All right, well, thank you very much for this warm welcome here at the
KIT Climate and Environmental Center.
It's a great pleasure to be here.
So I hope in the next 45 to 50 minutes I can share with you a few
thoughts about climate change and something that concerns me
personally as well since a few years.
The question, what happens if Paris fails?
Or perhaps the question before, can Paris fail?
We'll see.
Now, we're all basically in climate change research when it comes to
asking about anthropogenic climate change and its impact on people and
on other systems on this planet, guided by this Article 2 of the
United Nations Framework Convention on Climate Change, which says that
the ultimate objective of this convention is to stabilize greenhouse
gas concentrations in the atmosphere at a level that prevents
dangerous interference with the climate system.
This is really a fundamental article that is in this convention, that
is in force since March 1994.
It's quite a long time ago.
And until December 2015, it wasn't really clear what we regard as
dangerous interference.
And so I'd like to recall this historic moment of 12 December 2015,
when the Paris Agreement finally was concluded in consensus by 195
countries.
That was in 2015.
Two countries were not present at that time.
It was Nicaragua, for reasons not really known, and Syria.
Nicaragua has joined in the meantime, but another larger country has
announced that they will withdraw from the Paris Agreement.
Now in the Paris Agreement, we have three key statements that are the
cornerstones of the Paris Agreement.
The first is that efforts should be made that the temperature increase
relative to pre-industrial stays well below two degrees Celsius.
And note the well below.
That's in this article in there, and it often gets forgotten when we
talk about the two degree target of Paris.
The second one, equally important, and the reason why actually a large
number of countries, in particular in the Pacific region, have joined
in consensus, is this more ambitious target of 1.5 degrees Celsius
above pre-industrial levels.
And finally, a sentence that comes out of decades of research and is
no longer questioned, is this one, to achieve a balance between
anthropogenic emissions by sources and removals by sink of greenhouse
gases in the second half of this century.
Of course, you realize that these are politicians' crafted sentences,
a balance between sources and removals by sinks.
It wasn't possible to say emissions should go to zero, so they wanted
to have the possibility in there that emissions continue, but they are
compensated by sinks.
All right, the scientific basis of this historic achievement of the
Paris Agreement was really laid even before the legendary Earth Summit
in Rio that took place in 1992.
The Intergovernmental Panel on Climate Change was founded in 1988, and
just two years after the first assessment report came out.
And I remember still when I was a postdoc, I was reading in awe this
thick report that combined essentially the world's knowledge,
scientific knowledge, about anthropogenic and climate change in
general.
I was very impressed.
I still remember one of the lead authors came by our institute in
Canada and lamented about the humongous task that was before him to
complete this chapter in time.
So very similar effects happened for every of these five reports.
You see that these reports appear in a frequency of about every five
years.
The last one, 2013, and as you also are aware, the sixth assessment
report is well underway.
On October 8, the first installment of the sixth assessment report in
the form of a special report will be announced to the public.
Just to give you a little impression what that means, I co-chaired, as
was mentioned already, Working Group 1 during seven years together
with my colleague from China.
If you carefully look at this picture, I lost a lot of weight during
this process, in particular in the four days in which we negotiated
the summary for policymakers.
This is a summary of 27 pages.
Every single word, every figure, every detail is basically open to
negotiation, and any country can raise their hands and say, oh, maybe
we're not quite sure whether this is a robust result.
Could you not please reformulate that?
And so you have to negotiate, you have to revise, until consensus is
established.
And to lead this process cost me quite a few kilograms in these four
days and a couple of nights, of course.
But then on September 27, 2013, we had a few really tangible
statements in our summary for policymakers, which, as it is customary
for United Nations documents, were accepted in consensus.
And I show you some of those.
Warming of the climate system is unequivocal.
That may sound trivial to you, but in 2013, we were in a special
circumstance where media and other interested circles made a lot of
noise about the so-called climate pause, the fact that the global mean
temperatures haven't risen as steadily as they did in the last 60
years for the last 13 years.
And that was pounded over and over again, to the extent that at the
press conference I had again to respond to this question, which we did
address indeed in the summary for policymakers.
So it was important to reiterate that statement that was already there
in the 2007 Forest Assessment Report.
Warming of the climate system is unequivocal, a consensus statement
that you find in the summary for policymakers.
