i'm going to give you a an overview of
what it is that that we do as a as a
group and what we do collectively as
scientists to try and understand what
we're dealing with with with climate and
the climate system and climate change
the world is extremely complex and
dynamic the patterns that you can see
here in these clouds which is not real
where this is a computer simulations is
not this is this isn't a this is in a on
a laptop not on a non a satellite but
the patterns that you can see a very
similar to the ones that you see in the
satellite you can see storms you can see
convection you can see waves going
through you can see things repeating but
not quite right
that's the essence of the system that
were talking about it's a it's a
complicated chaotic dynamic system it
never quite repeats and yet all of the
processes that are going on the
underlying all of the things that are
going on with these clouds there
understandable there are computable we
can go and measure all of those
different individual things how do we
deal with that the challenge is is one
of scale the scales of the climate
system range from micrometers for small
aerosol particles that are from the
nuclei of clouds in the atmosphere all
the way out to the size of the planet
itself which is about 10 to the 8th
meters that's about 14 orders of
magnitude that's an enormous scale range
in which to encapsulate all the things
that are going on and even in time you
know you're going from things that are
happening on micro second scales to
things that are happening over millennia
again 14 orders of magnitude an enormous
range of scales to comprehend them play
everything together that's enormous
challenge what you have when you build a
model then is-is-is you have some
fundamental concerns we don't have
infinite computer power right so how
does that work well with weather models
right the ones that produce the forecast
that you see every day
the kind that the kind of result physics
the things that we can expressly
included in these models go from the
global scale down to about the
50-kilometer scale right that's only a
very small part of that huge range of
scales that that actually impact of
climate and the weather right the stuff
that we can resolve the stuff that we
can say okay we totally understand that
we can put in the exact equations is
just that small part all the rest of it
is what we call these subscale processes
now that stuff is is how a cloud
actually forms how rainfall actually
comes from a cloud system how
evaporation works at other very very
small scale and all of those things need
to be approximated in some way we need
to have some empirical phenomenological
approximation to that physics to allow
the rest of it to work and that's a real
challenge right there's this is this is
turbulence this is a small-scale
heterogeneity this is small mountains
and small hills and small lakes all of
those things have to be squeezed into
our approximation of those subscale
processes so there's no guarantee that
this works right there's no guarantee
that this is even a program that will
lead to successful predictions and so
the test all of this program is whether
it does actually produce successful
predictions
now you might not like the weather
forecast that you get you might think
that they're terrible but actually
they're much much better than they used
to be where the models are skillful of
producing forecasts three four five six
days almost 10 days out in ways that
were unforeseen able even 20 years ago
now climate models are slightly
different beast climate models have to
use longer timescales because time is a
longer time scale and so that compromise
they make is they don't go to quite such
fine detail
and so back in the nineteen nineties
climate models really only occupied that
very small part of that of that space
now we can go a little bit further so in
the 20,000 tens that so the models that
were working with now you know we're
coming out about the same spatial
resolution as the weather models and
we're taking up more times you know
we're going out for a thousand years and
working on the physics at the same
potential and yet we still have this
large large range of subjects scale
processes that we still have to include
this is a climate model I this is an old
tram or you'll be pleased to know we
don't use punch cards anymore it's a
single line of Fortran we still do you
use for transfer any of the old-timers
here who think that that their skills
are no longer valid
they asked a valid yes you can have a
job with each of these colored bands
with a single subroutine a single
calculation of some physical aspect of
the code arm and you would put them into
a machine one at a time and if you got
them in the wrong order you have to
start over again it would take months to
produce any output arm and it was a very
very clunky thing and so obviously if
you have to write out every line using
punch cards you don't include or of
comments so you know we inherited this
code and we're going
what does this go do we have no idea
anyway so it doesn't quite look like
that anymore but the the essence the the
idea of what we're doing is directly
related to what we did back in the
nineteen eighties and in the missus
before that 1970 ok so how do we
actually go around building a model we
do it one piece of the time and i use
the a jigsaw analogy by the beginning
and I'll kind of work with that a little
bit now it's very much like putting
together pieces of a jigsaw so this is a
piece of the jigsaw it's a picture of
arctic sea ice taken from a flight going
across the North Pole each of those ice
floes that you can barely see there are
a few tens of kilometers across and you
can see leads
the middle i was the summertime so the
ice is breaking up
