Lesson video

Hi, geographers.

My name's Ms. Hoggett, and I'm really excited you're here to learn some geography with me today.

I'm sure if you try your absolute best, you're going to be absolutely fantastic.

Don't worry if you haven't studied this topic before.

I'm here to help you every step of the way.

Today's lesson is titled "Causes of Climate Change," and this sits within the unit, "Weather and Climate: How do they vary?" Our learning outcome for today's lesson is that I can understand the physical and human causes of climate change.

We have a number of keywords that are going to be really useful to us in getting through to today's lesson.

Climate change cause greenhouse gas and greenhouse effect.

Climate change is a large scale and long-term change in the planet's climate, including weather patterns and average temperatures.

A cause is the reason why something happens.

Greenhouse gas are gases that trap heat in the atmosphere, contributing to the greenhouse effect.

And the greenhouse effect is the retention of heat in the atmosphere caused by the buildup of greenhouse gases.

So climate change cause greenhouse gas, and the greenhouse effect are going to really help us in today's lesson.

Today's lesson is split into two learning cycles.

The first one, what are the physical causes of climate change? And the second one, what are the human causes of climate change? We are going to start with our first one now, what are the physical causes of climate change? So climate change refers to the large scale and long-term changes to the planet's climate.

On the screen, you can see a graph, which shows us how the climate has changed over time.

We can see that temperature is listed, and we have glacial and interglacial periods.

Our glacial periods are where the temperature drops below zero degrees on average.

So we know our interglacial periods are a little bit warmer.

This graph goes back 450,000 years.

Now, if we look at the last 450,000 years, the global average temperature has switched between those colder periods, glacials, and warmer periods, interglacials.

This suggests that there must be natural causes of climate variation because humans can't be to blame for all of the changes 450,000 years ago.

Now, there are several natural causes of climate change.

They include volcanic eruptions, sunspots, and Milankovitch cycles.

Now, it's important to remember here, geographers, that we do expect our climate to change naturally.

So all of these things are things that occur without human intervention.

Now, the greenhouse effect is the retention of heat in the atmosphere, caused by the buildup of greenhouse gases.

The greenhouse effect is a natural process that keeps most parts of the Earth warm enough for life to flourish.

Without it, Earth would have an average temperature of minus 18 degrees Celsius, and that would be really chilly.

As we can see in the diagram, we've got the sun heating up parts of the Earth.

And it says, "The Earth absorbs energy from the sun." "Greenhouse gases in the atmosphere trap heat that warm the Earth, whereas some heat escapes back into space." So where the greenhouse gases are trapping the heat in the atmosphere? We know that that is where the greenhouse effect is being created.

So the sun sends heat to Earth, some of which is reflected back into space.

Gases like carbon dioxide, more commonly known as CO2, and methane, CH4, trap heat, keeping the Earth warm.

And extra greenhouse gases stop more heat from escaping, making Earth warmer.

That's the greenhouse effect.

So let's check your understanding so far and complete Jun's sentence to show the importance of the greenhouse effect on global temperature.

So Jun says, "The greenhouse effect is a natural process that keeps most parts of Earth warm enough for life.

Without it, Earth would have an average temperature of." Pause the video and have a go at completing Jun's sentence.

Well done for giving that a go, geographers.

Let's see if you've got the answer correct.

So without it, Earth would have an average temperature of minus 18 degrees Celsius.

So I think it's important to remember here that the greenhouse effect isn't all bad.

Actually, it's really helpful in regulating our temperature.

Now, by studying ice cores from Greenland and Antarctica, scientists have been able to link changes in global temperature to changes in the amount of carbon dioxide in the Earth's atmosphere.

We can see in the image that the scientists there has collected an ice core from the ground, and they look like cylinders created by a big drill that we can see in the image.

As the amount of carbon dioxide goes up, so does the temperature.

Carbon dioxide absorbs radiation, trapping this heat in our atmosphere.

It's a greenhouse gas.

Let's check your understanding of that.

So as the amount of carbon dioxide in the atmosphere increases, what happens to the temperature? A, it increases, B, it stays the same, or C, it decreases.

Pause the video and have a go at picking the correct answer.

Well done If you said, A, it increases.

Absolutely spot on.

We know that as the amount of carbon dioxide in the atmosphere increases, our temperature also increases.

Good work, geographers.

Now, when volcanoes erupt, they release ash and greenhouse gases into the atmosphere.

In the short-term, the ash particles block the sunlight, causing temporary global cooling.

But in the long term, the effect is slightly different because the carbon dioxide released into the atmosphere by the eruption contributes to the greenhouse effect and global warming.

So we can see that the short term and long term impacts of volcanic eruptions can vary.

