By reading the six introductory questions and trying out some of the suggested activities children get a background understanding of climate and climate research.
They can then follow me on my journey to southern Africa this May where I will collect valuable samples that I use to reconstruct how climate has changed in the past.
By studying the past we get a better understanding of Earth’s complex climate system and how it will change in the future.

What is climate?

When you wake up in the morning and look out your window, what do you see? Is it sunny or cloudy? Is it warm or cold? Is it windy? Is it raining or even snowing? What you are looking at is the weather. This is something that changes just a little bit every day.

But what is climate? Think of climate as a cake. When you have certain amounts of flour, egg and sugar, you get one type of cake. If you change how much flour you put in, you get a different kind of cake.  In the same way, when you have certain amounts of rain, sun or wind you get one kind of climate. If you change these ingredients you get a different climate.

A good way to get a picture of different climates is to think about the plants and trees you see. Trees and plants are outside all year. Some plants can only grow where it is warm enough or wet enough, and sometimes trees will be bigger or smaller in some climates. In Stockholm where I live, there are trees with leaves and some trees with needles, such as oaks, birch, pine and spruce. The climate in Stockholm has cold winters and warm summers. We call this a temperate climate. If we go up to the mountains, the winters are much colder and longer and the summers are shorter and not as warm as in Stockholm. Here you see that there are not as many trees and that the trees that are there are much smaller. The climate in the mountains is too cold for the trees to grow big! Have you ever seen a palm tree growing outside in Sweden? Of course not! It is too cold. Have you ever seen a cactus? No, it is too wet and cold!

Think about places you may have seen on TV, or read about or even travelled to. How is the climate different from where you live? Describe where you live and how wet or dry it is, how warm or cold it is, how cloudy or sunny it is.

What is the green house effect?

Have you heard about other planets? I am sure you have. So you probably know that no other planet has people on it. Why is that? It is because on Earth we have an atmosphere. The atmosphere is like a little bubble around our planet where we have air. The atmosphere keeps us nice a warm like a blanket and protects us from the sun and its strong rays.


Breathe in deeply. Air is around you now and going in and out of your body as you breathe. There are a lot of different things in this air called gases. You can’t really see or feel gases most of the time. You may have noticed though that when you boil a pot of water, you can see steam. Steam is water in the form of a gas.

One really important gas is carbon dioxide. You may not know it but when you breathe out, you are breathing out carbon dioxide. Carbon dioxide is one of the gases that keeps our planet warm through the green house effect.

Think about when you have been in a greenhouse or even in a room with a lot of windows. It gets awfully warm doesn’t it? That is because the sun’s rays warm up the room but then they can’t get back through the glass. In the atmosphere, carbon dioxide acts as this glass keeping in some of the sun’s warmth in the atmosphere. This makes our planet the perfect home for us.

You can make a very simple green house at home to test the green house effect. Save two glass jars from the recycling, it is even better if they are the same. On one jar put two layers of cling film keeping it in in place with a rubber band. Take a thermometer and put it through the plastic film. Then put another thermometer in the second jar.
Put the jars in the sun and then watch what happens. Which of the two jars has a higher temperature? Can you figure out why?

What is climate change?

You may have heard that our climate is changing. A big part of this has to do with carbon dioxide. When we breathe out, we breathe out carbon dioxide. This carbon dioxide is food for plants. They take in our carbon dioxide and release another gas called oxygen. This is very important since we need oxygen to live.

Carbon dioxide also comes from cars, planes and factories, which are putting a lot of extra carbon dioxide into the air. This means that more and more of the sun’s warmth stays in the atmosphere instead of going back into outer space. In a way, we are making the glass on our green house thicker. This is why our planet has been getting warmer and warmer over the last 100 years.


The film below shows a map of the world. As the film plays we travel through time from 1880 (which is before your grandparents were born) all the way to 2010. The blue colours on the map represent cooler temperatures while the red colours represent warmer temperatures. Towards the end of the film what colour do you see the most? Play the film again if you need!

It might not sound like much but the Earth getting warmer by even just a few degrees is a big deal! You can think of the Earth’s climate like walking on a balance beam… too hot or too cold, and we fall off. In some places they already have a hard time getting enough water to cook, wash and grow food. If the climate gets warmer it will also get dryer where they live and people will not be able to grow the food they need.

