*preroll music*
Herald: It's simple when ice gets above 0°, it melts. But is it really that simple
if we are not talking about a small ice cube, but a big sheet of ice covering an
entire continent? Is that really the only factor? And, am I right with my
assessment? I'm looking forward to be enlightened by Professor Doctor Ricarda
Winkelmann. Ricarda Winkelmann is a professor of climate science at the
University of Potsdam, and she's also a researcher for climate impact. She leads
the Ice Dynamics Working Group and Co- leads PIK Future Lab on Earth Resilience
in the Anthropocene. Her research focuses on tipping elements from the Earth system.
And today she'll be talking about the Greenland and Antarctic ice dynamics and
the future sea level rise that are impacted by them. It appears like she's
surely an expert on all things related to ice. So please give a warm hand of
applause for Professor Doctor Ricarda Winkelman with her talk: "The Big Melt:
Tipping Points in Greenland and Antarctica" Have fun!
[no audio] *in between music*
Ricarda Winkelmann: *audio not working* Thanks and welcome. Today, we're going to
take a little excursion to the far north and the far south, to our polar ice sheets
on Greenland and Antarctica. As this year is coming to a close, I thought we'd take
a brief moment to reflect back. 2020 has certainly been an exceptional year for all
of us. It was supposed to be a super year for nature and the environment, as world
leaders put it at the beginning of the year. It's five years after the Paris
climate accord. It's five years after the Sustainable Development Goals have been
announced. However, 2020 turned out to be the year when we've had to face several
global crises, including the ongoing covid-19 pandemic and also the ongoing
climate crisis. What almost got lost in the turmoil is that this year also saw
several weather and climate extremes, which spaned the globe from pole to pole,
with temperatures reaching record highs in the Arctic and Antarctica with +38°C in
the Arctic and in Siberia. That's the highest temperature that was ever recorded
north of the Arctic Circle and it's roughly 18° warmer than the average
maximum daily temperature in June, when this was recorded. And we also saw +18° at
the Antarctic Peninsula, which is, again, the highest temperature ever recorded in
Antarctica. And this was followed by widespread melting on nearby glaciers.
Now, if we're kind of zooming out and taking a look at the bigger picture, we're
also at a very significant point in Earth's history. Here you see the global
mean temperature evolution since the last glacial maximum. So the last ice age until today.
And whenever I look at this graph, I see two things that still strike me to this
day. One is that the Holocene, the interglacial or the warm age, in which
human civilizations have developed and thrived, has been characterized by very
stable climate conditions, by a very stable global mean temperature. And the
other thing is that the difference between an ice age, here, 20 000 years ago
roughly, and a warm age, that's roughly three to four degrees of global average
temperature change. And right now we're on the verge of achieving the same
temperature difference, but at much, much faster rates. So here you see several
future temperature projections from the IPCC. And what you can see is, that in all
of them, the temperature increase, even the lowest one, the temperature increase
is much faster than it was ever recorded before. So I think it's safe to say that
we have truly entered the Anthropocene and that humans have become a geological
force. So in the Anthropocene, humans have become the single most important driver of
global change affecting the entire Earth system, including our ice sheets. But it
was kind of the opposite in the past. Like no other forces on the planet, ice ages
have actually shaped our surroundings and thereby determined our development as
human civilizations. For instance, we owe our fertile soils, to the last ice age,
that also carved our current landscapes that we see all around us, leaving
glaciers behind, rivers and lakes. So even though the ice sheets on Greenland and
Antarctica might seem far away sometimes, they're actually crucial also for us here
today. And today, I want to leave you with an impression why they are so important.
