Environmental science

36127 Topic: SCI 207 Our Dependence upon the Environment

Number of Pages: 1 (Double Spaced)

Number of sources: 2

Writing Style: APA

Type of document: Essay

Academic Level:Undergraduate

NCategory: Environmental Issues

Language Style: English (U.S.)

Order Instructions: Attached

Week 4 – Assignment 1

Greenhouse Gases and Sea Level Rise Laboratory

[WLO: 3] [CLOs: 1, 3, 5]

This lab enables you to create models of sea level rise resulting from melting of sea ice and glacier ice and examine the effects of this potential consequence of climate change.

The Process:

Take the required photos and complete all parts of the assignment (calculations, data tables, etc.). On the “Lab Worksheet,” answer all of the questions in the “Lab Questions” section. Finally, transfer all of your answers and visual elements from the “Lab Worksheet” into the “Lab Report.” You will submit both the “Lab Report” and the “Lab Worksheet” through Waypoint.

The Assignment:

Make sure to complete all of the following items before submission:

Read the Greenhouse Gases and Sea Level Rise Investigation ManualPreview the document and review The Scientific Method (Links to an external site.)Links to an external site.presentation video.

Complete Activities 1 and 2 using materials in your kit, augmented by additional materials that you will supply. Photograph each activity following these instructions:

When taking lab photos, you need to include in each image a strip of paper with your name and the date clearly written on it.

Activity 2, Step 12 will require you to make a line graph. Should you desire further guidance on how to construct a graph, it is recommended that you review the Introduction to GraphingPreview the document lab manual. (You are not expected to complete any of the activities in this manual.)

Complete all parts of the Week 4 Lab WorksheetPreview the document and answer all of the questions in the “Lab Questions” section.

Transfer your responses to the lab questions and data tables and your photos from the “Lab Worksheet” into the “Lab Report” by downloading the Lab Report TemplatePreview the document.

Submit your completed “Lab Report” and “Lab Worksheet” through Waypoint.

Carefully review the Grading Rubric (Links to an external site.)Links to an external site. for the criteria that will be used to evaluate your assignment.

ENVIRONMENTAL SCIENCE

GREENHOUSE GASES AND SEA LEVEL RISE

Overview

In this lab, students will carry out several activities aimed at

demonstrating consequences of anthropogenic carbon emissions,

climate change, and sea level rise. To do this, students will first

create a landform model based on a contour map. They will create

models of sea level rise resulting from melting of sea ice and

glacier ice and examine the effects of this potential consequence

of climate change. Students will critically examine the model

systems they used in the experiments.

Outcomes

• Explain the causes of increased carbon emissions and their likely

effect on global climate.

• Discuss positive and negative climate feedback.

• Distinguish between glacial ice melt and oceanic ice melt.

• Construct a three-dimensional model from a two-dimensional

contour map.

• Evaluate and improve a model system.

Time Requirements

Preparation:

Part 1……………………………………………………………….. 5 minutes,

then let sit for 24 hours before starting Activity 1

Part 2 ……………………………………………………………………2 hours

Activity 1: Sea Ice and Sea Level Rise ……………………………..1 hour

Activity 2: Glacier Ice and Sea Level Rise…………………….2.5 hours

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Key

Personal protective

equipment

(PPE)

