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Climate Change
Luc Ikelle
2011
Motivations
• Earth is the place where we live – Climate change.
• It provides food through the farming of its soils. It
provides energy resources (e.g., oil, gas, and coal)
and minerals (e.g., gold, diamonds, uranium, and
thorium) – Energy resources.
Motivations
• Yes, Earth also kills, even more frequently these
days; earthquakes and volcanic eruptions are the
major sources. – Earthquakes and volcanoes.
Key References
• Solomon, S., Qin, D., Manning, M., Chen, Z.,
Marquis, M., Averyt, K., Tignor, M., and Miller,
H., 2007, Climate change 2007: The physical
science basis: Cambridge University Press, New
York, NY.
• National Research Council, 2002: Abrupt climate
change, inevitable surprise: National Academy
Press, Washington, DC.
• European parliament report: Scientific evidence of
a possible relation between recent natural disasters
and climate change (IP/A/ENVI/FWC/2005-35).
Key References
• Reynolds, S.J., Johnson, J.K., Kelly, M.M.,
Morin, P.J., Carter, C.M., 2010, Exploring
geology, 2nd edition, McGraw-Hill Company
Inc, New York, NY.
• Bloom, A.J., 2010, Global climate change:
Convergence of disciplines, Sinauer Asspciates,
Inc., Sunderland, Ma.
• Emanuel, K., 2007, What we know about
climate, The MIT Press, Cambridge, Ma.
Key References
• Stott, P.A., Stone, D.A. and Allen, M.R. 2004:
Human contribution to the European Heatwave
of 2003, Nature, 432, pp. 610-614.
• Trenberth, K., 2005, Uncertainty in Hurricanes
and Global Warming, Science, 308, 17.
• Travis, D.J., Carleton, A.M., and Lauritsen,
R.G., 2002, Climatology: Contrails reduce daily
temperature range, Nature, 418, 601.
“Climate is what we expect; weather
is what we get.”
Mark Twain (1897)
Weather
• Weather refers to hour-to-hour and day-to-day
changes in temperature, plus cloudiness,
precipitation, and other meteorological
conditions.
• The weather pages in The Eagle newspaper
includes information on daily maximum and
minimum temperatures, humidity, precipitation,
and wind speed and direction.
• The accuracy of weather forecasts can be
confirmed by observing the actual weather.
Climate
•
Long-term averages of meteorological
conditions (e.g., temperatures, humidity,
precipitation, wind speed and direction) define
the climate in your area. In other words, longterm weather patterns characterize the climate.
•
For example, a Mediterranean climate is
characterized by relatively hot, dry summers
and cool, wet winters.
Climate Change
•
Plate tectonic theory has just taught us that
Earth’s surface changes with space and time.
Climate is not infinitely stable, either; it
changes with time and space.
•
Climate changes are not caused just by human
actions; climates also change naturally.
Climate Change
•
•
Climate changes naturally on a range of spatial
scales, from local and regional to global, on a
range of time scales: decadal (10s of years),
centennial (100s of years), millennial (1000s of
years), and longer (glacial cycles, e.g., ice
ages).
For example, a longer winter characterizes
climate change in time, and the monsoon rains
occurring farther south characterize climate
change in space.
11
Climate Change
•
Within the past three million years or so, our
climate has swung between mild states, like
today’s, and lasting from 10,000 to 20,000
years; and periods of 100,000 years or so in
which giant ice sheets, in some places several
miles thick, covered northern continents.
•
Moreover, climate changes between cycles are
often sudden, especially as the climate recovers
from glacial eras.
12
Climate Change
•
Around 50 million years ago, the earth was free
of ice, and giant trees grew on islands near the
North Pole, where the annual mean temperature
was about 60 degrees Fahrenheit, far warmer
than today’s mean of about 30.
•
There is also evidence that the earth was almost
entirely covered with ice at various times around
500 million years ago; in between, the planet
was exceptionally hot.
Why Should We Be Interested in
Climate Change?
• Climate determines the type and location of humanmanaged ecosystems, such as agricultural
farmlands.
• For example, changes in climate will impact on
crops and livestock. Rising temperatures cause a
shift in budburst, shorter growing seasons, earlier
harvest dates, lower crop quality, and changes in
soil temperatures.
• Climate determines the quantity and quality of
water available for human use.
Why Should We Be Interested in
Climate Change?
• A warming of 1°C is sufficient to move climate
belts about 150 km south. A regional temperature
change of 2°C likely to have a serious impact on
most life forms and on most ecosystems and
agricultural areas.
• Some climate changes are abrupt—that is, rapid
and unpredictable. In the past, the average global
temperature has risen or fallen > 6º C in less than
10 years.
Abrupt climate change : inevitable surprises / Committee on Abrupt Climate Change, Ocean Studies Board, Polar Research
Board, Board on Atmospheric Sciences and Climate, Division on Earth and Life Studies, National Research Council.
How About Recent Extreme
Weather Events?
• The 2010 Pakistan floods began in July 2010 following
heavy monsoon rains in the Khyber Pakhtunkhwa,
Sindh, Punjab and Balochistan regions of Pakistan.
Present estimates are that more than 2,000 people have
died and more than a million homes have been
destroyed.
• Hurricane Katrina, which took place during the 2005
Atlantic hurricane season, was the costliest natural
disaster and one of the five deadliest hurricanes, in the
history of the United States. At least 1,836 people lost
their lives in the hurricane and the subsequent floods.
How About Recent Extreme
Weather Events?
• The European heat wave in the summer of 2003 caused
massive loss of life; the deaths of at least 22,146 people
have been attributed to the heat.
• Hurricane Mitch in 1998 killed more than 10,000 people in
Central America.
• The 1970 Bhola cyclone was a devastating tropical cyclone
that struck East Pakistan (now Bangladesh) and India's West
Bengal on November 12, 1970. It was the deadliest tropical
cyclone ever recorded and one of the deadliest natural
disasters in modern times. Up to 500,000 people lost their
lives in the storm, primarily as a result of the storm surge.
Natural Hazards
•
•
Geosphere (Chapter 1):
Earthquakes (fire, floods, etc.)
Volcanic eruptions
Landslides
Tsunamis
Atmosphere (Chapter 3):
Hurricanes
Cyclones
Droughts
Wildfires
Plan
•
•
•
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•
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Basic physics of the atmosphere
Glaciers and ice ages
Tools of climate sciences
Natural forcing factors
Human forcing factors
Global climate model and global warming
Climate change and natural disasters
Abrupt climate change
Mitigation and adaptation
Terminology
•
•
A monsoon is caused by winds that reverse
direction, depending on the season. In some
areas, the changing wind patterns cause
torrential rainstorms.
Tropical hurricanes, typhoons, and cyclones are
all names for immense storms that form
primarily in the warm waters of the Atlantic,
Pacific, and Indian oceans, respectively. They
are characterized by swirling high-velocity
winds, heavy rain, and high storm surges that
cause high waves and flooding ahead of the
storm.
Terminology
•
•
Molecules. A molecule is a stable group of two or
more atoms held together by strong chemical
bonds. A molecule may consist of atoms of a
single chemical element, such as oxygen (O2), or
of different elements, such as water (H2O),
methane (CH4), and carbon dioxide (CO2).
Isotopes are different types of atoms (nuclides) of
the same chemical element, each having a
different number of neutrons. Isotopes differ in
mass number (or number of nucleons) but never
in atomic number (e.g., 16O, 17O, and 18O).
Terminology
•
•
•
IPCC refers to the Intergovernmental Panel on
Climate Change.
SRES refers to the Special Report on Emissions
Scenarios (SRES) prepared by the IPCC.
CAFE refers to Corporate Average Fuel
Economy. In the aftermath of the 1973 oil
embargo, the U.S. Congress enacted the CAFE
regulations. The regulations established the
average fuel economy of passenger cars in a
manufacturer’s U.S. fleet in order to spur the
development of more fuel-efficient technologies.
