Lesson video

This lesson is called global warming 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 describe some evidence for global warming and see how it is linked to human activities.

In our lesson today, we're also going to 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 to make a note of them, but I will introduce them to you as we come across them.

In our lesson today, we're going to have a look at the greenhouse effect and see how it and global warming are linked.

And then we're gonna have a look at greenhouse gas emissions and see how they are linked to global warming.

So are you ready to go? I certainly am.

So let's get started.

So let's have a look first at the greenhouse effect.

What is the greenhouse effect and how does it happen? Well, it is caused by greenhouse gases present within the atmosphere, which surrounds the surface of the Earth.

So the sun warms the Earth and the Earth's atmosphere, and a lot of that heat is radiated or escapes into space.

But the greenhouse gases in the atmosphere help to trap some of that heat and keep it in the atmosphere and warming the surface of the Earth.

And the presence of those greenhouse gases within the atmosphere mean that the atmosphere is warmer than it would be if those gases weren't present.

And this means that the Earth's surface is warmer than it would be otherwise.

So the greenhouse effect is caused by greenhouse gases present within the Earth's atmosphere, which are trapping extra heat radiated from the sun in the atmosphere of the Earth and causing the Earth's atmosphere and its surface to be warmer than it would be otherwise.

Now, this is a natural process.

The greenhouse effect is a natural process, and it's a very important process because what it does is increase the Earth's average surface temperature to a level which can sustain life.

Now, if the greenhouse gases weren't present within the atmosphere, Earth would be, on average, a very chilly minus 20 degrees.

But because of the role that the greenhouse gases play by creating the greenhouse effect, Earth's average temperature is a much more pleasant plus 15 degrees centigrade.

And this means that lots of different types of life can survive on Earth.

Now, this has been a process that has been going on for many millions of years and has led to the great diversity that is present on Earth.

It has helped to keep Earth warm enough so that it has liquid water in our oceans and rivers and lakes, solid water at our poles in the form of ice and snow, and gaseous water present within our atmosphere.

And all of this means that life has been able to survive and thrive on Earth.

So what is the greenhouse effect? Is it A, greenhouse gases in the atmosphere keeping Earth's surface warmer than it would be otherwise? Or B, the emission of greenhouse gases into Earth's atmosphere.

Or C, the warming of the Earth's atmosphere and surface by the sun.

I'll give you five seconds to decide.

Okay, so you should have chosen A, that the greenhouse effect is the greenhouse gases in the atmosphere keeping Earth's surface warmer than it would be otherwise.

Well done if you chose that option.

Now, we can measure the temperature of the Earth, and scientists do so in many, many places across the Earth.

You can see in the photograph there on the screen a weather station positioned on land.

And this is an example of the types of weather stations positioned across the globe, which are monitoring the temperature of the Earth at many different locations throughout the day and night.

Now, these measurements are data.

So data is the numbers that have been collected by these pieces of equipment, and they provide us with evidence in changes in the Earth's average surface temperature over time.

So we can take the data that we are collecting from these pieces of equipment, so the numbers that we are collecting, and we can study them and see if they are changing, and if so, how they are changing.

So let's have a look at some of that greenhouse effect.

Earth's average temperature is a much more pleasant plus 15 degrees centigrade, and this means that lots of different types of life can survive on Earth.

Now, this has been a process that has been going on for many millions of years and has led to the great diversity that is present on Earth.

It has helped to keep Earth warm enough so that it has liquid water in our oceans and rivers and lakes, solid water at our poles in the form of ice and snow, and gaseous water present within our atmosphere.

And all of this means that life has been able to survive and thrive on Earth.

So what is the greenhouse effect? Is it A, greenhouse gases in the atmosphere keeping Earth's surface warmer than it would be otherwise? Or B, the emission of greenhouse gases into Earth's atmosphere.

Or C, the warming of the Earth's atmosphere and surface by the sun.

I'll give you five seconds to decide.

