Transcript Earth system and climate change

Chapter 1:
Earth System and Climate system
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The Habitable Earth
The earth is the only habitable planet in our solar system.
Oceans: 70% of the surface
Land: 30%
Earth’s climate is favorable to life.
In the era of population explosion, climate change is
critical to human life.
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We will discuss:
1. What are the components of Earth system, especially
Earth’s climate system?
2. How does climate change differ from day-to-day
weather?
3. Climate Classification
4. What factors drive changes in Earth’s climate?
5. How does the climate system work?
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Earth system
composed of 4 interacting parts
driven by solar energy:
•Atmosphere
•Hydrosphere
•Solid earth
•Biota
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Schematic diagram
of the Earth system,
showing
interactions among
its four
components.
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Weather versus Climate
Weather
The condition of atmosphere at a given time and
place
 Short-term (and large) fluctuations that arise from internal instabilities
of the atmosphere
 Occurs as a wide variety of phenomena that we often experience
 Effects are immediately felt
 Social and economic impacts are great but are usually localized
 Governed by non-linear chaotic dynamics; not predictable
deterministically beyond a week or two
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Low Pressure
Cyclonic Turning:
Convergence
leads to upward
vertical motions.
High Pressure
Anti-Cyclonic
Turning:
divergence
leads to downward
vertical motions.
Cold Air
Warm Air
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Impacts of Weather
Figure 1.15
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Impacts of Weather
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Hurricane: Gustav in New Orleans. 2
Million people evacuated (Sep. 1, 2008)
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Climate versus Weather
Climate
 Defined as the average state of the atmosphere over a finite time
period and over a geographic region (space).
 Can be thought of as the “prevailing” weather, which includes the
mean but also the range of variations
 The wide range of natural variability associated with daily weather
means small climate changes are difficult to detect
 Intimate link between weather and climate provides a basis for
understanding how weather events might change under a
changing climate
 Involves atmospheric interactions with other parts of the climate
system and external forcing
 Climate prediction is complicated by considering the complex
interactions between, as well as changes within, all components.
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• Climate is typically described by the statistics of a set of
atmospheric and surface variables, such as temperature,
precipitation, wind, humidity, cloudiness, soil moisture,
sea surface temperature, and the concentration and
thickness of sea ice.
• The statistics may be in terms of the long-term average,
as well as other measures such as daily minimum
temperature, length of the growing season, or frequency
of floods.
• Although climate and climate change are usually
presented in global mean terms, there may be large local
and regional departures from these global means. These
can either mitigate or exaggerate the impact of climate
change in different parts of the world.
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 Climate is what you expect and weather is what you get.
 Climate tells what clothes to buy, but weather tells you what clothes
to wear.
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Review Questions
Which of the following statements relate more to
weather (A) and which relate more to climate (B)?
1. The
summers in Prince George are cool and dry.
2. It is 30°C right now, partly sunny, and south winds
10 to 20 miles per hour.
3. September 2001 was the 2nd coolest September of
record for Prince George International Airport.
4. The pressure now is 29.75 inches and steady, and
humidity is 84%.
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Review Questions
Which of the following statements relate more to weather
(A) and which relate more to climate (B)?
1. The
summers in Prince George are cool and dry. (B)
2. It is 30°C right now, partly sunny, and south winds 10 to
20 miles per hour. (A)
3. September 2001 was the 2nd coolest September of
record for Prince George International Airport. (B)
4. The pressure now is 29.75 inches and steady, and
humidity is 84% (A).
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Koppen's Worldwide Distribution of Climatic Regions II
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A: Tropical moist
• Tropical wet (Af)
• Tropical moonsoon (Am)
• Tropical wet and dry (Aw)
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B: Dry Climate
• Arid (BW) – the “true desert”:
• Semi-arid (BS):
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C: Moderate Climate
• Humid sybtropical (Cfa):
• Marine (Cfb):
• Dry-summer subtropical (also referred to
as Mediterrannean) (Cs):
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D: Continental Climate
• humid continental with hot summer (Dfa)
• humid continental with cold summer (Dfb)
• subplot (Dfc)
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E: Polar Climate
• Tundra climate
• Ice Cap climate
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Koppen's Worldwide Distribution of Climatic Regions II
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Earth History
Earth’s age:
4.55 billion years
(Byr)
= 4,550,000,000
years
= 4.55 × 109 years
This course
focuses on only
recent 10% of its
age.