This one was seemingly more difficult.
The scientists who drafted the summary for policymakers proposed this
sentence, human influence on the climate system is clear, full stop.
And this sentence was among ourselves, and with the scientists, people
said, well, you will lose the sentence.
Don't even try.
This is too clear, too simple, and too
provocative in a way, in a circle where some of the countries actually
say, well, we're not quite sure whether climate change is actually
caused by human activity.
And so we took a stride and said, okay, we'll propose that sentence to
the policymakers and the delegates.
And in fact, given the evidence that was in the area of detection and
attribution of climate change, a science direction that has started
around 2001 with some key papers and has evolved ever since into a
mature subtopic in climate change science, delivered so many results
that the policymakers and the delegates in fact accepted that sentence
only after 20 seconds of my announcement.
This is the sentence.
Please raise your hands if you would like to comment on that or
propose revisions.
Nobody raised their hands and I could gavel it down.
This one is also an interesting sentence because it speaks directly to
the Paris Agreement that was in the process of being prepared and
developed in 2013, two years ahead of that conference.
Limiting climate change requires substantial and sustained reductions
of greenhouse gas emissions.
Some people accused me of being an activist when we had that sentence
passed and accepted.
Well, they didn't take the English language too seriously.
If you really read it out, limiting climate change is actually
conditional.
If you want to limit climate change, then the following has to happen.
A substantial and sustained reduction of greenhouse gas emissions.
And again, that's a sentence in consensus.
So Australia was in agreement, Saudi Arabia, Venezuela, the United
States of America, all these countries unanimously said yes, that is a
valid statement out of the scientific assessment.
And you can see that with this framework, in fact, the scientific
basis was laid for an informed discussion and negotiation about the
Paris Agreement.
All right, so that's sort of the preface to the things that I would
like to show to you tonight.
This is certainly the most important photograph.
It's almost 50 years old in December 1968, taken by Apollo 8.
For the first time, we see our home from a completely different
perspective.
From a perspective that shows how fragile our planet is, how habitable
it is, and how such in a close-by location, there is actually
inhabitability, as you see with the surface of the moon.
So habitability is something very special.
Of course, you know why that is.
I want to address four points tonight.
Know the present, estimate the future, what do we lose if we fail in
Paris, and the synergy of ambitions.
This is, as you very well know, but I still show it in every lecture
on climate change, the most important factual data that tells us
something is changing and something is changing fast and large.
It is the concentration of the second most important greenhouse gas in
the atmosphere after water vapor, carbon dioxide, that has been
measured since 1958 in very high precision.
And every month you can download the actual, the most up-to-date data
delivered by NOAA.
This delivery and this service has survived to do new presidency of
the United States of America, so regularly every month you still have
these fantastic data.
Of course, you may ask the question, well, has that concentration been
at that high level already before in sort of human history?
And this is a topic that we work on, have been working on for many
decades at the University of Bern in my division.
That is the analysis of polar ice cores.
This is an ice core from Antarctica, from the EPICA project, the
European project of ice coring in Antarctica.
That ice contains air in the form of bubbles.
The air, of course, is composed of the major gases, but also the trace
gases, and in particular the greenhouse gases.
So if we manage to date the bubbles based on the level of depth that
these ice samples are coming from, and if we are able to analyze the
composition of that air, then we're able to respond to that question.
And here is the most up-to-date figure here over the last 800,000
years.
And we can now affirm that, yes indeed, in 2018 we are way off the
concentrations that have been present in the atmosphere over the last
800,000 years.
In fact, 30 percent higher than ever in the last 800,000 years.
You see here the very nice sequence of the ice age cycles.
About eight ice ages have followed one another in the last 800,000
years, with the last glacial maximum where most of Switzerland was
covered by ice about 20,000 years ago, a warm period around 130,000
years ago, and so on.
So the chemical composition of the atmosphere has changed
fundamentally, and the reason is also clear from many studies.
That is also a scientific fact.
This increase of carbon dioxide has been caused by the burning of
fossil fuels, coal, gas, and oil, and deforestation, or more general
land use.
Other things have changed too, of course.
The global mean temperature, or the hemispheric mean temperatures, as
you see them here in this graph, have increased by about one degree
Celsius since the beginning of the 20th century.