Atmosphere
Atmosphere:
Mean temperature:
N2, O2, H2O, and a little CO2
+ 15o C
Photo http://visibleearth.nasa.gov
Earth’s Atmospheric Gases
Nitrogen (N2)
Oxygen (O2)
Argon (Ar)
Non-greenhouse Gases
> 99%
Water (H2O)
Carbon Dioxide (CO2)
Methane (CH4)
Greenhouse Gases
< 1%
Greenhouse Gases
Water
Nitrous oxide
Carbon dioxide
Sulfur hexafluoride
Methane
Major Greenhouse Gases
Concentration
(ppb)
•
•
•
•
•
Carbon dioxide 380,000
Methane
1,850
Nitrous oxide
324
Carbon monoxide
130
Sulfur hexafluoride 0.006
Lifetime
(years)
120
12
114
0.25
3,200
Warming
potential
1
25
298
2
22,800
ppb: parts per billion.
warming potential: Total radioative effect per molecule over 100 years relative to C02
Source: IPCC 2001; Forster et al. (2007)
One Part Per Million Parts (ppm)
•
•
•
•
The expression “1 ppm” means a given solute
exists at a concentration of one part per
million parts of the solution.
One-millionth of a gram per gram of sample
solution
One gram of solute per million grams of
sample solution
Notice that ‘gram’ is used just above. This is
because ‘gram’ is used almost exclusively
when the term “parts per million” is used.
One Part Per Million Parts (ppm)
•
•
•
Pollutants in air and water are frequently
measured in parts per million (ppm) or parts per
billion (ppb).
One part per million would mean that there is
one gram of the pollutant in every one million
grams of air.
At ordinary temperature and pressure, air has a
density of 0.00012 gram per cubic centimeter.
Atmospheric Composition
• Air is a mixture of many discrete gases.
• Dry air is composed almost entirely of two
gases: 78% nitrogen and 21% oxygen. These
gases are important for life on Earth but have
no significant effect on weather and climate
changes.
Atmospheric Composition
• The remaining 1 percent of dry air is mostly inert
gas (0.93 percent) plus a number of other gases.
Carbon dioxide (0.038 percent) is an important
constituent of air because it has the ability to
absorb heat energy radiated by Earth and thus to
heat the atmosphere.
• Air includes many gases and particles that vary
significantly from time to time and from place to
place. Important examples include water vapor
and tiny solid and liquid particles.
Atmospheric Composition
• The amount of water vapor in the air varies
considerably, from practically none at all up 4
percent by volume.
• Water vapor is the source of clouds and
precipitation.
• It has the ability to absorb heat energy given off by
Earth as well as some solar energy. Water vapor is
therefore important when we examine the
warming of the atmosphere.
Climate science
IPCC FAQs 1.3 Fig 1
Greenhouses
Naturally produced
Natural-produced greenhouse
gases
(water vapor, carbon dioxide, etc.)
Human-produced greenhouse
gases
(carbon dioxide, methane, etc.)
Human produced
Human produced
Source: NewSci, National Academy of Sciences
Electromagnetic Radiation
• The greenhouse effect has to do with radiation,
which in this context refers to energy carried
by electromagnetic waves, which include such
phenomena as visible light, radio waves, and
infrared radiation.
• All matter with temperatures above absolute
zero emits radiation.
The Electromagnetic Spectrum
(Range of Wavelengths)
wavelength
• Visible light is part of the electromagnetic spectrum.
• Its wavelength is a little less than a millionth of a meter.
Electromagnetic Radiation
• The hotter the substance, the more radiation it
emits, and the shorter the average wavelength of
the radiation emitted.
• The same object can emit and absorb radiation:
when an object emits radiation, it loses energy,
and this has the effect of cooling it; absorption, on
the other hand, heats an object.
• Most solids and liquids absorb much of the
radiation they intercept, and they also emit
radiation rather easily.
Electromagnetic Radiation
•
•
•
A fairly narrow range of wavelengths
constitutes visible light.
The average surface temperature of the sun is
about 10,000 degrees Fahrenheit. It emits much
of its radiation as visible light of about half a
micron.
The earth’s atmosphere’s average temperature is
around 0 degrees Fahrenheit. It emits radiation
at an average wavelength of 15 microns.
The Electromagnetic Spectrum
• All objects at any temperature emit electromagnetic radiation.
• Hot objects radiate infrared (which we feel as heat), and even
hotter ones glow with visible electromagnetic radiation.
Solar Radiation
Solar radiation consists of a range of light at
different wavelengths (spectrum):
• Ultraviolet – largely absorbed by ozone in the
stratosphere (high altitude)
• Visible – sunlight, the easiest to reach the ground
• Infrared (heat) – absorbed and trapped by water
vapor and certain gases, such as carbon dioxide
Solar Radiation
• Visible light is absorbed by the soil, oceans, and
plants.
• A percentage of this infrared
radiation is kept from escaping
back into space by greenhouse gases.
• If greenhouse gases increase in concentration,
more infrared radiation is trapped, and global
temperatures rise.
Absorption Spectra
for Greenhouse Gases
H 2O
Absorption Spectra
for Greenhouse Gases
H 2O
CO2
Absorption Spectra
for Greenhouse Gases
H 2O
CO2
CH4
That means that even if the atmosphere is saturated with water vapor a lot of infrared
still gets through. CO2 and CH4 absorb IR wavelengths that H2O doesn’t.
Plan
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Basic physics of the atmosphere
Glaciers and ice ages
Tools of climate sciences
Natural forcing factors
Human forcing factors
Global climate model and global warming
Climate change and natural disasters
Abrupt climate change
Mitigation and adaptation
How Are Glaciers Formed?
Margin of the Greenland Ice Sheet. http://tvl1.geo.uc.edu/ice/Image/pretty/green.html
The Formation of Glaciers
• Glaciers are formed from layers of snow that
collect in cold areas.
• More snow is collected than is melting each year,
so it piles up.
• The snow on the bottom is compressed into ice.
• Before long there is an expanding field of ice that
covers the ground.
Types of Glaciers
• Continental glaciers (ice sheets)
– 96% of all glaciers
– Found in Antarctica and Greenland
– Covered most of Canada and the northern
USA during the last ice age (up until about
18,000 years ago)
• Mountain or valley glaciers
– Found in the valleys of some mountains
– Rivers of ice
Continental Glaciers
• Continental glaciers are
very large ice sheets that
spread outward in all
directions like pancake
batter.
– Ice caps are very large
continental glaciers.
– Some examples:
Antarctica, Greenland
Ice Sheet on Ellesmere Island, Canada
Photo credit: Geological Survey of Canada
http://www.uwsp.edu/geO/faculty/ritter/images/lithospher
e/glacial/glacier_Ellesmere_GSC.jpg
Mountain Glaciers
• Mountain or valley
glaciers begin in the
mountains at high
altitudes.
• As they thicken, they
flow downhill,
following the shape of
the valley.
Donjek Glacier in the Saint Elias Range, Yukon Territory, Canada.
(Source: Natural Resources Canada. Photograph by Douglas Hodgson.
Copyright Terrain Sciences Division, Geological Survey of Canada.)
http://nsidc.org/glaciers/gallery/donjek_glacier1985.html
What Is an Ice Age?
An "ice age" or, more precisely, "glacial age" is a period of long-term reduction in the temperature of the Earth's surface and atmosphere,
resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers. Within a long-term ice age, individual
pulses of extra cold climate are termed "glacial periods" and intermittent warm periods are called "interglacials".
Ice Ages
• The earth has experienced warm and cold spells.
• Successive years of cold weather constitute an ice
age.
• Glaciers are formed during years of cold weather.
In the past million years,
the earth has seen some
dramatic climate flux.