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Time Scales of Climate Change
Earth’s climate changes all the time, e.g., last 300
Myr, last 3 Myr, last 50,000 yr, and last 1000 yr.
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Development of Climate Science
19th century – early 20th century:
isolated studies.
Middle 20th century – 1980s: rapid
development into a mature science.
In the past two decades: earth system
approach.
Multidisciplinary & interdisciplinary.
“Your tools
are terribly
antiquated
and
imprecise”
Climate Modeler
How scientists study climate change:
Observations  Theory
“You
produce
junk and
waste a lot
of money”
Field-Geologist
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• How scientists study climate changes
(1) spend much time to gather and analyze
data from the kind of climatic archives. To
publish results in peer-reviewed journals.
(2) need to explain and interpret results –
Hypothesis, theory.
(3) Models
(4) Charles Darwin: Evolution
Plate tectonics
It is time to expect a new revolution in
knowledge of Earth history.
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Components of the Climate System
Five major components: air (atmosphere), water (hydrosphere), ice
(cryosphere), vegetation (biosphere), and land (lithosphere).
Major processes: energy cycle, water cycle, carbon cycle, …
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Climate System Components
Atmosphere
• Fastest changing and most responsive component
• Previously considered the only “changing” component
Ocean
• The other fluid component covering ~70% of the surface
• Plays a central role through its motions and heat capacity
• Interacts with the atmosphere on days to thousands of years
Cryosphere
• Includes land snow, sea ice, ice sheets, and mountain glaciers
• Largest reservoir of fresh water
• High reflectivity and low thermal conductivity
Land and its biomass
• Slowly changing extent and position of continents
• Faster changing characteristics of lakes, streams, soil moisture
and vegetation
Human interaction
• agriculture, urbanization, industry, pollution, etc.
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The Climate System Components
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Climate Forcing: can be defined as an imposed
perturbation of Earth’s energy balance.
(1) natural forcing: luminosity of the sun;
volcanic eruption; earth’s orbit
(2) Anthropogenic forcing (fossil fuel burning) –
greenhouse gases
forcing (unit:
2 )  changes in global
w/ m
temperature.
Climate Sensitivity
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Forcing and Response: A Bunsen Burner Experiment
Three major kinds of
climate forcing in
nature:
Tectonic processes
Earth-orbital changes
Changes in Sun’s strength
Flame is far enough away
Anthropogenic forcing
Urbanization
Deforestation
Burning fossil fuels
Agriculture
Response time depends
on “materials” or
“components”.
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Climate: An Engineer’s View
Anthropogenic
forcing
Machine
Output
Input
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• Climate sensitivity:
The sensitivity of the climate systems to a forcing is commonly
expressed in terms of the global mean temperature changes that
would be expected after a time sufficiently long for both the
atmosphere and ocean to come to equilibrium with the change in
climate forcing.
An important factor of climate sensitivity is feedback of
components of the climate system. An example: if CO2
concentration doubles (forcing 4w/m^2), the temperature will increase
1.2C if no feedback. However, the situation is very complicated due to
feedbacks. For example, CO2 up => T up => ice melting => surface
color changes => more sun lights absorbed => T up….
feedbacks cause uncertainty in climate changes..
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Response Times of Various Climate System Components
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Feedbacks
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Feedbacks
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Water Vapor Feedback
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warming
Decreased
snow and ice;
less reflectivity
More solar
radiation absorbed
at surface
Ice-Albedo Feedback
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Initial Change
Climate
warming
Reduced
Warming
Uncertain
Increased
clouds
Greater
reflected
radiation
Cloud Radiative Feedbacks
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FEEDBACKS INVOLVED IN GLOBAL WARMING
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CLIMATE SENSITIVITY
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CLIMATE SENSITIVITY
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CLIMATE SENSITIVITY
The ‘commitment’ to
future warming
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