Climate ChangeMr. Dvorin

Muir Middle School

Expectations■ E2.4B - Explain how the impact of human

activities on the environment (e.g., deforestation, air pollution, coral reef destruction) can be understood through the analysis of interactions between the four Earth spheres.

■ E5.4A – Explain the natural mechanism of the greenhouse effect, including comparisons of the major greenhouse gases (water vapor, carbon dioxide, methane, nitrous oxide, and ozone).

■ E5.4B – Describe natural mechanisms that could result in significant changes in climate (e.g., major volcanic eruptions, changes in sunlight received by the earth, and meteorite impacts).

Expectations• E5.4C – Analyze the empirical relationship between the emissions of carbon dioxide, atmospheric carbon dioxide levels, and the average global temperature over the past 150 years.• E5.4D – Based on evidence of observable changes in recent history and climate change models, explain the consequences of warmer oceans (including the results of increased evaporation, shoreline and estuarine impacts, oceanic algae growth, and coral bleaching) and changing climatic zones (including the adaptive capacity of the biosphere).

Expectation 1

■ E2.4B - Explain how the impact of human activities on the environment (e.g., deforestation, air pollution, coral reef destruction) can be understood through the analysis of interactions between the four Earth spheres.

Impact of Human ActivitiesDeforestation is the permanent destruction of indigenous forests and woodlands (biosphere).

Often the land is cleared for conversion into agricultural land to feed growing numbers of people, cattle ranching, or to obtain firewood or building materials.

Forests and woodlands act as major carbon stores. Removing these stores means that carbon dioxide levels in the atmosphere will climb. Trees also help to circulate water in the local ecosystem (hydrosphere), removing them leads to the possibility of a drier climate.

Impact of Human ActivitiesAir pollution (atmosphere) comes from a number of sources. These include industrial sites, home heating, transportation vehicles, and even outdoor burning.

Human activities can release substances into the air, some of which cause problems for humans, plants, and animals.

People (biosphere) with health problems such as asthma, heart, and lung disease may also suffer more when the air is polluted.

Impact of Human ActivitiesCoral reefs are stony structures built by a symbiotic relationship between coral, an animal (biosphere), and single-celled algae -- a plant (biosphere). The coral houses the algae, which use photosynthesis to make sugar that helps feed the coral. The coral's waste products, including nitrogen and phosphorus compounds, fertilize the algae. Live coral polyps grow on the dead bodies of their ancestors, allowing coral to build up to tremendous depths if left alone.

Coral reef destruction can occur when seawater (hydrosphere) warms up. The coral expels the algae, losing its major source of food. The algae give the reefs its color, so “bleaching” occurs. Over fertilization is another problem.

Expectation 1

E5.4A – Explain the natural mechanism of the greenhouse effect, including comparisons of the major greenhouse gases (water vapor, carbon dioxide, methane, nitrous oxide, and ozone).

Greenhouse EffectOne of the ways in which the gases of the atmosphere absorb and reradiate infrared rays, can be compared to the process that keeps a greenhouse warm. The Earth’s atmosphere allows visible light and infrared rays from the Sun to pass through and warm the surface. However, certain atmospheric gases slow the escape of energy that radiates from Earth’s surface. This is called the greenhouse effect.

Major Greenhouse Gases

■ Water Vapor (H2O)■ Carbon Dioxide (CO2)■ Methane (CH4)■ Nitrous Oxide (N2O)

Major Greenhouse Gases

■ Water Vapor (H2O)■ Not increasing as a direct result of

industrialization.■ As global temperatures rise, more water is

evaporated from ground storage (rivers, oceans, reservoirs, and soil).

■ With warmer air, relative humidity can increase, leading to more water vapor in the atmosphere.

■ More water vapor absorbs more thermal infrared energy radiated from the Earth (this is know as a “positive feedback loop”).

