Transcript Lecture 13:Climate Change

CLIMATE CHANGE
READINGS:
FREEMAN, 2005
Chapter 54
Pages 1259-1261
CLIMATE CHANGE
• Climate refers to the long-term weather
conditions of a particular place; a community,
biome or the biosphere.
• When the weather condition is temperature
and the place is the biosphere (ecosphere),
then the change is called global warming.
• When changes go beyond warming to the
causes and effects of warming, then the
change is called global change.
• One of the earliest predictions of global
change related increase in atmospheric
carbon dioxide to increased warming.
The Carbon Dioxide Question
• Over 110 years ago (1896), a Swedish
chemist Svante August Arrhenius recognized
that carbon dioxide allows short-wavelength
solar radiation to penetrate the atmosphere
but traps this energy when it is reradiated
back from earth at higher wavelengths.
• He concluded that the more carbon dioxide,
the more warming.
• It was postulated that this had happened on
Mars and Venus, but would it happen on
earth?
Seeking Answers to the
Carbon Dioxide Question
• In 1956 Roger Revelle and Hans Suess,
geochemists at the Scripps Institute, saw a
need to measure carbon dioxide in the air so
as to get “a clearer understanding of the
probable climatic effects of the predicted
great industrial production over the next 50
years.”
• They realized the necessity to set up
monitoring equipment far from local sources
and sinks of CO2 and hired Charles David
Keeling for the project.
Carbon Dioxide Is Increasing in the
Atmosphere (Mauna Loa)
• Unambiguous data on
changes in atmospheric
CO2 has been
available only since
1958 when a monitoring
station was established
on Mauna Loa.
• Since that time, CO2
concentration has
increased from around
315 ppm to 380 ppm in
2006 or about 1.35 ppm
per year.
ppm is parts per million.
Carbon Dioxide Is Increasing in the
Atmosphere (Antarctica Ice Bubbles)
• The half-centuary record at
Mauna Loa is convincing but
too short to address
concerns about the effects of
fossil fuel burning.
• A long term perspective has
been gained from measuring
CO2 in air bubbles trapped
in ice cores.
• The records for the last
1,000 years show an
average of around 280 ppm
up until the beginning of the
industrial revolution in the
mid to late 1800’s.
ppm is parts per million.
Carbon Dioxide Is Increasing in the
Atmosphere
• Measures of CO2
concentration from a variety
of sites confirm a dramatic
increase associated with the
burning of fossil fuels.
• There is no question that the
atmospheric concentration of
this gas is increasing, but
what is the greenhouse effect
that Arrhenius spoke of over
100 years ago?
The Greenhouse Effect
• The term greenhouse
effect draws an analogy
between the temperature
holding capacity of a
greenhouse (glasshouse)
and the earth’s
atmosphere.
• Just as a glasshouse holds
some of the radiant (heat)
energy of the sun, so does
the earth’s atmosphere.
The Greenhouse Effect: Heat
Trapping By Atmosphere (I)
• The physics of the heat trapping capacity of
the atmosphere is well known.
• A simplified accounting is as follows:
30% of incoming solar energy is reflected
back into space either from clouds, particles
in atmosphere or earth surface.
70% is absorbed and reemitted at infrared
wavelengths by the atmosphere and the
earth’s surface.
The Greenhouse Effect: Heat
Trapping By Atmosphere (II)
• As seen from space, the earth radiates
energy of a body at -18 Co. Thus, the average
temperature at the earth’s surface is around
33 degrees higher than it would be without
trapping.
• Of the energy radiated from earth, nearly
30% drives atmospheric processes and the
remainder is absorbed by greenhouse gases
before being reemitted out into space.
Greenhouse Gases
• Five greenhouse
gases absorb
infrared radiation
thus retain heat.
• Sulfur dioxide has a
negative greenhouse
effect by reflecting
light.
GAS
EFFECT
CO2
+
CH4
+
N2O
+
SO2
CFCl3 & CF2Cl2
+
O3
+
The Mass of Greenhouse Gases in
the Atmosphere
GAS
g x 1015
CO2
2,800
CH4
4.96
N2O
2.42
CFCl3 &
CF2Cl2
0.0319
• The most abundant
greenhouse gas in
the atmosphere is
carbon dioxide.
• Methane is second
and has increased
at a rate of 1% per
year; much more
rapidly than CO2.
What is the Predicted Temperature
Increase Based on Increase in CO2?
• When CO2 was 280 ppm in 1860’s the
atmosphere is estimated to have trapped 153
watts per square meter of outgoing radiation.
• At 370 ppm in the 1990’s the increased CO2
would have trapped an additional 2.1 watts
per square meter resulting in a rise in
temperature of 0.6 Co.
• By 2050, temperatures could be 1-5 Co higher
with over 550 ppm of CO2.
Global Records of
Temperature Change
• Reliable records of
temperatures have
been made since the
mid 1800’s.
