Lesson video

This lesson is called The Greenhouse Effect and is from the unit Climate change and living sustainably.

Hi there, my name's Mrs. McCready, and I'm here to guide you through today's lesson so thank you very much for joining me today.

In our lesson today, we're going to explain what causes the Earth's greenhouse effect and see why it affects global surface temperature.

So in our lesson today, we're gonna come across a number of keywords, and they're listed up here on the screen for you now.

You may wish to pause the video and make a note of them, but I will introduce them to you as we come across them.

So in our lesson today, we're going to first of all look at the Greenhouse Effect and see what it is and how it works before we consider how human activity and the greenhouse effect are interrelated.

So, are you ready to go? I certainly am.

So let's get started.

Now, as far as we know, the Earth is the only planet that supports life.

We've not found another planet either within our solar system or beyond it that supports life.

But of course, whilst that might well be possible, it's still unproven.

And the Earth supports life for many reasons but one of the reasons that it is able to support life is because of a natural process that occurs on Earth called the greenhouse effect.

And the greenhouse effect keeps the Earth warm enough for life to survive and thrive on Earth, so it's not too hot, it's not too cold, but it is just right.

Now, if the greenhouse effect didn't occur, if there was no greenhouse effect, then the Earth would be much colder.

And instead of being about on average plus 15 degrees, it would be probably more like a chilly minus 20 degrees on average.

So just colder than your freezer.

So it would be much less able to support the abundance of life on Earth.

But why is the greenhouse effect called the greenhouse effect? Well, it is named after a greenhouse, such as like a gardener might use.

So maybe you have a greenhouse in your garden or allotment or maybe you know somebody or have a relative who has one.

And you can see an example of a greenhouse in the picture on the screen.

But what does a gardener use a greenhouse for? And why is a greenhouse helpful? What do you think? Well, maybe you've come up with some suggestions like Jacob and Sophia.

So Jacob thinks that a gardener uses greenhouses for growing plants, such as fruit and vegetables.

Maybe that's what you or your friend or your relative uses their greenhouse for.

And why is a greenhouse helpful? Well, maybe you've suggested something like Sophia has, that it keeps plants inside it warm.

So let's look at that in a bit more detail.

What's actually happening in a greenhouse? Well, we know that the sun warms the air and it warms everything else inside and outside the greenhouse.

Now, when the sun is radiating warmth down onto the greenhouse and onto the internal and external environment, the air inside the greenhouse is warmed, but it's trapped inside the greenhouse.

And so, that heat can't easily escape, and that means that the greenhouse gets warmer.

And so, even on cold days, the greenhouse will be slightly warmer than outside.

And on warm days, it will be much warmer than outside.

And what that means is that the temperature inside the greenhouse will be much better for growing plants and allowing them to thrive in that environment than outside.

And because the temperature is at a better range, the plants will grow faster and produce more fruit or vegetables.

So what does a greenhouse do? Does it A, keeps the temperature inside the greenhouse warmer than outside? B, keeps the temperature inside the greenhouse cooler than outside.

Or C, keeps the temperature inside the greenhouse exactly the same as outside.

I'll give you five seconds to decide.

Okay, so you should have said that a greenhouse keeps the temperature inside the greenhouse warmer than outside.

Well done if you chose that option.

So how does this apply to the greenhouse effect and what is the greenhouse effect? Well, the greenhouse effect is a natural process and it is caused by the atmosphere.

So the atmosphere, as you can see on the diagram there, is a layer of gases that surrounds the planet.

And if we look at this word atmosphere, it's made up of two smaller words.

The word sphere means ball and I'm sure you've come across the word sphere in mass lessons, for instance.

And the word atmo, which means air or vapour.

So the word atmosphere means a ball of air or vapour, which is a good description of the atmosphere because it is a ball of air and vapour, which surrounds the Earth and extends many miles out from the surface of the Earth into space.

Now, the atmosphere is a mixture of lots of different gases.

So it's made up of mainly nitrogen.

About 78% of the atmosphere is made of a gas called nitrogen.