A good example of this is when Mount Pinatubo in the Philippines erupted in 1991.

In the short term, this caused global temperatures to drop by about 0.

6 degrees for more than a year.

But in the longer-term, the addition of the greenhouse gases into the atmosphere continue to contribute towards global warming.

So we can see that the short and long-term impacts of Mount Pinatubo's eruption were very different.

Another physical cause of climate change are sunspots.

Now, these are dark spots on the surface of the sun where the sun is slightly cooler.

They are often surrounded by intense heat.

When there are lots of sunspots, the sun gives off more energy, which warms the Earth.

When there are very few sunspots, global temperatures drop.

This occurred from 1965 to 1715, which was the coldest period of the so-called "Little Ice Age" in Europe.

On the screen, we can see a graph which shows those warm and cold periods, and the Little Ice Age is highlighted.

And we can also see "A scene on the ice" taken in 1650.

So we know that our climate used to be different.

And our final cause of climate change that's a physical cause are our Milankovitch cycles.

And these are the natural changes in the way the Earth moves around the sun.

They affect how much sunlight the Earth receives, and therefore, they impact the climate.

The first one we have is the wobble, then we have the tilt.

And lastly, we have the orbit around the sun and the orbit shape.

As we can see, these are all ways in which the Earth moves around the sun and on its axis.

The Earth's changing orbit is really important because it impacts global temperature really significantly.

When the orbit is more circular, as you can see here, the climate remains consistent.

But when it's more oval, as we just saw, Earth gets closer and further from the sun at different points, causing the temperature to fluctuate.

So we can see that the changing orbit is really important in how our temperature fluctuates.

So let's check your understanding.

True or false? Climate change is entirely caused by humans.

Pause the video and have a go at completing that question.

Well done if you said false.

We know that physical causes of climate change include volcanic eruptions, sunspots, and orbital changes.

So climate change isn't entirely caused by humans.

We are now going to practise what you've learned so far.

So on the screen, you have a blank diagram of the greenhouse effect.

For the first part of this task, I would like you to add the labels to the correct place in the diagram to show the greenhouse effect.

So some heat escapes back to space, Earth absorbs energy from the sun, and greenhouse gases in the atmosphere trap heat that warm the Earth.

And for part two of this practise task, I would like you to explain each of these natural causes of climate change.

So you're going to complete the table for volcanic eruptions, sunspots, and Milankovitch cycles, specifically orbital changes.

Pause the video and have a go at completing this practise task.

Well done for giving that a really good go, geographers.

Let's check your answers.

So as we can see, in the centre of our diagram, we should have, "The Earth absorbs energy from the sun." Then, we should have that, "Some heat escapes back to space." And we should have that, "Greenhouse gases in the atmosphere trap heat that warms the Earth," on the right-hand side.

For part two, we should have the, when volcanoes erupt, they release greenhouse gases, such as carbon dioxide into the atmosphere.

These gases contribute to global warming because they absorb radiation and they trap heat in our atmosphere.

Then, for sunspots, we should have, sunspots are dark spots on the surface of the sun where the sun is slightly cooler.

They are often surrounded by intense heat.

When there are lots of sunspots, the sun gives off more energy, which warms the Earth.

And lastly, for Milankovitch cycles, specifically orbital changes, we should have, the Earth's changing orbit impacts global temperature significantly.

When the orbit is more circular, the climate remains consistent.

When the orbit is more oval, Earth gets closer and further from the sun, causing the temperature to fluctuate.

You are doing a fantastic job, geographers.

Well done.

We are now at the end of learning cycle one, and we are ready to move on to learning cycle two.

What are the human causes of climate change? So this graph shows the amount of carbon dioxide in the atmosphere and how it's fluctuated over time.

So the title is, "Concentrations of carbon dioxide in the atmosphere from 800,000 years ago to present day." Now, we can see that we've got years listed along our X-axis, and then our Y-axis is looking at carbon dioxide concentration, so the amount of parts per million in the atmosphere.

We can see that that's changed, and it's typically stayed below about 300 parts per million.

However, in recent years, we can see that this has massively increased to above 400 parts per million.

Now, the amount of carbon dioxide is measured in parts per million.

In 2015, it reached 400 parts per million.

Today, the concentration of carbon dioxide may be the highest it's been for millions of years.

So, true or false? Today, the concentration of carbon dioxide may be the highest it has been for millions of years.

Pause the video and have a go at completing this check for understanding.

Well done for giving that a go, geographers.

Did you get the right answer? The answer's true.

Because in 2015, the concentration of carbon dioxide in the atmosphere reached 400 parts per million, significantly higher than it's ever been in the past.