And one reason why they are so important is because they're an amazing climate
archive. Here you see an ice core taken from one of the deepest parts of an ice
sheet. And this is basically like counting tree rings. You can go back to the past
and you can see what the climate was like in the deep past, ranging several hundreds
of thousands of years back. And you can see the conditions, for instance, in the
CO2 change, the temperature change over this really long timescales. So that's one
of the reasons why the ice sheets are so important. Another one is their so-called
sea level potential. Greenland and Antarctica are truly sleeping giants. And
to give you an idea of the sheer size of these two ice sheets, one way of doing
that is to compute their ice volume in the so-called sea level equivalent. What this
means is, if we were to melt down the Greenland ice sheet and distribute that
meltwater around the entire globe, then this would lead to a global sea level rise
of roughly seven meters. For the West Antarctic ice sheet, it's about five
meters, and for East Antarctica, the tenfold. So more than sixty five meters in
total of sea level potential that are stored in these two ice sheets. Now, over
the past decades, the ice sheets have both been losing mass and they've been losing
mass at an accelerating pace. In fact, we're currently on track with the worst
case climate change scenario. Here you see the observations in gray and you also see
several of the projections from the past for the ice sheets. And as you can see,
we're tracking this upper branch here. So we're really on track with the worst case
climate change scenario for the ice sheets. And what this means is even if we
were to stop global warming today, the ice sheets would still keep losing mass
because of the inertia in the system. So sea levels would keep rising for decades
or even centuries to come. Why is that? Well, there are several processes that we
need to understand in order to keep track of sea level change and also to understand
the ice sheet's evolution in the past and in the future. Here, you see sort of an
exemplary cut through an ice shelf system, where the ice sheet is in contact with the
atmosphere. You have a grounded part and then in many places, you also have these
extensions, these floating extensions, the so-called ice shelves that surround
particularly Antarctica. The separation between the two is the so-called grounding
line. Now, generally ice sheets gain mass through snowfall just on top of the ice
sheet, which then is compressed into ice and over time, due to the sheer gravity
and the sheer size of the ice sheets, it's basically pushing its own mass towards the
ocean. And that's one of the reasons why there's a constant flow of ice. So ice is
really not only a solid, it's also a fluid. The ice sheets can also lose mass
through surface melting, but also through melting at the underside of the floating
ice shelves, where they're in contact with warmer ocean waters. And then there can,
of course, also be ice shelf calving, so icebergs that break off at the margins of
the ice sheet. Now, what we see here, this left hand side, that's a typical situation
for the Greenland ice sheet. The Greenland ice sheet is generally grounded above sea
level in most parts and it's not only much smaller than Antarctica, but it's also
located further south, so further away from the pole. And that means it's
generally warmer in Greenland, leading to more surface melt for the Greenland ice
sheet. Whereas in Antarctica, it's not only much colder there, but also the ice
sheet is covered and surrounded by floating ice shelves almost all around the
coastline. And that means that one of the most important driving processes for mass
loss in Antarctica is this melting underneath the ice shelves, so the
subshelf melting in contact with the warmer ocean waters. Just to give you an
impression of the sheer ice thickness, I brought this picture here. This is my very
first impression of the Antarctic coastline, the ice shelf margin. This is
close to the German research station Neumayer III. And I will never forget the
moment that I first saw the ice shelf edge. It was in the middle of the night,
but we were there in summer, so we had twenty four hours of daylight. And I woke
up because it suddenly got dark in our cabin. So I went up to the bridge to see
what was going on and I saw myself in front of a wall, like really a cliff of
ice. And knowing that these ice shelves behave like the ice cubes in the water
glass, so only roughly 10 percent are visible above the sea level, this means
that in this case, we had an ice shelf edge that was more than 100 meters thick.
And that really impressed me. I immediately had to think of this German
expression, "das ewige Eis", the eternal ice. And I really wondered if this is
maybe the right expression because it seemed like it was so static and nothing
was moving. However, that's not true because even in equilibrium, the ice is
constantly moving. It's here just visualized by these little snowflakes and
you can see how the ice is moving from the interior towards the coastlines. And we
have a wide range of velocities at the surface, ranging from almost zero in the
interior of the ice sheet to several kilometers per year in the larger ice
shelves and also the so-called ice streams, the faster flowing ice. If I were
able to take a dive underneath the ice shelves and I could actually take a look
at the grounding line, this would probably be what what I could see. This is the
triple point basically where solid earth, the ice and water all come together. And
this grounding line is a very important role for Antarctic ice dynamics and also
for the future fate of Antarctica. So what makes the dynamics of the ice sheets and
shelves so particularly difficult to understand and also to project the future