Abundance and Heat-Trapping Capacity

■ Water Vapor (H2O)■ Uncertainty exists in defining the extent

and importance of the positive feedback loop.

■ We currently have poor measurements of global water vapor.

■ Satellite data, balloon data, and some ground measurements indicate generally rising trends in global water vapor.

Major Greenhouse Gases

■ Carbon Dioxide (CO2)■ The natural production and absorption of

carbon dioxide is achieved through the terrestrial biosphere and the ocean.

■ Through the burning of coal, oil, natural gas, and wood, humankind has altered the natural carbon cycle.

■ Carbon dioxide levels fluctuate because of the larger landmass in the Northern Hemisphere and its vegetation.

Abundance and Heat-Trapping Capacity

■ Carbon Dioxide (CO2)■ Measurements indicate that concentrations

have risen well over 30% since the Industrial Revolution.

■ The concentration oscillates with the seasons (photosynthesis).

■ Recognized as the most important greenhouse gas to reduce.

Major Greenhouse Gases

■ Methane (CH4)■ It is released as part of the biological

processes in low oxygen environments (swamp lands and at the roots of certain plants).

■ Human activities such as growing rice, raising cattle, using natural gas, and mining coal have added to the atmospheric concentration of methane.

■ Worries about melting permafrost releasing more methane.

Abundance and Heat-Trapping Capacity

■ Methane (CH4)■ Direct measurement shows an increase in

methane by about 1% each year from 1978 to 1990. Since 1990 there has been little sustained increase.

■ New studies show melting of the permafrost is releasing stored methane gas.

■ Second most important greenhouse gas to reduce.

Major Greenhouse Gases

■ Nitrous Oxide (N2O)■ Produced by microbial processes in soil and

water, including those reactions which occur in fertilizer containing nitrogen.

■ Some industrial processes (fossil fuel-fired power plants, nylon production, nitric acid production, and vehicle emissions) have contributed to its atmospheric load.

Abundance and Heat-Trapping Capacity

■ Nitrous Oxide (N2O)■ Increased use of fertilizers containing

nitrogen in the last century have led to increased global concentrations.

■ This greenhouse gas seems to have a smaller impact than the others.

Expectation 2

E5.4B – Describe natural mechanisms that could result in significant changes in climate.

Take a moment and jot down a few natural mechanisms that you can think of that affect climate.

(e.g., major volcanic eruptions, changes in sunlight received by the earth, and meteorite impacts).

Volcanic EruptionsThe lava, gases, and ash that erupt into the atmosphere during a volcanic eruption can darken the skies for hundreds of kilometers. In the months after an eruption, some of the material settles to Earth, but much of it remains in the atmosphere, where wind currents disperse it around the globe.

Sulfur dioxide released during an eruption combines with water to become sulfuric acid, which reflects the sun’s energy back into space. Thus, large amounts of sulfur dioxide have a cooling effect on Earth’s surface.

Mount St. Helens eruption (1980)

Volcanic EruptionsVolcanoes also release large amounts of water and carbon dioxide (greenhouse gases). When these two compounds are in the form of gases in the atmosphere, they absorb heat radiation (infrared) emitted by the ground and hold it in the atmosphere. This causes the air below to get warmer. Therefore, you might think that a major eruption would cause a temporary warming of the atmosphere rather than a cooling. However, there are very large amounts of water and carbon dioxide in the atmosphere already, and even a large eruption doesn't change the global amounts very much. In addition, the water generally condenses out of the atmosphere as rain in a few hours to a few days, and the carbon dioxide quickly dissolves in the ocean or is absorbed by plants.

Changes in SunlightChanges in the shape of Earth’s orbit (eccentricity), changes in Earth’s tilt (obliquity), and the wobble (precession) of Earth on its axis can lead to climate changes.

The combination of these factors is described by the Milankovitch theory. Milutin Milankovitch was a Serbian mathematician who discussed these cycles while working on his theory of climate change from 1920 to 1941.

