Lesson video

Hello, I'm Mrs. Adcock, and today's lesson is on carbon dioxide in the atmosphere.

We are gonna be looking at the carbon cycle, and using this to help us think about how does carbon dioxide enter the atmosphere and what processes remove carbon dioxide from the atmosphere.

We are then going to look at how we monitor those levels of carbon dioxide in the atmosphere, and look at some of the data to see what has been happening to the carbon dioxide levels in our atmosphere in recent years.

In today's lesson, the outcome is, I can explain how changing factors in the carbon cycle affect the amount of carbon dioxide in the atmosphere over time.

Some of the key words we will be using in today's lesson include carbon cycle, atmosphere, combustion, and decomposers.

You may be familiar with some of these key words, but they are written here in a sentence for you.

If you would like to pause the video now and you can read through those sentences or you might like to pause and then make some notes that you can refer back to later in the lesson when needed.

Today's lesson on carbon dioxide in the atmosphere is split into three main parts.

The first part is on the carbon cycle.

The second part of today's lesson is on increasing levels of carbon dioxide in the atmosphere, and we are going to look at why those levels of carbon dioxide in the atmosphere continue to increase.

And the third part of the lesson is on monitoring carbon dioxide levels.

So we will look at where carbon dioxide levels are monitored and look at some of the data that we have on carbon dioxide levels.

Let's get started on the first part of today's lesson, on the carbon cycle.

Studying the carbon cycle helps us to understand some of the processes that remove and release carbon dioxide into the atmosphere.

We can see a basic diagram here of the carbon cycle, where the arrows represent the movement of carbon within the cycle, and the carbon cycle as a whole just shows us the movement of carbon between different carbon reservoirs or stores within the cycle.

Firstly, we're gonna look at how carbon dioxide is removed from the atmosphere.

So we know that there's about 0.

04% of our atmosphere is carbon dioxide.

When plants photosynthesise, they remove carbon dioxide from the atmosphere.

So they absorb carbon dioxide, then they undergo the process of photosynthesis, and they release oxygen gas back into the atmosphere.

And carbon dioxide is also removed from the atmosphere as it dissolves in the oceans.

Carbon moves within the carbon cycle.

So we've looked at how it's being absorbed from the atmosphere, now it's going to move within the carbon cycle before we can look at how it's going to be released back into the atmosphere.

Carbon in the oceans now can react to formed carbonates, and these are carbon-based compounds, and you will find carbonates in shells and bones.

Dead organisms and waste transfer carbon to the soil.

When plants and animals die, the carbon from them is returned to the soil.

Carbon is stored in fossil fuels.

Dead plants and animals over millions of years can form fossil fuels, and some of the carbon atoms from those organisms will now be stored within fossil fuels.

And finally, carbon is transferred from plants to animals that eat them.

So as an animal eats the plants, the carbon atoms from that plant are transferred to the animal.

Let's have a look now how some of the carbon dioxide is released into the atmosphere.

When plants and animals respire.

So we've looked at photosynthesis that removes carbon dioxide from the atmosphere, but when plants and animals respire, they release carbon dioxide into the atmosphere.

By combustion of fossil fuels.

When we burn fossil fuels to release energy, then carbon dioxide and water are the products, and that carbon dioxide is now released into the atmosphere.

Decomposers also release carbon dioxide into the atmosphere, and decomposers are organisms that break down dead and decaying matter.

There's a huge number of decomposers that are microorganisms, but they can be large organisms such as earthworms that break down dead and decaying matter.

And decomposers are essential, because without decomposers, we would have dead plants and animals covering the surface of the earth.

Time for a check for understanding.

Which of the following are ways carbon dioxide is removed from the atmosphere? A, photosynthesis by plants.

B, respiration by plants and animals.

C, combustion of fossil fuels.

D, dissolving in the oceans.

Now remember, you need to think about which ones are removing carbon dioxide from the atmosphere.

Choose any answers that you think are correct.

The correct answers are photosynthesis by plants and dissolving in the oceans, are ways that carbon dioxide is removed from the atmosphere.