evolution is that both ice sheets are subject to several so-called positive, so
self-reinforcing feedback mechanisms. Here are just some examples with some of the
major ones we know very well. One is the ice-albedo-feedback and another one is the
so-called melt-elevation-feedback. As I said, in Greenland we observe a lot of
surface melting. If you've ever flown across the Greenland ice sheet in summer,
you can really see these rivers forming and then even lakes forming at the ice
sheet surface. And over the recent decade, Greenland has been subject to several
extreme melt events, including particularly the year 2010, 2012 and also
last year. And the reason there's this extreme melting at the surface is due to a
combination of factors, it has to do with the duration of the summer, but also even
here in Europe, we observed very warm and dry summers. And that's also something
that was observed for Greenland. So that, for instance, in the year 2019 in August,
almost the entire ice sheet surface was covered with meltwater. Now, why is this
surface melting so important? The reason is that there is also a self-reinforcing
feedback that could be driven by surface melting. And we all know this mechanism
from mountain climbing. If you climb down from the peak of a mountain towards the
valley, it gets warmer around you. And the same is true also for the ice sheets. So
if there's enough melting, it could actually lower the surface to a region
where the temperatures are higher, the surface temperatures are higher, leading
to more melting, which again lowers the surface elevation, leading to higher
temperatures, leading to more melting and so on and so on, so that this can trigger
these self-reinforcing dynamics. And whenever we have such a positive or self-
reinforcing feedback mechanism, we can also have a tipping point. And here is the
depiction of a very simple way of computing, where this tipping point might
be for the Greenland ice sheet, where we've really done this with just
analytical work. So pen and paper, trying to understand where we go from a stable
Greenland ice sheet into unstable regime, which would then lead to a meltdown of the
entire ice sheet until basically no ice is left at the surface. So this is something
that we can understand in theory, but also something that we find in more complex
numerical ice sheet models. And they find that this warming threshold that leads to
basically a decay of the entire ice sheet lies somewhere between 0.8°C and 3.2°C of
warming above pre-industrial levels. And you can see that between these
temperatures, somewhere there's almost a step change. This is now the computed sea
level rise. So up here, this means that Greenland is ice free. So we're going from
an intact Greenland ice sheet to an ice free Greenland somewhere between these
temperatures. What this looks like can be visualized with numerical ice sheet
models. And here you see that once this threshold is exceeded, basically the
eigendynamics lead to a complete meltdown off the ice sheet, until there's almost no
ice left except for in the highest regions here in the east where there are some
small ice caps remaining. Now, something similar, but also different is going on in
Antarctica because, as I said earlier, in Antarctica it's much colder. So we have
very little surface melt at the moment. But at the same time, it's surrounded by
the floating ice shelves and they play the major role in driving sea changes in
Antarctica. Antarctic mass loss has tripled over the recent years, especially
in the so-called Amundson and Bellingshausen Sea regions. So these are
these regions here where you see all these red parts. So this is all ice loss that's
been detected here. And the reason for this is due to the ice shelf ocean
interactions. So here you now see the ocean temperatures surrounding Antarctic
ice shelves. And you can see a stark difference between the temperatures here
around the Amundson and Bellingshausen regions and the temperatures, for
instance, here in the Weddell Sea or in the Ross Sea, the temperature difference
being roughly two degrees. So there's really been a switch from a colder to a
warmer cavity, for instance, here in the Amundson Sea region. And that drives more
sub shelf melting, which in turn leads to a decrease of the so-called buttressing
effect. What this means is, well, first of all, the ice shelves do not contribute to
sea level rise directly, at least not significantly. The reason being that they
are like ice cubes in a water glass. And if that melts down, it also doesn't raise
the water level in the glass. So it's similar with the ice shelves, but at the
same time they are still attached to the grounded part of the sheet. So if the ice
shelves melt or there are larger calving events in the ice shelves, that means that
the flow behind them from the interior of the ice sheet into the ocean accelerates.
It's almost like pulling a plug. And this is what is the so-called buttressing
effects, so the backstress at the grounding line. So if we have enhanced ice
shelf melting, that means that this buttressing effect, this buffering effect
is reduced and therefore we have accelerated outflow into the ocean. Now,
the question is, how does this impact the ice sheet dynamics overall, in particular,
the stability of the West and East Antarctic ice sheets. You may have come
across some of these headlines in recent years. My favorite one is still this one
up here from 2014 where the "Holy Shit Moment of Global Warming" was declared.
And the reason for this were these observations from the Amundson region in
West Antarctica. So we're now taking sort of a flight into the Amundson Sea region.
And what was observed over the recent decades is not only that the glaciers here
have accelerated, so everything that's shown in red is accelerated ice flow, but
at the same time, the glaciers have also retreated into the deeper valleys behind.