Okay, so you should have chosen A, that the greenhouse effect is the greenhouse gases in the atmosphere keeping Earth's surface warmer than it would be otherwise.

Well done if you chose that option.

Now, we can measure the temperature of the Earth, and scientists do so in many, many places across the Earth.

You can see in the photograph there on the screen a weather station positioned on land.

And this is an example of the types of weather stations positioned across the globe, which are monitoring the temperature of the Earth at many different locations throughout the day and night.

Now, these measurements are data.

So data is the numbers that have been collected by these pieces of equipment, and they provide us with evidence in changes in the Earth's average surface temperature over time.

So we can take the data that we are collecting from these pieces of equipment, so the numbers that we are collecting, and we can study them and see if they are changing, and if so, how they are changing.

So let's have a look at some of that data.

So this graph shows the average surface temperature of the Earth over the past 2,000 years.

Now, you need to first of all understand that an average surface temperature has been concluded from the temperatures recorded between 1850 and 1900.

So the surface temperature of the Earth was recorded during that period of time and then averaged, and that is marked as zero on the y-axis, on the left axis.

And then how the temperature has fluctuated, has increased or decreased from that temperature over the last 2,000 years has then been plotted on this graph.

So zero on the left axis is the average temperature recorded between 1850 and 1900, and then the line is showing how that temperature has fluctuated, both above and below the average temperature over the course of that 2,000-year period.

So you can see that for the first 900 years or so, the average temperature was slightly above the average temperature recorded between 1850 and 1900.

And then from about 1100 through to about 1750 or 1800, the temperature dipped and was below, more or less, below the average temperature recorded between 1815 and 1900.

So you can see on the graph then that when we take the average temperature from 1850 to 1900 and mark that as zero on the y-axis, on the left axis, we can see how the temperature has fluctuated, both above and below that temperature over the course of the last 2,000 years.

So have a look at the data on that graph.

What conclusions can we draw from that data? So we can see that the average temperature has stayed within a fairly small range of plus or minus 0.

3 degrees for the best part of the 2,000-year period that this graph shows.

But in the last 100 years or so, there has been a very unusual and very rapid increase in average temperature.

And now the temperature is well above one degrees higher than the average that was recorded between 1850 and 1900, which is plotted as zero on the y-axis of the graph.

Now, this unusual and very rapid increase in Earth's average surface temperature is called global warming.

That is what we are referring to when we talk about global warming, this very rapid, very unusual increase in surface temperature.

Now, we can explore that data in different ways, and we can present it in lots of different ways.

And NASA has made this really interesting colour animation showing the average surface temperature over the course of 140 years from 1880 through to 2020.

Now, when the colours are blue, it's not showing that the Earth is cold, but it's showing that it is cooler than the average as recorded between 1850 and 1900.

So that is at points where, on the previous graph that we were looking at, the temperature was below the zero mark on the y-axis.

And when the colour is recorded as orange and into red, we can see that that is where temperatures are above that average, that average that was recorded between 1815 and 1900, so the zero on the y-axis.

And you can see how between 1880 and 2023, the Earth's average temperature has increased on the whole.

It hasn't increased absolutely everywhere, but the large majority of the surface of the Earth, it has increased.

And particularly since 1950, there are increasing areas of orange and then into red as we move further and further away from that average that was recorded between 1850 and 1900.

So what conclusions can we make from the data in the graph? So here's that graph again where we've got this average temperature recorded between 1850 and 1900, which is plotted as zero on the y-axis, and how the temperature, the average temperature of the Earth has fluctuated over the last 2,000 years from that point.

So which of these conclusions can we draw? Can we say that A, the average temperature doesn't usually change from year to year? Or B, the average temperature stayed within a narrow range for almost 2,000 years.

Or C, there has been an unusual rapid increase over the last century.

I'll give you another five seconds to decide.

Okay, so we can conclude from this graph that the average temperature stayed within a very narrow range for almost 2,000 years and that there has been an unusual rapid increase over the last century.

Well done if you chose both of those options.