and so there's a lot of physics is going
on there right there is the physics of
the Sun coming in reflecting off the ice
because it's white
there's the physics of the of the the
heat being absorbed in the ice melting
it from the top and is melting from the
bottom going on at the same time there's
dynamics how each of the ice floes
interacts with each other all of those
things can be encapsulated measured and
put into some kind of formula so here
are some of the formulas
yeah so physics you know I don't expect
you two to look at these your critique
these are but this is basically what we
do we write down what the boundary
conditions are we use calculus we use
basic conservation of energy that's
that's a big deal and for each of those
different things we then take some code
and you get lots and lots of lines of
code there are some comments now that
that's pleasing arm mr. the last bit
that there's some melting and we make
that one piece into like a component and
so okay well when we do see ice that's
the piece of code that we're going to
use and we can add in lots of different
processes so that was the sea-ice
process now there's one other processes
associated with clouds there's a process
associated with radiation and the solar
radiation coming through the atmosphere
and being absorbed at the different
layers of the atmosphere that's one more
piece there are other pieces the winds
and the way use and other pieces the
flow of water through plants the flow of
water and rivers back down to the ocean
so the point is that each of those bits
makes up part of the picture of the
climate system now I've left and pieces
out because our picture of the timing
system is not complete right we don't
know everything about the system and yet
when we put it all together we end up
with a simulation
that has all of the emergent properties
that we can see in the real world right
so these storm systems in the Southern
Ocean you can anybody has been to the
Southern Ocean knows exactly what they
look like or storms in the North
Atlantic Kevin can tell you about those
tropical cyclones in in the Pacific the
convective bands in in the was a couple
of tropical cyclones are going to cycle
around each other kind of meat
yeah now within the code there was no
code that says hey do an atmospheric
River that hits Oregon there's no code
that says do tropical cyclones and make
them dance around each other right
all of these things are emergent
properties that just arise from the fact
that the system that you're modeling is
chaotic is dynamic and all of the
different processes that we put together
intersect and interact in ways that you
can't predict a priori now just having
done that i think is a intellectual
endeavor worthy of of of Cato
and-and-and Chomsky right trying to
understand exactly what's going on in
such a complex system and being
successful at doing so is an enormous
challenge and i think one we can rightly
be proud of but we're not just doing it
to understand the system we're doing it
because that system can be kicked in
many many different ways and right now
humans are kicking this system in a very
particular way so let's look at some
ways in which the system can be kept
right so there are waffles in the
Earth's orbit these bubbles kind of make
a difference on ten thousand two hundred
thousand year time scales and a big
driver of the of the of the Ice Age
cycle that we've been seeing for the
past 2.5 million years right so Iceland
used to have a lot more ice
it's not quite as I see
as it used to be and and and it will get
messy as well with 10,000 years ago
20,000 years ago
Iceland was almost completely emaciated
right all right yeah and that's due to
these bubbles so that's that's a very
powerful kick to the system right that's
everything changed
you know can we understand that ok there
are changes because of the Sun the Sun
has cycles that has activity and it's
over its lifetime of the lifetime of the
earth has expanded and become more
active by about thirty percent over the
last four billion years that has an
impact on the climate the set the solar
cycles an 11-year cycle have an impact
on the climate we need to understand
those things volcanoes as have also well
aware have an impact on the climate not
just locally but they can have a global
impact on the climate by the injection
of sulfates into the stratosphere
changing the albedo of the palette
changing the amount of energy coming
into the system right so you're getting
the idea there are lots of different
ways in which we can change the climate
right or the system itself can be
changed whether its biomass burning
ozone depletion land-use change
contrails or of course greenhouse gases
all of these change the balances and the
flows of energy in the system and when
you change the balances and flows of
energy in the system you change the
climate so what we need to understand is
whether the simulations that i discussed
before where the weather models are the
climate models whether they have skill I
want to be very clear about this
these models are not complete right
there were holes in the jigsaw there's
whole bunches of things that we have to
and empirically fill-in write the word
that we can't predict from a priori
considerations
so why do we think that these things are
useful
we think that they're useful because
they have
demonstrated skill skill is I model
results skillful if it's better than
what you would have had otherwise
that's not to say it's perfect it's not
to say that there are uncertainties but
it's something that's better than what
you had before with the weather forecast
you could stick your finger in the air
and predict what the weather is going to
be tomorrow based on just persistence of
the weather today that probably doesn't
work very well here but it works quite