So you see this browning at the surface now. So all of these changes where the
glaciers have basically retreated and with this comes another self reinforcing
feedback, the so-called marine ice-sheet instability. For the marine ice sheet
instability to occur, we need two conditions to hold. One, as depicted here,
is that the ice sheet is grounded below sea level, which is true for many parts of
West Antarctica, but also some parts of East Antarctica. And also we need to
generally have a retrograde sloping bed. So that means that the bedrock elevation
decreases towards the interior of the ice sheet. And when these two conditions hold,
then we can show in two dimensions, mathematically, we can prove
mathematically that an instability occurs in this case. The reason is that we have
an feedback between the grounding line retreat and the ice locks across the
grounding line. If the grounding line retreats in a case where we have a
retrograde sloping bed and the ice is ground below sea level, that means that
the ice thickness towards the interior is larger. And this generally also means that
the ice flux across the grounding line is larger, leading to further retreat off the
grounding line and so on and so on. So again, we have a positive feedback
mechanism that could drive self-sustained ice loss from parts of the West and East
Antarctic ice sheet. And the concern is now that this marine ice sheet instability
is potentially underway in the Amundson basin here in West Antarctica. Now, what's
unclear is, how fast this change would actually occur. So if we have actually
triggered the marine ice sheet instability in this region, and that means we have a
committed ice loss of roughly one meter sea level equivalent, then the question is
still, how fast does this occur? And for this, it really matters how much further
global warming continues. So and at which rate the temperature will change in the
future. So this is what's happening in part of the West Antarctic ice sheet. We
were also asking ourselves, weather could something like this also happen for East
Antarctica and how stable are each of the different ice basins in Antarctica? So we
did something of a stability check on the Antarctic ice sheet to assess the risk of
long term sea level rise from these different regions. What you will see next
is an animation where we're increasing the global mean temperature, but we're
increasing it very, very slowly, at a much slower rate than the typical rate of
change in the ice sheet to test for the stability of these different parts. And
what we see is that at roughly 2°C, we are losing a large part of the West Antarctic
ice sheet. So there's a first tipping point around 2°C. And then as the
temperature increases, also the surface elevation is lowered. And that leads to,
potentially then also triggering these surface elevation and melt elevation
feedbacks in East Antarctica. So around 6°C to 9°C, there's another major
threshold. And after this, large parts of the East Antarctic ice sheet could also be
committed to long term sea level rise. At about 10°C, the Antarctic ice sheet could
potentially become ice free on the long term. And, this is really important. What
we're seeing here are not projections, but what we're seeing here is a stability
check. So we're not looking at something that's happening within the next century
or so, but rather we're interested in understanding, at which temperatures the
Antarctic ice sheet could still survive on the long term. We also wanted to see if
some of these changes are reversible. And what we find is a so-called hysteresis
behavior of the Antarctic ice sheet. That means, as we're losing the ice and we'll
then cool the temperatures back down, the ice sheet does not regrow back to its
initial state, but it takes much, much colder temperatures to regrow the same ice
sheet volume that we are currently having at present day temperature levels. So
there's a significant difference between this retreat and the regrowth path. And
this can be up to 20 meters of sea level equivalent in the difference between these
two paths. What this looks like regionally, you can see here. So again, we
have the retreat and the regrowth path at 2°C of global warming, and 4°C of global
warming. So these are the long term effects at these temperature levels. And
you can see that, for instance, for 4°C large parts of East Antarctic and also of
the West Antarctic ice sheet do not regrow at the same temperature level. So we
clearly observe this hysteresis behavior. That's another sign that the Antarctic ice
sheet is the tipping element in the climate system. So both Greenland and
Antarctica are tipping elements in the climate system. There are a number more
candidates for tipping elements, including some of the larger biosphere components,
for instance, the Amazon rainforest, the tropical coral reefs, and also the boreal
forests, as well as some of the large scale circulations. So, for instance, the
Atlantic thermohaline circulation, what we often term the Gulf Stream, and the Indian
summer monsoon are tipping candidates in the climate system. Now, if we go back to
our temperature evolution since last glacial maximum, and we now insert what we
know about the tipping thresholds of these different components in the Earth system,
then this is what we get. And we see, that there are basically three clusters of
tipping elements in comparison to the global mean temperature here. And you see
in these burning ember diagrams that some of these tipping elements are at risk of
switching into a different state, even within the Paris range of 1.5 - 2°C of
warming. And among these most vulnerable tipping elements are the West Antarctic
ice sheet and the Greenland ice sheet and in general, the cryosphere elements which
seem to react to global warming and climate change much faster and therefore
belong to the most vulnerable parts of the Earth system. So, if there's one thing
that I would like you to take away from this talk, it is that ice matters. I've
presented you with three reasons why. First of all, polar ice acts as a climate
archive. It also acts as an early warning system. Secondly, glaciers and ice sheets
are important contributors already to current sea level rise, but they will
become even more important in the future as the global mean temperature keeps
rising. And thirdly, both Greenland and Antarctica are tipping elements in the
Earth system. And one of the next things we need to understand is how these tipping
elements interact with one another. Because we have a very good understanding
by now of the different mechanisms behind these tipping elements and of the
individual temperature thresholds. But one of the, I think, most important questions
we need to ask ourselves, is how the interaction of the tipping elements
changes the stability of the Earth system as a whole and if there could be something
like domino effects in the Earth system. And with this, thank you so much for your
attention. And I'm very much looking forward to questions.