goggles gloves apron

follow

link to

video

photograph

results and

submit

stopwatch

required

warning corrosion flammable toxic environment health hazard

Made ADA compliant by

NetCentric Technologies using

the CommonLook® software

Table of Contents

2 Overview

2 Outcomes

2 Time Requirements

3 Background

10 Materials

10 Safety

11 Preparation

13 Activity 1

14 Activity 2

15 Submission

15 Disposal and Cleanup

16 Lab Worksheet

18 Lab Questions

Background

For the last 30 years, controversy has

surrounded the ideas of global warming/climate

change. However, the scientific concepts behind

the theory are not new. In the 1820s, Joseph

Fourier was the first to recognize that, given

the earth’s size and distance from the sun,

the planet’s surface temperature should be

considerably cooler than it was. He proposed

several mechanisms to explain why the earth

was warmer than his calculations predicted,

one of which was that the earth’s atmosphere

might act as an insulator. Forty years later,

John Tyndall demonstrated that different

gases have different capacities to absorb

infrared radiation, most notably methane (CH4

),

carbon dioxide (CO2

), and water vapor (H2

O),

all of which are present in the atmosphere. In

1896, Svante Arrhenius developed the first

mathematical model of the effect of increased

CO2

levels on temperature. His model predicted

that a doubling of the amount of CO2

in the

atmosphere would produce a 5–6 °C increase

in temperature globally. Based on the level of

CO2

production in the late 19th century, he

predicted that this change would take place

over thousands of years, if at all. Arrhenius used

Arvid Högbom’s calculations of industrial CO2

emissions in his equations. Högbom thought

that the excess CO2

would be absorbed by the

ocean; others believed that the effect of CO2

was insignificant next to the much larger effect

of water vapor.

It was not until the late 1950s, when the CO2

absorption capacity of the ocean was better

understood and significant increases in CO2

levels (a 10% increase from the 1850s to the

1950s) were being observed by G. S. Callendar,

that Arrhenius’s calculations received renewed

attention.

The Atmosphere

Weather is the condition of the atmosphere in a

given location at a specific time. Climate is the

prevailing weather pattern over a longer period

of time (decades or centuries).

The atmosphere is a thin shell (~100 km) of

gases that envelops the earth. It is made up

principally of nitrogen (78%), oxygen (21%),

and argon (0.9%). Trace gases include methane

(CH4

), ozone (O3

), carbon dioxide (CO2

), carbon

monoxide (CO), and oxides of nitrogen (e.g.,

NO2

) and sulfur (e.g., SO2

) (see Figure 1).

Water vapor is sometimes included in the

composition of gases in the atmosphere, but a

lot of times it is not because its amount varies

widely, from 0%–4%, depending on location.

The concentration of gases in the atmosphere

is not uniform either; the atmosphere consists

of several concentric layers. Some gases are

concentrated at certain altitudes. Water and

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GREENHOUSE GASES AND SEA LEVEL RISE

Background continued

carbon dioxide are concentrated near the

earth’s surface, for instance, while ozone is

concentrated 20 to 30 kilometers above the

surface. Energy transfer from the sun at and

near the surface of the earth is responsible for

weather and climate. Solar radiation heats land,

the oceans, and atmospheric gases differently,

resulting in the constant transfer of energy

across the globe.

Several factors interact to cause areas of the

earth’s surface and atmosphere to heat at

different rates, a process called differential

heating. The first is the angle at which the sun’s

light hits the earth. When the sun is directly

overhead, as it is at the equator, the light is

direct. Each square mile of incoming sunlight

hits one square mile of the earth. At higher

latitudes, the sun hits at an angle, spreading

the one square mile of sunlight over more of the

earth’s surface. Thus, the intensity of the light

is reduced and the surface does not warm as

quickly (see Figure 2). This causes the tropics,

near the equator, to be warmer and the poles to

be cooler.

Different materials heat and cool at different

rates. Darker surfaces heat faster than lighter

surfaces. Water has a high heat capacity, which

is important on a planet whose surface is 72%

water. Heat capacity is a measure of how

much heat it takes to raise the temperature of

a substance by one degree. The heat capacity

of liquid water is roughly four times that of air.

Water is slow to warm and slow to cool, relative

to land. This also contributes to differential

heating of the earth.

Differential heating causes circulation in the

atmosphere and in the oceans. Warmer fluids

are less dense and rise, leaving behind an area

of low pressure. Air and water move laterally to

distribute the change in pressure. This is critical

in developing prevailing wind patterns and in

cycling nutrients through the ocean.

The Role of the Oceans

The oceans play an important role in regulating

the atmosphere as well. The large volume of the

oceans, combined with the high heat capacity

of water, prevent dramatic temperature swings

in the atmosphere. The relatively large surface

area of the oceans, ~70% of the surface of the

earth, means that the oceans can absorb large

amounts of atmospheric CO2

.

