Video Transcript
In this video, we will learn how to
explain the rise in temperature of the Earth’s atmosphere and the potential
problems.
We often hear that climate change
is happening on the Earth. But what does this mean? Climate change is a change in the
Earth’s climate caused by human activity that alters the composition of the global
atmosphere in addition to natural climate variability. The layer of gases that surrounds
the Earth is known as the atmosphere. These gases are essential to
sustaining life on our planet. The four main gases in Earth’s
atmosphere are nitrogen, oxygen, carbon dioxide, and water vapor. Nitrogen and oxygen make up most of
the atmosphere. In the troposphere, which is the
part of the atmosphere closest to Earth’s surface, the gases are mixed together
uniformly to make the air we breathe.
So, what does it mean to alter the
composition of the global atmosphere? Altering the composition means we
are changing the relative amounts of gases or adding new gases to the atmosphere
that would not normally be there. The main change that humans have
made to the atmosphere that is causing climate change is increasing the amount of
greenhouse gases.
Having more greenhouse gases in our
atmosphere has altered Earth’s natural climate variability. If something is variable, this
means it is changing or fluctuating. Climate in areas of the world does
change naturally over time. Climate includes, for example, the
average temperature or rainfall. But climate change refers to a
change of Earth’s natural climate patterns due to human activity. In other words, human activity is
disrupting the Earth’s normal climate patterns and leading to extreme weather
events.
People often confuse climate change
with global warming, but they are not the same thing. Global warming is the long-term
increase in Earth’s average global temperature. Scientists can calculate the
average temperature near the surface of the Earth by measuring it at many locations
around the planet. The graph shows an example of how
the average global temperature increases and decreases by a small amount over
time. In other words, in a short period
of time, the average global temperature naturally goes up and down by a small
amount.
Scientists describe global warming
as a long-term change. What does this mean? On the second graph, the 𝑦-axis
represents the mean or average global temperature, just like the first graph. But the 𝑥-axis represents a much
longer period of time. It shows the time in years from
1880 to 2020, which is 140 years. Between 1880 and 2012, the average
global air temperature increased by 0.85 or almost one degree Celsius. This is a much larger change than
the small changes that happen naturally.
Scientists predict that global
temperature will continue to increase by almost three degrees Celsius by 2100. Between the 18th and early 20th
centuries, the industrial revolutions happened. Since then, the average global
temperature has continually increased. This rise is due mainly to the
burning of fossil fuels by humans, which is increasing the amount of greenhouse
gases in Earth’s atmosphere.
So, what exactly are greenhouse
gases? Greenhouse gases are gases found in
the atmosphere, both naturally and through human activity, that absorb and emit IR
radiation emitted by the Earth’s surface, the atmosphere itself, and clouds. We already know that Earth’s
atmosphere is made up of the following gases. Of these gases, only carbon dioxide
and water vapor are greenhouse gases. Other common greenhouse gases
include methane, nitrogen oxides, ozone, and chlorofluorocarbons, which have the
abbreviation CFCs. Let’s discuss each of these in more
detail.
Water vapor is the gaseous form of
water. Of all the greenhouse gases in the
atmosphere, water vapor is found in the greatest amount. During the water cycle, water
evaporates from bodies of water like oceans and lakes. Water also moves into the
atmosphere from plant leaves during a process called transpiration.
Now, let’s discuss carbon
dioxide. Carbon dioxide, or CO2, gets into
Earth’s atmosphere by both natural processes and human activity. One way CO2 enters the atmosphere
is through the respiration of organisms on Earth. Volcanic eruptions and forest fires
also release CO2 into the atmosphere. But over the last century, the
amount of carbon dioxide in the atmosphere has increased mostly because of the
combustion of fossil fuels by humans. Finally, deforestation also leads
to higher CO2 levels.