Herald: Yeah, OK, fine, good, läuft, könnt ihr mich also hör'n, und ihr müsst mir
also sagen, wann ich wieder drauf bin. Off: Du bist live.
H: Hallo, wilkommen zurück! Thanks for this awesome talk, Ricarda, and we are now
going to have a Q&A. And if you have any questions regarding this awesome talk,
then please post them to the signal angels. They are following on Twitter and
the Fediverse here, using the hashtag #rc3one, because this is rc1. And you can
also post your questions to the IRC. You know, I already have a first question. I
don't know, Ricarda, if you can hear me, but is there anything that this specific the CCC
community of nerds and hackers can do more than anyone else to help with this issue?
What do you think that we can do to help this?
R: Yeah, thank you so much. Great question. Let me start by saying I'm a
nerd and hacker myself. I'm a developer, or code developer, of the parallel ice
sheet model. That's one of the ice sheet models for Greenland and Antarctica that's
being used around the globe with many different applications. So, yeah, as a
fellow nerd and hacker, I can say there's lots we can do, in particular towards
understanding even better the different dynamics of the Greenland and the
Antarctic ice sheet, but also beyond that, for the Earth system as a whole. I think
we're now at a point where we understand the individual components of the Earth
system better and better. We also have better and better observations, satellite
observations, but also observations at the ground to further understand the different
processes. But what we need now is to combine this with our knowledge in the
modeling community and also with some of the approaches from big data, machine
learning and so on, to really put this together, all the different puzzle pieces
to understand what this means for the Earth system as a whole. And what I mean
by that is, we now understand that there are several individual tipping points in
the Earth system. And we also know that as global warming continues, we're at higher
risks of transgressing individual tipping points. But what we still need to
understand is what does this mean for the overall stability of our planet Earth?
H: Thank you for this extended answer to this question. I have another one. I would
like to know, I mean, you showed a slide where you showed the browning of the ice
surface and then explained that this speeds up the process of melting as well.
But, can we just paint it white or with a reflective paint on it? Has this been
simulated? Is this of interest to you scientists?
R: Yeah, very good question. So basically what you're addressing here is the
question of the so-called ice albedo feedback. We all know this. As we're
wearing black clothes in summer, it's warmer than when we're wearing white
clothes. And the same is basically true for our planet as well. So the ice sheets
and also the sea ice in the Arctic and Antarctica, they contribute considerably
to a net cooling still of the planet. So if we didn't have these ice landscapes,
that would mean that the planet would warm even faster and even further than it
already is today. So currently, the ice albedo feedback is still helping us with
keeping the temperatures at lower levels than they would be without the ice
landscapes. And, yeah, therefore, it is definitely of interest to further
understand what would this mean for, for instance, the global mean temperature, but
also regional changes, if we were to lose our ice cover completely? And also the
reverse question, of course, if we were to whiten parts of the planet, then how would
this affect temperature? One thing that we found out is that if we were to lose the
ice sheets and the sea ice in terms of the ice albedo feedback alone entirely, then
this could already lead to an additional global warming of roughly 0.2°C. Now, that
may not seem very much, but it certainly is important in the grand scheme of
things. As we're thinking of, for instance, the Paris range of 1.5°C to 2°C
of warming, every tenth of a degree matters. So, yeah, very interesting
question. And this is something that has been done with numerical models, just to
understand what kind of an effect these kind of what-if-scenarios would have also
in terms of the albedo. H: Very interesting. So should we now
start to develop drones who can spray paint?
R: *laughs* That's a good question. I don't think that's the solution. I think
we have a much better solution. And that is we know that we need to to mitigate
climate change and reduce greenhouse gas emissions. And that is one that would work
for sure. Whereas these questions of, well, should we spray paint all of our
buildings at the at the top white? That is something that cannot be done at such a
large scale as we would need it in order to reverse global warming. And another
thing to keep in mind is that even if we were able to reduce the global signal,
this still doesn't mean that we could also reverse the regional scale changes. We're
already experiencing a large increase in extreme weather and climate events. And
that is certainly something that I haven't seen so far, that this could also be
reversed just by reversing the global mean temperature change as a whole.