The climate pause, I can question you and quiz you, do you see a
climate pause here?
Of course, in 2013, when we had to deliver our assessment, it was kind
of evident, but who has ever followed a course in primary school knows
that in order to make a statement about climate and climate change,
you have to measure at least for 30 years.
That was not the case in that media discussion.
So the climate pause is not visible here.
It was this little episode here, and sure enough, 2014 to 2017, every
year in sequence, has been a record year, with the exception of 2017,
a little bit less, but these are the four warmest years since 1880, on
a worldwide level.
I've here a few slides from my colleague Christoph Scherr from ETH
Zurich, who has written in 2004 a very famous paper on the extreme
summer 2003, and he has kind of followed that line right up to 2018,
which was again a very extreme summer.
As you can see here on this temperature scale for the summers, all
summers that we have available measurements in Switzerland since 1864
get a tick mark here, a bar on this chart, and you see that the
summers since 1991 have been exceptional.
They all lie to the right side of this Gaussian distribution, and in
fact 2003, which was also an extreme summer in parts of Germany, in
particular in France and in Switzerland, stands out really largely on
this scale to the far right.
2015, 18 and 17, again record summers, and just to give you an
impression on the return periods that you would estimate from the
Gaussian distribution, these have been truly exceptional summers on
the order of exceeding a thousand-year return period if you assume,
and this is of course not the correct assumption I should stress, if
you assume a random process.
These times will actually change if you assume an autoregressive
process or if you actually consider the linear or steady increase of
temperatures since the beginning of the 20th century.
In any case, we can extend this consideration to all the seasons, and
this is even more impressive.
You see again in red all those seasons that are following 1991.
Again, for every season, the red bars are to the right of the
distribution, and we can make a few statements about this graph.
Several hot temperature records since 1991, you can read them off in
every season.
So it's not only summer that has become extreme, it's also the three
other seasons.
We have no cold temperature records anymore since 1991.
Not a single red bar here on the left side of the distribution.
There is one tiny one here, but nothing extreme.
And we have extreme hot temperatures exceeding this 1,000 year
threshold in all seasons.
So for example, 2003 we've mentioned already, but in winter 2007 in
Switzerland was really warm.
So this is a telling story about temperature, but also about the
seasonality of the temperatures.
And I think it's these observations that let us convince that really
warming of the climate system is unequivocal.
And if it's warming, then of course other things have to change as
well in a physical system.
For example, sea level has to increase simply by the expansion of the
water that is slowly warmed, but also of course because of the
discharge of fresh water from the glaciers that melt from the ice
sheets of Greenland and Antarctica.
These are the latest measurements taken together since 1993, as you
see here from satellite missions.
And I think something that we did not really put to the front line in
the fifth assessment report in 2013, is the fact that the scientists
are now more and more confident about, and that is the acceleration of
sea level rise.
You see here this acceleration in this most recent study was actually
quantified at definitely positive at 0.08 millimeters per year per
year.
So in fact this curvature of the mean curve here, this regression, is
actually positive.
Something that is of serious concern of course.
One contribution to sea level rise comes from the ice sheets I've
already mentioned from Greenland.
And if you go to Greenland with the satellites above, you can now
measure the movement of the ice on the surface.
An incredible thing if you think about it, that we're able from
satellite missions to quantify how fast the ice actually goes into the
ocean.
There are a few outlet or hotspots in northern Greenland.
Here I've indicated them.
The fastest one is Jakobshavn, Isbry, with 13 kilometers per year of
discharge.
Of course these outlet glaciers have always discharged ice to the
ocean.
But the question is, what is their temporal evolution of that
discharge?
And how does that compare to the overall mass balance?
And the overall mass balance, we know that from GRACE, is actually
negative.
Greenland, as well as Antarctica, are on a serious diet.
They lose mass every year, gain a little bit of mass in winter, but
then they lose even more mass in summer.
And here you see such a picture if you fly along the terminus of
Jakobshavn ice stream.
The terminus is here, so you have a view into the ice sheet at an
increasing slope here.
And just to give you a scale here, this iceberg that has just
discharged from the ice body, that flank here is about 50 meters in
height, which means that the iceberg goes down about 450 meters into
the fjord.
These are massive icebergs that are discharged into the fjord and then
being emanated into Disko Bay and into the ocean.
