Stocks and Flows [The Climate Leader]
Summary
TLDRThe video script introduces the concept of 'stocks and flows' as a critical tool for climate leaders. Stocks represent accumulations, while flows depict changes over time. Using the analogy of a bathtub, the script explains how inflows and outflows affect stock levels. Examples include people engaged in climate action, financial balances, and atmospheric CO2 levels. The script emphasizes the importance of understanding this dynamic for effective climate change strategies, highlighting the need for significant emission reductions to stabilize CO2 levels.
Takeaways
- 🛁 Stocks represent accumulations (like gallons or people), while flows represent changes per time (like gallons per day or people per month).
- 💧 The dynamics of stocks and flows can be visualized with icons, similar to how calculus represents integral and differential equations.
- 🚿 A bathtub analogy is used to explain how stocks and flows work: inflow (water in) and outflow (water out) affect the stock (water level in the tub).
- 📈 If the inflow exceeds the outflow, the stock increases; if the outflow exceeds the inflow, the stock decreases; if they are equal, the stock remains in dynamic equilibrium.
- 🌱 Examples of stocks and flows include people engaged in climate movements, personal finances, and levels of hope regarding climate change.
- 💳 A credit card balance is a stock, affected by the flows of charging and payments, illustrating how changes in flows can impact the stock differently.
- 🏭 The construction and retirement of power plants are a chain of stocks and flows, highlighting the long-term commitment to energy sources and their environmental impacts.
- ⚖️ The script emphasizes the importance of understanding stock and flow dynamics for effective climate leadership and decision-making.
- 🌐 The carbon bathtub analogy is introduced to explain the relationship between CO2 emissions (inflow), atmospheric concentrations (stock), and natural sequestration (outflow).
- 🔍 To stabilize CO2 levels, emissions must be significantly reduced, as merely leveling off emissions will not stop the increase in atmospheric concentrations.
Q & A
What is the main concept of the 'bathtub' analogy used in the script?
-The 'bathtub' analogy is used to explain the dynamics of stocks and flows in systems thinking. It represents how stocks (accumulations) and flows (rates of change) interact, similar to water filling and draining from a bathtub.
What are stocks and flows in the context of the script?
-Stocks are accumulations measured in units like gallons or people, and flows are rates of change that affect the level of stocks, measured in units per time, such as gallons per day or people per month.
How does the script relate the concept of stocks and flows to climate leadership?
-The script uses the concept of stocks and flows to help climate leaders understand and communicate the dynamics of climate change, particularly in terms of carbon emissions and atmospheric concentrations.
Why is it important to distinguish between stocks and flows when discussing climate change?
-Distinguishing between stocks and flows is crucial because it helps to understand that even if emissions (flows) level off, the concentration of CO2 in the atmosphere (stock) can continue to rise due to the imbalance between emissions and natural sequestration processes.
What is the significance of the integral and differential equations mentioned in the script?
-Integral and differential equations are mathematical tools used to model and understand the behavior of stocks and flows over time, which is essential for predicting and managing complex systems like the climate.
How does the script illustrate the relationship between inflow, outflow, and the level of a stock?
-The script explains that if the inflow is greater than the outflow, the stock level increases; if the outflow is greater, the stock level decreases; and if they are equal, the stock level remains in dynamic equilibrium.
What is an example of a stock mentioned in the script related to climate change?
-One example of a stock related to climate change mentioned in the script is the level of hope that we can address climate change, which is increased by building hope and decreased by losing hope.
How does the script use the credit card balance analogy to explain stocks and flows?
-The script uses the credit card balance as a stock, with charging (inflow) and payments (outflow) as flows. It demonstrates that if charging exceeds payments, the balance (stock) increases, similar to water accumulating in a bathtub.
What is the key takeaway from the script regarding the reduction of emissions to stabilize CO2 levels?
-The key takeaway is that to stabilize CO2 levels in the atmosphere, emissions need to be significantly reduced, by at least 50%, and possibly more, to ensure that the inflow (emissions) is less than or equal to the outflow (net removals).
How does the script suggest communicating the concept of stocks and flows to non-experts?
-The script suggests using the 'bathtub' analogy to simplify and clarify the concept of stocks and flows, making it more accessible and understandable for non-experts, such as museum visitors or the general public.