About 21% of the atmosphere is oxygen, and then the rest is divided into lots of other gases and other things.

So 0.

04% of the atmosphere is made of carbon dioxide and the rest is made of other gases including methane and water vapour.

So the atmosphere is a mixture of all of these different gases.

And because it's a mixture, it means that we could, if we had the right equipment, we could separate it into the various different components and have all the nitrogen in one blob and all the oxygen in another.

Now, carbon dioxide, methane, and water vapour are all known as greenhouse gases.

And greenhouse gases play a very important role within the greenhouse effect.

So let's look at that in a little bit more detail.

How do greenhouse gases cause the greenhouse effect? Well, it all starts with the sun.

So the sun warms the Earth and it also warms the atmosphere surrounding the Earth.

Now, the greenhouse gases are present within the atmosphere, and what they do is help to trap some of that heat from the sun and stop it from escaping into space.

And so, more of the heat from the sun is trapped within the atmosphere.

And so the atmosphere is warmer than it would be if the greenhouse gases weren't present.

And what this means is that the surface of the Earth is then warmer than it otherwise would be as well.

So the greenhouse gases are playing a really important role here.

They are trapping some of the heat from the sun in the atmosphere, stopping it from radiating out into space, and thus causing the Earth to be warmer than it would be if those gases weren't present in the atmosphere.

So this is called the greenhouse effect, and it's being driven by the presence of greenhouse gases in the atmosphere.

So which of the named gases are greenhouse gases? Is it carbon dioxide or methane and water vapour, or nitrogen, or oxygen? I'll give you five seconds to decide.

Okay, so which gases are greenhouse gases? Well, you should have said that both carbon dioxide and methane and water vapour, they are all greenhouse gases.

Well done if you chose all three of those in the two options there.

So what I'd like you to do is to summarise the first part of our lesson today by firstly completing the labels to explain how the greenhouse effect works.

So which words are missing from the spaces in these sentences to explain the greenhouse effect? And once you've done that, I would like you to consider the ideas that Aisha and Lucas have about the greenhouse effect.

So Aisha says that, "The atmosphere is a layer of glass.

It's like the walls of a greenhouse." And Lucas says, "Without the greenhouse effect, Earth would be too hot for living organisms." But they have both made mistakes.

So how would you explain the correct ideas to both Aisha and Lucas? So pause the video and come back to me when you are ready.

Okay, let's review your work.

So firstly, I asked you to complete the labels to explain the greenhouse effect, and you should have said that the sun warms the Earth and the atmosphere.

That greenhouse gases in the atmosphere keep it warmer than it would be without them.

And this keeps Earth's surface warmer than it would be otherwise.

Well done if you've got all four of those words correctly filled into those spaces.

Then I asked you to consider Aisha and Lucas' ideas about the greenhouse effect and explain the correct ideas to them.

So for Aisha, you should have said that the atmosphere is a layer of gases, not a layer of glass.

And these gases surround our planet and include some greenhouse gases.

And you might have mentioned the word atmosphere and you might have stated those greenhouse gases, carbon dioxide, methane and water vapour as part of your response.

Well done if you've added that extra work in.

And for Lucas, you should have said that without the greenhouse effect, the Earth would be too cold, not too hot for living organisms. And well done if you've added that.

Okay, let's move on to the second part of our lesson now, which is about how human activity and the greenhouse effect are linked.

So let's start with what Sam is thinking.

So they've said that if the greenhouse gases make up less than 1% of the atmosphere, why do they matter? And that's a good question to ask, and maybe you've asked it or maybe you've heard other people asking a similar type of question.

Well, we know that greenhouse gases are really important because they drive the greenhouse effect and the greenhouse effect causes the Earth's surface temperature to be warmer than it otherwise would be.

Now we need greenhouse gases in order for the greenhouse effect to occur.

And these greenhouse gases are present in the atmosphere and keep the Earth at a nice warm enough temperature for life to thrive on Earth.