The combustion or burning of a
fossil fuel is a chemical process that produces carbon dioxide directly. Gasoline is combusted to run a
car. And many people around the globe
get electricity from the burning of coal in power plants. Deforestation also leads to higher
CO2 levels. During photosynthesis in the leaves
of trees, carbon dioxide and water are used to make glucose and oxygen. If there are fewer trees on the
Earth, then fewer CO2 molecules can be removed from the atmosphere.
Methane is another greenhouse gas
that enters Earth’s atmosphere by both natural and human causes. The decomposition of food waste in
landfills increases the amount of methane in the atmosphere. Livestock also produce methane
during their digestion of food and as their manure decomposes.
Nitrogen oxides are greenhouse
gases that are composed of the elements nitrogen and oxygen. The formula NO𝑥 is used for
nitrogen oxides because the gases can have different numbers of nitrogen and oxygen
atoms. For example, common nitrogen oxides
are nitrogen monoxide, or NO, and nitrogen dioxide, or NO2. Using fertilizers, manufacturing
nitric acid, and burning fossil fuels and biomass all increase the amount of
nitrogen oxides in the atmosphere. Nitrogen oxides also cause the
depletion of the ozone layer.
Two other important greenhouse
gases are ozone, or O3, and chlorofluorocarbons. Ozone in the ozone layer is helpful
because it protects life on Earth from harmful UV radiation. But when ozone is produced in the
troposphere, it is harmful to human health. Finally, chlorofluorocarbons are
very strong greenhouse gases, and they also cause the breakdown of the ozone
layer.
The greenhouse gas produced most by
humans is carbon dioxide. Two-thirds of all greenhouse gases
produced by humans is the CO2 made from the burning of fossil fuels. Another 11 percent is the carbon
dioxide that is rising because of how humans use land. This includes deforestation. Methane, nitrous oxide, CFCs, and
other gases make up only about 25 percent of the greenhouse gases produced by
humans.
Now, let’s discuss how greenhouse
gases contribute to global warming. Greenhouse gases contribute to the
greenhouse effect. When direct sunlight shines through
the glass of a greenhouse, the air inside the greenhouse heats up. The greenhouse effect is the
process through which gases in the Earth’s troposphere trap the Sun’s heat in the
form of IR radiation. We know greenhouse gases absorb and
emit IR radiation emitted by the Earth’s surface, atmosphere, and clouds. Let’s go through this process step
by step.
Visible light and shortwave
ultraviolet, or UV, radiation from the Sun move through the atmosphere. Some of this radiation is reflected
back into space by the atmosphere. If the radiation makes it through
the atmosphere, some of it is also reflected by Earth’s surface. Shortwave UV light is absorbed by
the ozone layer in the stratosphere. And some UV and visible light are
absorbed by Earth’s surface. Some of the radiation that is
absorbed by the Earth is emitted as infrared, or IR, radiation. Most of this IR radiation is
absorbed by greenhouse gases. The energy is then released from
the gas molecules as thermal energy. So, the IR radiation remains
trapped in the troposphere and warms the Earth.
Earth’s atmosphere is essential for
sustaining life. The Earth must be warm enough, but
not too hot. Too many greenhouse gases leads to
global warming. But if we removed all the
greenhouse gases from the atmosphere, the global temperature would be too cold.
Let’s summarize some of the main
ideas. Greater amounts of greenhouse gases
cause an increase in the greenhouse effect. This leads to global warming. As the global temperature rises,
climate change happens.
So, what is being done to help slow
down global warming and climate change? Many scientists around the world
are studying global warming and climate change to understand it better and come up
with ways to stop it. The Intergovernmental Panel on
Climate Change, or IPCC, is a part of the United Nations that keeps track of and
evaluates this research.
Climate change affects different
parts of the Earth in different ways. In some areas, there are changes in
rain and snow patterns, droughts, or heat waves. In other areas, flooding,
wildfires, or hurricanes may become more frequent or severe. Because of rising global
temperatures, glacier ice, sea ice, and continental sheet ice is melting. Habitat for animals such as polar
bears and seals is being destroyed because of this melting. The melting ice has led to rising
sea levels. This is causing more flooding in
coastal areas and more loss of habitat.