• Here is a global record
of temperature change,
past and projected.
• Projected change is
based on different
assumptions of CO2
emissions.
Continental Records of
Climate Change
• Remember that climate refers to
prevailing long-term weather
conditions in a particular region.
• Here is a rainfall and
temperature record for Australia
since the late 1800’s.
• Note the temperature increase
since the late 1800’s
corresponds to a rise of about
0.9 Co.
• Also most of the rise was since
the 1940’s.
Human Activities That
Increased Atmospheric CO2
• Fossil fuel use and
land use, particularly
forest destruction,
contribute to CO2
emissions.
• Both have increased
dramatically since
the late 1940’a.
• See Freeman
(2005) Figure
54.18a.
Per Person Energy Use
Temperature Change, CO2
PPM and Carbon Emissions
for Past 1,000 Years
• Note that carbon
emissions prior to the
mid 1800’s were
primarily from clearing
the land.
• Notice how all three
have increased
dramatically since the
industrial revolution.
% of World Carbon Emissions
from Fossil Fuels by Country
Country
%
Country
%
U.S.
24
Canada
2
China
14
U.K.
2
Russia
6
S. Korea
2
Japan
5
Italy
2
India
5
France
2
Germany
4
Mexico
2
Per Person of World Carbon
Emissions from Fossil Fuels
Country Metric Tons
U. S.
5.4
Canada
4.2
Germany
2.8
Russia
2.7
Japan
2.5
U. K.
2.5
Country Metric Tons
S. Korea
2.2
Italy
2.0
France
1.7
Mexico
1.1
China
0.7
India
0.3
World Carbon Emissions from
Fossil Fuels
• U. S., China, Russia, Japan and India, are
responsible for over half of C emissions (54%).
• The United States emit nearly one fourth (24%) of
the world total.
• U.S. citizens on the average puts 5.4 metric tons or
11,905 pounds of CO2 into the air each year!!!!
• The most rapid growth in C emissions is among
developing nations.
• “Prosperity and fertility lie at the root of global
warming.”
Carbon Emissions from
Deforestation
• Deforestation of tropical
forests in particular
accounts for about 20% of
world carbon emissions.
• Burning adds CO2 rapidly
to the air; decomposition
of unburned plant material
adds it over longer time
periods.
The Geography of Carbon
Emissions from Deforestation
• Tropical forests are
the targets of most
of the world’s land
use changes.
• Deforestation is
most active in
Central and South
America.
A Highly Simplified Global
Carbon Cycle
• Freeman (2005,Figure
54.17) provides a highly
simplified version of sources
and sinks of “humaninduced” carbon addition to
the biosphere.
• Sources are fossil fuel
burning and deforestation.
• Sinks are ocean, land and
atmosphere.
• In this version, C is being
added to the atmosphere at
a rate of 3.9 gigatons per
year.
1 gigaton = 106 grams
= 2,004.6 pounds
Another Version of the Global
Carbon Cycle
• This version of the C cycle shows
that the ocean is also releasing
CO2 to the atmosphere, but uptake
by physical exchange (absorption)
is greater than release.
• The excess carbon dioxide that
enters the ocean each year results
in an increase in pH.
• Studies indicate that the ocean has
absorbed fully half of all the fossil
C released to the atmosphere
since the beginning of the
Industrial Revolution.
Dangers of Ocean Acidification
• pH of pristine seawater is slightly
basic (8 to 8.3).
• Dissolved CO2 combines with H2O
to produce carbonic acid,
bicarbonate ions, carbonate ions
and hydrogen ions. Over all the
chemistry of lower pH reduces
carbonate ions that are important for
making shells of coral and many
important zooplankton.
• These species of zooplankton are
important food sources for marine
fish and mammals, including some
species of whales.
Consequences of Global
Warming
• Global warming has the potential for direct impact both on
human well being and natural ecosystems.
• The most direct threats to humans involve rising sea levels,
drought in already dry areas, increasing violent storms,
floods and hurricanes and spread of cholera, malaria, West
Nile virus, encephalitis, hantavirus and other less well
known “fever” diseases.
• The beginnings of changes in plant and animal distribution
(species ranges) have already been observed and are
ongoing. Species that can’t keep up with these changes
will be lost. The community structures of our National
Parks and Local Preserves will be altered.
Ice Cap of Antarctica and
Rising Sea Level
• Three fourths of the earth’s
freshwater is tied up in the
Antarctic and Arctic ice
caps.
• Melting of these caps
results in an increase in sea
level.
• The Antarctic cap is
shrinking but at a rate that
is predicted to increase sea
level at a rate of 2 cm per
year.
Ice Cap of Arctic and Rising
Sea Level
• The Artic cap has decreased in size since
the first satellite were taken in the 1970”s.
• Melting of sea ice has been the most
dramatic, but it does not rise sea levels as
glaciers do.
