What You Can Expect
First of all, you do not need any prerequisites to understand this article. It is meant to fire up your inner child’s curiosity about our world. In the whole section of climate science articles, I will always state how hard it will be (in my opinion) to follow along an article. The scale consists of three worlds, ranging from easy to understand to hard to digest.
Did you ever ask yourself how climate scientists come up with forecasts of our future climate? What do they actually mean, if they mention ‘climate models’ ? In this article we will answer those questions and even more on a basic level. We will dive into what a climate model consists of, how we can simplify our amazing world and why we actually keep on working and improving climate models on daily basis.
Let’s share #allmarvelsoftheworld together!
Why Do We Model the World?
Rainbows. Sunny days. Glassy waves. Powder snow. Warm rain. Green trees. Mild wind. Calm rivers. Peaceful forests. Clean oceans. And look at all those animals! Whales, Giraffes, Lions, Eagles, Colibri, Monkeys, Gekkos, Butterflies…
Butterflies? Hurricanes. Storm surges. Floodings. Tsunamis. Heavy rainfall. Thunder storms. Snow storms. Avalanches. Heat waves. Droughts.
The world offers us a lot. From peace of mind and joy in the beauty of nature to the most wild conditions and fear of loss of our loved ones and homes.
Did you ever experience any of those natural wonders from above?
Have you ever been truely captivated by nature or terrified by it?
When we understand our world better, we can not only safe people from serious damage through extreme events like the ones I mentioned. We can also increase our experience with nature and live more in alignment with it.
If we understand how our world operates,
we know how we can operate within the world.
So the purpose of a (earth-system) model is this: It is there to help us unravel the mystics of how our world is working. This does not mean though that a model explains all details of our world. Just like a tree grows into a complex arrangement of branches and leaves from a simple seed, any model is based on the most fundamental observations and grows from that into a more complex model. On the one hand this means that the beauty of a model is in its simplicity, on the other it is suggesting that the wonders are found in the detail. Think about this: How would you build a model of our world? What would be the main components? What do you think, is most important and should not be missing? Is it the oceans, the forests, animals, us as humans? If you immerse into those questions you might realize that the answers are not that simple. There is no hierarchy at all. Everything is connected with each other. Yet, there must be a way to explain our world in a simple way, right?
How Can We Simplify Our World?
If you would explain a five year old child our earth (world) in five sentences, what would they be? Here are mine.
- The world is shaped like a ball and we live on this ball together with animals and plants.
- We can live on this world, because the sun is shining on it and our world is using that sunlight.
- You can travel around the world and depending on where you are, you will either wear a T-shirt or a really warm jacket.
- There is way more (salt) water on earth than land.
- The earth is rotating around itself and around the sun, which is why we have day and night as well as winter and summer.
This is it. Now, why did I actually choose those 5 sentences and how can we use them to get an idea of a climate model? From the first one we can see that the earth is round and it’s 3D (if you stated the word ‘frisbee’ somewhere here, feel free to think it’s 2D – it will simplify your model). Sentence number two suggests, that our life depends on the suns energy in some way. Even though the sun seems to shed light and energy on the earth, there is not only areas where it is warm but there is also regions where it is really cold. So it is important to know where on the world you are right now. Apparently water plays a big role, and for climate models it is especially the ocean’s water. Last but not least, the world rotates, which gives us a sense of time.
So what we learn from this is that we should incorporate the following elements into a model of our world:
- The knowledge about space and time in a sense that we must have the ability to distinguish certain regions on earth.
- We have to represent the ocean / water, the land-area, animals and plants as well as us humans.
- The suns influence on the earth or any other source of life or energy. We can call this ‘forcing’ of the world from which everything else evolves.
Let us check, how we can translate those points into a model. Did you realize the title picture of this blog post? What you see there is a ball separated into little boxes. If you open Google Earth you have the ability to actually apply this separation on our earth. Also Google Maps and any navigation-system uses these boxes or grid-cells behind its curtains . And this is what is actually done in climate models. These models separate our world into grid-cells, depending on the complexity either 2D or even 3D.
Each grid-cell then contains information about everything in it. This can be things like temperature of the atmosphere or water, the speed of wind and ocean currents as well as their directions, the number of people living within in that area and so on. In this way, we can reduce the complexity of the whole world and only analyze the behavior within each grid-cell and its direct neighbors. Instead of trying to observe the tiniest spots on earth, we reduce the observations to grid-cells.
The way we simplify our world is by seeing it as a grid with each grid-cell containing information of our interest.
The lines of this grid actually do have a name.
Lines pointing from the North to the South are called longitudes. If you would travel along a longitude of your choice, you will eventually pass all climate zones we have on our planet. This is actually what Axel Werner did and documented starting at a longitude of 8°. You can try it as well. Check out on what longitude you are living with Google Earth, and follow along that longitude. What countries will you cross? Will you have to climb mountains?
Lines pointing from West to East are called latitudes. If you move along them, you are moving either with the earth rotation or against it. This is why you will move faster when you are walking from West to East compared to walking from East to West, try it out! Well, that’s actually not true but if you are travelling along a latitude, you will travel in time and eventually get jetlagged.
The reason for this is actually that you are switching your position of longitude. And longitudes are used as a baseline for time-zones, because no matter where you are on a longitude, the sun is at its highest point at the very same time. Or in other words, you have lunch together with all the people living at the same longitude.
Now, this gridding is a great tool for simplification and gives us a sense of space and time but this is not all. How are we actually representing the ocean, the atmosphere, our plants and animals and all other amazing things on our world? The answer is actually pretty simple, maybe even too simple. We use a model for each of those things.
