This is the first part of my series on climate science. This post is about the term climate, how it is different to ‘weather’ and how it works. I hope this series will help you understand the complexities of climate change and why it is so important that we all start changing our lives bit by bit.
Alright, let’s dive right into it, we have a lot to discuss…
1. How is ‘climate’ different from ‘weather’?
Quite often we hear people saying something like ‘where is your warming now he?’ when it is colder than usual for a day. Or we hear people be like ‘I don’t mind when it’s getting warmer here, then we could grow wine even in the UK haha’.
So, what’s the difference here?
…is the short-term condition of the atmosphere above a certain point on Earth, like the city you live in for example. In that sense, weather is a rather small scale phenomenon that may span over a region but rarely over a whole continent or multiple countries at the same time. We can see and feel weather by looking out of the window or when we step outside. It is what we recognize as sunshine, clouds, rain, snow, hail, wind, heat or cold. The weather can change rather quickly, it can be rainy in the morning, sunny in the afternoon and hailing in the evening, as we experience sometimes.
Weather is driven by pressure differences in the atmosphere. High pressure is generally associated with nice, dry weather while low pressure is correlated with cold, moist weather. Also, the warm, high pressure air sinks down to the Earth’s surface and flows towards low pressure areas where the air rises again and forms rain and clouds. Especially in places close to the sea, high and low pressure can appear and change rather quickly and so does the weather.
is a statistical measure of a longer time period than just days or months. The climate is for example the average temperature over the last 30 years above a certain point on Earth. This means we take for example July 11 and look at how the Temperature was the last 30 years. Then we take the average of all those temperatures to see all possible weather situations for one place on that particular day. Climate is always a period of 30 years or longer. In contrast to the weather, the climate is not so much influenced by small-scale, temporary high and low pressure areas.
2. How does ‘climate’ form?
Climate is rather influenced by the interaction of the Earth’s spheres, meaning the oceans, continents and the atmosphere. Also, climate is influenced by the activity of the sun and changes in the rotation and axis of the Earth. Yes, we don’t notice it but our planet is not always wobbling around the sun on the very same path. There are slight differences in the orbit and the tilt of the axis over time which also have an influence on the temperature.
These things happen in cycles that climate scientists are very aware of. Like, the activity of the sun fluctuates every 11,1 years. The cycle can be a bit shorter or longer, also depending on the appearance of sun spots that make the sun a bit cooler but still warm enough so we usually don’t even notice.
Changes in the rotation of the earth also happen within cycles that we know very well. This phenomenon is called the Milankovic cycles after the guy who first became aware of them. For example the axis of our earth is not straight but tilted and every 41.000 years the angle becomes a bit steeper or a bit flatter. There are more cycles that I don’t want to bore you with but in general, those cycles also guide our planet into ice ages or warm periods. So, by looking back at past climates with the activity of the sun and the Milankovic cycles in mind, we can make a very informed guess about what should be happening now or in the future.
This is the reason why you sometimes hear that we are heading towards an ice age. That is, by the laws of nature, it would be time for an ice age. It should be getting colder but that’s only if there were no humans. Humans managed to change these forces of nature by emitting all those greenhouse gasses that trap the heat under the shield we call the atmosphere.
What else has an influence on the climate?
As mentioned above, the climate is generally influenced by interactions between the different layers of the Earth. Continents interact with oceans and by that they interact with the atmosphere and form huge wind patterns that travel around the whole planet.
You may have heard about trade winds or the jetstream which make up one of the most prominent wind patterns on Earth.
The jetstreams travel from east to west and have an influence for example on how long it takes to travel from Europe to the US or back. Flying time from the US is usually shorter than the other direction because the plane can kind of surf along the jetstream.
The jetstream is not a straight line, it rather wobbles north and south in a curved line. This is because cold air masses from the Arctic or Antarctic push the air south/north and warm air masses from the tropics push it the other way. Depending on the strength of those cold or warm air masses, the jetstream is stronger and more or less curved. In other words, as we discussed earlier, the higher the pressure differences between tropics and poles – or, the colder it is in the arctic and the warmer in the tropics, the stronger the winds of the jetstream. This also means that there will be more or less rain depending on the strength and position of the jetstream. You can check out this great video from NASA if you want to see a better version than my graph above…
How does this affect the climate?
The jetstream has an effect on the short term weather but also on the long-term climate. Especially in 2018 we noticed (maybe without knowing), that the jetstream is weaker.
1 Why is it weaker?
You guessed it – because of what humans do.
Because of all the greenhouse gasses we emit, the Earth in general is getting warmer. Also the Arctic is warming and the temperate zone in which most of us live. This means the temperature and pressure difference between the poles and tropics is not so big anymore. Therefore, the wind slows down. We remember, wind or air travels from high to low pressure. Now, if there is rather high pressure everywhere, there is no need for the air to move. At least it’s not moving as fast as it used to.
2 How were we supposed to notice?
Because the wind is weaker, the air above us is simply trapped. That’s one of the reason for the persisting heatwave in summer 2018. The pressure difference between the poles and the tropics was simply not big enough for air to move as fast as we are used to. That’s why the hot weather stayed for such a long time. Also, I don’t know if you have noticed but the weather, at least in Europe, is not such a small scale phenomenon anymore which can be partly attributed to the changing wind patterns.
I used to live in the Netherlands the past 6 years and usually when I called home, the weather was completely different in Austria than it was in Amsterdam. In 2018 I noticed a change in that. We often had the very same weather and temperatures in the Netherlands as my family had in Austria. This is for the same reason, air does not travel as fast anymore, warm air can spread and just stay until the pressure difference is big enough for it to move on.
This is of course a simplified version of our atmosphere and its interaction with the oceans and continents. Still, I hope I was able to show you that humans do have an impact and we already notice it more than we would like.
Imagine we emit even more and the winds slow down even more. Then the heats and droughts as well as the rain and floods will last longer and longer. What do we do then? In Europe customers complain about ugly small potatoes for example. Well, why are they so ugly? Because of the heatwaves that we caused. In the future, the potatoes won’t grow bigger and be less ugly, it’s rather the opposite. In that sense the whole growing-wine-in-the-UK-thing is not as funny as it seems, is it?
In other words, to secure our future that depends on having food, clean air and water, we have to act. Are you on board?