KS3 Chemistry - The Atmosphere and Climate Change

In this video we're going to learn about the atmosphere and climate change. So we'll cover the gases in the Earth's atmosphere and why the concentration of carbon dioxide is increasing, how greenhouse gases contribute to global warming, and then we'll finish up by looking at climate change and some of its consequences. Let's start by looking at the main gases that exist in the Earth's atmosphere. Spread around the surface of the Earth is a protective layer of gases which we call the atmosphere. And if we take a look at what the atmosphere is made up of, it's about 78% nitrogen, 21% oxygen, 1% argon, and around 0.04% carbon dioxide. Now, even though this carbon dioxide percentage seems tiny, it's actually really important. This is because its concentration is increasing rapidly, mostly due to humans. And because carbon dioxide is a greenhouse gas, this is causing the planet to warm up through a process called global warming. We'll learn more about this later on in the video. For now, let's focus on two of the big reasons why the concentration of carbon dioxide is increasing. Burning fossil fuels and deforestation. For burning fossil fuels, this releases a lot of stored energy, but it also releases a lot of stored carbon into the atmosphere as carbon dioxide. Deforestation then is when humans cut down trees, which we do on a huge scale because it produces wood for things like building materials, but it also clears land. Normally, trees absorb carbon dioxide from the atmosphere, but when they're cut down, they can't do this anymore. So deforestation massively reduces how much carbon dioxide is removed from the atmosphere. At the same time, when humans want to get rid of trees to clear land, the trees are often burned, which releases even more carbon dioxide into the atmosphere. Next, let's explore how greenhouse gases contribute to global warming. We mentioned earlier that the problem with all this extra carbon dioxide is that it causes the planet to warm up, and this is because carbon dioxide is a greenhouse gas. The way that greenhouse gases work is that when heat energy from the sun passes through the Earth's atmosphere, these greenhouse gases trap this heat energy, which in turn warms up the atmosphere. However, when there are too many greenhouse gases, it warms up the atmosphere too much and causes global warming, which just means an increase in the average temperature of the planet. Now, one of the main consequences of global warming is that it causes climate change, which are the changes in the long-term weather patterns of the planet. Climate change has a lot of different impacts on our planet and the organisms that live here, but to keep things simple, let's take a look at four different examples of the effects of climate change. One of the consequences is that rare weather events will be more common and severe, like droughts, hurricanes and floods. The second is an increase in the risk of disease outbreaks, partly because the higher temperatures allow a disease-carrying insects to spread to new parts of the world. A third consequence is sea level rise. This happens because the higher temperatures cause more ice to melt that then flows into the oceans, but also because as the water in the oceans warms up, it expands. This rise in sea levels means there's more flooding across the world and in some places entire islands and coastal towns might be submerged under water as well. And then our fourth example of a climate change consequence is that some species might become extinct. This happens because unfortunately lots of species can't adapt or migrate quickly enough, meaning they aren't able to move to better regions. If you haven't heard yet, you can find all of our videos on our website, cognito.org. You'll also find questions, flashcards, exam-style questions and passpapers, and we track all of your progress so that you always know what to study next. So sign up for free by clicking here or browse our playlist here on YouTube.