A number that you may wish to remember, Greenland today is losing
about a cubic kilometer of ice.
About a cubic kilometer of ice every day.
And that cubic kilometer of ice, when it's melting, is contributing,
among the other contributions, to the increase of sea level.
Let's estimate the future.
You're all familiar with this graph.
I don't want to belabor that.
It's the projection of global mean temperature based on two scenarios.
The red one of business as usual and the blue one, the so-called RCP 2
.6 scenario, which is more or less Paris compatible.
So you see here for the 21st century an additional one degree warming.
Add to that the one degree during the 20th century and you are about
at two degrees.
Whereas in business as usual you will have about a warming of five
degrees over pre-industrial.
This, plus many other evidences from the climate model projections,
led us to formulate in the synthesis report of the fifth assessment
report the following affirmation.
Further warming will increase the likelihood of severe pervasive and
irreversible impacts.
It's quite a drastic and dramatic language, but again the language
that is supported by the scientific evidence and accepted by all in
consensus.
Of course nobody lives in global mean temperatures, so you see here
the regional distribution of the temperature.
Again a pattern in fact that we already observed today.
More warming over land because of the reduced heat capacity.
Less warming over the oceans because of the absorption of heat into
the ocean.
And in order to close the budget we are also able now to quantify the
amount of heat that has already penetrated the ocean.
In fact worldwide down to about 700 meters and in the high latitudes
down to about two kilometers.
Here is a more recent result that has now turned the attention to
basically the dominant surface of the planet and that is the ocean.
There have been years of studies about extreme events on land, all
kinds of different types of extreme events, but extreme events in the
has come under the focus only very recently.
Thomas Fröhlicher and Charlotte Laufkutter at our institute, they have
looked at the occurrence of ocean heat waves.
And you see in the past few years there have been a number of such
heat waves already measured at the earth's surface.
But here is a more disturbing message and that is the estimate how
these extreme warm events will actually compare to the extreme warm
events on land.
This is just an analysis of the probability of the occurrence of warm
events in a two degree world.
And you see that of course there will be more heat waves on land.
We can quantify that about a little bit less than doubling of that
occurrence of heat waves on land.
But in the ocean you have a totally different situation.
Since the ocean is a heat reservoir, the variability is actually
subdued.
That is why this distribution is not as wide as over the land.
But any small change, and you see here this delta t is actually quite
smaller than the delta t over land, which is compatible of course with
the previous map.
But even if that delta t at the ocean surface temperature is smaller,
you see that the occurrence of extreme marine heat waves increases by
a factor of over eight.
So we are really looking at extreme or massive changes in the
statistics of extreme events also in the marine area.
And there is still a lot of unknowns with regards to the impacts that
such extreme events may have.
Here is another graph of a recent paper by that colleague.
And the question here is, what if Paris fails?
So we compare here the impact of these marine heat waves in a metric
of cumulative intensity.
That's a metric that is measured in degrees Celsius times days.
So the duration is an issue and the intensity of the heat waves.
And you see here on the horizontal the global warming and on the
vertical this metric.
On this graph different model simulations from CMIP5 for the two
scenarios.
Paris compatible, if I may say, and business as usual, RCP 8.5.
And by 2090, that is by the end of the 21st century, for Paris
compatible, you're here at around 40 in this metric.
Whereas if you go business as usual, you're at around 240.
So in other words, a factor of 6 increase in this impact related
marine heat wave metric.
Something extremely impressive.
And it tells you just by this example how much is at stake if we fail
to keep temperatures increase relative to pre-industrial well below
two degrees Celsius.
This slide should explain to you how urgent this problem is.
How imminent the failure of the two degree target is.
And that is probably the most important progress that we could report
in the fifth assessment report.
And I tell you that concept took us one and a half days to get
accepted.
There were some very fierce nations who opposed the concept of
cumulative carbon and the concept that the sum of all emissions
actually determines the warming in the 21st century.
But in the end, science prevailed and that is now figure 10 of the
summary for policy makers.
It tells you something about the carbon budget for any climate target.
For the two degree target, that budget is plus or minus, with
uncertainty of course, but about 800 billion tons of carbon.
That's the amount that we can emit to the atmosphere so that the
warming stays essentially below two degrees.
Since or up to 2017, we have used 575 billion tons of carbon through
the burning of fossil fuels and land use change.