Which of the following are ways carbon dioxide is released into the atmosphere? So is carbon dioxide released by, A, photosynthesis by plants, B, respiration by plants and animals, C, combustion of fossil fuels, or D, dissolving in the oceans? Again, take your time, read over those again, and choose any answers that you think are correct ways that carbon dioxide is released into the atmosphere.

Well done if you chose options B and C.

So both respiration by plants and animals and combustion of fossil fuels release carbon dioxide into the atmosphere.

Time for our first practise task for today's lesson.

So this first part is on the carbon cycle, and you need to describe what is happening at each stage of the carbon cycle.

There are nine labels there where you need to say what is happening.

You will notice that there are two arrows which are both labelled eight, and that is because the same process is happening at each of those arrows.

Pause the video, have a go, and then come back when you're ready to go over the answers.

Hopefully, you are able to describe what was happening at each stage of the carbon cycle.

So at number one, photosynthesis is removing carbon dioxide from the atmosphere.

So you may have written something similar.

Number two, carbon dioxide dissolves in the oceans.

Three, carbon dioxide in the oceans forms carbonates in shells and bones.

Four, over millions of years, fossil fuels are formed.

Five, carbon is transferred to animals when they eat plants.

Six, waste material and dead organisms return carbon to the soil.

Seven, decomposers in the soil break down the dead and decaying matter, and they return carbon dioxide to the atmosphere.

Eight shows the combustion of fossil fuels, and that releases carbon dioxide into the atmosphere.

And nine is plants and animals respiring, and that also releases carbon dioxide to the atmosphere.

Well done if you got those correct, and you were able to describe what is happening at each stage of the carbon cycle.

Hopefully, you've got a better understanding of some of the processes that release and remove carbon dioxide from the atmosphere, and how carbon is transferred at other points within the carbon cycle.

We are now going to move on to the second part of our lesson where we look at increasing levels of carbon dioxide.

So that's CO2 in the atmosphere.

Combustion of fossil fuels releases carbon dioxide into the atmosphere.

We can see this in the equation below where we have a hydrocarbon fuel and we react that in a plentiful supply of oxygen, and we will produce carbon dioxide and water, and these are released into the atmosphere.

And we as humans are burning fossil fuels all the time in things such as to cook our food, we burn petrol and diesel which are fuels in our cars, and also, we burn fossil fuels when we generate electricity.

Photosynthesis, however, removes carbon dioxide from the atmosphere.

So when plants photosynthesise, they take carbon dioxide from the atmosphere, react that with water to produce glucose and oxygen.

So this doesn't look like there's a problem because we as humans are combusting fossil fuels and releasing carbon dioxide.

However, plants are absorbing that carbon dioxide for the process of photosynthesis.

However, in recent years, human activities have been releasing more carbon dioxide into the atmosphere than is being removed by natural processes.

So this is leading to increased levels of carbon dioxide in the atmosphere.

The levels of carbon dioxide in the atmosphere are now 50% higher than they were before the industrial revolution.

And some people might think, "Well, the levels of carbon dioxide in the atmosphere are still really low because they are about 0.

04%." However, before the industrial revolution, the levels of carbon dioxide in the atmosphere were more like 0.

03%.

So this is a large increase in the amount of carbon dioxide in the atmosphere.

So burning fossil fuels increases the rate of addition of carbon dioxide into the atmosphere, and deforestation is decreasing the rate of removal of carbon dioxide from the atmosphere.

So we said that burning fossil fuels releases carbon dioxide and plants absorb carbon dioxide, but humans are now cutting down trees, and that's deforestation, so we're decreasing the rate at which carbon dioxide is being removed from the atmosphere.

Again, this leads to increased levels of carbon dioxide in the atmosphere.

Lucas has got a solution to this.

He says, "To reduce the levels of carbon dioxide in the atmosphere, we should just plant more trees." And all across the world, trees are photosynthesising, which helps to reduce the atmospheric, carbon dioxide, CO2 levels.

However, there's a limit to how much carbon dioxide those trees can absorb from the atmosphere.

And globally, trees may only absorb and store as much as 30% of the carbon emissions released by human activities.

And carbon dioxide levels will continue to rise in our atmosphere if carbon dioxide is being released at a greater rate than it is being absorbed.

Time for a check for understanding.

