AHS 104 HillMurray High School Atmospheric Science Worksheet

AHS 104Lab 13: A Simple Climate Model
Name ____________________
In this lab you’ll use the Very Simple Climate Model (VSCM) to help understand the
relationships between the rate at which humans release CO2 into the atmosphere and the
atmospheric CO2 concentration and global temperature. The VSCM will let you experiment with
various “what if” scenarios to explore how the climate could change in the future.
Note: a major educational point of this model is that temperatures depend on concentration,
which rises whenever emissions are greater than zero. This model is very, very simple. It doesn’t
include wind or precipitation patterns that might influence or be influenced by warming; it
ignores other greenhouse gases; and so on. In this model, the temperature is determined entirely
by the atmospheric CO2 concentration.
Below are four scenarios. Test them out on the VSCM and see for yourself what the future may
hold. You’ll find the model at https://scied.ucar.edu/simple-climate-model.
Scenario 1: What if the amount of carbon dioxide that humans release into the atmosphere each
year doesn’t change over time? We currently emit around 10 billion tons (10 gigatons) of carbon
per year (10 GTY) into the atmosphere. To explore this scenario, set the controls along the left
side of the model to the following:
Set Carbon Dioxide Emissions to 10 GTY and click the Play button. Let it run until the graph
reaches the year 2100.
Why do the blue dots (the emission rate of CO2 in GTY) make a horizontal line?
The atmospheric concentration of CO2 is shown by the black triangles, which represent how
much carbon has accumulated in the atmosphere over time. Units are “parts per million by
volume” (ppmv). For reference, the actual concentration is around 410 ppmv currently.
Why does the atmospheric concentration of CO2 climb steadily?
In this model run, what is the CO2 concentration in the year 2100? __________
Red squares represent average global temperature in degree Celsius. What is the temperature
forecast for the year 2100? ________°C How much did the temperature rise between 2020 and
2100? ______°C. The horizontal red line is the recommended temperature limit, which many
scientists think we should not exceed in order to avoid dangerous impacts of climate change.
How does the predicted temperature in the year 2100 compare to the limit target?
It (exceeds, equals, is less than) the target by _________°C.
Scenario 2: People will rise to the challenge and employ new technologies and policies to limit
the emissions of greenhouse gases in the atmosphere. In this scenario, let’s assume that people
will keep emitting carbon dioxide at an increasing rate until the middle of the century, after
which the rate will fall.
1.
2.
3.
4.
Click the Start Over button.
As before, start with carbon emissions set at 10 GTY.
Click the Step Forward button (first button on the left) once to advance “model time” to 2020.
Increase emissions by 1 GTY (to 11 GTY) and advance the model to 2030 by clicking the Step
Forward button twice. Increase emissions to 12 GTY) and advance the model to 2040 by
clicking the Step Forward button twice. Finally increase emissions to 13 GTY) and advance
the model to 2050. Once you reach the year 2050 start decreasing the emission rate by 1 GTY
for each decade (to 12, 11, 10, etc.). Run the model to the year 2100.
What specific actions by humans could cause the emission rate to decrease?
You should see that emissions (blue triangles) increased until 2050, then steadily decreased
through 2100, but the CO2 concentration in the atmosphere (black dots) continued to rise. Why?
Does reducing the rate of growth of carbon dioxide emissions reduce the temperature (red) too?
________ What effect does it have on temperature?
So, reducing the rate of growth of greenhouse gas concentration isn’t enough to reduce
temperatures.
What is the temperature forecast for the year 2100 and how does it compare to Scenario 1?
Scenario 3: What if people instead release more and more carbon dioxide into the atmosphere
over time? This would mean that carbon emissions would rise steadily throughout the 21st
century.
1. As before, start with carbon emissions set at 10 GTY. Click the Step Forward button once to
advance “model time” to 2020.
2. Increase emissions by 1 GTY (to 11 GTY) and advance another 10 years by clicking the “Step
Forward” button twice.
3. Keep increasing the emission rate by 1 GTY (to 12, 13, etc.) for each decade, running the
model to the year 2100.
Note that emissions (blue) rose steadily until 2100. Atmospheric CO2 concentration (black)
rose as well. What is the temperature forecast for the year 2100, and how does it compare to
Scenarios 1 and 2? ______°C
Scenario 4: Turn off CO2 emissions completely (set to 0 GTY). Run the model to the year
2100. Does the CO2 concentration and temperature fall during that time? ________ Can we
reach the pre-industrial temperature (13.8°C) by the year 2100 in this scenario?