• Artic glaciers are shrinking at an
increasing rate and contribute to a rise in
sea level of only 0.2 cm per decade.
• The Greenland Ice Sheet appears to be
melting, but more research is required for
predictions of what this means for rising
sea level.
Drought, Storms and Hurricanes
• Global warming will have a
direct impact on the
circulation of the
atmosphere and ocean.
• The dry regions of the
earth will become dryer.
• Hurricanes will become
more frequent and
stronger.
• Violent storms on land will
result in more flooding and
tornados.
Health Risks of Global Warming
• As the world warms, disease
carrying mosquitoes will
disperse into areas that were
once too cold for maintaining
populations.
• There is already evidence of
cases of West Nile virus and
malaria in areas of the US
where the disease was
unknown.
• Increased flooding favors water
born diseases such as cholera.
• Increased drought frequency in
the southwest will likely increase
outbreaks of hantavirus that is a
rodent-borne disease.
Earlier Springs and Timing of
Reproduction, Migration and
Growing Season
• Hundreds of mammal, bird,
amphibian, insect, plant and
other species have undergone
changes in population size and
distribution in ways expected
from warming temperatures.
• These changes disrupt
established population
interactions and weaken links in
food chains and food webs.
Earlier Flowering Time for a
Native Legume Genus
Impact of Global Warming on
Dispersal of Tree Species
• Climate change may require tree species in
temperate regions to move north at a rate of
10-53 km/decade.
• Estimated rates of tree dispersal during last
ice age were 1-54 km/decade.
• Recent forest fragmentation inhibits tree
dispersal.
• The project rate of climate change is faster
that tree species can disperse.
Impact of Global Warming on
Forest Communities
• Potential forested areas in the US decrease
by 11%.
• Northeast mixed forests decrease by 72%.
• Alpine ecosystems in western mountains all
but disappear.
• Eastern hardwood forests decrease an
average of 34%.
• Oak-hickory forests expand 34%.
• Oak-pine forests expand 290%.
Proposed Ways of Slowing
Increases in Atmospheric CO2
• Photosynthesis removes CO2 from the
atmosphere. Early speculation thought that
plants could be counted on to draw down
more CO2 the atmosphere.
• This stimulated research on growing plants in
elevated carbon dioxide environments.
• Experiments have now been conducted for
several decades and cast doubts that
increased CO levels necessarily translate into
increased net primary production and that
plants will serve as sinks for increasing levels
of atmospheric carbon dioxide.
Plant Life in a CO2-Rich World
• Investigation plant and
ecosystem responses to
enriched carbon dioxide
atmospheres has greatly
increased our understanding
of C cycling.
• The evidence is clear that
while plants do respond to
increased atmospheric
carbon dioxide levels; the
response is mainly in the first
few years of growth and is
not enough to solve the
carbon dioxide problem.
Can Marine Phytoplankton
Solve the Carbon Problem?
•
•
•
•
Marine diatoms and dinoflagellates
play an important role in regulating
the earth’s climate by removing
dissolved CO2 and carbonates from
the ocean.
In fact, their photosynthetic activity is
about the same as land plants (4050 Gt/year).
However, under even the most
optimistic conditions of adding iron*
as a fertilizer, they could remove
only about 15% of current CO2
release.
These gains are not worth the risks
of the unpredictable consequences
of altering natural marine
ecosystems.
* See Figure 54.5 in Freeman (2005).
Solutions to the Carbon
Dioxide Problem
• A number of solutions exist to slow the
addition of carbon dioxide to the
atmosphere. They fall into five categories:
-- end-user efficiency and conservation
-- power generation
-- carbon capture and storage
-- alternative energy capture
-- agriculture and forestry
End-User Efficiency and
Conservation
• Increase fuel
economy cars from
30 to 60 mpg.
• Reduce miles driven
from average of
10,000 to 5,000
miles.
• Cut energy use in
homes, offices and
stores by 25%.
Power Generation
• Raise efficiency of
large coal-fired
plants from 40 to 60
percent.
• Replace old coalfired plants with gasfired plants.
Carbon Capture and Storage
• Install carbon capture
and storage (CCS)
facilities at coal-fired
power plants.
• Use CCS in coal plants
to produce hydrogen for
fuel cell vehicles.
• Use CCs at coal to
syngas facilities.
Alternative Energy Sources
• Expand solar cell and
solar-thermal systems
by increasing efficiency
and lowering cost.
• Expand wind turbine
farms in the Great
Plains states.
• Supplement corn with
switchgrass farms to
produce ethanol.
Agriculture and Forestry
• Expanding no-plow tillage to
100% of cropland would
reduce fuel consumption for
plowing and fertilizer
production.
• End conversion of natural
ecosystems to farmland and
clear cuts. Take past clear
cuts and reforest. Do the
same with abandoned
farmland through grassland
restoration.
CLIMATE CHANGE
READINGS:
FREEMAN, 2005
Chapter 54
Pages 1259-1261