• 5 major glaciations
• 30 minor glaciations
Recent Climate Change
• The past 15,000 years (the Holocene)
– Warming led to deglaciation, yet temperatures still
fluctuate.
– Several cold periods have punctuated this interglacial
period.
Duan (2009)
Recent Climate Change
• Holocene is the name given to the last 15,000
years or so of the earth's history; the time since
the end of the last major ice age.
• Since then, there have been small-scale climate
shifts—notably the “Little Ice Age” between
about 1200 and 1700 A.D. –but in general, the
Holocene has been a relatively warm period in
between ice ages.
Recent Climate Change
• Several ice ages have caused the northern United
States to be covered with glaciers.
• The last ice age was at its maximum
approximately 25,000 years ago.
• Glaciers 1 to 2 kilometers thick covered the
mountain peaks of New England.
• By 15,000 years ago, the ice had all melted and
retreated, leaving behind a changed landscape.
Plan
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Basic physics of the atmosphere
Glaciers and ice ages
Tools of climate sciences
Natural forcing factors
Human forcing factors
Global climate model and global warming
Climate change and natural disasters
Abrupt climate change
Mitigation and adaptation
Thermometer Records
• Thermometers provide a means of direct
measurement of air temperature. The record
shows average global variations in temperature
for the past 150 years.
• It appears that average temperatures have
increased over the last century.
• Before 1940, the data show a relatively cool
period.
• Modest (0.5o C) global warming substantially
increases the risk of extreme weather events.
Thermometer Record
57
Borehole Temperatures
• Temperatures deep in the ground respond to
changes near the surface. For example, a
sustained heat wave at the surface will cause
warming to propagate slowly downward, taking
roughly 100 years for the perturbation to reach
a depth of 150 m.
• Therefore, the vertical distribution of
temperatures in boreholes from drilling
operations contains information about past air
temperatures.
Borehole Temperatures
• There are thousands of boreholes around the
world, and measurements of temperature with
depth are compared to predicted subsurface
temperatures to infer temperatures.
• This approach has the advantage of measuring
temperature directly. The disadvantage is that
various soils and rocks differ in how they
transfer heat and distort the temperature signal
from the surface, so the precision of
temperature measurement declines rapidly with
depth.
Borehole Temperatures
Reynolds et al. (2010)
Glacier Length
• Quantitative assessments of the size of glaciers
for the past 400 years are available.
• Glaciers flow from areas of snow accumulation
to lower elevations. The dynamics and energy
flow of glacier movement and retreat are well
understood.
• A simple relationship exists between glacier
length and average air temperature.
Glacier Length
Reynolds et al. (2010)
So where
are the proofs of the
climate changes going back
thousands and millions of years ago
that we have described in the
previous slides?
Tools of Climate Sciences
• The problem with accurately assessing climate
change is that historical records of most
meteorological variables go back, at best, only
160 years or so (to about 1850).
• The length of this record is just too small to
describe the range of natural climate variability
over thousand- and million-year periods.
Tools of Climate Sciences
• Also, the data that we do have are not
necessarily consistent, as issues such as changes
in instruments, urbanization, and the advent of
satellite data complicate the matter significantly.
• Yet to understand fully the behavior of the
atmosphere and to anticipate future climate
change, we must somehow discover how climate
has changed over broad expanses of time.
65
Tools of Climate Sciences
• To overcome the lack of direct
measurements, scientists have turned to
indirect measurements to reconstruct past
climates.
• Such proxy data come from natural
recorders of climate such as glacial ice, treegrowth rings, coral reefs, seafloor sediments,
etc.
Tools of Climate Sciences:
Ice Cores
• Ice cores allow us to reconstruct past climates.
Cores taken from Greenland and Antarctic ice
sheets have changed our basic understanding of
how the climate system works.
• Scientists collect samples with a drilling rig like
a small version of an oil drill. A hollow shaft
follows the drill head into the ice, and ice cores
are extracted.
Tools of Climate Sciences:
Ice Cores
• Ice cores provide a detailed record of changing
air temperatures and snowfall. Air bubbles in the
ice record variations in atmospheric
composition.
• Changes in carbon dioxide and methane are
linked to fluctuating temperatures.
• The core information also includes atmospheric
fallout such as windblown dust, volcanic ash,
68
pollen, and modern-day pollution.
National Ice Laboratory
69
Tools of Climate Sciences:
Ice Cores
Ice cores from Antarctica tell us that the
current polar climate is warmer than it has
been at any time in the past 250,000 years.
Tools of Climate Sciences:
Tree Rings
• Every year, trees in temperate regions add a layer
of new wood under the bark.
• Characteristics of each tree ring, such as size and
density, reflect the environmental conditions that
prevailed during the year when the ring formed.
Favorable growth conditions produce a wide ring;
unfavorable ones produce a narrow ring. Trees
growing at the same time in the same region
show similar tree-ring patterns.
Tools of Climate Sciences:
Tree Rings
Annual tree rings indicate not only tree age; the ring width
indicates growth spurts due to warmer temperatures.
Tools of Climate Sciences:
Tree Rings
Tools of Climate Sciences:
Tree Rings
Reynolds et al. (2010)
Tools of Climate Sciences:
Coral Reefs
• Corals are marine animals that form
exoskeletons of calcium carbonate. Colonies of
corals produce reefs in clear, shallow waters.
These animals generate denser layers in their
exoskeletons during months with severe weather
and less-dense layers during months with morebenign weather. As a result, corals develop
discernible annual bands that can be counted to
establish the age of a sample.
Tools of Climate Sciences:
Coral Reefs
• Useful information on past climate conditions is
gathered by analyzing the changing chemistry of
coral reefs with depth.
• The ratio of heavy to light oxygen isotopes in
shells of marine organisms decreases with the
temperature of the surrounding seawater.
• The strontium/calcium ratio in coral skeletons
decreases with temperature.
Tools of Climate Sciences:
Coral Reefs
Fiji coral reefs
Tools of Climate Sciences:
Coral Reefs
Fiji coral reefs
Tools of Climate Sciences:
Coral Reefs
Reynolds et al. (2010)
Tools of Climate Sciences:
Sea Level
• Global sea levels rise and fall depending on the
volume of the ocean basins versus the water in
them.
• Changes in the volume of ocean basins occur
over million of years and are not directly related
to climate (plate tectonics).
• However, changes in water volume may occur
relatively rapidly (in less than 100,000 years) and
depend on global temperatures.
Tools of Climate Sciences:
Seafloor Sediments
• Seafloor sediments are useful recorders of
worldwide climate change because the numbers
and types of organisms living near the sea
surface change with the climate.
82
Comparing Temperature
Reconstructions
83
Plan
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•
Basic physics of the atmosphere
Glaciers and ice ages
Tools of climate sciences
Natural forcing factors
Human forcing factors
Global climate model and global warming
Climate change and natural disasters
Abrupt climate change
Mitigation and adaptation
Causes of Climate Change
• What cause climate change?
• Humans started emitting greenhouse gases only
after the advent of the industrial era, which
began in the late 1700s.
• Given that there are fairly large temperature
fluctuations in the proxy data well before the
1700s, what are the reasons for these climate
changes?
Natural Causes of Climate Change
• The sun is Earth’s main energy source. The sun’s
output is nearly constant, but small changes over an
extended period of time can lead to climate changes.
In addition, small changes in the earth’s orbit affect
how the sun’s energy is distributed across the planet,
giving rise to ice ages and other long-term climate
fluctuations over many thousands of years.
• Our objectives here is to describe how the sun’s
output affects climate change as well as other
natural processes that may influence climate change.
Forcing Factors
• The earth’s temperature is influenced by many
factors. These factors are known as climate
forcings.
• Prediction of the future of Earth’s climate
requires a thorough understanding of these
factors.