well in New York but we can do better
than that with models right weather
models a skillful despite the fact that
there was that whole range of things
that we had to empirically include and
so we need to demonstrate that climate
models are skillful at estimating the
changes to the climate when you kick
that system in all of the different
myriad ways that that system can be
kicked
okay so is that true is there are the
models skillful so well they know
volcanoes are a current topic of
interest in in Iceland I said well
actually not not anymore right we're
done with the volcanoes right so that's
it for the next week right
remember no more volcanoes ok
all models skillful with respect to big
volcanic forces so the large big volcano
that we had that had a global impact was
magnitude but went off in june nineteen
ninety one arm and this is a graph of
how much stuff basically there was in
the stratosphere are from the main
eruption and then it took like three or
four years for all that stuff to kind of
fall out of the atmosphere
ok so this is actually quite a large
amount of stuff right on the amount of
stuff that that is there that's the
technical term stuff and got some people
pay attention okay
the amount of stuff that was there cause
the radiation to be from the Sun to be
significantly less than it was right
because each of those little particles
is white and so when the Sun shines on a
white particle it reflects back to space
and that reduces the total amount of
energy coming in the amount of energy
going out was pretty much the same and
so you have less energy coming into the
system right so basic conservation of
energy suggest that that would lead to a
cooling of the planet but by how much
how much should the planet call with a 3
watt per meter squared energy imbalance
over a few years you have to do the
calculation and the climate models allow
you to do that calculation so what do
they suggest well what they suggested
are the the little thin lines that you
can see there's a bit of noise because
of the different weather and each of
those models and then the red line there
is what actually happened
so the models were able to estimate
quite precisely the rate at which this
the climate called because of this
forcing and we know that is better than
what we could just worked out by doing a
calculation on the back of the envelope
and in fact the first time that we did
that calculation we did it in October
1991 and made this prediction before any
of those changes had actually occurred
the model was skillful and it wasn't
just fearful estimating the global
cooling which you know kind of my energy
balance arguments you might argue was
the easy part but it was also skillful
at predicting that in the wintertime you
got a strange pattern in Europe where
you actually get winter warming after a
big volcano and that turns out to be a
dynamic response changes in the winds
that are affected by the temperature
changes our loft that actually push more
warm water over more warm air over over
Europe during the wintertime and that is
also captured by the model and the
models are skillful even with the
dynamics and the radiation and the
temperature there are lots of other
example
solar cycles you know we can measure and
calculate the change in ozone in the
stratosphere because of this change in
the sun with models are skillful because
of that in overall changes those wobbles
in the Earth's orbit like even 6,000
years ago they were relatively important
and we can look at that difference and
the models are skillful estimating how
the northern hemisphere temperatures got
better because our change because of
that ok
the response to the ice sheets 20,000
years ago the models are successful are
getting that right
the 20th century multi-decade all trends
were successful getting that right
models are skillful even bizarre things
that have happened to the climate about
8,000 years ago there was a huge great
lake that covered most of Manitoba and
Ontario much larger than all of the
great lakes that exists right now and it
was kept in place by the remnant by the
remnant ice sheet that was kind of
standing over hudson bay about 8,000
years ago that I sheet finally broke and
all of that water that was kept in that
Lake rushed into hudson bay and into the
labrador sea and into the North Atlantic
around here and at that same time there
is evidence of a cooling event that
happened in the Greenland ice cause in
Europe and in Newfoundland and all
around here and I'm sure that they would
a nice and have been affected as well
the models are skillful at responding to
that water going in by changing the
circulation in the in the ocean and by
changing the temperatures in the
rainfall patterns associated with that
the models are skillful across a whole
range of different ways that we can kick
that system
ok
and that system is complicated and
global right this is a simulation again
of tiny little atmospheric particles and
all the different kinds of particles
that you can have these orange swirls
are dust coming from the Sahara Desert
and you can see them affecting the
climate and affecting a deposition of
stuff all the way across the Atlantic
the white wispy parts over over Europe
you can see that's atmospheric pollution
sulfates right and you can see that
what's happens in Europe does not stay
in Europe the green and the Reds
indicate where there is our where there
are fires and whether its biomass
burning and where is organic carbon and
black carbon being put into the
atmosphere and again these things don't
just stay where they are stuck there
they started you can see the pollution
over China that again does not just stay
in China the blue dots associated with
the big tropical storms are associated
with sea salt particles so as the winds
