GCSE Chemistry - Greenhouse Gases & Climate Change (2026⁄27 exams)

Now, you've probably heard of global warming and climate change. In this video, we're going to take a look at the difference between the two of them, what causes them, and what the consequences could be. If we take a look at the Earth, spread all the way around the surface is a protective layer of gases, which we call the atmosphere. And it basically acts like an insulating blanket, or a greenhouse, keeping in the perfect amount of the sun's heat energy, so that the Earth stays at a nice temperature all the time. To see how this works, let's zoom in to the surface of the Earth. As the sun's heat energy comes down towards the Earth, in the form of short wavelength radiation, it passes through the atmosphere, and hits the surface of the Earth. Some of this energy is absorbed, and heats up the ground. But most of it is either re-emitted, or reflected back into the atmosphere towards space, in the form of longer wavelength radiation. Although some of this energy does make it back into space, most of it actually ends up hitting particles of gas in our atmosphere, which absorb the energy. And after a short delay, they re-emit that energy in random directions. This means that some of the energy will be re-emitted towards space, and some towards the Earth. Either way though, just like before, most of the energy will collide with other gas particles, before it can leave the atmosphere. And this process of being absorbed, and then re-emitted by different gas particles, happens over and over again. Which means that the heat energy stays close to Earth, far longer than if there was no atmosphere. Which keeps the Earth at a nice warm and stable temperature. As you can see here, this happens with lots of different molecules. Including carbon dioxide and methane, but also with water vapour. We call this group of gases, greenhouse gases. And the warming that they cause, the greenhouse effect. The problem is that because humans produce so much of these gases, their concentrations in our atmosphere is increasing. And so the greenhouse effect is getting stronger. Which has led to global warming. For carbon dioxide, there are two main reasons that levels are rising. One is because we're burning loads of fossil fuels, which release the carbon that was locked up inside the fuel as carbon dioxide. And the second is that we're chopping down loads of trees, which is called deforestation. This means that there's less photosynthesis, which is an important process that removes carbon dioxide from the atmosphere. Likewise, there are also two main reasons that methane levels are increasing. Firstly, farm animals produce methane during digestion, which then gets released into the atmosphere. And the second is that we produce huge amounts of waste, which sometimes releases methane as it's decomposed by microorganisms. Now we pretty much know for certain that the Earth is getting warmer, because we have records going back hundreds of years. And can see the steady increase. However, the consequences that this warming will have on our planet are much harder to know, because there are so many variables to take into account. Which makes it hard for scientists to make models of what will happen. What we do know though, is that global warming will have a significant impact on our planet. And we can refer to this impact as climate change. It's kind of a hard term to describe, but it basically refers to all of the effects of global warming on the climate. And remember climate just describes long-term weather patterns across the entire planet, rather than a daily weather in a particular place. For example, one of the consequences of global warming is that rare weather events like droughts, hurricanes and floods, will become both more common and more severe. So we can describe these changes with the term climate change. Another consequence of global warming is sea level rise, which actually happens for two different reasons. One is that the higher temperatures will cause more ice to melt, which will then flow into the oceans. And the second is that as the water in the oceans warms up, it expands. And so its volume will increase, making the sea levels rise even more. And in some places this might lead to seasonal flooding, and even the submersion of entire islands and coastal towns. In addition to all of this, climate change will also have a more general impact on the wild organisms across the world. As temperatures and rainfall patterns change, species that were perfectly adapted to their environment might not be able to survive anymore. In some cases, species might be able to adapt to the new conditions. Or migrate to other regions where the conditions are better. Unfortunately though, lots of species can't adapt or migrate fast enough. And biodiversity is likely to fall dramatically in the coming decades. 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.