• There are two categories of forcing factors:
external (outside of Earth and its atmosphere;
e.g., solar energy) and internal (factors
originated on Earth; e.g., greenhouse gases in
Earth’s atmosphere).
Natural Forcing Factors
• Some of the internal forcing factors are due to
human actions, and others occur naturally.
• All external forcings occur naturally. These
include galactic variations, orbital variations,
and sunspots.
• We will first focus on naturally occurring
forcing factors; that is, external forcings and
natural internal forcings.
External Forcing Factors:
Galactic Variations
•
•
Our sun lies in the Milky Way, a swirling spiral
galaxy of more than 200 billion stars. Every 150
million years or so, our solar system rotates
around the Milky Way.
The quality and quantity of energy reaching
Earth from nearby star systems and from the
gases and dust that pervade interstellar space
vary during this rotation.
External Forcing Factors:
Galactic Variations
•
•
The cyclical fluctuations in this energy are so
long and so uncertain that they obscure the
influence of galactic rotation on Earth’s climate.
Nonetheless, several major climatic events, such
as tropical temperature changes, are separated by
about 150 million years and therefore may be
related to the period of galactic rotation.
Since 1979, when we began taking measurements from space, the data show no
long-term change in total solar energy, even though Earth has been warming.
External Forcing Factors:
Orbital Variations
•
•
Relying on ice cores and sediment cores from the
deep ocean, scientists have learned that the iceage cycles of the past three million years are
caused by periodic oscillations of the earth’s
orbit.
These oscillations do not greatly affect the
amount of sunlight that reaches the earth, but
they do change the distribution of sunlight with
latitude.
External Forcing Factors:
Orbital Variations
• The distribution matters because land and water
absorb and reflect sunlight differently, and the
distribution of land and water is quite different in
the northern and southern hemispheres.
• Ice ages occur when, as a result of orbital
variations, the Arctic regions intercept relatively
little summer sunlight, and ice and snow do not
melt as much.
External Forcing Factors:
Orbital Variations
Orbital variations are characterized by their
eccentricity, obliquity, and precession.
External Forcing Factors:
Orbital Variations (Eccentricity)
The elliptical shape of
Earth’s orbit around the
sun is characterized its
eccentricity, a measure
of the deviation of an
orbit from a perfect
circle. The red line is a
near-circular orbit, and
the blue line is an
elliptical orbit.
Reynolds et al. (2010)
External Forcing Factors:
Orbital Variations (Eccentricity)
Eccentricity: 100,000 years
External Forcing Factors:
Orbital Variations (Tilt)
Earth’s daily rotation
around its own axis has
an angle with respect to
its orbital plane around
the sun. This angle is
called the axial tilt or
obliquity.
Reynolds et al. (2010)
External Forcing Factors:
Orbital Variations
Maximum tilt angle
Present-day tilt angle
Minimum tilt angle
Reynolds et al. (2010)
External Forcing Factors:
Orbital Variations (Tilt)
Obliquity: 41,000 years
External Forcing Factors:
Orbital Variations (Precession)
Earth behaves like a wobbling top,
and its precession, the alignment of
its axis of diurnal with its distance
from the sun, oscillates with an
average period of about 21,000
years.
Due to this wobble, a climatically significant alteration
must take place. The tilt toward Vega means that the
Northern Hemisphere will experience winter when the
earth is farthest from the sun and will experience summer
when the earth is closest to the sun. This coincidence will
result in greater seasonal contrasts.
Reynolds et al. (2010)
Orbital variations vs. Temperature
Precession
(21 ky)
Obliquity
(41 ky)
Eccentricity
(100 ky)
Temperature
1000 900 800 700 600 500 400 300 200 100 0
Age (kya)
External Forcing Factors:
Milankovitch Theory
•
The episodic nature of the earth’s glacial and
interglacial periods within an ice age is caused
primarily by cyclical changes in the earth’s
circumnavigation of the sun.
•
Variations in the earth’s eccentricity, axial tilt,
and precession comprise the three dominant
cycles, collectively known as the Milankovitch
cycles. They are named for Milutin Milankovitch,
the Serbian astronomer who is generally credited
with calculating their magnitude.
External Forcing Factors:
Milankovitch Theory
•
•
Taken together, the variations in these three
cycles create alterations in the seasonality of
solar radiation reaching the earth’s surface.
These times of increased or decreased solar
radiation directly influence the earth’s climate
system, thus impacting the advance and retreat of
the earth’s glaciers.
External Forcing Factors:
Orbital Variations (Good News)
•
Currently the obliquity of Earth’s orbit is
intermediate, its eccentricity is small, and its
processional alignment is such that Earth is
farthest from the sun during June and July.
•
If the orbital variations were the sole forcing
factors, Earth’s climate would remain about the
same for the next 40,000 years or so.
External Forcing Factors:
Each of these
Sunspots
sunspots spanned
an area several
times that of Earth.
External Forcing Factors:
Sunspots
•
•
Periodic changes in the alignment between the
sun’s rotational axis and the gravitational
center of the solar system produce intense
fluctuations in the vertical magnetic fields of
the sun. These divert heat flow from deeper
layers in the sun and generate patches of
fluctuating temperatures on the surface that
manifest as sunspots.
Optical telescopes can be used to detect
sunspots.
External Forcing Factors:
Sunspots
•
•
•
The number of sunspots varies. There is an
approximately 11-year period as well as a lesspredictable longer cycle.
Solar energy reaching Earth increases during the
time of high sunspot activity, therefore
increasing the earth’s surface temperature.
However, the sunspots accounts for only a 0.03degree Celsius variation in global temperature.
•
•
•
•
Internal Forcing Factors:
Plate Tectonics
Orogeny is the process by which tectonic
movements of Earth’s crust or volcanic
activities form mountains.
Mountains disrupt global atmospheric
circulation.
Mountains tend to accumulate ice and snow that
increase the percentage of solar energy reflected
by the earth
The uplifting of mountains also exposes rocks
that undergo chemical weathering and absorb
carbon dioxide.
In the distant past, drifting continents make a big difference in climate over millions of years by changing ice caps at the poles
and by altering ocean currents, which transport heat and cold throughout the ocean depths.
Internal Forcing Factors:
Plate Tectonics
Times of relatively rapid mountain building (say, from 40
million years ago, when the Himalayas and the Sierra
Nevada first arose, until today, as these ranges continue to
uplift) are usually cooler periods.
Last Hope Sound, Chile
Mountain ranges intercept
wind and water vapor,
causing rain shadows,
concentrated rainfall, and
other climatic effects.
Tectonic uplift also
exposes land to chemical
weathering, which
removes carbon dioxide
from the atmosphere.
Reynolds et al. (2010)
Internal Forcing Factors:
Plate Tectonics
•
•
•
•
Epeirogeny is the formation of continents and
ocean basins through deformations of Earth’s
tectonic plates.
The global distribution of landmass determines
the amplitude of glacial-interglacial cycles.
Mid-ocean ridges release large amounts of
energy and greenhouse gases.
The sea level rises and falls as new plate
materials modify the shape of ocean basins.
Internal Forcing Factors:
Volcanism
Volcanic activity
releases carbon
dioxide and water
vapor, which cause
atmosphere warning.
Volcanic ash and
sulfur dioxide gas
from volcanoes reflect
solar radiation,
causing regional or
global cooling.
Reynolds et al. (2010)
Internal Forcing Factors:
Volcanism
The June 1991 eruption of Mount Pinatubo had a
global impact. The sulfur dioxide (SO2 ) in this
cloud – about 22 million tons – combined with
water to form droplets of sulfuric acid, blocking
some of the sunlight from reaching the earth and
thereby cooling temperatures in some regions by
as much as 0.5 degrees C. An eruption the size of
Mount Pinatubo could affect the weather for
several years.