So let's consider Izzy and Andeep.

They've been sharing their ideas about the greenhouse effect and global warming.

And Izzy says, "Over the past 100 years, there's been a fast rise in average global temperature." And Andeep says, "This recent sharp rise in global temperature is called the greenhouse effect." So firstly, can you decide who is correct, Izzy or Andeep? And then how would you explain the correct ideas to the person who is incorrect? So pause the video and come back to me when you're ready.

Okay, let's check your work.

So who is correct, Izzy or Andeep? Well, you should have said that Izzy is correct and therefore, Andeep is incorrect.

So how would you explain the correct ideas to Andeep? Well, you could have said that the greenhouse effect is the effect of gases in the atmosphere, which is keeping the Earth's surface warmer than it would be without them.

And this recent sharp rise in global temperature is actually called global warming and not the greenhouse effect.

Well done if you made both of those points.

Okay, let's move on to having a look at how greenhouse gas emissions and global warming are linked.

So we've seen this graph now on a few occasions.

What do you think might have caused the recent and very rapid increase in Earth's average surface temperature? Well, if we compare this graph to other data, we might be able to come to a more certain conclusion.

So let's compare that graph, which is now sitting on the right of the screen with the graph on the left looking at the number of greenhouse gas emissions, which have been released from burning fossil fuels.

And if we look at these data, we can see that over the same period of about 100 years, there was a rapid increase in greenhouse gas emissions from human activities, so from burning fossil fuels, as shown in the data on the left.

And there was a rapid increase in the Earth's average surface temperature, as shown in the graph on the right.

So these two data points, these two datasets show a very similar trend.

As one factor changes, another factor also changes.

Now, this is called a correlation, a match.

As one piece of data changes, the other changes to match it.

But a correlation does not always mean that one factor is directly causing or even linked to the other factor.

It just means that the patterns are similar.

Now, 99.

9% of scientists agree that global warming, which is this rapid and unusual increase in Earth's surface temperature, has been caused by the increase in greenhouse gas emissions from human activities, such as burning fossil fuels.

But in order to be sure that there is a link between these two factors and not just a correlation or a match in their data, we need to have a mechanism, a way of explaining that link.

And the greenhouse effect can provide that explanation and it can explain why the data on greenhouse gas emissions is correlated, is matched to the data on global surface temperature.

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

We know that greenhouse gases in the atmosphere are causing the greenhouse effect because of the way they help to trap extra heat from the sun in the atmosphere, which warms the surface of the Earth.

We also know that we have, over the last 150 years or so, been adding more greenhouse gases into the atmosphere.

And we also know that if we add more greenhouse gases into the atmosphere, it will enhance the greenhouse effect.

And if we enhance the greenhouse effect, we are trapping more heat on the surface of the Earth, and therefore, we should see an increase in the average surface temperature of the Earth.

And if we see an increase in the average surface temperature of the Earth, especially one which is unusual and very rapid, we can call that global warming.

So there is a direct link between the greenhouse effect and global warming.

And if we increase the number of greenhouse gases in the atmosphere, we are enhancing the greenhouse effect, which is driving global warming.

So what type of human activities release greenhouse gases into the atmosphere? Well, we can group them into two separate classes.

One involves the burning of fossil fuels, coal, oil, and gas.

And this includes power stations, which are burning coal, oil or gas in order to generate electricity and heat.

And then all of the types of transport that we use to move us and goods around the world.

And most of those use fossil fuels in order to make them move.

So cars, lorries, buses, trains, boats, aeroplanes , most of those use fossil fuels in the form of petrol, diesel or aviation fuel to make them move.

So burning fossil fuels, coal, oil and gas, when we do that, we release carbon dioxide into the atmosphere, and this is a type of greenhouse gas.

So that's one group of human activities, which generate greenhouse gas emissions.

Another are other processes and activities that release greenhouse gas emissions but don't involve burning fossil fuels.

