Wikipedia | Public Domain
Wikipedia | GNU
NASA accessed via Wikipedia
Before Thermometers …
•
•
•
•
instrumental observations of the Earth’s climate go back about
150 years in the USA and about 350 years in Europe
ancient civilizations kept records of floods, droughts, extreme
hot/cold events, and harvesting times
human records/accounts can only take us back hundreds to
thousands of years remember the Earth is 4.5 billion years old
other tools are needed to understand the history of past climate
variations
Paleoclimatology
study of climate prior to instrumental measurements
0 natural recorders of climate known
as “proxy data/records”
0 tree rings
0 ice cores
0 corals
0 fossils
0 pollen
0 ocean/lake sediments
0 extends archive of climate data back
hundreds to thousands and even
millions of years
Wikipedia | Creative Commons
NOAA accessed via Wikipedia
0 past temperature, precipitation, wind
patterns, chemical composition of
atmosphere inferred from proxy data
0 studying past climate variations can
provide clues about what to expect
NOAA accessed via Wikipedia
Instrumental Data
0 since 1850’s (USA)
0 technology increases
accuracy of measurements
0 industrialization –
urban heat island
0 coverage almost global
Proxy Data
0 hundreds to thousands
and even millions of
years
0 not a direct
measurement –
uncertainty
0 specific locations
Wikipedia | Robert A Rohde
What causes Earth’s climate to change naturally?
•
Earth’s orbit
•
Sun’s intensity
•
Volcanic
eruptions
•
Carbon Dioxide
greenhouse gas concentration
natural carbon cycle
•
Ocean currents
NASA
Earth’s climate has changed
NASA
courtesy of the U.S. Geological Survey
… and always will be changing
Milankovitch Cycle:
The Earth travels through space around
the sun, three orbital variations of the
Earth - sun geometry combine to produce
differences in the amount of solar energy
that reaches Earth (NASA)
Earth – Sun Geometry:
Orbital Eccentricity
0 Earth’s orbit around the
sun is an elliptical shape
0 Eccentricity: variations in
the shape of the orbit
0 varies between 0.005 and
0.06 (currently 0.017)
0 100,000 year cycle
0 greater eccentricity
enhances the other orbital
variations
NASA
Earth – Sun Geometry:
Obliquity
0 Earth’s axis tilted 23.5°
0 Obliquity: changes in the
angle of Earth’s axial tilt
0 changes from 22.1° to
24.5°
0 40,000 year cycle
0 affects the magnitude
of the seasons
NASA
Earth – Sun Geometry:
Precession
0 Earth rotates around an axis
(but it wobbles)
0 Precession: direction of Earth’s
axis of rotation changes
0 Polaris will not always be the
“North Star”
0 26, 000 year cycle
0 alters Earth’s orientation
relative to aphelion and
perihelion
NASA
Climate
Connections …
0 Earth’s orbit changes slowly over
time (tens and hundreds of years)
0 eccentricity, obliquity, and
precession (combination of) alter
the strength and location of solar
energy
0 significant drivers of ice ages
©1997-2011 University Corporation for Atmospheric Research. All Rights Reserved
Here comes the sun
0 energy from the sun is very
important to Earth
0 strongly affects Earth’s
climate by the intensity of
solar radiation
0 heats the surface, ocean, and
Wikipedia | Creative Commons
atmosphere
Structure
of the Sun
1. Core
2. Radiative zone
3. Convective zone
4. Photosphere
5. Chromosphere
6. Corona
7. Sunspot
8. Granules
9. Prominence
Wikipedia | GNU
0 Approximately 150 million kilometers away
0 Sun has a diameter of 1.4 million km
0 The temperature of surface is 5780K
0 Luminosity
The amount of electromagnetic energy the sun radiates out every second
(3.86 X 1026 W)
0 Solar constant (Insolation):
The amount of incoming solar energy per unit area reaching Earth
every second (1367 W/m2)
0 Energy escapes into space at the speed of light (c = 3.0*108 m/s)
0 About 8.5 minutes later, solar energy reaches Earth in the form of
infrared, UV, and visible light
NASA accessed via Wikipedia
Radiant
Energy
The Sun radiates
massive amounts of
energy into space
across all
wavelengths of the
electromagnetic
(EM) spectrum
©1997-2011 University Corporation for Atmospheric Research. All Rights Reserved
Radiant Energy absorbed by
Earth’s Atmosphere
© 2011 The Pennsylvania State University
Why the Earth’s surface is
heated unevenly
Spreading the light
0 Earth is a sphere
0 incoming solar
radiation
concentrated and
direct at the equator
0 at the poles the sun’s
intensity is less
because it is spread
out over a larger area
Quite a slant
0 Earth’s axis tilted at an
angle ~23.5°
0 tilt causes the change in
seasons
0 number of hours of
daylight varies by latitude
Energy In = Energy Out
NASA
Incoming
Radiation
• Shortwave radiation from the Sun
• 6% reflected from the
atmosphere
• 20% reflected from clouds
• 4% reflected from the surface
(including land, water and ice)
• 51% is absorbed by land and
water
• 19% is absorbed by the
atmosphere and clouds
NASA
Outgoing
Radiation
NASA
•
Combination of reflected solar radiation
and radiation emitted from the Earth
including the atmosphere and clouds
•
Earth emits longwave IR radiation
•
23% is transferred from Earth to the
atmosphere and clouds by latent heat flux
•
7% is transferred from Earth to the
atmosphere by sensible heat flux
•
6% is radiated directly back to space from
Earth
•
15% is transferred from Earth to the
atmosphere by radiation, then reradiates
back to space
•
19% that was absorbed by the atmosphere
and clouds is radiated into space
NASA
NASA
NASA
Remember that a budget that is
out of balance can cause the
Earth’s atmospheric
temperature to increase or
decrease which will affect our
climate
NASA accessed via Wikipedia
Sunspots
0 Sunspots are “dark”
regions that appear on
the surface of the sun
0 A dark central region
known as the umbra
surround by lighter
region called the
penumbra
NASA
0 The sun can have
hundreds of sunspots
or none at all!