Which statement best explains why carbon dioxide levels in the atmosphere have increased? Is it A, because the rate of addition has been greater than the rate of removal, B, the rate of addition has been equal to the rate of removal, or C, the rate of addition has been less than the rate of removal, or D, the rate of addition has increased? The correct answer is A, the rate of addition of carbon dioxide into the atmosphere has been greater than the rate of removal, and this has led to increased levels of carbon dioxide in the atmosphere.

If the rate of addition and the rate of removal were equal like in B, then the levels of carbon dioxide in the atmosphere would stay at a constant level.

And D is not correct.

The rate of addition has increased.

This doesn't provide us with enough details because if the rate of addition increased, and we don't know what's happened to the rate of removal, we can't say whether that would lead to increased levels of carbon dioxide in the atmosphere.

Well done if you chose option A and got that question correct.

Carbon dioxide is a greenhouse gas, so as the levels of carbon dioxide increase, this results in an increase in earth's temperatures.

As carbon dioxide is a greenhouse gas, this means that it will absorb some of that infrared radiation that's at a lower frequency, that has been emitted from the earth's surface.

And rather than allowing it to escape out to space, it will be absorbed by carbon dioxide and then it will be radiated out in all directions.

This increase in temperature leads to increase in the ocean temperatures, reducing the quantity of CO2 that is dissolved in them.

Colder water is able to dissolve more carbon dioxide than warmer temperatures.

So as the temperature of the oceans increases, then that carbon dioxide that's dissolved in them, some of it is gonna escape back into the atmosphere.

CO2 from the oceans is released into the atmosphere, further increasing atmospheric CO2 levels.

We can see here a picture of the oceans to reinforce that carbon dioxide that is currently dissolved in the oceans is gonna be released from the oceans as the temperatures of the ocean increases.

And this is a bit of a vicious cycle because as that CO2 is then released, we're gonna have more carbon dioxide in the atmosphere, which will lead to more of the infrared radiation being trapped, and therefore increasing earth's temperature.

This is gonna increase the temperature of the oceans, which will then hold less CO2 in them.

So the CO2 that's currently dissolved in the oceans will be released into the atmosphere, further increasing the levels of CO2 in the atmosphere.

Time for a check for understanding.

Increasing ocean temperatures have led to, more CO2 dissolved in the oceans, the same amount of CO2 dissolved in the oceans, or less CO2 dissolved in the oceans.

Well done if you chose option C.

As the temperature of the oceans increases, this leads to less carbon dioxide dissolved in the oceans, and instead, that carbon dioxide is released from the oceans into the atmosphere.

For our second practise task of today's lesson, you need to, firstly, describe the pattern shown in the graph.

Now when you are describing patterns in graphs, your answer would normally include the word increase or decrease, or stay the same.

And for the second part of the task, you need to answer the question, how have increasing ocean temperatures affected the amount of carbon dioxide in the atmosphere? If you pause the video now, have a go at those two questions, and then come back when you're ready to go over the answer.

Welcome back.

Let's go over the answers.

Question one, describe the pattern shown in the graph.

Let's, first of all, just have a look at the graph.

You can see the title is atmospheric carbon dioxide, along the x-axes, we've got the year, and the year goes from just before 1960s where our first records are, and this goes up to current day.

And then on the y-axes, we've got the amount of carbon dioxide, and that's measured in the amount of carbon dioxide in parts per million.

So your answer may include, between 1960 and 2020, the amount of carbon dioxide measured in parts per million in the atmosphere has increased.

So we've described the trend seen in that graph.

How have increasing ocean temperatures affected the amount of carbon dioxide in the atmosphere? Your answer may include, as the ocean temperatures have increased, the amount of carbon dioxide dissolved in them has decreased, causing an increase in the amount of carbon dioxide in the atmosphere.

So, well done if you answered question one and two correctly.

Time for us to move on to the final part of our lesson on monitoring carbon dioxide levels.

Carbon dioxide released into the atmosphere can spread to other areas globally.

So there might be areas of the world that are releasing more carbon dioxide than others, but it doesn't really matter because it affects us all the same.

Carbon dioxide, once it's in the atmosphere, it can spread to all areas of the globe.