Internal Forcing Factors:
Volcanism
In April 1815, the cataclysmic eruption of
Tambora volcano in Indonesia was the most
powerful eruption in recorded history. Tambora’s
volcanic cloud lowered global temperatures by as
much as 3 degrees C. Even a year after the
eruption, most of the northern hemisphere
experienced sharply cooler temperatures during
the summer months. In parts of Europe and North
America, 1816 was known as “the year without a
summer.”
Internal Forcing Factors:
Natural Albedo
•
•
Albedo is the percentage of solar energy
reflected by Earth. The albedo of various
materials ranges from about 85% for pure,
fresh snow to 5% for asphalt parking lots or
deep, still water. The global average is about
29%.
Deserts and snow-covered regions have a
high albedo, whereas forests have a low
albedo.
Reflection/absorption, Changes in the concentration of greenhouse gases, which occur both
naturally and as a result of human activities, also influence Earth’s climate.
Source: OSTP
Internal Forcing Factors:
Natural Greenhouse Effect
• A significant amount of greenhouse gases in the
atmosphere is due to past natural forcings and is
not the result of human actions.
Internal Forcing Factors:
Natural Greenhouse Effect
• The greenhouse effect plays a critical role in the
earth’s climate.
• The greenhouse effect has to do with radiation,
which in this context refers to energy carried by
electromagnetic waves, which include such
phenomena as visible light, radio waves, and
infrared radiation.
Internal Forcing Factors:
Natural Greenhouse Effect
• Greenhouse gases absorb much of the long
wavelength, the infrared radiation that
passes through them.
• To compensate for the heating that this
absorption causes, greenhouse gases must
also emit radiation, and each layer of the
atmosphere thus emits infrared radiation
upward and downward.
Electromagnetic Radiation
• The hotter the substance, the more radiation it
emits, and the shorter the average wavelength of
the radiation emitted.
• The same object can emit and absorb radiation:
when an object emits radiation, it loses energy,
and this has the effect of cooling it; absorption, on
the other hand, heats an object.
• Most solids and liquids absorb much of the
radiation they intercept, and they also emit
radiation rather easily.
Internal Forcing Factors:
Natural Greenhouse Effect
• The surface of Earth receives radiation from
the atmosphere as well as from the sun.
• Actually, the surface receives more
radiation from the atmosphere than directly
from the sun.
• To balance this extra input of radiation, the
earth must warm up and thereby emit more
radiation itself. This is the essence of the
greenhouse effect.
Source: OSTP
Internal Forcing Factors: Clouds
• The amount of water vapor in the air varies
considerably, from practically none at all to as
much as 4 percent by volume.
• Water vapor is the source of clouds and
precipitation.
• It has the ability to absorb heat energy given off
by Earth as well as some solar energy. Water
vapor is therefore important when we examine
the warming of the atmosphere.
Internal Forcing Factors: Clouds
• Clouds reflect sunlight back to space and also act
like a greenhouse gas by absorbing heat leaving
the earth’s surface.
• Low clouds tend to cool (reflect more energy than
they trap) while high clouds tend to warm (trap
more energy than they reflect).
• The net effect of cloudiness on surface
temperatures depends on how and where the
cloud cover changes. This is one of the largest
uncertainties in projections of future climate
change.
Internal Forcing Factors:
Ocean Currents
One major pattern of ocean currents, the thermohaline circulation
or global consurface belt, involves the northward flow of warm
surface waters from the Caribbean along the Atlantic coast of the
United States. It is known as the Gulf Stream.
Reynolds et al. (2010)
Internal Forcing Factors:
Ocean Currents
• Ocean waters circulate around the globe in
established patterns or currents that derive from
different factors:
- Differences in solar energy received by the equator
and the poles
- Topography of the sea floor and coastal landmasses
- Changes in seawater density
- Rotation of Earth around its axis
- Atmospheric winds
Internal Forcing Factors: Storms
• There are six conditions for major tropical storms:
(i) Sea temperatures must be above 26.5 degrees
Celsius to a depth of 50 m.
(ii) Air temperatures must cool rapidly with the
altitude.
(iii) The relative humidity must be high.
(iv) A location must be more than 500 km away from
the equator.
(v) Vertical wind shears between the sea surface and
the middle atmosphere must be less than 10 m/s.
(vi) A storm must already be brewing.
Summary on Ice Ages
• The timing of the ice ages is essentially the result
of the earth’s orbit.
• But the orbital variations do not explain either
the slow pace of the earth’s descent into the cold
phases of the cycle or the abrupt recovery to
interglacial warmth.
• Large climate swings – from glacial to
interglacial and back – are caused by relatively
small changes in the distribution of sunlight with
latitude.
Summary on Natural Forcings
• Variations in the energy output of the sun
• Variations in Earth’s orbit and tilt
• Plate tectonics
• Changes in atmospheric composition from
volcanoes, biological activity, and weathering
of rocks
• Ocean currents
Plan
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Basic physics of the atmosphere
Glaciers and ice ages
Tools of climate sciences
Natural forcing factors
Human forcing factors
Global climate model and global warming
Climate change and natural disasters
Abrupt climate change
Mitigation and adaptation
Greenhouse Gases
• Many chemical compounds found in the earth’s
atmosphere act as greenhouse gases.
• These gases allow sunlight to enter the
atmosphere freely. When sunlight strikes the
earth’s surface, some of it is reflected back
toward space as infrared radiation (heat).
• Greenhouse gases absorb this infrared radiation
and trap the heat in the atmosphere.
Human Forcings:
Anthropogenic Changes
• Over time, the amount of energy sent from the sun
to the earth’s surface should be about the same as
the amount of energy radiated back into space,
leaving the temperature of the earth’s surface
roughly constant. In other words, over time, there
is a natural balance between positive (warming
factors) and negative (cooling factors) forcings.
• Human actions are introducing forcings into the
climate system which are altering this balance and
thus causing a change in the earth’s temperature.
We characterize these forcings as human.
Human Forcings:
Anthropogenic Changes
• Rising concentration of greenhouse gases from
deforestation, agricultural practices, and fossil-fuel
burning (greenhouse effect; H2O, C02, CH4, CFC,
..)
• Rising concentration of particulate matter from
agricultural burning, cultivation, and fossil-fuel
burning (aerosols; )
• Alteration of Earth’s surface reflectivity by
deforestation and desertification (albedo)
• Increase in high cloudiness, caused by aircraft
contrails (clouds)
Because human actions affecting
climate change originate on Earth, we
can consider human forcing as
internal. Our objective now is to
describe human forcing factors
(anthropogenic factors).
Greenhouse Effect: Water Vapor
• Human-added H2O is not a
big problem – it soon rains
out again.
• Water vapor goes in and out
of the atmosphere very
quickly, in a few days on
average. When there is too
much, it rains out.
• Also, more water vapor
implies more clouds, which
reflect sunlight and reduce
the warming effect.
Greenhouse Effect: CO2
Carbon dioxide (CO2) has both
natural and human sources, but
CO2 levels are increasing,
primarily because of the use of
fossil fuels, deforestation, and
other land-use changes. The
increase in carbon dioxide is the
single-largest climate forcing
contributing to global warming.
Only about 50% of the increased CO2 stays in the atmosphere. The
rest is absorbed by the oceans and other sinks.
Greenhouse Effect: CO2
A percentage of the infrared
radiation emitted by Earth is
kept from escaping back into
space by greenhouse gases.
More CO2 concentration
implies more warming.
More infrared radiation is
trapped; therefore global
temperatures rise.
Carbon dioxide molecules
remain in the air for ~ 120
years.
Greenhouse Effect: CO2
Greenhouse Effect: CH4
• Methane (CH4) is another greenhouse gas with
both human and natural sources. The levels of
methane have risen significantly since preindustrial times due to human activities such as
raising livestock, growing rice, filling landfills,
and using natural gas (which releases methane
when it is extracted and transported).