Changes In Earth’s OrbitEccentricity Cycle: Over a time period of approximately 100,000 years the Earth’s orbit varies from elliptical to more circular. This affects the distance the Earth is from the Sun.

Obviously, this will affect the amount of heat received by the Earth, changing the surface temperature.

Changes in Earth’s Tilt

Obliquity Cycle: Over a time period of approximately 41,000 years the Earth’s tilt varies between 22.2° and 24.5°. Our planet currently has a tilt of 23.5°.

The greater the tilt angle is, the more solar energy the poles receive.

Decreasing tilt decreases temperature differences between seasons (cooler summers, warmer winters), while increases in tilt will increase temperature differences (hotter summers, colder winters).

Axis WobblePrecession of the Equinoxes: Over a time period of approximately 19,000-23,000 years the Earth’s axis experiences a “wobble”. This wobble affects the amount of solar radiation that reaches different parts of Earth’s surface at different times of the year.

The wobble of Earth on its axis changes the direction of Earth’s tilt and can reverse the seasons.

Meteorite ImpactsOn occasion, the Earth is struck by a large enough meteoroid that impact craters are created. These impacts have occurred throughout the history of our planet.

About 65 million years ago, a giant meteorite crashed into the Earth in the area of the Yucatan Peninsula (Mexico). It is believed that the impact raised enough dust to block the sun’s rays for many years. As Earth’s climate became cooler, plant life began to die, and many animal species became extinct.

Thus, large meteorite impacts not only have the capability of cooling the surface temperature of the Earth, but they could potentially kill of many species of life.

Expectation 3

E5.4C – Analyze the empirical relationship between the emissions of carbon dioxide, atmospheric carbon dioxide levels, and the average global temperature over the past 150 years.

Carbon Dioxide EmissionsSince the Industrial RevolutionSince the Industrial Revolution, human activitiesSince the Industrial Revolution, human activities such as the burning of oilSince the Industrial Revolution, human activities such as the burning of oil, coalSince the Industrial Revolution, human activities such as the burning of oil, coal and gas, and deforestation have greatly increased CO2 concentrations in the atmosphere. As we can see from the top figure, almost all CO2 emissions (about 96.5%) come from fossil fuels emissions (about 96.5%) come from fossil fuels use. The 3 types of fossil fuels emissions (about 96.5%) come from fossil fuels use. The 3 types of fossil fuels that are used the most are coal emissions (about 96.5%) come from fossil fuels use. The 3 types of fossil fuels that are used the most are coal, natural gas emissions (about 96.5%) come from fossil fuels use. The 3 types of fossil fuels that are used the most are coal, natural gas and petroleum emissions (about 96.5%) come from fossil fuels use. The 3 types of fossil fuels that are used the most are coal, natural gas and petroleum. When fossil fuels are combusted, the carbon stored in them is emitted almost entirely as CO2.

This figure highlights one of the most alarming trends in today's modern economy. The impact that transporting people and goods has on greenhouse gasThis figure highlights one of the most alarming trends in today's modern economy. The impact that transporting people and goods has on greenhouse gas emissions and climate change This figure highlights one of the most alarming trends in today's modern economy. The impact that transporting people and goods has on greenhouse gas emissions and climate change is so large that it has surpassed emissions from all industrial manufacturing. This trend started in the 1990's and has continued ever since.

Carbon Dioxide LevelsCarbon dioxide is the most important greenhouse gas caused by human activities and is primarily emitted by fossil fuel use and deforestation. Since the mid-1700s, carbon dioxide in the atmosphere has increased 30% from 280 parts per million (ppm) to over 370 ppm.

Long-term data demonstrate that atmospheric levels of carbon dioxide are currently higher than at anytime in the past 650,000 years.