Basically our planet is considered to consist of five spheres,
which are used to represent the dynamics on our world.
Those spheres are there to explain what is going on in the air, in the water, amongst living things, around the ice and on land. Of course this is a very simplified way to think about it, in reality they are more specifically defined. If you want to look them up, search for
- Atmosphere (air)
- Hydrosphere (water)
- Biosphere (life)
- Cryosphere (ice)
- Lithosphere (land)
So this is it. These are the main simplifications that we need to build a model. We need a grid and we need an idea of what sphere we want to look at. Later on you can obviously try to combine models of different spheres (say an ocean-atmosphere model) but lets postpone that.
Now we know how to simplify the world and narrow it down to grid-cells. But how are we actually representing the dynamics within each cell and across them? How are we bringing the model to life?
What Are the Rules of the Game?
Go outside. Look at the world around you. Look at the people, the trees, the clouds, the waves. What can you observe? Do you see any patterns, any structures, any repeating behaviors? Can you manifest any rules about our world?
If you went through those observations you probably realized, that everything is moving. People are walking around, trees are swinging in the wind, clouds are coming and going just like the waves are crashing on the shoreline and disappear in the ocean again. Everything is moving, everything is full of life, everything has energy. So what is fueling the world? You already know it. It is the sun. Everyday when it rises and its rays reach earth, it supplies our planet with energy. Plants process the rays to produce oxygen, the oceans, atmosphere and land absorb some of the energy and turn it into heat (thermal energy). But when there is thermal energy, there is also the possibility for motion. So the sun is our main supplier of energy and this energy is then converted into life (oxygen, motion, heat, smiles on peoples faces). The main point here is that energy does not disappear!
All energy in the world is conserved.
It is only exchanged between objects and changes its form.
This principle of conservation of energy does also apply to all objects (mass) in the world and also to moving things, like water and air, right? Try it yourself. If you rub your hands, you use energy of motion (kinetic energy) and turn it into heat (thermal energy). You have just experienced conservation of energy. If you hide your mess of your room under your bed, it does not disappear, it just has changed places (trust me, I’ve been there). This is a clear case of conservation of mass. If you blow towards a lit candle, you will see it flicker or distinguish. This is because of the conservation of momentum. Your initial blow accelerates the air-masses close to your mouth and forces them to move towards the candle. Because momentum is conserved, the candle starts to flicker.
The ideas of conservation of energy, mass and momentum are the foundations of every climate model.
Well, from here on things can get pretty wild in terms of physics and mathematics. We will not bother with that for now. If you are interested I will make a blog-post on it later and link it here. But let me just state, that these principles of conservation give us insight about how the dynamics of our world function. For instance the conservation of momentum leads by Newtons Law (Force = mass x acceleration) to the equations for horizontal velocities. If we know those velocities, we can describe the flow of any fluid parcel, like air or water, in the direction of longitude and latitude. Awesome, right? Just like this, we can derive governing behaviors (laws, equations) for temperature, mass, vertical velocities, waves and much more. Mind-blowing, right?
Now here is a thing. Just imagine you had to solve those equations in order to know what happens tomorrow. Without even showing the equations here (for a hint, check out the Navier-Stokes-Equations) I can imagine that this would be a terrible idea. It is not only very complicated, it would also take ages if we would do it by hand. That is why we need to rely on computers to do the task for us. But guess what, they are not only solving one equation. They are actually solving those equations at each grid-cell, which we used to simplify our world. All of a sudden this simple idea of gridding the world becomes a very time-consuming task. And it is also connected to a dilemma, right? Think about this: What would we have to do in order to get a better, higher resolved picture of our world? Try it out and look at what happens to the grid if you zoom in on Google Earth. Do you see it?
Grid-cells of a climate model are like pixels of a camera. If you want to increase the resolution, you need to have more of them.
If you zoom in on Google Earth, there are more and more grid-cells. Just like a picture increases in resolution by increasing the amount of pixels on an area a model of the world increases its resolution by increasing its grid-cells. This means, that the grid-cells are enclosing a smaller area at higher resolution compared to coarser resolution. It also means, that the computer has to solve more of those underlying equations of dynamics. Now just imagine how long it would take for you to even solve one. The amount of grid-cells actually increases the computing time of a climate model substantially. Some models actually run for weeks in order to produce a projection of the state of the world. Because of the lack of computing power, there is a limit in the models resolution. This is why climate models actually struggle to represent tiny dynamics like butterflies flapping their wings. But this is also why climate scientists still try to improve climate models and work on them in order to completely understand our world.
Five Key Points To Remember
- If we understand how our world operates, we know how we can operate within the world
- The world is separated into multiple grid-cells and several spheres, mainly the atmosphere and the hydrosphere (oceans).
- The sun is the driving force of our world. It supplies us with energy, which eventually leads to motion and life around us.
- Energy, momentum and mass are conserved in our world, which leads to a system of equations explaining the dynamical behavior of the world.
- Grid-cells of a climate model are like pixels of a camera. If you want to increase the resolution, you need to have more of them (which is expensive)
Related Posts, Books & Discussions
A lot of foundational knowledge about climate models can be found in the book 'Climate Change and Climate Modeling' from J. David Neelin. It derives the governing equations I was talking about and goes into more depth regarding climate change and its effects.
Thank You So Much For Staying Curious of All Marvels of the World!
I am so thankful for every single one of you for reading this post. If you have any questions or comments, please share them with me right now. Write me an Email or message me on Instagram. Let me know what you want read more of and make sure to share your best insights and quotes from this post with everyone who could be interested in it. Keep on exploring and remember;
Together we share #allmarvelsoftheworld