• Methane dioxide can remain in the air for ~ 12
years.
Greenhouse Effect: CO2 and CH4
Four hundred thousand years
of greenhouse-gas and
temperature history is based
on bubbles trapped in
Antarctic ice.
The time scale has been
expanded for the last 150
years (right side of diagram).
CO2 and CH4 levels are far
above the range of natural
variation in the current
geologic era.
The last time CO2 was > 300
ppm was about 25 Million
year ago.
Hansen,Clim.Change 68, 2005
Greenhouse Effect: N2O and O3
Nitrous oxide (N2O) concentrations
have primarily risen because of
agricultural activities and land-use
changes.
Ozone (O3) forms naturally in the upper
atmosphere, where it creates a
protective shield that intercepts
damaging ultraviolet radiation from the
sun. However, ozone produced near the
earth’s surface via reactions involving
carbon monoxide, hydrocarbons,
nitrogen oxide, and other pollutants is
harmful to both animals and plants and
has a warming effect. The concentration
of O3 in the lower atmosphere is
increasing as a result of human
activities.
Greenhouse Effect: Soot and CFC
• Black carbon particles or “soot,” which is produced
when fossil fuels or vegetation is burned, generally
have a warming effect because they absorb incoming
solar radiation. Black carbon particles settling on snow
or ice are a particularly potent warmer.
• Halocarbons, including chlorofluorocarbons (CFCs),
are chemicals that have been used for a variety of
applications, such as refrigerants. In addition to being
potent greenhouse gases, CFCs also damage the ozone
layer. The production of most CFCs is now banned, so
their concentrations are starting to decline.
Human-Enhanced Albedo
Deforestation and other
changes in land use
modify the amount of
sunlight reflected back to
space from the earth’s
surface. Changes in land
use can lead to positive
and negative climate
forcing locally, but the net
global effect is a slight
cooling.
Reynolds et al. (2010)
Aerosols
• Most aerosols (airborne particles and droplets),
such as sulfate (SO4), cool the planet by reflecting
sunlight back to space. Some aerosols also cool the
earth indirectly by increasing the amount of
sunlight reflected by clouds. Human activities such
as industrial processes produce many kinds of
aerosols. The total cooling that these aerosols
produce is one of the greatest remaining
uncertainties in understanding present and future
climate change.
Aircraft Contrails
Contrails over Paris rooftops
Source: IPCC
Aircraft Contrails
• Jet airplanes flying at high altitudes generate
contrails. These behave like clouds in that they
reflect incoming solar radiation and decrease
daytime temperature maximums but absorb
long-wave radiations from Earth’s surface and
increase nighttime temperature minimums.
• Contrails have the potential to diminish
temperature differentials between day and night.
Aircraft Contrails
• Commercial air traffic was shut down in the
United States for three days on September 11-13,
2001. During this interval, day-night temperature
differentials in the continent United States
jumped by 1.8o C above during the 3-day periods
immediately before or after (Travis et al., 2002).
• The change was significantly greater in the
regions where contrails are most abundant.
IPCC SynRep
History and Projections
Carbon Intensity (tC/toe)
1.2
Carbon Intensity of:
1.1
Wood = 1.25
Coal = 1.08
1.0
0.9
Oil = 0.84
0.8
0.7
Gas = 0.64
0.6
0.5
1900
0.4
1920
1940
1960
1980
2000
2020
2040 2050
Source: National Academy of Engineering, 1997
Human Forcings: Summary
Global Warming
source: http://www.environment.sa.gov.au/sustainability
Human Forcings: Summary
Plan
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Basic physics of the atmosphere
Glaciers and ice ages
Tools of climate sciences
Natural forcing factors
Human forcing factors
Global climate model and global warming
Climate change and natural disasters
Abrupt climate change
Mitigation and adaptation
The models project possible climates based on scenarios that cover a range of assumptions
about global population, greenhouse gas emissions, technologies, fuel sources, etc. The
model results provide a range of possible impacts based on these assumptions.
• A climate system includes the atmosphere, hydrosphere, lithosphere, biosphere, and
cryosphere (cryosphere refers to the ice and snow that exist at the Earth’s surface).
• The climate system involves the exchanges of energy and moisture that occur among
the five spheres.
Global Climate Model (GCM)
• Climate models are computer-based simulations
that use mathematical formulas to re-create the
chemical and physical processes that drive
Earth’s climate. To “run” a model, scientists
divide the planet into a three-dimensional grid,
apply the basic equations, and evaluate the
results.
• Basic equations are conservation of momentum
(also known as Newton’s second law; force =
mass x acceleration), conservation of mass, and
heat flows between systems.
Global Climate Model (GCM)
• Models are tested to see if they generate past
known climate patterns.
• Atmospheric models calculate winds, heat
transfer, radiation, relative humidity, and
surface hydrology within each grid and evaluate
interactions with neighboring points. Climate
models use quantitative methods to simulate the
interactions of the atmosphere, oceans, land
surface, and ice.
http://www.ipcc.ch/
SERS Emission Scenarios
• A1 - a future world of very rapid economic
growth, global population that peaks in midcentury and declines thereafter, and the rapid
introduction of new and more-efficient
technologies. Three subgroups: fossil-intensive
(A1FI), non-fossil energy sources (A1T), or a
balance across all sources (A1B).
• A2 - A very heterogeneous world. The underlying
theme is that of strengthening regional cultural
identities, with an emphasis on family values and
local traditions, high population growth, and less
concern for rapid economic development.
SERS Emission Scenarios
• B1 - a convergent world
with the same global
population, which peaks in
mid-century and declines
thereafter, as in the A1
storyline.
• B2 - a world in which the
emphasis is on local
solutions to economic,
social, and environmental
sustainability.
Prediction of Temperature Increase
Source: IPCC
Prediction of Sea-Level Rise
Source: IPCC
Other Modeling Results
Unless measures are taken to reduce greenhousegas production,
• Rainfall will continue to become
concentrated in increasingly heavy but lessfrequent events.
• The incidence, intensity, and duration of
both floods and droughts will increase.
• The intensity of hurricanes will continue to
increase, though their frequency may
dwindle.
Where Has the Ice Gone?
Sunday Times, 2007
Some Issues with GCM
• Uncertainties on climate system sensitivity to
clouds, water vapor, and snow.
• Need to improve understanding of whether and
how human impacts may alter natural climate
variability.
• Uncertainties on abrupt climate changes.
• Insufficient understanding of effects of
anthropogenic forcings on extreme weather
events.
• Limited capabilities at regional scales.
Human Attribution
• Recent modeling attempts have
tried to isolate the impact of
anthropogenic versus natural
forcing.
• Continued greenhouse gase
emissions at or above current
rates can cause further warming
and induce many changes in the
global climate system during the
21st century that would very
likely be larger than those
observed during the 20th
century.”
Warming of the climate system is clear. Human-caused warming over last 40 years has is visible.
Source: IPCC
Human Attribution
• Forecasting the future is a very difficult and dangerous
exercise; erroneous forecasts can have catastrophic
effects.
• In 1997, experts claimed that oil prices would neither
fall below $15/barrel nor increase to more than
$25/barrel, at least until the demand exceeded 80
million barrels of oil production per day.
• However, by the end of 1998, oil prices had plunged to
as low as $10/barrel, resulting in huge layoffs in the oil
and gas industry. The low oil price was due to a 1
percent overproduction, and its increase to $26/barrel
in late 1999 was related to about a 1.5 percent
reduction in world production.
Human Attribution
• In the context of reducing human forcings, forecasting
future challenges does not have similar consequences.
• If the forecast global climate model (GCM) turns out
to be too conservative, we will have at least started
reducing human responsibility for climate change.
• If the GCM forecast is overstated and the whole
exercise of reducing human forcings was futile, we
will at least have taken our responsibility for future
generations seriously, and we will be better prepared
for peak-fossil fuels.
