Fossil Fuels, Greenhouse Gases, and Global Warming

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  • 0:05 The Effect of Humans…
  • 2:55 Greenhouse Gases
  • 3:22 Global Warming
  • 6:41 Is Global Warming the…
  • 8:08 Lesson Summary
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Lesson Transcript
Instructor: Joshua Anderson
In this video lesson, you'll learn what roles fossil fuels and greenhouse gases play in global warming, as well as what life on Earth can expect due to rising carbon dioxide levels within Earth's atmosphere.

The Effect of Humans on the Carbon Cycle

Fossil fuels release CO2 into the air.
fossil fuels

Over the past 200 years, humans have started to have a measurable effect on the carbon cycle. Part of this is due to deforestation. If we look at biomass per acre, forests contain the highest density of biomass on the planet. So deforestation removes carbon from biomass, and where do you think it goes? Some of it is turned into wood and paper products, but a lot of it has gone into the atmosphere.

However, an even bigger change to the carbon cycle has occurred as a result of the widespread use of fossil fuels. Burning fossil fuels releases carbon dioxide, also known as CO2, into the atmosphere. This adds carbon that has been out of circulation for millions of years directly to the atmosphere.

The immediate result of these human activities is that in the past 200 years, the concentration of carbon dioxide in the atmosphere has dramatically increased. In 1800, the carbon dioxide concentration in the atmosphere was about 280 parts per million, but the most recent readings from June of 2012 measured the concentration at 395 parts per million. Scientists measure carbon dioxide in the atmosphere in parts per million, which is another way of saying, 'Out of every million molecules of air, how many are carbon dioxide?' If 280 molecules out of every million are carbon dioxide, then the air has a CO2 concentration of 280 parts per million, or ppm.

In 1958, scientists started taking direct measurements of atmospheric CO2 on a continuous basis. From these direct measurements, we know that the concentration of carbon dioxide has been steadily increasing year after year for the past 54 years in a remarkably regular seasonal pattern. The pattern is so steady that CO2 levels have reached a new high each May for the past 46 years straight.

CO2 levels have reached yearly highs each of the last 46 years.
fossil fuels 2b

It's also very predictable. In fact, I'll predict that in May of 2013, CO2 levels will rise to a new peak level of 398.6 ppm, plus or minus 1 part per million, and that CO2 levels will break above 400 ppm for the first time in more than a million years in either April or May of 2014. To check the accuracy of these predictions, or to just check out the data yourself, you can go to this National Oceanic & Atmospheric Administration website and you'll see the latest atmospheric CO2 data.

Greenhouse Gases

So what does this mean? Why should we care that the concentration of carbon dioxide in the atmosphere is steadily increasing each year? The reason is: carbon dioxide is a greenhouse gas, which is a gas in the atmosphere that absorbs infrared radiation from the Earth and slows the rate of heat loss. The three major greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, and methane.

Global Warming

These greenhouse gases act like a giant blanket for the Earth, helping it to retain heat. And when the concentration of greenhouse gases goes up, it's like adding another layer of blankets. When this happens, then global warming, or an increase in the average worldwide temperature caused by higher concentrations of greenhouse gases in the atmosphere, is the logical result. Now, this may sound theoretical, like I'm guessing that if CO2 levels rise, then we expect the Earth to get warmer. However, the fact is we have actual scientific evidence that when CO2 levels rise, so does the average temperature of the Earth.

These two graphs show the correlation. The top graph shows the carbon dioxide concentration in the atmosphere, and the bottom graph shows the average global temperature. Both graphs cover the 800,000 years preceding 1950. As you can see, every time CO2 concentrations spiked higher, the temperature went up too. And when CO2 levels bottomed out, so did the temperature.

Warmer oceans send water vapor and possibly methane into the air.
fossil fuels 3

Now, like almost all true scientific data, there are some small anomalies and the data doesn't always match up perfectly, but even with these small imperfections, this is one of the closest correlations that you will ever find in the natural world. The history is clear. In the past 800,000 years, whenever CO2 levels rise significantly, the temperature rises too.

There's one other interesting thing to point out about past CO2 levels. In the past 800,000 years, the concentration of CO2 never rose much above 300 parts per million - that is, until about a hundred years ago, when we blasted right through the 300 mark on the way to our present level in 2012 of a little over 390 parts per million.

So what will happen now? There are lots of different estimates and claims that many people make, but in the past century the global temperature has risen 1.4 degrees Fahrenheit. That may not seem like a lot, but the temperature has been rising at a faster rate in the last few decades. In addition, we have 800,000 years of history that show that temperature is highly correlated to atmospheric CO2 levels. We are continuing to burn fossil fuels, and the atmospheric CO2 levels continue to rise at a steady, predictable rate.

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