Unit C Lesson 7: Changes in the Atmosphere due to Human Activity
Completion requirements
Unit C Lesson 7: Atmosphere Changes due to Human Activity |
Learning Targets |
Big Question: What changes can occur in the atmosphere due to human activity?
Earth's atmosphere might be invisible to us most of the time, but our actions are showing how important a predictable atmosphere is to many aspects of our lives.
Earth's atmosphere might be invisible to us most of the time, but our actions are showing how important a predictable atmosphere is to many aspects of our lives.
At the end of this inquiry, you should be able to answer the following questions:
- What causes global climate change?
- What is the greenhouse effect?
- Why is the ozone layer important?
Pages 229, 230, and 232 in your textbook will help you answer these questions about changes in the atmosphere due to human actions.
Introduction
Energy Budget – What Goes in Must Go Out... or else!
To understand how Earth's atmosphere is changing, you must first understand what "normal" conditions are. First, consider that Earth is a system. For any system to be stable, the energy coming in must equal the energy going out. If the energy coming in consistently exceeds the energy going out, the system will get hotter. If the energy coming in is consistently less than the energy going out, the system will get colder.
Earth normally is a very stable system. The energy coming in from the Sun is normally pretty much equal to the energy going out in the form of reflected sunlight and heat radiated into space. Earth's average temperatures have changed over many thousands of years, but that change has been by small amounts and has occurred very, very slowly.
What humans have done is disrupt a normally stable system by making rapid changes the system cannot adapt to. Humans, over the last 150 years, have added large amounts of greenhouse gasses to the atmosphere. As a result, more energy is trapped in the system, and the normal balance is upset. Temperature and greenhouse gas data collected by scientists shows this situation is getting worse – with more energy being trapped, the Earth is gaining more energy than it gives off, and that means the average temperature of Earth is steadily increasing at a very fast, potentially dangerous pace.
To understand how Earth's atmosphere is changing, you must first understand what "normal" conditions are. First, consider that Earth is a system. For any system to be stable, the energy coming in must equal the energy going out. If the energy coming in consistently exceeds the energy going out, the system will get hotter. If the energy coming in is consistently less than the energy going out, the system will get colder.
Earth normally is a very stable system. The energy coming in from the Sun is normally pretty much equal to the energy going out in the form of reflected sunlight and heat radiated into space. Earth's average temperatures have changed over many thousands of years, but that change has been by small amounts and has occurred very, very slowly.
What humans have done is disrupt a normally stable system by making rapid changes the system cannot adapt to. Humans, over the last 150 years, have added large amounts of greenhouse gasses to the atmosphere. As a result, more energy is trapped in the system, and the normal balance is upset. Temperature and greenhouse gas data collected by scientists shows this situation is getting worse – with more energy being trapped, the Earth is gaining more energy than it gives off, and that means the average temperature of Earth is steadily increasing at a very fast, potentially dangerous pace.
Figure 1 – In a stable system, the energy going in is roughly equal to the energy going out.
Figure 2 – Projections from the IPCC (Intergovernmental Panel on Climate Change) show that at current rates of warming, global surface temperatures could change (in comparison to
historical averages) by as much as 4 degrees Celsius by the year 2100.
Energy Budget – A Detailed Look
Take a careful look at Figure 3 below. It may look complicated, but actually it's quite simple – it is a breakdown of how the Earth system, when in balance, has energy coming in roughly equal to energy going out.
If you look at the only the yellow arrows in the Figure 3, you'll see that 30% of the Sun's energy is reflected back into space. The other 70% is absorbed by the land, oceans, clouds, and atmosphere.
Again, when in balance, all of the absorbed by the Earth is goes back out into space, shown by the red arrows in Figure 3. A balanced system such as this will have a stable temperature – but if energy that normally goes back out into space is trapped, it will result in a system that increases in temperature.
Take a careful look at Figure 3 below. It may look complicated, but actually it's quite simple – it is a breakdown of how the Earth system, when in balance, has energy coming in roughly equal to energy going out.
If you look at the only the yellow arrows in the Figure 3, you'll see that 30% of the Sun's energy is reflected back into space. The other 70% is absorbed by the land, oceans, clouds, and atmosphere.
Again, when in balance, all of the absorbed by the Earth is goes back out into space, shown by the red arrows in Figure 3. A balanced system such as this will have a stable temperature – but if energy that normally goes back out into space is trapped, it will result in a system that increases in temperature.
Figure 3 – The energy budget of Earth when the system is balanced.
Climate Change
The phrase "global climate change" has become familiar to many people as one of the important environmental issues of our day. What exactly is global climate change? Is there anything that we can do to stop it?
Without the energy from the sun, no life could exist on Earth. As shown in Figure 3, about 30 percent of the sunlight that beams toward Earth is deflected by the outer atmosphere and scattered back into space. The remainder that reaches the planet's surface and is absorbed, and then in turn, is re-radiated upward again back out into space.
The phrase "global climate change" has become familiar to many people as one of the important environmental issues of our day. What exactly is global climate change? Is there anything that we can do to stop it?
Without the energy from the sun, no life could exist on Earth. As shown in Figure 3, about 30 percent of the sunlight that beams toward Earth is deflected by the outer atmosphere and scattered back into space. The remainder that reaches the planet's surface and is absorbed, and then in turn, is re-radiated upward again back out into space.
Greenhouse gases such as water vapour, carbon dioxide, ozone, and methane, which slows the escape of heat (infrared radiation) from the atmosphere. Greenhouse gases are only approximately 1% of the air, but their ability to absorb and trap heat is enormous.
