Download BIOL 103 Global climate change science

BIOL 103
Global climate change science
Warning: You will need to be able to describe
the Keeling Curve to pass this course
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Lecture outline
1. The “greenhouse effect”
2. Anthropogenic greenhouse emissions
3. Changes to the atmosphere
4. Changing climate
5. How to study climate
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Let’s start by discussing this
diagram in more detail
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A primer on radiation:
Sunlight is a mixture of different types of radiation
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We can think of light as small packets of
energy (called photons) traveling in a wave
Photon
Photons are not matter or atoms
(Which was why plants can’t use as a raw material
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Colors are radiation with different wavelengths
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Radiation with wavelength shorter than violet
or longer than red are invisible to human eye
Ultraviolet
radiation
has shorter
wavelength
than violet
Infrared
radiation
has longer
wavelength
than red
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Electromagnetic radiation:
Particles of energy traveling at speed of light in waves
Wavelength determines properties
Notice: Gamma rays, x-rays, ultraviolet radiation, visible light, infrared
radiation, microwaves, and radio waves differ only in their wavelength
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When radiation strikes something, it
can do three things:
Reflect: Bounce off
Absorb: Energy taken
up by material
Transmit: Pass through
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E.g. x-rays pass transmit through
tissue but are absorbed by bone
Visible light can’t pass through either
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Sunlight hitting atmosphere will either
reflect, transmit, or absorb
About half of sunlight is
absorbed by the ground
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What happens to sunlight after being
absorbed?
• It doesn’t disappear.
• Energy never disappears.
• It causes ground to warm up.
• If this was the entire story, earth would get
warmer and warmer (forever).
• However, earth radiates this energy back to space.
• This radiation is called infra-red radiation.
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Infra-red radiation
Radiation with longer wavelength than light
We perceive infra-red radiation as heat
We are radiating infra-red radiation constantly
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Earth’s atmosphere absorbs infra-red
radiation more than sunlight
This causes greenhouse effect.
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Summary of greenhouse effect
1. Sunlight passes through
atmosphere.
2. Sunlight absorbed by
earth.
3. Earth emits infra-red
radiation.
4. Infra-red radiation
absorbed by
atmosphere (warming
atmosphere)
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Composition of Earth’s Atmosphere
Nitrogen
Oxygen
…
Carbon dioxide
…
Methane
78%
21%
0.03%
0.002%
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Several types of “greenhouse” gases trap heat
Gas
Relative heat trapping ability
Carbon dioxide
1
Methane
23x*
Nitrous oxide
296x
Hydrochlorofluorocarbons
12,000x
*Indicates each methane molecule traps 23x as much heat as each CO2 molecule.
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The natural greenhouse effects warms earth 59°F
Make life as we know it possible.
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2. Human populations have grown
rapidly
Population
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Air pollution
Water pollution
Soil erosion
Overfishing
Deforestation
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2
0
0
500
1000
Year
1500
2000
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Burning coal, oil, or natural gas releases
CO2 to the atmosphere
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A useful word:
Anthropogenic (adj)
Caused by humans
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Greenhouse gas emissions
85% of world’s energy comes from
coal, oil, natural gas
Oil
Coal
Bio (e.g. wood)
Gas
Nuclear
Renewables
Nearly half of U.S. electricity comes from coal
Hydro
Oil
Renewable
Gas
Coal
Nuclear
Source of US electricity
Electricity production is largest source of
CO2 emissions in the United States
50% of electricity is produced by burning coal.
20% produced by burning natural gas.
Both release CO2.
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Transportation is second largest
source of emissions
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There are 136,000,000 passenger cars and 99,000,000
SUVs and light trucks in the United States
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Recall: A Subaru Forester wagon releases
almost 7 tons of CO2 per year!
386 grams / mile × 15,000
miles = 5,790,000 grams =
12,764 pounds
~ 6 ¾ tons of CO2
per year!
*Source: www.fueleconomy.gov
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Global CO2 emissions
from fossil fuels
62,000,000,000,000 (62 trillion) pounds
Or 31 billion tons
Or 31 gigatons
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Deforestation is another major source
of CO2 emissions
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Even cow farts are a significant source
of greenhouse gases (methane)
100 million cattle in U.S.