Scientists are still working on the GCM. The IPCC’s 5 th report is planned for 2013-2014. Climate
models are being improved, more data is being collected.
2009 Carbon Emissions Fall
Smaller Than Expected
• Carbon emissions fell in 2009 due to the recession
- but not by as much as predicted, suggesting the
fast upward trend will soon be resumed.
• Those are the key findings from an analysis of
2009 emissions data issued in the journal Nature
Geoscience a week before the UN climate summit
opens.
• Industrialised nations saw big falls in emissions but major developing countries saw a continued
rise.
Environment correspondent, BBC News,
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Basic physics of the atmosphere
Glaciers and ice ages
Tools of climate sciences
Natural forcing factors
Human forcing factors
Global climate model and global warming
Climate change and natural disasters
Abrupt climate change
Mitigation and adaptation
Extreme Weather Events:
Mt. Kilimanjaro
Extreme Weather Events:
Drought: Lake Chad
Adapted from Bloom (2010)
Extreme Weather Events:
2005 Hurricane Katrina Crossing the
Gulf of Mexico
Extreme Weather Events:
Summer 2003 Temperatures
From NASA’s
Moderate
Resolution Imaging
Spectrometer,
courtesy of Reto
Stöckli
Climateprediction.net
U.K.: Train rails buckle
Germany: Lowest river
levels this century
France: >14,000
deaths
Switzerland: Melting
glaciers, avalanches
Portugal: Forest fires
2003 European Heat Wave
Extreme Weather Events:
Pakistan Floods July-August 2010
www.pitt.edu/~super/
Climate Change and Natural
Disasters
•
•
Climate change is predicted to have a range of
serious consequences, some of which will have
impact over the longer term, like sea-level rise,
while some have immediate impacts, such as
intense rain and flooding.
The latter are obvious and easily grasped by the
public at large, thanks to the Internet, which
makes the images of these events available to
the four corners of the globe in a matter of
minutes or hours.
Climate Change and Natural
Disasters
•
•
Recent examples of extreme weather events
include the 2010 Pakistan flood (more than
2,000 deaths), the 2005 Hurricane Katrina
(more than 1,600 deaths), the summer 2003
heat wave in western Europe (more than
22,000 deaths).
The question about these extreme weather
events is whether they are caused by natural
climate forcings or human forcings.
In other words, can the global climate model
(GCM) shed light on possible links between
these events and anthropogenic greenhouse
gas emissions?
Climate Change and Natural
Disasters
Before we attempt to answer this question, let us
group extreme weather events into three
categories:
•
•
•
Extreme temperature highs – heat waves
High levels of precipitation and associated
flooding; lack of precipitation and associated
drought
Storms, including windstorms, hurricanes, etc.
Climate Change and Natural
Disasters: Heat Waves
•
•
•
Increasing high-temperature extremes are
among the easiest to identify.
The GCM suggests that cold and warm
extreme temperatures are rising globally. In
Europe, daily high temperatures are rising
more in summer than in winter, and warm
extreme temperatures are rising twice as fast as
cold extremes are warming.
There are fewer deaths from cold and more
from heat.
http://www.ipcc.ch/
Climate Change and Natural
Disasters: Heat Waves
•
•
The magnitude of the rise in mean temperatures
and the existence of severe extremes, such as the
European heat wave in the summer of 2003, are
inconsistent with natural cycles, and the most
plausible explanation is climate change.
These changes are consistent with the modeled
influence of anthropogenic greenhouse gases,
enhancing confidence that the phenomenon is
indeed largely attributable to human forcings.
There will always be natural variability, and some places and some years will be warmer or cooler than average. In general, however, summers will
get hotter, not only because of higher temperatures but also because humidities will increase. That means that heat waves, like the one that killed
over 20,000 people in Europe in 2003, will become more common. On the plus side, winters will be warmer in many places, reducing heating bills.
And the number of days with frosts is likely to decrease.
Climate Change and Natural
Disasters: Heat Waves
•
The analysis of Stott et al. (2004), suggests that it
is very likely that human forcings have already at
least doubled the risk of the 2003 heat wave
occurring again.
27
June-July-August temperature in France (°C)
26
25
24
23
22
21
20
19
18
17
16
1900
1920
1940
1960 1980
2000
2020
2040
2060
2080
2100
Climate Change and Natural
Disasters: Floods
•
•
•
Providing the link between climate change and
precipitation levels, and the resulting flooding or
contribution to drought, is more difficult than for
heat waves.
Precipitation and flooding are periodic
phenomena, making patterns in extreme events
harder to model.
Recent global-climate-modeling attempts are
capable of isolating the impact of anthropogenic
versus “natural forcing.” Isolating water-vapor
forcing may shed some light here.
Climate Change and Natural
Disasters: Droughts
•
•
•
Drought is very easy to recognize, but only
recent global climate models are able to
distinguish climate-change trends from natural
variability.
Precipitation changes imply droughts.
Droughts are cyclical, and severe events can
be expected every 10 years, with very severe
events recurring, on average, every 40 years.
Climate Change and Natural
Disasters: Droughts
•
The North Atlantic Oscillation is strongly
influential. When in its negative phase, as it is
now, it causes dryer winter weather and hence
less recharging of rivers and reservoirs,
exacerbating summer droughts.
•
Recent studies suggest that the land area of the
world affected by severe drought has doubled
since the early 1970s. Half of this trend is
estimated to be due to changes in precipitation,
and half due to warmer weather.
Climate Change and Natural
Disasters: Windstorms
•
•
•
While trends for temperature and precipitation are
somewhat more clear, the picture for the intensity of
windstorms is just emerging, and results seem to vary
in different regions of the world.
Recent studies indicate that the increased frequency of
storms is still probably due to natural cyclical variation.
Measurements show a noticeable rise in sea-surface
temperatures, which are a main determinant of the
strength of storms as well as the total column water
vapor and the available convective potential energy
(Trenberth, 2005).
Climate change and Natural
Disasters: Hurricanes
•
•
•
•
Studies show that the total number of
hurricanes has not changed.
However, the intensity of hurricanes has
increased (more category 4 and 5 hurricanes
and cyclones).
This change is probably due to higher seasurface temperatures (more energy).
It is difficult to know whether this trend will
continue.
Plan
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Basic physics of the atmosphere
Glaciers and ice ages
Tools of climate sciences
Natural forcing factors
Human forcing factors
Global climate model and global warming
Climate change and natural disasters
Abrupt climate change
Mitigation and adaptation
Abrupt Climate Change
• Some large natural climate changes have occurred
abruptly.
• In some instances, the average global temperature
has risen or fallen > 8º C in less than 10 years, and
at least one in as few as five years. An increase of
6° C in this century would be considered an
abrupt climate change.
• The trigger for the abrupt temperature rises is not
well understood, but it probably involves a
catastrophic release of methane and carbon
dioxide.
Younger Dryas
The best-known abrupt climate change is
called the Younger Dryas. It is also the beststudied abrupt climate change. It began
abruptly about 12,800 years ago and ended
even more suddenly about 11,600 years ago.
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Climate Change and Human
History
Medieval Warm Period
The above graphic, derived from sampling of an ice core in Greenland, shows a historical tendency for particular
regions to experience periods of abrupt cooling within periods of general warming.
R.B. Alley, from The Two Mile Time Machine, 2000
Abrupt Younger Dryas
Climate Change
The Younger Dryas at
About 12 kyBP
Source: Younger Dryas, Oceanographic Cruise off N. NovaScotia-July10Kybp
The Younger Dryas
• The Younger Dryas saw a rapid return to glacial
conditions in the higher latitudes of the Northern
Hemisphere between 12,800 and 11,600 years ago,
in sharp contrast to the warming of the preceding
interstadial deglaciation.
• Each of the transitions occurred over a period of a
decade or so.