So this includes a number of industrial processes, which make things, such as fertilisers, clothing, paint, bricks, those sorts of things, which aren't burning fossil fuels, but are releasing greenhouse gases as part of the process.

Then also farming, in particular, the use of things like fertilisers and farming cattle releases a lot of greenhouse gases as well.

Cows in particular because of the type of biological processes that are going on within their digestive system to enable them to digest grass, release a lot of methane gas into the atmosphere.

And then other processes, like the decomposition of waste within landfill.

So decomposition is about breaking big substances down into smaller substances, and it happens on things that were living.

So any fibres that we put into landfill, which have a natural origin, such as cottons and linens, wood and paper, for instance, these are decomposed and the process of decomposition releases greenhouse gases into the atmosphere as well.

So both burning fossil fuels and this whole host of other activities all contribute to releasing greenhouse gases into the atmosphere.

So is this true or false? Most scientists believe that global warming is caused by emissions of greenhouse gases from human activities.

Okay, so you should have said that that is true, but why? So you can explain that by saying that 99% of scientists agree that unusual rapid increases in temperature have been caused by the increase in greenhouse gas emissions, which has been generated from human activities, and these enhance the greenhouse effect, which has led to global warming.

Well done if you got that.

So what I'd like you to do now is to summarise this last part of our lesson, looking at greenhouse gas emissions and global warming by firstly describing the correlation that can be seen in the data in these two graphs.

Now, you need to remember that correlation means a match.

So how do these two graphs match each other? And when you're describing, you're saying what you see.

So describe the patterns and how they match.

And you can use data from the graphs.

So quote the numbers, for instance, from the graph axes to help you with that.

And then I'd like you to explain how this correlation could be due to the greenhouse effect.

So how are these two things linked? And explain how that is the case.

So how are greenhouse gas emissions linked to an increase in the average surface temperature on Earth? So pause the video, give this some good consideration, and come back to me when you're ready.

Okay, let's see what you've made of these tasks.

So firstly, I asked you to describe the correlation that can be seen in the data.

So you should have said that the data shows that over the same period of approximately 100 years, there was both a rapid increase in greenhouse gas emissions from human activities.

So that's the description of the shape of the graph from the first graph.

And a rapid increase in Earth's average surface temperature.

So that's coming from the second graph.

And so we can say that the temperature increased as the emissions increased.

So have you got those two descriptions of the data and also a description of the correlation, the match between them? Well done if you have.

Then I asked you to explain how this correlation could be due to the greenhouse effect.

So you should have included that firstly, the greenhouse effect occurs when certain gases in the atmosphere keep Earth's surface warmer than it would be without them.

And these are called greenhouse gases.

And perhaps you've stated which greenhouse gases they are, including carbon dioxide, methane, and water vapour.

You should also have said that emissions that add more greenhouse gases to the atmosphere enhance the greenhouse effect.

And an enhanced greenhouse effect increases the Earth's average surface temperature, and this is called global warming.

So we can show a link between the number of greenhouse gases emitted into the atmosphere and global warming or the unusual and rapid increase in Earth's surface average temperature.

Well done if you got all of those points, but do add to your work if you've missed anything out.

Okay, we've come to the end of our lesson today, and what we've seen in our lesson is that greenhouse gases in the atmosphere cause a natural greenhouse effect, and this helps to keep the Earth's surface nice and warm, warm enough for life.

And we've measured the temperature of the Earth's surface in many, many places over many, many years.

And this data has shown an unusual and very rapid increase in Earth's average surface temperature, which has happened over the last 100 years or so.

Now, this increase, this very rapid and unusual increase is called global warming.

And when we look at both the change in average surface temperature and the number of greenhouse gases which are being emitted into the atmosphere, we can see a correlation or a match in their patterns, and we can explain that by describing how greenhouse gases enhance the greenhouse effect, driving up Earth's surface temperature.

And we can call that global warming.

So thank you very much for joining me today.

I hope you found today's lesson very interesting, and I hope to see you again soon.

Bye.