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

• 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.

GAS g x 1015

CO2 2,800

CH4 4.96

N2O 2.42

CFCl3 & CF2Cl2

0.0319

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 %

U.S. 24

China 14

Russia 6

Japan 5

India 5

Germany 4

Country %

Canada 2

U.K. 2

S. Korea 2

Italy 2

France 2

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 “human-induced” 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 (40-50 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 coal-fired plants with gas-fired 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