In 2015, the Paris Agreement began
so that countries could work together to combat global warming and climate
change. One of the main goals of the
agreement is to reduce greenhouse gas emissions. Carbon dioxide makes up most of the
greenhouse gas emissions. And we know most of it comes from
burning fossil fuels. So, if we burn less fossil fuels,
we may be able to slow down global warming and climate change.
One way to do this is to drive cars
less. We can walk, bike, or use public
transportation instead. Another way to reduce CO2 emissions
is to use less electricity. A lot of electricity comes from the
burning of fossil fuels, such as coal. To use less electrical energy, we
can turn off lights when they are not needed and turn off and unplug computers,
televisions, and appliances when we are not using them. If possible, we should use
energy-efficient appliances and light bulbs.
Before we summarize all that we’ve
learned, let’s take a look at a question.
What term do scientists give to the
fact that the average temperature near to the surface of the Earth has steadily
risen over the past 100 years? (A) Scorched Earth, (B) climate
change, (C) global warming, (D) ozone depletion, (E) the greenhouse effect.
First of all, the rise in the
average global temperature over the past 100 years is due to increasing
concentrations of greenhouse gases in the atmosphere. Having more greenhouse gases in the
atmosphere amplifies a process called the greenhouse effect. In the greenhouse effect,
greenhouse gases in the Earth’s troposphere trap the Sun’s heat in the form of IR
radiation.
Over the last 100 years, the
concentration of greenhouse gases, such as CO2, have increased mainly from the
burning of fossil fuels. When radiation from the Sun enters
the atmosphere of Earth, some of the radiation is reflected back to space. Some of the radiation is absorbed
by the Earth and emitted in the form of IR radiation. Carbon dioxide and other greenhouse
gas molecules absorb the IR radiation that is emitted by the Earth and release it as
thermal energy. This thermal energy increases the
global temperature slowly over time. So, we can say that global warming
is the long-term increase in the Earth’s average global temperature.
It’s important to remember that the
average global temperature naturally increases and decreases by small amounts over
time. However, the term global warming
refers to the increase in global temperature that is caused by human activity. This increase in Earth’s
temperature over time has changed the climate of the planet.
The terms global warming and
climate change are often confused. The increase in average global
temperature is called global warming. Climate change refers to how the
climate in regions of the world changes because of global warming. Climate change involves changes to
the weather patterns, such as rainfall and snow. Weather events like flooding,
droughts, and heat waves may also become more frequent or severe.
In conclusion, the term scientists
give to the fact that the average temperature near to the surface of Earth has
steadily risen over the past 100 years is answer choice (C), global warming.
Now we’re ready to summarize our
learning with some key points. Climate change is caused by human
activity, which has changed the composition of Earth’s atmosphere and its natural
climate patterns. Global warming is the long-term
increase in the Earth’s average global temperature that is causing climate
change. Some of the effects of global
warming are the melting of Earth’s ice, loss of habitat, and rising sea levels. Climate change involves worsening
weather patterns, such as droughts, heat waves, hurricanes, and floods.
The greenhouse effect happens
because greenhouse gases in Earth’s troposphere absorb IR, or infrared, radiation
emitted by the Earth’s surface. These gases then release the energy
as thermal energy, which warms the Earth. Common greenhouse gases are water
vapor, carbon dioxide, methane, nitrogen oxides, ozone, and chlorofluorocarbons. Carbon dioxide makes up almost
two-thirds of the greenhouse gases produced by humans and comes mainly from the
burning of fossil fuels.
The Intergovernmental Panel on
Climate Change, or IPCC, evaluates research on climate change and helps countries
combat climate change. An individual can help reduce
global warming by driving a car less and reducing the amount of electricity used at
home.