Greenhouse Gases

The greenhouse effect is a natural process;

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Figure 2.

without it, the earth would be significantly cooler

(see Figure 3). The sun emits energy in a broad

range of wavelengths. Most energy from the

sun passes through the atmosphere. Some is

reflected by the atmosphere and some by the

earth’s surface back into space, but much of it

is absorbed by the atmosphere and the earth’s

surface. Absorbed energy is converted into

infrared energy, or heat. Oxygen and nitrogen

allow incoming sunlight and outgoing thermal

infrared energy to pass through. Water vapor,

CO2

, methane, and some trace gases absorb

infrared energy; these are the greenhouse

gases. After absorbing energy, the greenhouse

gases radiate it in all directions, causing the

temperature of the atmosphere and the earth

to rise.

Greenhouse gases that contribute to the

insulation of the earth can be grouped into

two categories: condensable and persistent.

Persistent gases—such as CO2

, methane,

nitrous oxide (N2

O), and ozone (O3

)—exist in

the environment for much longer periods of

time than condensable gases. These times can

range from a few years to thousands of years.

The longer residence allows them to become

well-mixed geographically. The amount of a

condensable gas is temperature dependent.

Water is the primary greenhouse gas in the

atmosphere, but because it is condensable,

it is not considered a forcing factor. Forcing

factors (forcings) are features of the earth’s

climate system that drive climate change; they

may be internal or external to the planet and its

atmosphere. Feedbacks are events that take

place as a result of forcings.

Carbon dioxide, methane, and other gases

identified by Tyndall as having high heat

capacities make up a relatively minor fraction

of the atmosphere, but they have a critical

effect on the temperature of the earth. Without

the naturally occurring greenhouse effect, it is

estimated that the earth’s average temperature

would be approximately –18 °C (0 °F). The

greenhouse effect also acts as a buffer, slowing

both the warming during the day and the cooling

at night. This is an important feature of the

earth’s atmosphere. Without the greenhouse

effect, the temperature would drop below

the freezing point of water and the amount

of water in the atmosphere would plummet,

creating a feedback loop. A feedback loop is

a mechanism that either enhances (positive

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Figure 3.

GREENHOUSE GASES AND SEA LEVEL RISE

Background continued

feedback) or dampens (negative feedback) the

effect that triggers it.

Since the beginning of the Industrial Revolution,

the concentration of CO2

in the atmosphere

has increased from approximately 280 ppm

to 411 ppm (see the Keeling Curve link). This

change is attributed to the burning of fossil

fuels—such as coal, oil, and natural gas—and

changes in land use, i.e., cutting down large

tracts of old-growth forests. Old-growth forests,

like fossil fuels, sequester carbon from the

atmosphere. Burning of either releases that

carbon into the atmosphere in the form of CO2

.

Clearing old-growth forests has an additional

impact on the carbon cycle because trees

actively remove CO2

from the atmosphere to

convert it to sugar and carbohydrates (see

Figure 4). Removing long-lived trees and

replacing them with short-lived crops and

grasses reduces the time over which the carbon

is removed from the atmosphere.

Determining the exact effect that the increase

in CO2

concentrations will have on atmospheric

temperature is complicated by a variety of

interactions and potential feedback loops.

However, the overall impact is an ongoing

temperature increase, known as global climate

change (see Figure 5).

Potential Feedback Loops

Some examples of potential positive feedback

loops that may enhance the effects of global

climate change are:

1. Higher temperatures allow the

atmosphere to absorb more

water. More water vapor in the

atmosphere traps more heat,

further increasing temperature.

2. Melting of sea ice and glaciers,

which are relatively light in

color, to darker bodies or water

decreases the albedo (the

amount of energy reflected

back into space) of the

earth’s surface, increasing

temperatures. Figure 6 shows an

ice albedo feedback loop.

3. Warmer temperatures melt more

of the arctic permafrost (frozen

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Figure 4.

ground), releasing methane into the

atmosphere, further raising temperatures.