Welcome to our 41st day of class:
25 April 2022
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Climate models
Assignments:
◆ Lecture quiz for today is due by 11:59 PM on
Wednesday, 27 April
◆ Lab 13 is due by 11:59 PM on Monday, 2 May
◆ Weather Notebook entry for today, if needed
04/25/2022
AHS 104 Day 41 Spring 2022
1
Review: global warming theory
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GHG are increasing; GHG absorb IR; therefore
climate should warm up
Note: warming would be reinforced by positive
feedbacks
◆ Ice-albedo feedback
◆ Water vapor-surface temp feedback
◆ Warming won’t happen without feedbacks!
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Testing the theory
Can’t do a ‘real’ experiment, don’t have
another Earth!
◼ Use climate models to test our theory of
global warming.
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What are the computer predictions?
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Climate should continue to warm up
◆ Greatest at high Northern latitudes
◆ More at night and in winter
Sea level should continue to rise
◆ About 21 to 48 cm by 2090’s in a likely scenario
It should rain more globally
Storm tracks should move north
Subtropical highs move poleward, etc.
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Wait: how do we know whether
the climate models are accurate?
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Testing the climate models
First let’s see if the models can reproduce
the climate of the past 150 years. Start by
doing experiments with “natural forcing”:
known solar changes, known volcanoes, etc.
◼ Then add human produced GHGs, or
“anthropogenic forcing”
◼ See if the climate of the 20th century can be
reconstructed
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“Anthropogenic signal revealed”
Black line is observed temperatures
Pink band is
spread of
predictions
by models
with GHG
forcing
Blue band is
spread of
predictions
by models
with “natural”
forcing only
GHG don’t seem to matter before ~1960 vs. “natural
forcing”, but after that they’re necessary to get the models
to agree with the observations.
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Now for some predictions…
The models seem to match the past global
average temperatures fairly well.
◼ Let’s see what they predict about the future.
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Colored lines are
predictions for
various scenarios
based on GHG
emission assumptions
Worst-case
scenario
Black line is
observed
temperature
GHG emissions
drastically reduced
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“Conservative”
Scenario
Arctic warms
the most
“Likely”
Scenario
More Extreme
Scenario
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Are these models just like
the earth’s climate system?
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No: models have shortcomings
▪ they simplify reality
▪ clouds and precipitation effects are not modeled
very well
▪ can’t simulate internal climate changes (like El
Nino) very well
They’re getting better though!!
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Other uncertainties
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Future GH gas concentrations unknown
Solar variations difficult to predict
Volcanoes can’t be predicted
How much CO2 released from permafrost?
How will ocean circulation change?
We don’t understand the limits of climate
predictability
We don’t know everything there is to know about
Earth’s climate system –let’s be honest!
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None of this means the global warming
theory is wrong, it means it needs further
refinement
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Our understanding of how climate works, the
observational data, and the computer models will
continue to improve
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You try it! Lab 13
◼
In this lab you’ll use a very simple climate model
to help you understand the relationships between
the rate at which humans release CO2 into the
atmosphere and the atmospheric CO2
concentration and global temperature. You can
experiment with various “what if” scenarios to
explore how the climate could change in the
future.
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Some misconceptions
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Misconception: There’ll be a greater number of
more powerful hurricanes
◆ Tropical atmosphere is predicted to get more
stable which implies fewer hurricanes
◆ Hurricanes may become more powerful due to
more water vapor in the air
At present, no global trend in numbers of
hurricanes
Change in strength? Highly debated!!
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Some misconceptions
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Misconception: There’ll be more severe cyclones.
◆ If ice-covered area is smaller, ability to generate cold
air will be reduced
◆ Mid-latitude cyclones, which produce severe weather,
get their energy from temperature differences.
⧫ Less energy and slower jet streams
◆ If subtropical high expands northward, area dominated
by sinking expands.
This is also very controversial among meteorologists.
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What makes some people skeptical?
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Everything is blamed on global warming.
◆ Drought in California
◆ Floods in Texas
◆ Bitterly cold winters
◆ Major hurricanes striking the coastlines
◆ Every single remarkable weather event!
Actually, we won’t be able to prove the effect of global
warming until it has been going on for a while
Everything about it is going to be bad!!
◆ Note: warming => longer growing seasons
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Some see this behavior as hypocrisy
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In our last lecture, we’ll take a
look at the question: what should
we do about global warming?
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Question 1 (1 point)
Most climate models predict that a gradual increase in global carbon dioxide over the
next 100 years will most likely bring about
a decrease in surface air temperature
an increase in surface air temperature
no change in surface air temperature
Question 2 (1 point)
Climate models predict that the greatest warming due to increasing greenhouse
gases will most likely occur in
the tropics
the middle latitudes
the polar regions
Question 3 (1 point)
Which of the following is not a likely consequence of global warming?
a rise in sea level
increased melting of the Greenland ice sheet
a decrease in global precipitation
increased melting of Arctic sea ice