We also know that carbon dioxide is a greenhouse gas and it, therefore, contributes to the greenhouse effect.

Now, if we look at how much carbon dioxide is in the atmosphere and trace this back over many thousands of years, we can see some interesting patterns in how much carbon dioxide is present within the Earth's atmosphere.

So looking at the graph here on the screen, this has measurements for the amount of carbon dioxide in the Earth's atmosphere going back 800,000 years using ice cores to give us that data.

So we've extracted ice cores from the polar regions and going back 800,000 years worth of ice in these ice cores, we can see how carbon dioxide levels have changed over time.

So you can see how for many thousands and thousands of years, and in fact for the majority of that 800,000-year period, the atmospheric carbon dioxide level has not exceeded 300 parts per million, until about 1950.

And since then, it has increased absolutely significantly and very, very quickly to more than 420 parts per million.

So we can see that the amount of carbon dioxide in the atmosphere has fluctuated.

It has gone up and down over the course of that period of time.

But for the vast majority of that period of time, it has stayed within a fairly narrow range and has done for 800,000 years or more.

But, and very recently since 1950, there has been this very unusual and extremely rapid increase in carbon dioxide levels in the atmosphere, and that's happened over the last century or so.

So looking again at this graph, which is showing carbon dioxide levels in the Earth's atmosphere over the last 800,000 years, which of these statements are supported by the data in the graph? A, there were natural changes in carbon dioxide levels over thousands of years.

B, the carbon dioxide level always increases as time goes on.

C, in 1950, the carbon dioxide level increased above 300 parts per million for the first time.

And D, the increase since 1950 is unusual.

But which of these statements are supported by the data in the graph? I'll give you five more seconds to decide.

Okay, so you should have said that there were natural changes in carbon dioxide levels over thousands of years.

That in 1950, the carbon dioxide increased above 300 parts per million for the first time.

And the increase since 1950 is unusual.

But you should not have chosen that the carbon dioxide level always increases as time goes on because it both goes up and down.

Well done if you chose all three of those options.

Now, the vast majority of scientists agree that the increase in carbon dioxide levels in the atmosphere has been caused by human activities.

Now what do we mean by human activities? Well, many human activities require the burning of fossil fuels.

We use fossil fuels to power our transport, our cars and buses and trains and boats and planes.

We also burn fossil fuels, coal, oil, and gas in our power stations to generate electricity.

And when we burn fossil fuels, we release carbon dioxide into the atmosphere.

So all of these activities that we as humans are undertaking are releasing carbon dioxide into the atmosphere, and these are called emissions.

The releases of carbon dioxide gases into the atmosphere.

Now, if we look at a graph which plots the carbon dioxide emissions over time, we can see that from 1750 to about 1850, the amount of carbon dioxide being emitted into the atmosphere is nearly zero.

It's negligible.

But from just after 1850 onwards, the amount of carbon dioxide being released into the atmosphere has been increasing.

And from after the Second World War, so from about 1950 onwards, the increase has become much more rapid.

So if we look at the data about which types of activities contribute to the emissions of greenhouse gases, the release of greenhouse gases into the atmosphere each year, we can see that 13.

8% of greenhouse gas emissions come from farming and food production.

12.

2% come from clearing forests for building or for farming.

4% comes from gas leaks, 19% from industry, 8.

6% from burning fuels for other purposes, 24.

9% from heating buildings and generating electricity, 14.

3% from transport.

And the final 3.

2% from decomposing waste.

That means waste being broken down into smaller pieces.

So these are various different activities that contribute emissions of greenhouse gases each year into the atmosphere.

So, according to the pie chart, which are the three greatest contributors to greenhouse gas emissions.

So look at the data and I'll give you five seconds to rank your top three.

Okay, so you should have put in first place heating buildings and generating electricity at 24.

9%.

Then in second place industry with 19%.

And in third place transport with 14.

3%.

Well done if you chose all three of those and extra well done if you put them in the correct order.

Now, we know that there are plenty of activities that humans are undertaking that release greenhouse gases into the atmosphere.