H: I have another question. I think that's quite interesting. How old is the oldest
ice in Antarctica? Are you aware of that? And how long would it take a minimum to
lose that entirely? R: Yeah, very good question. So the oldest
ice, there's actually an ongoing search for the oldest ice in Antarctica. So to
say, we know that Antarctica was ice free for the last time, roughly 34 million
years ago. So when we're talking about these scenarios that eventually Antarctica
could become ice free with, of course, very strong global warming scenarios of
about 10°C of global warming, then we need to keep in mind that this was the case for
the last time, about 34 million years ago. Now, as we're speaking, there
is an ongoing project, an international collaboration to find and and also drill
for the oldest ice so that we can really understand our Earth's history better and
better. And so this is a very exciting project because, as I said, the ice cores
are kind of like tree rings and we can count back in time and really understand
what our global climate was like several, hundreds of thousands of years ago. So,
yeah, with that being said, I think it's important to keep in mind that this is
something that humans certainly have never experienced and that's therefore
unprecedented in our world. H: ...for this very elaborate answer to
this question, I know it is not the core of your research, but someone from the
internet asked, if it's possible for old viruses and all the bacteria from back
when Antarctica was like beginning to freeze over or from like
millions of years ago, is it possible for them to thaw out again? Is that a danger
for us? R: Oh, that's also a very interesting
question. So I'm no expert on this, but I could imagine that at the temperatures
that we have, Antarctica, especially the core ice body, there we have temperatures
that go down to, well, I think the coldest temperature was something like -90°C that
was recorded there. But in any case, it's very cold there. So there might be some
bacteria that can survive these conditions. And I've read about bacteria
like that, but I wouldn't know that there are many bacterial species or specimen
that could survive these kinds of conditions. So to be honest, I would have
to read up on that. That's a very interesting question.
H: Yeah. Thank you for this answer. I remember that you watched, that you showed
an animation and a graph for a simulated ice decline to find the tipping points in
Antarctica. And on the x axis of that, I couldn't see a time scale. And now someone
asked on the internet, what are the timescales between reaching a tipping
point? And most of the ice being melted? Is that years, decades, centuries,
millennia? What's kind of the scale there? R: Yes, very important point. So it's
important to note that we're here showing this over the global mean temperature
change. And the reason for this is that the way these kind of hysteresis
experiments are run is that you have a very slow temperature increase. So slow,
in fact, that it's much slower than the sort of internal time scales of the ice
itself. And in this case, for instance, we had a temperature increase of
10^-4°C/year. And the reason for this is because this is the way you're approaching
the actual hysteresis curve that we were interested in. So this should not be
mistaken for sea level projections of any sort. So what we find here are the actual,
so to say, tipping points, the actual critical thresholds, that parts of the
Antarctic ice sheet cannot survive. Nonetheless, of course, we're also working
towards sea level projections and trying to understand what kind of sea level
change we can expect from the ice sheets over the next decades to centuries to
millennia. And one important thing there is that most of the ice loss that could be
triggered now, would actually happen after the end of this century. So very often,
when we see these sea level curves, we're looking until the year 2100. So for the
next decades, how does the sea level respond to changes in temperature? But
because we have so much inertia in the system, that means that even if the global
warming signal was stopped right now, we would still see continued sea level rise
for several decades to centuries. And that is something important to keep in mind. So
I think we really need to start thinking of sea level rise in terms of commitment
rather than these short term predictions. That being said, another important
question and factor is the rate of sea level change, because this is actually
what we need to adapt to as civilizations. When we think of building dams, there are
two questions we need to answer. One is the magnitude of sea level rise and and
also in its upper scale and upper limit to that. And the other question is the rate
at which this changes. And what we find is that on the long term, there is something
like 2.3m/°C of sea level change. So this is sort of a number to keep in mind when
we think of sea level projections. And yeah, I think it's really important to
consider longer timescales than the one to the year 2100 when we talk about sea level
rise. H: Thank you for this answer, very
interesting and we are out of time now, so thanks for all the questions and thank
you, Ricarda, for this amazing talk. The next talk on this stage will be about a
related topic, measuring CO2 indoors, but also in the atmosphere in general. But
before that, we have a Herald News Show for your prepared. So enjoy!
*Outro music*
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