Temperature LevelsHuman activities have added large amounts of greenhouse gases to the atmosphere, which have accumulated and increased the amount of heat that is held at the earth’s surface. The amplified greenhouse effect leads to global warming and changes in climate. Average temperatures around the world are 1.4 °F (0.8° C) greater than they were in 1880 and many recent years have been the warmest on record. In 2007, the Intergovernmental Panel on Climate Change (IPCC) issued its fourth report on climate change, providing a definitive statement that global warming has occurred and will continue to change the climate.

■ Ten Hottest Years on Record, 1880-2011

■ Rank Year Average Global Temperature in C

■ 1 2010 14.63■ 2 2005 14.62■ 3 2009 14.58■ 3 2007 14.58■ 5 2002 14.56■ 5 1998 14.56■ 7 2003 14.55■ 7 2006 14.55■ 9 2011 14.52■ 10 2004 14.48

Expectation 4

E5.4D – Based on evidence of observable changes in recent history and climate change models, explain the consequences of warmer oceans (including the results of increased evaporation, shoreline and estuarine impacts, oceanic algae growth, and coral bleaching) and changing climatic zones (including the adaptive capacity of the biosphere).

Impact of Warmer OceansAn increase of only a few degrees worldwide could melt the polar ice caps and raise sea level by adding water to the oceans. On a shoreline that has a gentle slope, the shoreline could shift inland many miles. Many coastal inhabitants would be displaced, and freshwater and agricultural land resources would be diminished.

Because approximately 50% of the world population lives near coastlines, this sea-level rise would have devastating effects.

Shoreline ImpactsGlobal sea level can rise for a couple of reasons:

1. When water gets hotter, it expands.

2. When water is added to the ocean, it changes its mass (when glaciers melt).

A rise in global sea level has been occurring since 1993 at an average annual rate of three millimeters.

Rising sea level will submerge many coastlines, displacing large groups of populations.

Projected coastline changes in the (1) southeastern U.S., (2) northern Europe, and (3) China.

1 2 3

Disruption of Ocean CurrentsIf a large piece of the Greenland ice sheet were to slip into the ocean, the oceans salinity would change and many ocean currents, including the Gulf Stream, would shut down. This would decrease the temperature in Western Europe to the point where it could fall into an ice age.

Increased Evaporation

As the oceans warm up they will release more carbon dioxide into the atmosphere (as opposed to colder water storing the carbon dioxide).

Warmer oceans mean that evaporation rates will increase. Water vapor is another greenhouse gas.

Warmer oceans provide fuel for stronger hurricanes. Hurricane season could grow, leading to even more storms.

Estuarine ImpactsEstuaries are semi-enclosed coastal bodies of water, with one or more rivers or streams flowing into it, and with a free connection to the open sea. These coastal areas feature an abundance of wildlife. An increase in ocean levels means a disturbance to these coastal areas, possibly impacted numerous species.

Coral Bleaching

Coral bleaching occurs when ocean water becomes abnormally warm and reef building corals become stressed. The stress results in the breakdown of the special symbiotic relationship between the coral and single-celled algae called zooxanthellae. As a result of this stress, the colored zooxanthellae leave, turning the coral white. If the water cools down again, the zooxanthellae return, and the coral is colorful again.

Coral reefs are home to many varieties of ocean life. The eventual death of a coral reef devastates this ocean community.

Oceanic Algae GrowthPhytoplankton (a type of algae) forms the base of the ocean food chain. Research shows that phytoplankton thrive in nutrient-rich, cold water. When ocean water warms up, phytoplankton disappear, giving fish little to eat. This leads the death of many types of animals dependent upon fish for their food source.

Phytoplankton bloom as seen from space.

Changing Climatic ZonesAn increase in global temperature can lead to an increase in evaporation. On land, increased evaporation could cause some areas to become drier than they are now. Some plants and animals would not be able to live in these drier conditions. An increase in evaporation could also cause crops to suffer damage.

However, an increase in temperatures due to global warming might improve conditions for crops in colder, northern regions. Plants can quickly adapt to a longer growing season.