What is the role of systems thinking and system dynamics in addressing climate change as per the script?
-Systems thinking and system dynamics are crucial for understanding the complex interactions and feedback loops in the climate system. They help in developing strategies and policies that effectively manage and mitigate climate change.
Outlines
🛁 Introduction to Stocks and Flows
The speaker introduces the concept of stocks and flows as a fundamental tool for understanding and addressing climate change. Stocks are accumulations measured in units like gallons or people, while flows are changes to stocks measured per time. The analogy of a bathtub is used to explain how inflows and outflows affect the stock level, with the potential for overflow or emptying depending on the balance between inflow and outflow. The speaker emphasizes the importance of understanding this dynamic for climate leaders.
🔄 Applying the Bathtub Model to Climate Change
The speaker applies the bathtub model to the climate change scenario, explaining how carbon dioxide emissions (inflows) and natural sequestration (outflows) affect atmospheric CO2 levels (the stock). Despite emissions leveling off, CO2 concentrations continue to rise due to the imbalance between emissions and removals. The speaker recounts a past experience where they struggled to explain this phenomenon to museum designers until they adopted the stock and flow perspective, which provided clarity.
🌱 The Carbon Bathtub and Climate Action
The speaker delves deeper into the 'carbon bathtub' analogy, illustrating how even with emissions leveling off, CO2 concentrations in the atmosphere continue to rise due to the persistent inflow of emissions over outflow of natural sequestration. To stabilize CO2 levels, a significant reduction in emissions is required, not just a leveling off. The speaker advocates for an 80% reduction in emissions by 2050 to achieve this stabilization, highlighting the importance of this insight for climate leaders.
🌐 Spreading the Message of Stock and Flow Systems
In the final paragraph, the speaker calls for the audience to disseminate the understanding of stock and flow systems widely. They emphasize the importance of this concept in systems thinking and system dynamics, particularly in the context of climate and energy systems. The speaker concludes by encouraging the audience to use this knowledge to inform and influence climate action strategies effectively.
Mindmap
Keywords
💡Stocks
💡Flows
💡Dynamic Equilibrium
💡Bathtub Model
💡CO2 Concentrations
💡Carbon Emissions
💡Net Removals
💡Climate Leadership
💡Power Plants
💡80% Reduction by 2050
Highlights
Stocks represent accumulations and are measured in units like gallons or tonnes.
Flows change the level of stocks and must be measured in units per time, like gallons per day.
Clouds in diagrams represent the source or destination of flows, which are assumed to be infinite but should be questioned.
Calculus can represent stock and flow systems through integral or differential equations.
A bathtub analogy is used to explain stocks and flows, where the faucet represents inflow and the drain represents outflow.
If inflow exceeds outflow, the stock accumulates; if outflow exceeds inflow, the stock depletes; if they are equal, the stock remains in dynamic equilibrium.
Examples of stocks include people engaged in the climate movement, measured in people, and flows are the numbers getting engaged or disengaging per month.
Another example is cash flow, where income and spending are flows measured in dollars per month, and the cash balance is the stock measured in dollars.
Hope levels can also be considered a stock, increased by building hope and decreased by losing hope.
Credit card balance is a stock, with charging and paying being the flows that affect the balance.
Reducing charging does not necessarily reduce the credit card balance if charging remains above paying.
To reduce debt, one must pay more than they charge, aligning the payment flow above the charging flow.
Power plants can be seen as a chain of stocks and flows, from construction initiation to retirement.
Investing in coal or gas plants is a long-term commitment to carbon emissions due to the long lifespan of power plants.
The stock and flow concept was used to explain a career-saving moment involving climate change models and museum exhibit design.
CO2 in the atmosphere is a stock, with emissions as the inflow and net removals as the outflow.
Even if emissions level off, CO2 concentrations will continue to rise due to the imbalance between emissions and removals.
To stabilize CO2 levels, emissions need to be significantly reduced, by around 80% by 2050.
Stock and flow thinking is a fundamental building block of systems thinking and system dynamics.