We also have a lot of ice on our planet that stores huge amounts of water. This ice is located both on land and in the sea and in a warmer world will melt this ice. Do you think this could be a problem? Let’s test this! Get a glass bowl and place a rock; this represents an island where people live. Make sure your island is big enough for a few pieces of ice. Now fill your bowl halfway up with water. Using a marker, make a line on the side of the bowl where the water level is. Now put ice (I have put some dye in mine) on your island and let it melt. When it is finished use the marker to mark the new water level. What has happened? You can try the same experiment but start with the ice in the water. What happens to the water level this time? What do you think this could mean for people living near the sea?

How do we study past climate?

How do we know that the Earth has been getting warmer? It became common in many places in the world to measure temperature and record weather patterns during the 1850s. Making a record of changes in weather started even earlier in some places. From the Stockholm Observatory we have one of the longest unbroken records of weather observations in the world, which started in 1754!  

What do we do when we want to know about climate from before we started measuring with thermometers? Well, we can read diaries and record books from farmers or ship captains for example, where they mention the weather. We can also look at old paintings to see how people lived in the past. Several hundred years ago many places experienced much colder temperatures than usual. When we look at paintings from this time we see people skating on rivers and canals that today would never be frozen. In London there were even “frost fairs” celebrating that the Thames was frozen.

Thames Frost Fair, 1683-84, by Thomas Wyke


We are interested in going even further back in time to when people weren’t affecting the climate as we do today. To do this we look at archives. Archives are things that grow over time and as they grow they store information about the environment. An archive that you have all surely seen are trees. Have you looked at a tree stump and noticed that there are rings? The rings towards the middle are from when the tree was younger. As the tree grows rings are added on the outside making the rings from the edge from when the tree was oldest.

Tree rings from a pine tree.

Researchers diving in a lake to find old trees to study.

You probably know that you can count these rings to find out how old the tree is but look a bit closer at the rings. There are light and dark rings and these can be different thickness. The light ring comes from the spring when the tree grows quickly as the weather warms into summer. The darker ring comes when tree growth gets slower in the autumn. If the tree has had plenty of warmth, water and food, the ring for that year will be thick. If it has been a bad year for the growth of the tree the ring will be thinner. In this way we can say how the climate has changed over the life of the tree.

Try to find a tree stump and look at the rings. Count backwards from the edge to go back in time. Can you see if the tree grew more in some years than in others? You are making a climate record!

What is sediment?

Lakes are another place where you can collect information on past climates. To do this we use sediment as our archive. When you swim in lakes or the ocean, the stuff you feel oozing between your toes when you walk on the bottom is sediment.

But what is sediment made of? Sediment is partly made up of rock that has been broken down into smaller and smaller pieces through erosion. Water, wind and ice work at rocks to make them weaker and eventually they break apart. As you can see here we start with bedrock. This is the rock that is complete and found under all the loose rocks and plants in the picture. Over time this is broken down to gravel, then sand of bigger and then smaller grains, until finally we get clay. All of these rocks of different size can get washed into the lake by rain and melting snow or blown in by the wind.

We also have plants and animals living and dying around our lake. Like the broken down rocks, dead plants and animals can get washed into the lake as well. You can imagine that your lake is like a bowl that is slowly filling up as time passes. The sediment at the bottom of the bowl was put in first and is therefore, oldest. Over time we get many different kinds of materials getting washed into the lake, which can tell us about climate. This can make for many different kinds of sediment.

These sediments all come from different lakes. The first shows a black layer of ash from a volcano that erupted and the ash from the air settled on the lake bottom.

The middle two sediments come from lakes where ice has been growing and shrinking, bringing clay and sand to the lake.

The last sediment comes from a peat bog and is made only of dead plants; you can see pieces of wood in the sediment.

You can sample lake sediments just like a climate scientist! Ask an adult to help you cut a piece of plastic pipe or the bottom off a strong plastic bottle.

Keeping the pipe or bottle straight up and down, slowly turn your tube, pushing down into the lake or sea bottom. Try to get your your hand underneath the opening and gently pull up on your sampling tube.

Once above water, carefully tip the tube to get rid of the extra water from the top. Then you can gently shake out your sediment from the bottom.

At the bottom is the oldest sediment and at the top is the youngest sediment. Can you see any differences?

If there are not too many rocks in your sediment you can also cut the bottom off a strong plastic bottle.

What can sediment tell us about past climate?

When we use sediments to study climate change we collect sediment cores. This is like a long tube of sediment, which keeps all the layers in place so that we know that at the bottom of the core we have the oldest sediment while at the top we find the youngest sediment. When broken down rocks, plants and animals get washed into our lake they get buried deeper and deeper as we get more and more sediment collecting on the bottom of the lake. But how do we use this to tell us about climate?