4. Higher temperatures may result in greater

rainfall in the North Atlantic, and melting of

sea ice creates a warm surface layer of fresh

water there. This would block formation of

sea ice and disrupt the sinking of cold, salty

water. It may also slow deep oceanic currents

that carry carbon, oxygen, nutrients, and heat

around the globe.

Other factors may work as negative feedbacks,

dampening the effects of global climate change:

1. An increase in CO2

level in the atmosphere

leads to an increase in CO2

in the oceans,

stabilizing CO2

levels.

2. Increased atmospheric temperatures and CO2

promote plant and algae growth, increasing

absorption of CO2

from the atmosphere,

lowering the CO2

levels there, and stabilizing

temperature.

3. Warmer air, carrying more moisture, produces

more snow at high latitudes. This increases

the albedo of the earth’s surface, stabilizing

temperature.

4. Warmer, moister air produces more clouds,

which also increases the albedo of the earth’s

surface, stabilizing temperature.

The relative impact of each of these potential

effects is a subject of debate and leads to the

uncertainty in models used to predict future

climate change resulting from an increase in

anthropogenic (human-caused) greenhouse

gases. However, the consensus among climate

scientists is that the positive feedbacks will likely

overwhelm the negative ones.

Possible Consequences

Consequences of an increase in average

temperature are difficult to predict on a regional

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Figure 6.

Figure 5.

GREENHOUSE GASES AND SEA LEVEL RISE

Background continued

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crop growth. Climes that are more northerly may

experience an increase in productivity. These

shifts will put stress on ecosystems as well. How

resilient each community is to the change will

vary with location and other pressures.

Modeling

The atmosphere and climate are highly complex

systems that are challenging to understand

and predict. To explore such complex systems,

scientists frequently employ models. A model

is a simplification of a complex process that

isolates certain factors likely to be important.

Sometimes a model can be a physical

representation of something too big or too small

to see, such as a model solar system. However,

scientists frequently use mathematical equations

derived from observed data to predict future

conditions. With the addition of computers,

mathematical climate equations can be linked

together in increasingly sophisticated ways to

model multiple factors in three dimensions,

producing global climate models. Because

of computing limitations, some factors must

be simplified. How they are represented within

the model can lead to a degree of error in the

outcome predicted. Ultimately, the quality of

all models is determined by their success in

predicting events that have not yet taken place.

Contour Maps

To determine potential flood risks, scientists,

engineers, and insurance companies use a

number of tools, including historic river flow,

storm tide and rainfall data, hydrological

analysis, and topographic surveys.

scale; some, however, can be predicted with

a relatively high degree of confidence. One

of these is sea level rise. Sea level rise is

the result of two processes. The first is the

melting of glaciers and Antarctic continental

ice. Although the melting of sea ice can have

complex consequences due to the different

densities of salt and fresh water, it will not cause

sea level rise. Melting of glaciers and the deep

ice over the Antarctic continent, however, can.

The second cause of sea level rise, related to

warmer temperatures, is that water expands as

it warms. As the oceans warm, the water rises

farther up the shore. Countries and cities that

have large portions of their land area at or just

above sea level may be in jeopardy.

The loss of mountain glaciers is already

causing changes in freshwater availability.

As glaciers shrink, regions that depend on

seasonal meltwater for hydroelectric power or

for irrigation and drinking water are increasingly

affected. Whereas rainfall may increase in

these regions (even as the amount of snowmelt

decreases), rainwater is considerably more

difficult to control because it does not occur

at as predictable a rate as meltwater. River

systems may be overwhelmed by increased

runoff rates, which can cause flooding. One

of the richest agricultural regions in the world,

California, depends heavily on snowmelt from

the Sierra Nevada. One of the world’s most

populous river valleys, the Indus, is equally

dependent on snowmelt from the Himalayas.

Less predictable consequences are the shifting

of global weather patterns and the subsequent

changes in natural populations. Areas previously

ideal for agriculture may become too arid for

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Topographic surveys can be represented

graphically as maps with contour lines (see

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