Transcripts
hi I'm here to share with you a helpful
trick that saved me in my career and I
think it's gonna be helpful to you as a
climate leader it's all about a bathtub
here we go we'll start with the
mechanics and the icons of stocks and
flows stocks represent accumulations and
are generally measured in units like
gallons people tonnes and so on flows
change the level of stocks and must be
measured in units per time gallons per
day people per month tons per year and
so on here they are shown as an inflow
and an outflow the clouds represent
where something is coming from or going
to right now that's assumed to be
infinite but that should be questioned
calculus captures the same structure
this way first in an integral equation
or as a differential equation but it is
more helpful to think of a bathtub flows
are like the faucet and drain capturing
gallons per minute of water flow in and
out a stock is like the amount of water
in the bathtub an accumulation the units
show the important distinction between
between stocks and flows these flows are
measured in gallons per minute and a
stock is measured in gallons and here's
how stock and flow systems behave note
this may seem quite obvious but it'll
matter later
if the inflow is always greater than the
outflow the tub will overflow if the
outflow is greater than the inflow the
tub will empty if the inflow equals the
outflow the water will stay at the same
level in what we call dynamic
equilibrium there are the basics
stockin flows and their icons and the
ways that you diagram them and capture
them now let's look at some examples
consider this stock people engaged in
the climate movement this is all of us
and lots of other people flows numbers
of people getting engaged every month or
disengaging every month and note the
inflow and outflow would be measured in
people per month and the people engaged
is just measured in people here's
another a stock my cash flows income and
spending measured in dollars per month
they don't just need to be countable
just quantifiable consider the level of
hope that we can address climate change
it's a stock that's increased by
building hope and drained by losing hope
two very different processes by the way
we get to think what's a better way to
address things focus on the first or the
second another good example is my credit
card balance it's best to think about it
as a stock and flow credit card balance
is a stock measured in dollars how much
I owe the credit card company charging
increases the balance pain reduces it
both are measured in dollars per year
let's ignore all the interest charges
for a minute and imagine that my rate of
charging is constant over time and my
rate of pain is also constant but lower
I'm steadily charging more than I'm
paying the difference between what I
charge and what I pay each month adds to
the credit card balance it adds to the
stock so the stock is growing each month
see the balance going up and up it's
just like a bathtub with more water
flowing in than out but what if I try to
solve the problem and reduce my charging
say 20% or so here's where it gets
tricky
if charging goes down as many of you
probably know the balance doesn't
necessary
go down if charging remains above pain
see the little gap here then we will add
that much to the debt every month and
the balance goes up it goes up more
slowly but it still goes up for the
balance to go down and to get out of
debt I'd need to pay off more than I
charge see the charging line dropping
below the pain line now pain exceeds
charging and the credit card balance
goes down just like a bathtub with more
flowing out than in that's how these
bathtubs work that's how these stocks
and flows work sometimes these diagrams
can be chains of stocks and flows not
just a single stock and flow consider
the process of creating power plants
electrical production whether they be
coal gas nuclear wind or solar the first
flow is initiating construction perhaps
measured in megawatts per year then the
stock of power plants under construction
measured in megawatts then the flow
completing construction that builds up
the stock of power plants that are in
use generating electricity
then there's the flow that drains that
last stock called retiring because the
lifetime of a power plant is quite long
they sit in this final stock power
plants in use for an average of 30 years
so when we make an investment in a new
power plant we are locked into that
energy source and it's carbon emissions
for quite a long time so as climate
leaders we should be clear and we say to
the world that in an investment in a
coal or gas plant an investment in
fossil fuel based electrical production
is a long-term commitment to emitting
carbon not just a short term decision
okay that's enough on the stock and flow
concept for now let's talk about how
this idea
he saved me and my work it was 2003 and
I've been working with my friend Tom
finnerman who had been a graduate
student with me when we were together
he had this model on climate change that
was really cool and I was showing it to
some museum designers who wanted to
incorporate it into one of their
exhibits I was making this presentation
and I hit a wall you'll see first I
showed the group this graph of global
fossil fuel carbon dioxide emissions in
a business-as-usual case from 2000 to
the end of the century we burn in this
scenario more coal and more oil and gas
we chop down more trees emissions go up
and up and up i next showed carbon
dioxide concentrations this is the
amount of co2 collected in the
atmosphere no surprise it goes up and up
as well