1.2 billion cattle, sheep,
goats worldwide
Methane emissions being collected from a cow.
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3. Changes to global atmosphere
CO2 levels are now being measured around the world
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CO2 levels are gradually increasing
CO2 Concentration (ppm)
400
390
380
Highest levels in past 650,000 years
370
360
350
340
330
CO2 levels will probably double this
century
320
310
300
1960
1970
1980
Year
1990
2000
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390
388
CO2 Concentration (ppm)
386
384
382
380
378
Annual increase caused by
fossil fuel emissions
376
374
372
370
2004
2005
2006
Year
2007
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Global CO2 levels
from Antarctic ice cores
350
CO2 concentration
300
250
200
150
Ice Ages
100
400,000
300,000
200,000
100,000
0
Years before present
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Projected CO2 levels for 2100
600
CO2 concentration
500
400
300
200
100
400,000
300,000
200,000
100,000
0
Years before present
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Carbon dioxide,
Methane,
Nitrous oxide
levels have all risen
dramatically over past
10,000 years
Graphs show 10,000 years of data
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Who put the extra CO2 in the
atmosphere
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China is world’s largest CO2 emitter
United States emits most per capita
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Not all CO2 emissions end up in
atmosphere
Where does CO2 go?
40% atmosphere
30% forests (increased tree growth)
30% oceans (dissolved)
(These numbers are approximate and are
poorly known. This is an active area of
research.)
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Greenhouse gases won’t escape out the
ozone hole
The ozone hole
is not similar to a
hole in an air
mattress.
It is a reduction
in a gas that
makes up a tiny
fraction of the
atmosphere.
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Nor does ozone hole “let in” sunlight
Note: CFCs’ and ozone molecules do have a small impact on global
warming.
But for all practical purposes, global warming is unrelated to the
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ozone hole.
4. Global warming
Swedish physicist predicted in 1896 that doubling CO2 would
raise earth’s temperature by 9°F
Svante
Arrhenius
Arrhenius predicted burning fossil fuels would take
3000 years to double CO2 levels.
Viewed warming as a good thing - avoid ice age, help feed planet.
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Length of glacier
1 unit = 1km
Glaciers have been
retreating all around
the world
Year
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“The Hockey Stick Graph*”
Average global temperature rose 1°F last century
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*This is an important graph.
Amount of warming in 21st century will
depend on many social factors
• Human population growth
• Rate at which wind, solar, nuclear
power replace fossil fuels
• Energy efficiency
• Urban sprawl & public
transportation
• Industrialization in the developing
world (esp. India & China)
• Deforestation in the Amazon
• How much meat people eat
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Best estimate: 5°F of warming
Graph shows projections for different scenarios
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Does this mean a 5°F
warming is inconsequential?
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Temperature
80
60
40
20
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan
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No. Ice ages were only 8°F cooler!
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Study guide
• Read Chapter 18, “Global climate change,” thoroughly. (It is the basis for 3 lectures.)
• Be able to describe the greenhouse effect.
• Be able to identify how much the planet warmed in the 20th century, and how
much sea levels rose.
• Be able to sketch the “hockey stick graph.”
• Be able to describe why CO2 and methane levels in the atmosphere are
increasing.
• Be able to identify how much CO2 a typical car releases into the atmosphere
annually.
• Be able to describe two other sources of greenhouse gases besides burning of
fossil fuels.
• Be able to discuss how US and China CO2 emissions compare.
• Be able to identify which countries have released the most CO2 into the
atmosphere.
• Review “Baloney detection kit” from lecture 2 and be able to apply it to climate
change controversy.
• Be able to use all of the above points to evaluate arguments.
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Sample exam questions
How much did the earth warm in the 20th century?
How much did sea levels rise in the 20th century.
Use a diagram to explain the greenhouse effect.
Evaluate the following statement: “Because industrialized countries burn the
most fossil fuels, they are only countries that will be able to prevent global
warming in the 21st century.”
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The end
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