The global levels of carbon dioxide are monitored in many places worldwide, but this monitoring began in Mauna Loa Observatory in Hawaii in 1958.

So we've got records of the levels of carbon dioxide in the atmosphere that date back to 1958.

Where is Hawaii, where we have this monitoring of the carbon dioxide levels? Hawaii is just a group of islands in the middle of the Pacific Ocean, so you can see it marked there on that world map.

And it's not near built-up areas, yet because the carbon dioxide can spread globally, we are able to, in Hawaii, measure the global levels of carbon dioxide in the atmosphere.

And it's a good place to have this observatory because it's not affected by local levels, because there's not much transport and vegetation, et cetera, that would affect the local levels of carbon dioxide.

Time for a check.

Burning fossil fuels in a UK city produces carbon dioxide.

How far can the carbon dioxide molecules travel? Do they travel, A, to the edges of the city, B, to a distant countryside, C, to a Spanish beach on mainland Europe, D, to a Hawaiian island in a large ocean? Choose any answers that you think may be correct.

How far can the carbon dioxide molecules travel then? Yes, they can go to the edge of the cities.

They could travel to a distant countryside.

They could travel as far as mainland Europe, but also to a Hawaiian island in a large ocean.

So carbon dioxide molecules, it doesn't matter where they were produced or released into the atmosphere, they can travel globally.

On the graph here, we can see some data that you looked at earlier, and this is data that was collected from the Mauna Loa Observatory in Hawaii.

And it shows that carbon dioxide levels in the atmosphere have been increasing since 1958 when those records began.

It shows us more than just that there's an increase in carbon dioxide levels throughout the year.

If we actually look closely, we can see that the line's going up and down like this.

So there's peaks and troughs in the carbon dioxide levels throughout the year.

What's causing these peaks, so slightly higher levels of carbon dioxide, and troughs where it's slightly lower throughout the year, even though the overall trend is that the carbon dioxide levels are still increasing throughout the year.

While summertime growth of plants in the Northern Hemisphere causes a seasonal drop in carbon dioxide levels.

In the Northern hemisphere, when they grow plants, and those plants are photosynthesising, they are removing carbon dioxide from the atmosphere and this is causing drops in the CO2 levels.

However, in the winter, when those plants die and then decay, the decay of the plants causes global peaks in carbon dioxide levels.

And you might wonder, why is the Northern Hemisphere having such an impact on global carbon dioxide levels? And that's because 90% of the world's population lives in the Northern Hemisphere.

What has happened to global atmospheric carbon dioxide levels since 1958 when records began? Is it A, carbon dioxide levels have increased, B, carbon dioxide levels have stayed constant, or C, carbon dioxide levels have decreased? The correct answer is A.

Since records began in 1958, carbon dioxide levels have increased.

So, well done if you chose option A.

For our final practise task of today's lesson, we are gonna be using the data that has been collected from the Mauna Loa Observatory in Hawaii.

And I would like you to explain why the levels of carbon dioxide in the atmosphere fluctuate over the year.

If you pause the video now and then come back when you're ready to go over the answer.

Your answer may include, there are seasonal changes to the carbon dioxide levels in the atmosphere, and this is caused by plant growth in the Northern Hemisphere.

In summer, plants photosynthesise, reducing atmospheric carbon dioxide levels.

And in the winter, plants decompose, causing increases in atmospheric carbon dioxide levels.

Just as a reminder, overall, there is still an increase in atmospheric carbon dioxide levels over the year.

Well done if you were able to correctly mention that in the summer, plants photosynthesise, and in the winter, the plants decompose, and how both of these processes affect the global levels of carbon dioxide.

We've reached the end of today's lesson, so we will just finish with a summary of the key points we have covered in our lesson today.

Burning fossil fuels adds more carbon dioxide to the atmosphere.

Carbon dioxide produced from a combustion reaction may eventually spread throughout earth's atmosphere.

Increased ocean temperatures reduce the quantity of carbon dioxide that is dissolved in them.

And the difference between the rates of addition and removal of carbon dioxide changes its overall levels in the atmosphere.

You've worked really hard today.

So, well done.

I hope you've enjoyed the lesson on carbon dioxide in the atmosphere, and that you are able to join me for another lesson soon.