Hello, in the last video, we learned about the greenhouse effect. In particular, how it works and how it affects the Earth. In this video we are going to learn about four of the main greenhouse gases that contribute to the greenhouse effect. Remember, greenhouse gases trap or hold heat created by the Sun. The four gases we will look at in this video are water vapor, carbon dioxide, methane, and nitrous oxide. Let's start by looking at water vapor, the most common of all the greenhouse gases. Water vapor is made of two elements. An element is the simplest form of a substance. The two elements that make up water vapor are hydrogen and oxygen. There are two hydrogen atoms and one oxygen atom in water vapor. An atom is the smallest piece of an element So how is water vapor made? Water vapor is made through evaporation. Evaporation is the process of a liquid turning into a gas. Water vapor is a natural part of our atmosphere and plays a big role in weather and climate. Water vapor is directly connected to evaporation. That means, that the warmer the Earth gets, the more water vapor there is in the atmosphere. As water vapor increases, it traps more heat in the Earth's atmosphere. This causes temperatures to get warmer. This is called a positive feedback loop. The second most common greenhouse gas is carbon dioxide. Carbon dioxide is made up of two elements, carbon and oxygen. There is one carbon atom and two oxygen atoms in carbon dioxide. So how is carbon dioxide made? Carbon dioxide is made by natural processes such as breathing, the decomposition or decay of living things, and volcanic eruptions. It is also made by humans through actions like the cutting down of trees, known as deforestation, and the burning of fossil fuels. Fossil fuels are natural materials such as oil, coal, or gas that are burned to create energy. There has been a large increase in the amount of carbon dioxide in our atmosphere over the past several decades because of human activity. Such as making electricity and driving cars. This increase in carbon dioxide has been identified as a main factor of global warming and climate change. The third most common greenhouse gas is methane. Methane is made up of two elements, carbon and hydrogen. There is one carbon atom and four hydrogen atoms in methane. So how is methane made? Methane is created by natural things such as wetlands, termites, and oceans. It is also made by humans through things like fossil fuel production, agriculture or farming, and waste. Although there is less methane in the atmosphere, it traps more heat than other greenhouse gasses. The last greenhouse gas we will learn about is nitrous oxide. Nitrous oxide is made up of two elements, nitrogen and oxygen. There are two nitrogen atoms and one oxygen atom in nitrous oxide. So how is nitrous oxide made? Nitrous oxide is created by natural things such as soil and the oceans. Natural sources create the majority of nitrous oxide in our environment. Like many of the the greenhouse gasses, human activity also creates nitrous oxide. These activities include things like agriculture, the burning of fossil fuels and industrial processes. As we know, the greenhouse effect is a good thing because it makes the Earth warm enough for us to live. However, recently, these greenhouse gases have increased in the environment because of human activity. This increase in these greenhouse gases is the main cause of climate change. In this video, we learned about four of the main greenhouse gases that contribute to the greenhouse effect. In the next video, we will learn more about the natural causes of the greenhouse effect. And how the Earth's environment tries to get rid of greenhouse gases through something called natural sinks.