Now, since the 1970s, there's been an extraordinary rise in the average global temperature.

And we can see that on this graph here, looking at global surface temperatures.

The rise has been matched by the rise in carbon dioxide and other greenhouse gases in the atmosphere.

So I want us to have a think, "What has caused this rise?" Pause the video and tell the person next to you any ideas of why you think we're seeing this increase since the 1970s.

Did you have a think? Did you come up with any ideas? Let's see if you got them spot on.

So, human activities, such as burning fossil fuels like coal, oil, and natural gas have added greenhouse gases to the atmosphere, especially carbon dioxide.

All of this extra greenhouse gas has added to or enhanced the greenhouse effect.

Izzy says, "It's like we've added extra blankets around the Earth, and now we are too warm." Absolutely spot on, Izzy, that's a really good way of putting it.

So let's think about this enhanced greenhouse effect then.

So the sun sends heat to Earth, some of which is reflected back into space.

Gases like carbon dioxide, CO2, and methane, CH4, trap heat, keeping Earth warm.

Then we see human activities like burning fossil fuels, adding more greenhouse gases.

And then, extra greenhouse gases stop more heat from escaping, making Earth warmer.

This is slightly different to the natural greenhouse effect, which we saw trapping some heat, but releasing some into the atmosphere.

And here, less is being released into the atmosphere.

So let's check your understanding of that.

What has happened to global temperature since the 1970s? A, they've increased.

B, they've stayed the same.

Or C, they've decreased.

Pause the video and have a go at completing this check for understanding.

Well done for giving that a good go.

Yes, the temperature since the 1970s has increased.

Good work, geographers.

So there are different key ways in which humans have increased the volume of greenhouse gases, and they include burning fossil fuels, farming, and deforestation.

Now, industries burn fossil fuels such as coal, oil, and natural gas to produce energy.

This is used to power machines.

However, burning fossil fuels is also the main cause of recent climate change.

This is because it releases carbon dioxide into the atmosphere.

The industrial revolution, which began in Britain and was driven by coal, marked an important change for our global climate.

This is because the amount of greenhouse gases released by human activities has rapidly increased ever since.

Using fossil fuels to create the heat and power we need for modern life is the key cause of global warming.

Farming is another human cause of climate change.

Farmers use fossil fuels to power machinery such as tractors, livestock such as cows and sheep produce methane, which is a powerful greenhouse gas And to make space for livestock and crops, woodland may be cleared or bogs drained.

These actions also release carbon dioxide.

So we can see that farming can contribute to climate change as well.

In addition, trees lock away carbon in wood.

This means that when trees are felled and the wood rots, carbon dioxide is released into the atmosphere.

If logs are burnt, the process is even faster.

So, therefore, deforestation contributes to climate change too.

So we're going to practise what we've learned so far, and I'd like you to read Sofia's comment below.

Do you agree? I'd like you to write a paragraph explaining your answer.

Sofia says, 'Deforestation is the only thing humans are doing to cause climate change." I'd like you to have a think about lots of different options in your answer.

Pause the video and have a go at completing this practise task.

Well done for giving that a really good go, geographers.

Let's see what your answer may have included.

Now, you may have written your answer in a slightly different way to me, and that's absolutely fine.

But we want to check that you've got the key points.

So I've put, deforestation is not the only thing humans are doing to cause climate change.

There are other important human activities as well.

Industrial processes also play a big role in climate change.

Factories and power plants burn fossil fuels like coal, oil, and gas to produce energy.

This releases CO2 and other greenhouse gases to the atmosphere, which trap heat and cause Earth to warm up.

Burning fossil fuels is the main cause of recent climate change.

Farming also contributes to climate change.

Animals like cows and sheep produce methane, a powerful greenhouse gas, when they digest food.

Therefore, I disagree with Sofia as deforestation is just one part of the problem.

So within our answer, we've covered that farming, industrial processes, and deforestation, all contribute to climate change.

And therefore, Sofia would be incorrect to suggest that deforestation is the only cause.

Well done, geographers.

You've absolutely nailed today's session and you've come to the end of learning cycle two.

Good work.

To summarise today's lesson, there are both human and physical causes of climate change.

Volcanic eruptions, sunspots, and the Earth's changing orbit around the sun are all natural causes of climate change.

However, it's the release of greenhouse gases into our atmosphere as a result of human activities that is the cause of global warming since the 1970s.

Burning fossil fuels releases greenhouse gases, including carbon dioxide into our atmosphere and is the main cause of recent climate change.

Farming of livestock and deforestation are other key human causes.

Well done, geographers.

You've done an excellent job today and you've absolutely excelled in this lesson.

I hope you have a great rest of your day, and I will see you soon for our next lesson.