from the sun, it’s heating the atmosphere.
So what do we see as a result of that?
Basically we look at the Indian subcontinent and south of there,
in the southern hemisphere we see some warming because of the presence of particles in the atmosphere.
But you see especially over the land, and this continues into China,
you see very strong heating effect by the absorption of solar radiation by the black smoke in the atmosphere.
And that gives an additional warming of the order of 30 W/m2.
This should be compared with the greenhouse effect, which gives about 3½ W/m2.
So the atmosphere is warming, the earth surface is cooling,
and that sets up stable meteorological conditions in which maybe, or probably, the precipitation is suppressed.
So there will be less precipitation happening, say in the Asian region but also other regions,
where you saw emissions in the atmosphere are very large.
The earth surface is cooling, and with that also the ocean surface layers.
Why we of course have to look at this, especially of great importance is because Asia is not only increasing in population
but is also ambitious, you see the technological developments
which are very strong in India and China and other countries in that area.
So these effects may enhance in the future.
What should we do?
How should we get out of the mess?
Well, you can sort of caricature, we feel sometimes in the same situation.
So we don’t know what will happen, but coming back to my family,
I’m here and here is my grandson and he will know what has happened, but we are responsible for what is happening to him,
because the worst effects of climate change we haven’t seen yet.
That’s something in the next 50 years, that’s really bottleneck for climate improvement.
If we don’t do more strongly efforts against this development, independence from fossil fuels, we are in for a bad future.
And here I would like to stop, thank you very much.
(Applause).