NASA
NASA
Sunspot Cycle
NASA accessed via Wikipedia
0 Individual sunspots grow over a few days and last from days to months
0 The average number of sunspots changes year to year
0 The rise and fall in the number of sunspots is a cycle
0 The length of the cycle is about 11 years
0 Natural phenomena have been related to sunspots
NASA | SOHO
Climate Connections…
• amount of solar energy emitted
varies
• coincides with the sunspot cycle
• intensity of sunlight causes
warming (strong) or cooling
(weak)
Wikipedia | Robert A Rohde
Medieval Maximum
Maunder Minimum
0 1645 – 1715
0 1100 – 1250
0 high number of sunspots 0 not many sunspots
0 coincides with a
0 coincides with an
extended warm period
on Earth
period of
exceptionally cold
winters
(The Little Ice Age)
Modern Maximum
0 present
0 high number of sunspots
since 1900
0 link to current climate
changes?
Explosive Volcanic Eruptions:
admit hot magma, ash/dust, and gases into the atmosphere
Carbon Dioxide (CO2)
Sulfur Dioxide (SO2)
0 CO2 admit into
0 SO2 gas ejected into
atmosphere
0 GHG
stratosphere
0 bright haze layer forms
0 reduces incoming
0 warming effect
0 (now) humans emit
150X more CO2
radiation
0 last 1 – 3 years
0 (short – term) cooling
effect
USGS accessed via Wikipedia
Climate Connections…
Mount Pinatubo (Philippines) erupted June
1991
0 lowered global average temperature
(in 1992) by 1.5°F
Wikipedia | Creative Commons
Tambora (Indonesia) erupted 1815
0 lowered global average temperature
by 5°F
New England describes 1816 “the year
without a summer”
Other major volcanic eruptions exhibit cooler
global average temperatures lasting 1 to 3
years after their eruption
NASA accessed via Wikipedia
The connection between temperature and CO2
Does CO2 change in response to temperature or the other way around?
It works both ways
©1997-2011 University Corporation for Atmospheric Research. All Rights Reserved
If CO2 concentrations in the
atmosphere change,
temperatures will vary because of
the greenhouse effect
.
Wikipedia | Creative Commons
If global temperatures change,
the natural carbon cycle will respond
Climate
Connections …
During warming at the
end of ice ages,
CO2 was released from
the oceans
Variations in the natural
carbon cycle can produce
gradual cooling into ice
ages
NOAA
Variations in other GHG’s
modify the greenhouse effect
IPCC 4th Report WG1
Paleocene – Eocene
Thermal Maximum (PETM)
What happened
•
•
•
•
•
•
55 million years ago
global temperatures
rose 9°F (5°C)
massive amounts of
greenhouse gases
released
carbon dioxide levels
of 560 – 600 ppm
continents had
different configuration
lasted 120,00 –
220,000 years
The results
•
•
•
•
•
•
•
ocean circulation patterns
changed
ocean very acidic
did not cause mass
extinction (plants and
animals)
sea surface temperatures at
the North Pole 64°F (18°C)
no polar ice cap or
Greenland ice sheet
subtropical vegetation
grew in Greenland
tropical forests in northern
Wyoming
Heating or cooling of Earth:
trigger changes in the ocean motions
0 70% of Earth’s surface is covered by oceans
0 variations in temperature, salinity, and wind cause the
oceans to always be moving
0 ocean surface and deep currents distribute heat
around the Earth
0 Upwelling is a process that brings the dense, cooler
deep ocean water to the surface. Downwelling is a
process that sends water from the surface to the deep
oceans
0 ocean has had (and continues to have) an influence on
climate by absorbing, storing, and moving heat,
carbon, and water
©1997-2011 University Corporation for Atmospheric Research. All Rights Reserved
.
The El Niño-Southern
Oscillation (ENSO)
• combination of
changes in the
ocean and
atmosphere
• changes to weather
and climate around
the globe
• natural phenomena
NASA
that occurs every
3 – 7 year
• two phases: El Niño
and La Niña
NOAA
ENSO phases:
occur on average 3 – 7 years
El Niño
unusually warm ocean
surface temperatures
equatorial region of the
Pacific
La Niña
unusually cold ocean
surface temperatures
equatorial region of the
Pacific
conditions typically last
9 – 12 months
(have lasted 2 – 4 years)
conditions typically last
1 – 3 years
Strong El Nino Years: 19821983, 1986-1987, 19971998
Strong La Nina Years:
1985, 1988-1989, 19951996
Examples of ENSO phases
El Niño
La Niña
NOAA
NOAA
Effects of El Niño
NOAA accessed via Wikipedia
Effects of La Niña
NOAA accessed via Wikipedia
Interactive
video on
El Niño &
La Niña
Click to watch
NASA
FACT:
Earth’s climate always has and
currently is changing
FACT:
CO2 emissions have increased
because of humans since the
industrial revolution
FACT:
Global temperature is currently
increasing
Cause of current change?
• Natural?
• Anthropogenic (Humans)?
• Combination of both?
NASA