whip up the waves small particles of sea
salt which are a key element in the
production of low-level clouds you can
see them again in the in the Southern
Ocean all of these things are connected
and important and we can answer now with
the click with the with the computer
models that we have we can answer
questions that associate that are
associated with all of those things
how does pollution change climate and
air quality all at the same time I love
this but this this animation that they
they did a really nice job here this is
my colleagues at NASA Goddard Space
Flight Center and now there's another
volcano in Madagascar that just went off
and so you can include all thoughts of
things in these models and answer all
sorts of actually quite subtle and
interesting nuance questions
how things work over the 20th century
when we've seen an amount of global
warming right so is this is a model
simulation this is the observations you
can see the patterns of whether you know
they're not correlated the weather isn't
predictable 50 years in advance but the
emerging patterns have changed that you
see towards the end of the 20th century
and that we end up where we are today
those patterns are predictable they are
predicted by the models the models are
skillful at getting these patterns right
this warming in the Arctic compared to
the Antarctic the warming over land
compared to the ocean the warming in the
North versus the woman in the south
these are skillful models but then let's
think about the real reason why we need
models right and then this this comes
from a rebuttal that the two scientists
wrote when somebody you know they talked
about modeling of of future tropical
cyclones and somebody wrote a response
to them they say well why are you
looking observations and they responded
i think quite finally what if we had
observations of the future we obviously
would trust them more than models but
unfortunately observations of the future
and not available at this time and
that's funny but it's actually the real
reason why we build models we want to
have predictive capability of situations
where we don't yet have any observations
so that we can make plans accordingly
whether it's a weather forecast whether
it's a climate forecasts whether it's an
economic projection which we could get
into is as well but Sir what we want our
is an ability to make informed decisions
about the future right so predictable
lity and predicting the future is the
absolute fundamental reason why we're
looking at models right that's what
science is all about making predictions
testing your theories adapting them
making them better making them more
predictive so what does the future hold
what we have
in the future of course our choices and
we don't have to fall down one
particular line the economic an economy
technology how we structure societies
these things are not written in stone
we have choices society has choices you
individuals have choices and these
aren't you know completely accurate
labels we don't know really what will
happen if we just continue as we go
along this is an estimate of that we
have a pretty good idea of what it would
take to bring everything kind of back
down to the level that it was you know
at the beginning of this century this
aggressive mitigation i am kevin will
tell you this is not going to happen
this is the under two-degree world that
people talk about sometimes business as
usual
that's a 56 degree world that's a
totally different planet
remember how different the ice age was
to today
well that is just as different but in
the opposite direction the ice age was a
different planet different organization
of ecosystems where people lived where
things live where things grew the same
will be true for the business-as-usual
planet where were more likely to end up
in my opinion is some effort serious
mitigation not today not tomorrow maybe
in the next 10 years 20 years 30 is
armed and now I'll still be a planet
that has significantly warmer
temperatures particularly on land
particularly in the North particularly
in the Arctic this will be a radically
different planet as well but exactly how
different is still to be determined but
the choices are really ours to make
now I'm a scientist and and I spend my
time working on those small scale
processes and the encapsulation of all
of that physics that you store in those
animations
and these projections these predictions
put us in a very odd position and it was
very clearly encapsulated by showed
Rowland who are was the one of the the
chemists who discovered the reactions
that led to ozone depletion and some of
you here will remember spray cans and
freon and the Montreal Protocol and how
that was negotiated and how that changed
so sure Roland understood quite clearly
the consequences of having made
scientific discoveries that have
real-world implications and he said in
an interview what's the use of having
developed a science well enough to make
predictions if in the end all willing to
do is stand around and wait for them to
come true and that's really the dilemma
that people like me fais do we just
continue to make predictions or do we go
out and tell people about what these
predictions mean do we go and help
people work out what they should do
about the energy system i'm not an
expert in energy systems you know should
we use nuclear power should be used
geothermal power should we do this
should we do that
those are decisions that are not up to
me though I would like to think that the
information that we produce informs the
decisions that you make individually and
that you make as a city or as a country
and as the world and I don't know what
our future will hold arm but i'm i'm
hopeful that whatever future we choose
it's an informed future so thank you
very much