And we also know that greenhouse gases in the atmosphere cause the greenhouse effect.

So, we would expect then that if we increase the amount of greenhouse gases in the atmosphere, that the greenhouse effect would be enhanced.

And if the greenhouse effect is enhanced, then the average surface temperature of the Earth should increase because more heat will be trapped on the surface of the Earth.

Now, we know that when we're doing a similar thing in a greenhouse, so when we're trapping heat inside the greenhouse, it can sometimes become too hot for the living organisms within the greenhouse to survive.

And that means that they are more likely to die because they get dried out and they can stop working properly because it becomes too hot.

However, it's easy enough a problem to resolve, we can just throw open a window and let out some of the hot air.

And that reduces the temperature, puts it back to a much more pleasant temperature, and the plants can carry on growing in their optimal conditions, in their best conditions.

But we can't just throw open a window on the Earth's atmosphere and let some of the heat out.

That's obviously not possible to do that.

And so, enhancing the greenhouse effect by putting more carbon dioxide and other greenhouse gases into the atmosphere is a problem that is really difficult to solve.

So how do we solve it? Well, what we have to do is change our behaviours to reduce the amount of greenhouse gas emissions that are going into the atmosphere and driving the greenhouse effect in the first place.

And if we can lower the number of greenhouse gases that we are putting into the atmosphere, then this will reduce the effect of the greenhouse effect, and this will reduce the temperature on Earth.

But changing our behaviour is a really, really difficult thing to do, and it involves everybody doing that and not just a few people.

So, it's a difficult problem to solve, but it is solvable, but it will require everybody getting involved.

So can you complete the sentences using only the words increase and decrease to help you? So human activities have caused emissions of greenhouse gases to increase or decrease.

This is causing the greenhouse effect to increase or decrease, and this is causing Earth's surface temperature to increase or decrease.

I'll give you five more seconds to decide.

Okay, so you should have said that human activities have caused emissions of greenhouse gases to increase.

This is causing the greenhouse effect to increase, which is causing Earth surface temperature to increase.

Well done if you got all three of those correct.

And what I'd like you to do now is to summarise this second part of our lesson by looking again at the graph, which is showing emissions of carbon dioxide each year when released by burning fossil fuels.

And what I'd like you to do is to explain why the increase in emissions of carbon dioxide is causing the Earth's surface temperature to increase.

And to help you do that, I would like you to use these three keywords in your answer, greenhouse gas, atmosphere, and greenhouse effect.

So pause the video and come back to me when you're ready.

Okay, let's see what you've written.

So I asked you to explain why the increase in emissions of carbon dioxide is causing Earth's surface temperature to increase.

And you might have said that carbon dioxide is a greenhouse gas, that's the first keyword.

And greenhouse gases in the atmosphere keep it warmer than it would be without them, so that's the second keyword.

And this keeps the Earth's surface warmer than it would be otherwise and this is called the greenhouse effect, and that's the third word.

Now, you might also have stated some of the other greenhouse gases such as methane and water vapour, and you might have also maybe compared it to a gardener's greenhouse.

Check your work over and well done indeed.

Okay, we've come to the end of our lesson today and we've seen how a gardener can use a greenhouse to keep plants warm, and this helps to keep plants within the best temperature range for their growth and survival so they can produce lots of fruit and vegetables for us.

There's also the natural process of the greenhouse effect, which keeps the Earth's surface temperature warmer than it would be otherwise, and warm enough to support all the life on Earth that exists.

And this is caused by greenhouse gases in the atmosphere.

Greenhouse gases include carbon dioxide, methane and water vapour.

And they contribute to this natural process called the greenhouse effect.

However, human activities are increasing emissions of greenhouse gases into the atmosphere, and this is enhancing the greenhouse effect and causing Earth's surface temperature to increase as well.

But we can make changes to our behaviours, which will help to reduce the emissions of greenhouse gases.

So, I hope you've enjoyed our lesson today.

Thank you very much for joining me, and I hope to see you again soon.

Bye.