The Younger Dryas
• The mean temperature in the UK dropped to
approximately -5° C, and periglacial conditions
prevailed in lowland areas, while icefields and
glaciers formed in upland areas.
• Nothing of the size, extent, or rapidity of this
period of abrupt climate change has been
experienced since.
The Younger Dryas
Younger Dryas Cold Period
Pre-Younger Dryas Warm
Glacial Sediments
Source: Younger Dryas, Oceanographic Cruise off N. NovaScotia-July10Kybp
Younger Dryas
Oceanographic
Cruise off N. Nova
Scotia - July 10
Kybp
Source: Younger Dryas, Oceanographic Cruise off N. NovaScotia-July10Kybp
28,000 years ago
Today
Reynolds et al. (2010)
Plan
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Basic physics of the atmosphere
Glaciers and ice ages
Tools of climate sciences
Natural forcing factors
Human forcing factors
Global climate model and global warming
Climate change and natural disasters
Abrupt climate change
Mitigation and adaptation
Mitigation and Adaptation
• Mitigation here refers to measures to reduce the
pace and magnitude of the changes in global
climate being caused by human activities.
• Adaptation here means measures to reduce the
adverse impacts on human well-being resulting
from the changes in climate that do occur.
• Mitigation and adaptation are both very
important.
Mitigation
• Reduce energy needs and encourage recycling.
• Accelerate the development of alternate energy
sources with very little or no carbon (wind,
geothermal, hydro, solar, biomass, etc.); e.g.,
increase solar capacity 1,000 times.
• Capture and sequestrate CO2 when fossil fuels are
converted or burned.
• Halt deforestation; e.g., increase forest planting.
• Accelerate the development of the fuel efficiency of
cars, trucks, buses, trains, and aircraft; e.g., double
car fuel efficiency from 30 miles per gallon to 60
miles per gallon.
Mitigation
• Increasing the atmosphere’s reflectivity by
injecting reflecting particles into the stratosphere
might be affordable (& reversible), but would be
likely to deplete stratospheric ozone.
• Placing reflecting materials or mirrors in Earth
orbit (or at the Lagrangian equilibration point
between the Sun and the Earth) would be
staggeringly expensive.
• Develop technological ways of cleaning CO2 out of
the air?
• Add your own recommendations (no giant space
umbrella).
Adaptation
• Avoid new ocean coastal development. Ocean coastal
properties cannot be expected to survive routine future
hurricanes.
• Avoid structures elevated below 28 feet above sea level.
These structures are at risk of destruction by a storm
surge.
• Locate new development higher than 110 feet above sea
level because 80 feet of sea-level rise is likely. Also, as
aquifer withdrawal continues to negatively impact
irrigated landforms and sea levels rise due to icecap melt
and/or water/thermal expansion, these storm surges will
ride higher over time.
Adaptation
• Increase the use of light personal electromagnetic
flying rigs.
• Increase the use of electromagnetic power trains
for transit shipment and transport options.
• Add your own regulations.
2009 Carbon Emissions Fall
Smaller Than Expected
• Carbon emissions fell in 2009 due to the recession
- but not by as much as predicted, suggesting the
fast upward trend will soon be resumed.
• Those are the key findings from an analysis of
2009 emissions data issued in the journal Nature
Geoscience a week before the UN climate summit
opens.
• Industrialised nations saw big falls in emissions but major developing countries saw a continued
rise.
Environment correspondent, BBC News,
CO2 Sequestration
• The aim of CO2 sequestration in sub-seabed
geological formations is: permanent isolation.
The major steps are: (i) CO2 separation, capture,
and compression; (ii) Transport to injection site;
(iii) Injection into peep geologic formation (> 2500
feet); (iv) Measurement, monitoring, and
verification.
• CO2 requires better seals than other fluids for a
particular column (flat-lying strata, no faults, no
folds).
CO2 Sequestration
• To date, no leakage has been detected. However,
the study has shown that after the carbon dioxide is
sequestered, the chemical properties of the water
and the dissolved inorganic carbon change.
Changes include: (i) sharp drops in pH, (ii)
pronounced increases in alkalinity, (ii) significant
shifts in the isotopic compositions. Also, it has
shown that the CO2 can degrade carbonate
substances in the rock.
Steps in the CO2-Sequestration
Process
Image copyrighted by Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC)
CO2 Sequestration
Problems (1)
• Over the last 150 years, global average
temperatures have (a) cooled about 1.5 degrees
Celsius, (b) cooled about 0.5 degrees Celsius, (c)
not changed, (d) warmed by 0.5 degrees Celsius,
(e) warmed by 2.1 degrees Celsius. Select one
answer.
• Which one of the following measurements serves
as proxy measurements of temperature? (a) tree
rings, (b) relative amount of oxygen isotopes in
water, (c) relative amount of oxygen isotopes in
marine shells.
Problems (2)
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Which of the following factors contributes to
climate variability? (i) volcanoes, (ii) solar
luminosity, (iii) cloud cover, (iv) greenhouse
gases, (v) all of the above
As the eccentricity of Earth’s orbit increases, (a)
the amount of solar energy reaching Earth will
fluctuate more from summer to winter, (b) the
Arctic ice cap will completely melt, (c) the
Northern Hemisphere will retreat into darkness.
What is a proxy measurement?
Problems (3)
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List three greenhouse gases associated with natural
forcings. List three human-produced greenhouse
gases.
Preindustrial concentration of carbon dioxide in
Earth’s atmosphere was about (a) 200 ppm, (b) 270
ppm, (c) 430 ppm, (d) 550 ppm, (e) 970 ppm.
What is GCM in the context of climate change?
What is CO2 sequestration?
Why is human-added H2O in the earth’s
atmosphere not a major problem as far as global
warming is concerned?
Problems (4)
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Describe three evidences of a warming world.
List three natural forcing factors that affect
global climate change.
List four human forcing factors that affect global
climate.
List two causes of the CO2 build-up in the
Earth’s atmosphere in the last 150 years.
Problems (5)
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List four sources of anthropogenic methane
(CH4) in the atmosphere.
List two sources of anthropogenic soot in the
atmosphere.
Here are five major climate forcings: (i) the
sun’s output, (2) Earth’s orbit, (3) drifting
continents, (4) volcanic eruptions, (5)
greenhouse gases. Classify them as internal or
external and as natural or anthropogenic.
Problems (6)
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Based on direct and proxy measurements, the earth
is getting warmer. The temperature has been well
above normal for more than 25 years. (i) Define
the normal temperature. (ii) Define the range of
this increase by various measurements. (iii)
Compare the warming of land and oceans. (iv)
Compare the warming in higher latitudes as
opposed to warming in the tropics.
Cloud covers (a) tend to warm Earth more than
they cool it, (b) absorb electromagnetic radiation
emitted from Earth’s surface.
Problems (7)
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Scientists learn about past climate conditions
from such things as tree ring analysis, fossil
evidence, and analysis of patterns and chemical
compositions of coral skeletons and ice cores.
Are these direct temperature measurements or
proxy temperature measurements, or neither of
the above? Explain.
What does IPCC stand for in the context of
climate change? What is the difference
between IPCC and the World Meteorological
Organization (WMO). What are the products
of IPCC?
Problems (8)
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The main tools for both past and present
climate analyses are computer climate
models. Climate models simulate the climate
system with a 3-dimensional grid that extends
through the land, ocean, and atmosphere. The
models project possible climates based on
scenarios that cover a range of assumptions.
List four of these assumptions.
Problems (9)
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A common critique of climate predictions is, “If
weather model forecasts aren’t reliable more
than a week out, how can models predict climate
decades in the future?” (i) Propose an
explanation of this critique. (ii) How can we
establish confidence in our climate models?
How can we use climate models to differentiate
the effects of natural forcings and those of
anthropogenic forcings on global temperatures?