Let’s think about it. If we have a nice warm climate with just the right amounts of rain and wind, the plants around our lake can grow in both size and numbers. These plants then die with time and changes in the seasons. Eventually, what is left of these dead plants gets washed into the lake and is stored in the sediment. If the climate is completely the opposite however, being cold and dry, then not as many plants will manage to survive and fewer plant remains get washed into the lake. If we would compare the sediment from these two different climates we would see that the sediment has different amounts of dead plant material in it, which in turn gives us a clue about how warm, wet or windy it was around our lake.

We can even look at which plants were around the lake by using leaves, seeds and pollen from plants we find the in sediment. Small pollen grains are released into the air by plants during the spring, making it possible for new plants to form. When we know which plants have been around our lake we can then say how the climate was. For example, how do you think the climate would look if you found more pine needles in your sediment compared to oak leaves? We usually fine pine trees where it is cold and wet, don’t we? Oak on the other hand, likes a climate that is a bit warmer than pine.

Pictures from a microscope of leaves, seeds and pollen found in sediments:





Another clue to past climate comes from algae. Algae is the green stuff that grows on rocks in lakes, for example. There are many, many different kinds of algae and they are very particular about where they live. Some like warm water, some cold; some like lots of food while others can survive with less food; some like to live in deep water and some like to live in shallow water; some like to have murky water that you can barely see through while others like having lots of light. By looking at which kind of algae are living in our lake we can then describe the lake and the climate where it is found.

Small algae or diatoms seen under a very powerful microscope.


Just like algae, the larva of different kinds of small flies also like different temperatures, food, and so on.

Using a microscope the The mouth of the small fly larva are used to decide which type it is.


We can also find traces of old volcanic eruptions where small shards of glass blasted into the air can fall down and settle down on the bottom of the lake.

Ash from volcanic eruptions found in lake sediments.


So, now that you know why we collect sediment you can understand why we want to go to southern Africa to collect samples. We are hoping that we will be able to see how the climate has changed over the last 15 000 years using clues like these found in our sediment cores.



Day-by-day blog from my southern Africa journey

Day 8 – May 24th, Travel-day

Today was a travel-day for us. Before we left St Lucia we did however make a short stop at the local market.

On arrival to our accommodation we repacked our samples in preparation for the trip back to Sweden The dog that lived in the house were we were staying took a break from chasing monkeys and kept a good look on what we were doing.

Day 7 – May 23th, On the Game Reserve

Today was one of our more exciting days. We went iSimangaliso Wetland Park to look at a wetland called Mfabeni. Mfabeni is unique because it is very old with the bottom being 45,000 years old. Going to this place was extra special because it is on a reserve and filled with many of the African animals we think of, all roaming freely. As researchers we were given special permission to get out of the car and have a look. We were pretty nervous since there could be dangerous animals like hippopotamus waiting for us while we were walking. On the way into the park we saw kudu, which are the second largest antelope type here. You can tell how old they are by the numbers of curves the horns have. We saw zebras as well.

When we climbed out of the car we saw no animals and the ground was pretty dry. To help us walk through the high grass we used the hippo paths that were full of fresh prints.We walked to the middle of the wetland and had a look at the sediment.

Mbafeni is very beautiful and we really hope that we get to work on the sediments here.

We made it safely back to the car without running into any big animals but we did see leopard tracks on the way. Leopards are very shy though and we didn’t actually get to see one. We decided to drive further into the park and just as we pulled away we saw a rhinoceros. He was very impressive but I was glad to not have to meet him on foot!

After lunch we drove into town and hopped on a tour boat so that we could see some of the wildlife that lives in the lake. Over 1000 hippopotamus live in this lake along with sharks, crocodiles and many different birds. It didn’t take long before we ran into some hippos!

It was a beautiful way to end the day!

Day 6 – May 22th, St Lucia

I am writing this by candlelight as for the second day in a row the electricity has been shut off in the afternoon. They do this to save energy since there is not enough for everyone.

Today we packed up our things and started on our drive to the coast and a town called St Lucia. Along the roads and the highways, people are walking, even small children. We also saw many, many fields of sugarcane, which is used to make sugar.

We also saw row after row of trees planed to make wood. They only plant one kind of tree at a time and they are not even trees found here normally but in Australia.