That leaves us with 215 billion tons.
You need to know how much we emit every year as a global community,
about 10 billion tons of carbon.
It's really simple calculations and we can say under current
emissions, and these emissions are still at that level of about 10
billion tons of carbon, under current emissions the carbon budget will
be consumed before 2040 and in plain language that means we will have
lost the Paris target or Paris will have failed.
This is a dramatic message and I believe, and that's my opinion, that
this message has not yet arrived with the policy makers in its really
basic clarity.
One sort of discusses all kinds of scenarios but the fact that we are
on the brink of losing targets, the first one will be the 1.5 degrees
Celsius target, is something policy makers do not yet talk about.
So what do we lose if Paris fails?
Well, we need to recognize that climate change is a resource problem.
It was mentioned already in the introduction.
I believe personally that this is the most important element of our
public discussion regarding climate change today.
It is not only about degrees Celsius and millimeters per year, the
general public does not really like these physical units and has no
relationship to them, but it's about resources, about the resources
that are available to humans and the natural systems.
And I want to just highlight four resources.
The warming that we experience will affect the resource of health.
We don't talk a lot about the resource of health except when, for
example, in Switzerland every year the premiums for the health
insurance increase steady, almost as steady as the global mean
temperature.
Precipitation will change under global warming and therefore the
resource of water will be affected.
We will see how.
Sea level will increase under global warming and that concerns the
resource of land.
Everybody who has looked at house or land prices know how precious
land is to humans.
And finally, the general climate change impacts, they will affect the
resource of biodiversity.
Something that is covered in a completely different UN convention that
was also designed in 1992 at the Rio Summit and which we only start to
talk about very recently, about these interactions between climate
change and biodiversity.
Resource health, of course, it's evident to you that it's not very
healthy to be close to this bushfire.
These bushfires have increased in frequency and intensity even to the
extent that Sweden this year has experienced their first bushfires or
forest fires.
But what I want to draw your attention to is that there are also
physiological limits of our body to the increase of temperature.
And if it comes together with high levels of humidity, we don't really
like that.
In fact, we have the risk of heat collapses.
And this study here has looked at a quantification of so-called deadly
thresholds.
That means a threshold where you would not survive if you did labor
outside under such climatic conditions.
And based on model simulations, they estimated the number of such
risky days and the geographical extent.
This is sort of the historical extent of these risky days.
You see that India is quite affected by that on the order of perhaps
50 days per year where it's not quite good to be outside and do hard
labor.
Other regions are also colored in yellow.
But if you compare that to the distribution of that quantity in 2090
under a business as usual scenario, you see not only more intensive
colors, i.e.
more such days during a year, but also a much larger geographical
extension, an extension that covers essentially many highly vulnerable
countries.
And you can now start to imagine what the consequence of that is, not
only to the individuals who have to cope with that climatic condition
over the majority of a year.
Red colors mean somewhere between 250 and 300 days by the end of the
21st century of business as usual here.
Let's compare this to the Paris targets.
Two degrees warming, global mean.
This is a substantial benefit if you compare the two.
Substantial benefit.
That's the reason why this two degree target is a sensible and
reasonable target.
It will change, people will have to adapt, but the area and intensity
is much smaller, and the adaptability is really given in such a case,
or we can work towards it.
But in this case, in this case, we are reaching the limits of
adaptability in many countries, and that is a real issue.
Resource water.
This is just an impression.
That was the cover picture of the special report on extreme events in
the last IPCC round.
And of course, the water cycle changes significantly with climate
change.
This is out of the summary for policymakers.
It changes regionally, not all regions are affected by drought.
Some regions are affected by drought, and it's interesting to note
that it's these regions that already now are challenged by the
shortage of water.
They will be challenged even more and pushed more towards the boundary
of their adaptation capacity.
Whereas other locations here in the mid and high latitudes get more
precipitation when we don't really want them.
So we will have to adapt as well, for example, with the sewage systems
and with the electricity system that we all depend on.
So the water cycle here changes dramatically for a business as usual.
Resource land.
I've mentioned the third resource, loss of home and habitat.
That's very clear and undisputable.
If sea level rises, you will lose land, and that land loss can be
quantified.
This was another difficult problem in the last assessment report to
find consensus in the science about the projections of sea level rise.