Nitrogen and oxygen (which make up most of our air) absorb almost no radiation.
This phenomenon is called the greenhouse effect. It is actually a good thing in the right amount... without it, the average temperature on Earth would be colder by approximately 30° C; far too cold to sustain Earth's ecosystems. But too much greenhouse effect will mean increasing temperatures... which leads us back to, and explains the problem of global climate change.
This phenomenon is called the greenhouse effect. It is actually a good thing in the right amount... without it, the average temperature on Earth would be colder by approximately 30° C; far too cold to sustain Earth's ecosystems. But too much greenhouse effect will mean increasing temperatures... which leads us back to, and explains the problem of global climate change.
Watch
As you watch the video "The Greenhouse Effect", which clearly explains how the Greenhouse Effect occurs, answer questions 1 and 2.
1. Why are greenhouse gases important?
2. How would the earth's climate change if there were no greenhouse gases?
Greenhouse gases trap heat in the atmosphere and keep the earth warm.
The temperature of the earth would be much colder.
What is global climate change?
Global climate change is the increase of Earth's average surface temperature due to excess greenhouse gases entering the atmosphere through human activities, such as carbon dioxide emissions from burning fossil fuels or from deforestation. The
greenhouse gases trap heat that otherwise would escape from Earth.
Warmer temperatures lead to the following:
Earth's climate has changed many times in the past, and it will continue to change in the future. The difference this time is that our actions are contributing to the change, and the effects of the change are potentially going to change the way we live on our planet.
Warmer temperatures lead to the following:
- rising sea levels
- droughts
- changes in rain and snow patterns
-
melting glaciers and ice sheets
Earth's climate has changed many times in the past, and it will continue to change in the future. The difference this time is that our actions are contributing to the change, and the effects of the change are potentially going to change the way we live on our planet.
Interactive
The Greenhouse Effect
- Click here to watch the BrainPOP video "Greenhouse Effect", that explains further the Greenhouse effect and global climate change.
You will need a username and password to access the video.
- Username: 0099
- Password: students
- Click here to complete the BrainPOP quiz on the Greenhouse Effect. Remember to check your answers at the end!
The Ozone Layer
Ozone, O3, is a gas in the atmosphere that protects every living organism on the Earth from harmful ultraviolet (UV) rays that originate from the Sun. Without the layer of ozone in the upper atmosphere (stratosphere), nothing could survive on the Earth's surface. The ozone layer acts as a shield to absorb the UV rays and to prevent damage by UV rays at the Earth's surface.
Ozone, O3, is a gas in the atmosphere that protects every living organism on the Earth from harmful ultraviolet (UV) rays that originate from the Sun. Without the layer of ozone in the upper atmosphere (stratosphere), nothing could survive on the Earth's surface. The ozone layer acts as a shield to absorb the UV rays and to prevent damage by UV rays at the Earth's surface.
Unlike the good, protective ozone layer in the stratosphere, ground-level ozone is a harmful air pollutant that affects everything and everyone. Ground-level ozone irritates the respiratory tract and eyes. Exposure to high levels of ozone
results in respiratory problems such as chest tightness, coughing, and wheezing.
Ozone depletion is the term commonly used to describe the thinning of the ozone layer in the stratosphere.
Human activity is the major factor in tipping that natural balance. Ozone depletion is caused mostly by the use of chemicals called chlorofluorocarbons, CFCs, which were used in
These chemicals escaped the lower atmosphere and entered the stratosphere. In the upper atmosphere, CFCs react with the ozone in the ozone layer to cause ozone depletion.
The conditions in the South Pole’s stratosphere are perfect for ozone destruction. Ozone destruction occurs most rapidly in the presence of sunlight and CFCs when the atmosphere is extremely cold (below –80°C).
Ozone depletion is the term commonly used to describe the thinning of the ozone layer in the stratosphere.
Human activity is the major factor in tipping that natural balance. Ozone depletion is caused mostly by the use of chemicals called chlorofluorocarbons, CFCs, which were used in
- refrigerators and air conditioning systems
- aerosol cans
These chemicals escaped the lower atmosphere and entered the stratosphere. In the upper atmosphere, CFCs react with the ozone in the ozone layer to cause ozone depletion.
The conditions in the South Pole’s stratosphere are perfect for ozone destruction. Ozone destruction occurs most rapidly in the presence of sunlight and CFCs when the atmosphere is extremely cold (below –80°C).
Every spring, a hole as big as the USA develops in the ozone layer over the South Pole in Antarctica. A smaller hole develops each year at the North Pole over the Arctic. The Montreal Protocol was signed in 1987 by many countries to phase out
the use of ozone depleting substances. As a result, global ozone, including ozone in the polar regions, is no longer decreasing.
Ozone forms naturally in the upper atmosphere when ultraviolet radiation (UV) reacts with oxygen. Scientists are hopeful the ozone layer will be restored to the levels they were at in 1980 by 2050.
Ozone forms naturally in the upper atmosphere when ultraviolet radiation (UV) reacts with oxygen. Scientists are hopeful the ozone layer will be restored to the levels they were at in 1980 by 2050.
oxygen + UV radiation → ozone
Figure 1 – This animation shows NASA''s projection for the ozone layer without the Montreal Protocol.
Check Your Understanding
Ozone Layer
-
Click here
to watch the BrainPOP video "Ozone Layer" to understand the importance of the ozone layer.
You will need a username and password to access the video.
- Username: 0099
- Password: students
- Click here to complete the BrainPOP quiz on the Ozone Layer. Remember to check your answers at the end!