The sign that welcomed us as we came to this town warned us that there are hippopotamus around, especially at night. Hippos can be very dangerous and people should not be walking around at night. At the hotel we found out they even sometimes come to the pool.

After lunch we went and looked at another wetland. As you can see below it looks very different from the one we went to yesterday! It is called a swamp and it has high trees and other plants since it is so much wetter and warmer here
than at Dartmoor Vlei. Again, we tested to see how the sediment looks but we couldn’t get very far since the plants are so thick and close together.

We tried to get up a bit higher so we could see how big the wetland was. On the way we met a dung beetle and a grasshopper that was very cleverly hidden.


Day 5 – May 21th, The Midlands

Our new accommodation turned out to be a pleasant surprise;
besides really comfortable beds we also now have hot water, electricity, and toilets!

Facilities we were not spoiled with up in Lesotho.  

Today we went out on more field work. This time to Dartmoor Vlei, a wetland in the Kerkloof Nature Reserve. On the photo below we are standing on a hill and looking out over the wetland. It is winter and very dry here just now. That is why the plants on the wetland are brown, but it is still wet in the middle of the wetland. We know because we got wet feet!  

We crossed the wetland and Trevor (see picture) took up sediment so that we could see what it looked like. Peat, that is sediment made of plant remains, started growing here 12,000 years ago and is found 145 cm down from the surface we were standing on. While we were at Dartmoor Vlei we even took some soil samples from the surrounding hills.

On our way back to the car we got company of some cows! 


Day 4 – May 20th, On the Road Again

Today it was time to leave Lesotho and the mountains. We will miss the beautiful view from our rooms here.

On the way down we got a good look at the kind of rocks that make up the area. These are called basalts and they were formed by volcanic explosions 180 million years ago.

We even got to see some baboons as we drove down the mountain.

At lunch we met our colleagues Jemma Finch and Trevor Hill from the University of KwaZulu-Natal who are both experts on pollen. We said goodbye to Stefan and thanked him for all his help. We are now settled in a place called Hilton, which is halfway between the mountains and the coast. Tomorrow it is off to a new wetland!

Day 3 – May 19th, More Sampling

Today we spent the morning gathering more sediment samples.
In the afternoon we got some time to have a look at the village where we are staying.
We have even made a few friends.




The people live in round stone houses, which they need with the strong winds up here.

It is cold and many of the villagers wear coats that are like big blankets to stay warm like this little boy.

Tomorrow we will drive back down the mountain on this winding road to South Africa.

Day 2 – May 18th, Time for Fieldwork

Today we went to a large wetland. There we used a Russian corer (see picture) to collect peat which is sediment made of a lot of plant materials. The wetland is surrounded by mountains and we even saw sheep, horses, birds and “ice rats”.

After a good day of sampling we will go and have some supper! Good night from Jenny, Caroline and Malin!

Day 1 – May 17th, We’re Finally Here!

After 13 hours of flying we arrived in Johannesburg, South Africa.
The trip went just fine with no problems.
Waiting for us at the airport was our colleague Stefan Grab from the local University of Witwatersrand.






The plan for the day was to drive to the high mountain kingdom of Lesotho, which would take the whole day. The countryside for the first few hours of the drive was very open and very dry. Slowly we started seeing more and more mountains.

After many hours driving we came to an area with many hills and villages where people live.   

Finally, 7 hours later, we reached the border of South Africa where they checked our passports. The road was very bad and we needed a truck to get us over the rocks and through the streams.

We drove up, up, up the mountain through the clouds. We were scared to look over the edge because it was so steep. Eventually, we got to the top at about 2800 m above sea level. Here the air is very thin and you can feel a bit sick because there is less oxygen in the air. When we arrived, we went to the Lesotho border crossing to get our passports checked.

Now we are making some spaghetti for supper and will go to bed early since we are tired from our trip. We are living in a little village on top of the mountain and the wind is shaking the house. There is only electricity from a generator. They will soon turn it off. When that happens it is so dark you cannot even see your hand in front of your face but you can see the stars clearly above you.

Many thanks to Mark Johnson, Björn Gunnarson, Elin Norström, Peter Langdon, Anna Plikk, Jenny Sjöström, Minna Väliranta and Ewa Lind for their photo contributions.

The fieldwork is partly funded by The Swedish Secretariat for Environmental Earth System Sciences (

Bolin Centre for Climate Research
A collaboration between Stockholm University, KTH and the Swedish Meteorological and Hydrological Institute | Web administrator This email address is being protected from spambots. You need JavaScript enabled to view it.