emissions up concentrations up seems to
follow then the exhibit designers asked
for a scenario where emissions level off
around 2030 they don't rise they don't
fall they just level emissions would be
well below the business-as-usual case by
the way this would be great we would
reduce emissions a lot so I went ahead
and made the changes in the simulation
and I watched the results again we look
to concentrations and we saw the second
line right here wait what what is this a
missions level see the flat line right
here but concentrations continue to rise
and rise they rise a bit more slowly but
they still rise so the people looked at
me for an explanation and I muttered
something about the long lifetime of
molecules in the system and this and
that but they looked really lost and it
didn't go well
wah-wah then I immersed myself in the
work of Professor John Sturman at MIT
Sloan in several of his journal articles
he encouraged us to think of the climate
change problem as a stock and flow
problem or a bathtub problem and it shed
light on my awkward stock moment with
the museum designers he said think of
co2 in the atmosphere as a stock an
accumulation measured in parts per
million it's 400 parts per million on
average in 2014 this is equivalent to
the amount of water in a bathtub the
inflow is emissions Giga tons per year
of carbon dioxide mostly coming from
burning coal oil gas and land-use change
the outflow is net removals a large
amount of carbon dioxide gets
sequestered in plants and soils and
absorbed into the ocean note that a
large amount of co2 is moving from the
atmosphere to the plants and the oceans
and another large amount is moving back
in the opposite direction this flow were
showing right here of net removals
captures the net flow from the
atmosphere to the plants and soils and
oceans every year all right let's go
back to me standing in front of the
museum designers with the model the
emissions had leveled in 2030 but those
concentrations kept going up much to my
dismay emissions are an inflow to the
tub here just like this faucet and shown
on the graph here in this line measured
in gigatonnes per year and the outflow
is net removals shown here in this line
and indicating the flows of carbon
dioxide into oceans plants and soils
this bottom graph shows the stock or
accumulation of co2 in the atmosphere
the accumulated co2 is like the water in
the bathtub look at the top graph which
runs from 2000 to
look what's happening in 2020 the inflow
looks to be just about double the
outflow about 42 Giga tons per year here
as opposed to 23 here so we've got a
bathtub with double going in relative to
going out emissions from burning fossil
fuels is about double what's being
removed and sequestered every year with
42 going in 23 going out the bathtub
adds 42 minus 23 or 19 Giga tons per
year so what is that bathtub level doing
of course it is rising look at the
bottom graph in 2020 you can see co2 in
the atmosphere increasing in 2020 the
slope is positive see it going up up up
makes total sense now let's look at what
happens when the emissions a level off
in 2030 right here removals remain down
here below emissions so we kept
emissions well above removals we have a
bathtub with much more water flowing in
than flowing out look here at
concentrations of course co2 in the
atmosphere doesn't level off like it
thought it would of course it's still
increasing
even though emissions are level more is
flowing into the tub than is flowing out
I finally had a crystal-clear
explanation for the museum designers and
you won't have one for the world of
course that's the whole point here right
empowering you as climate leaders so we
have a really important point at least
about what won't work to address climate
change so what do we need to do to
actually stabilize carbon dioxide levels
well think about it for a second we have
a bathtub with double going in what's
going out alright there's about to have
double in going out how much do we need
to redo
the inflow in order to have it
stabilized think about it how much well
about 50% it would at least a 50%
reduction so I ran the next scenario
with a significant reduction in a
mission let's see what happens see the
reduction of emissions here it goes down
and down now look closely at this spot
2065 right here the inflow and the
outflow to the bathtub are equal
emissions equal net removals so the co2
concentration right here is level it's
just like a bathtub and look all here
and see the removals we need to reduce
emissions more than 50% because for
several reasons net removals would
actually decrease so the summary of the
main points about the carbon bathtub are
these first a bathtub is a really
powerful way to think about and just
explain to others the dynamics of
emissions concentrations and net
removals it's a good way to talk to
people about things secondly if all we
do is flatten our emissions we're gonna
have concentrations going up and up and
up temperature up and up and more and
more bad impacts over time third if we
really want to stabilize carbon dioxide
concentrations in the atmosphere we're
gonna need to significantly reduce
emissions on the order of 80% by 2050
and the last point we can do it so
that's it for stocks and flows there are
two main things hopefully you've just
gotten an understanding of another
building block of systems thinking and
system dynamics stock and flow thinking
and stock and flow diagramming and
secondly some insights into its
application in the climate and energy
system all right spread these messages
far and wide go get them
you
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