We did find it.
This is still an open topic, and I'm looking forward to the
projections in the forthcoming assessment report.
But given that, we have adapted to 19 centimeters of sea level rise in
the 20th century, but compare that to a business as usual requirement
of another 70 centimeters.
So there are many areas in the coastal zones where hundreds of
millions of people live where adaptation is required, either
technological adaptation like in the Netherlands or migratory
adaptation such as, for example, in Bangladesh and other low-lying
countries, Pacific Islands, etc.
These are huge tasks that lie in front of us, and if you just look at
the slope of these curves, the task is not over in the 21st century.
It continues well into the 22nd century because these curves will go
higher beyond 2100.
The fourth resource, and I could go on, but what I really find
important is that you make a connection between climate change, which
is something physical, and the question of resources.
The fourth resource is biodiversity and the effect of the compound
climate change impact.
Compound means, for example, temperature and precipitation change, or
temperature, precipitation, and land use change where you have managed
land.
And so I just quote a recent study here that was published in the
Transactions of the Royal Society this year on where are the locations
of biodiversity loss exceeding 10 percent caused by either land use in
blue or climate change in orange or both in black.
And you see here for RCP 2.6, the two-degree warming, yes, many areas
will face a biodiversity loss for various reasons.
You see here a rather colored picture, but compare this to the
business as usual case here with lots of black and now in particular
orange colors that point to the key driver of climate change when it
comes to biodiversity loss.
So I just want to close with the fourth point here to address also the
fact that there are the 17 UN Sustainable Development Goals.
We shouldn't forget them when we talk about climate change.
And one particular sentence in the synthesis report of the fifth
assessment report of IPCC is this one.
Climate change is a threat to sustainable development.
If we are serious about sustainable development, we need to address
and mitigate climate change.
And I just show you here the 17 goals.
They have sub-goals, a total of 169 goals that should be ticked off
and fulfilled by 2030.
That's the agenda 2030.
Of course, these are ambitions, but it's quite interesting to ask the
following question.
If we want to achieve some of these sustainable development goals, we
can do only if climate change is actually addressed and limited.
And here I have just a selection of these few goals that are to be
achieved or cannot be achieved, I should correct myself, cannot be
achieved if climate change is unchecked and is unlimited.
So for example, the problem of hunger or the problem of inequalities
from countries and regions to regions cannot be addressed if we have
ongoing and unlimited climate change.
So the climate change needs to be stabilized at a level, the Paris
target, to actually be able to achieve these goals.
That doesn't mean it's a sufficient condition, but it's a necessary
condition.
You can turn around that sentence and ask which sustainable
development goals need to be achieved to be able to mitigate climate
change.
And there is again here a selection, obviously that's a bit
subjective.
If I asked the audience here to all fill out, we would probably come
to slightly different results.
But it's clear that we need education, for example.
We need also innovation and infrastructure to mitigate climate change.
So you can now compare these two slides with one another and pick out
those that light up in both slides, which are these four.
And these four, I would argue, are those goals where you have to put
your focus on.
For example, obviously climate action, decent work and economic
growth.
Doesn't mean that the growth is measured in GDP, but there must be new
measures of economic growth, in quotes now, responsible consumption
and production, peace and justice and strong institutions.
Without these elements, I'm convinced we will not address climate
change and climate change mitigation.
And vice versa, we will not be able to achieve the sustainable
development goals.
With that, I would like to conclude just as a few take-home messages.
The science is clear.
We know what's happening, who's responsible and what options remain.
They don't remain forever, as I've shown to you.
Some climate targets can be lost.
And the climate targets are now precisely defined.
For many decades of climate research, as climate researchers, we could
not say at what level one should mitigate.
We could not say how much carbon dioxide we can still emit.
Paris has changed that for us.
The policymakers have identified these climate targets and now we can
make quantitative statements about what that means.
It's also clear that CO2 emissions must fall rapidly.
There's no doubt about that.
There are simply no sufficient sinks to compensate the emissions that
we have today.
And the essential resources are in danger.
Health, water, land, biodiversity.
And I strongly believe in the synergy between the UN Sustainable
Development Goals, that ambition and the ambition to mitigate climate
change.
So thank you very much and I look forward to the discussions,
questions and comments you may have.
Thank you very much.