Global Warming: Atmospheric Causes and Effect on Climate

Lesson Transcript
Instructor: Peter Jaeger

Pete currently teaches middle school Science, college level introductory Science, and has a master's degree in Environmental Education.

Global warming is a multifaceted and complex issue that involves both natural and human causes that increase the number of greenhouse gases. Learn how the atmospheric temperature can increase leading to global warming, explore some of its causes and how it affects climate change, and discover the role of the greenhouse effect on global warming. Updated: 08/19/2021

Global Warming Warm-up

Hello, and thank you for joining me on everyone's favorite news show Top Five Things to Know. I am your host, Temp R. Ture. 'Global warming' - just the mention of the words conjures up images of super storms, red thermometers, melting glaciers and polar bears (and that is just if you are lucky). There are as many opinions about causes, effects and who is to blame. There are celebrities, athletes, news talk shows and teachers who have something to say about this issue. What do we believe? What is real, and what are scare tactics? How do I know who to listen to or not listen to? How can I make an informed decision about this topic? What points are scientific, and which ones are not? We will take a look at this topic on today's edition of Top Five Things to Know!

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  • 0:05 Global Warming Warm-Up
  • 1:01 Global Warming Background
  • 1:42 Greenhouse Effect
  • 2:36 Greenhouse Gases
  • 3:48 Other Things to Know
  • 7:15 Lesson Summary
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Global Warming Background

Gases such as CO2 and CFCs trap infrared radiation in the atmosphere.
Greenhouse Effect Image

So, what is meant by the term global warming? It is often used in many ways to mean different things, and it is blamed for a myriad of problems. Global warming simply means an increase in the average temperature of the earth's atmosphere near its surface - either from natural or human causes - that may result in a change in global climate patterns. There it is, folks, plain and simple. Global warming means the globe is warming. But don't worry, that's not the end of our show. I have compiled a 'Top Five Things to Know' list about this thorny issue. So, without further hesitation, here are tonight's Top Five Things to Know!

Greenhouse Effect

Number five: Global warming is due to the greenhouse effect. The greenhouse effect is the normal trapping of the earth's heat in the lower atmosphere, due to the conversion of light into heat as it strikes the earth's surface. This is a normal feature of our atmosphere that helps regulate the extreme temperature fluctuations that might occur if we didn't have an atmosphere.

Visible light, as shortwave radiation (shown below in yellow), passes through the atmosphere and is converted to infrared radiation we know as heat (shown as grey). Some of the heat escapes back into space, and some stays in the atmosphere, trapped and reflected back to the earth by gases in the atmosphere. This is very similar to a greenhouse, which traps in heat to keep plants warm.

Visible light is converted to heat.
yellow and gray arrows showing greenhouse effect

Greenhouse Gases

This leads us to...

Number four: Greenhouse gases trap heat in the atmosphere. The reason the greenhouse effect works is that heat is trapped in by gases present in the atmosphere. These gases include carbon dioxide (CO2), methane (CH4), water vapor, nitrous oxide (N20) and CFCs (which are chlorofluorocarbons).

As the concentration of these gases change in the atmosphere, the amount of heat they hold in can also change. Greenhouse gases are necessary to regulate the temperature, but a rise in one of them can lead to what is known as the enhanced greenhouse effect. In this, the greenhouse effect is magnified by the rise in concentration of a greenhouse gas.

The natural causes for these gases include volcanoes and animal waste, while human causes include combustion of fossil fuels and increased animal waste production from livestock. I know the question you are all thinking. What is the concentration of these gases, especially carbon dioxide, like?

Pie chart of emitted greenhouse gases by sector
Greenhouse Gas Emissions Chart

Other Things to Know

Well, that leads us to...

Number three: The concentration of carbon dioxide in the atmosphere is increasing. Based on direct measurement of the concentration of carbon dioxide over the past 50 years, the concentration has risen from 315 parts per million (ppm) in 1960 to 391 ppm in October of 2012.

The estimated CO2 concentration during pre-Industrial Revolution times was 280 ppm. Measurements over long periods of time have shown that carbon dioxide levels naturally fluctuate, but were historically measured to be between 200 and 280 ppm. Since carbon dioxide is a greenhouse gas, scientists believe that the temperature fluctuated as a result of the cycling CO2 levels. Is this true? Does the earth's temperature naturally fluctuate?

Graph depicting the average temperature of Earth over time
Reconstructed Earth Temperature Graph

Number two: The average temperature of the earth is increasing. However, the average global temperature fluctuates over time. The earth's temperature is not constant now, nor ever has been. Much of the upper Midwest of the United States has geologic evidence of an ice age that occurred. The massive ice sheets that covered the area formed the Great Lakes and many other landforms.

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