Currently, I am taking a free online course by the University of Exeter on Climate Change. You can find this course on futurelearn.com. I want to share some of the new, interesting stuff that I am learning and my reflections on it on this blog in order to exchange with other learners on the course and to maybe inspire others to learn more about Climate Change. If you have not yet heard of this online course, please check it out as it is very professional and offers you great material to learn with. This post is only meant to help me remember what I have learnt and to maybe find gaps in my understanding. If you already learned the content of the first week of the online course, I would be delighted if you were able to take the time to check and see if you think I understood it correctly. If you do not really feel like doing that and are only here for some of my questions or comments, please look at the paragraphs in bold. 🙂
What was covered in week 1?
I have just finished the first week of learning with the online course and so far, I think it has given me a good basic understanding of what climate actually is and of why it is changing. The first week covered the key principles of climate change, the difference between climate and weather, types of greenhous gases, feedbacks and self-regulation and how humans have an influence on these systems.
Key principles of climate change
I have learned that the sun´s radiation reaches the earth in short waves which the molecules in the atmosphere let through. Some of it is then absorbed by the earth´s surface and the rest is re-emitted back toward space in long waves. This long-wave radiation can be absorbed by the greenhouse gas molecules in the atmosphere (water vapour, carbon dioxide, methane, nitrous oxide, ozone) and then re-emitted toward earth. Only some heat energy escapes into space or is not re-emitted by the molecules. This way, the radiation from the sun gets partly trapped in the atmosphere.
Furthermore, based on this, it is argued that we should not use the analogy of a greenhouse to explain this effect, but that of a blanket. The reason the greenhouse is warm is because it prevents airflow and thus traps the heat which it got through radiation from the sun. As this cannot be compared to molecules re-emiting heat radiation back to earth, the greenhouse analogy is not an ideal one. However, I have to say that I do not quite understand why the blanket metaphor would be better. Firstly, it completely leaves out the initial source of the heat – the sun. Secondly, I thought that blankets do just the same thing as greenhouses to keep the inside warm: prevent airflow and thus trap heat. Consequently, I have to say that both metaphors confuse me more than they help me. Maybe somebody could explain to me why the blanket effect is the better analogy in the comment section? It would be much appreciated 🙂
Another thing I was taught this week is that the “albedo” is the fraction of radiation which is reflected back from the earth´s surface. How much is reflected depends on which kind of surface we are looking at. For example, ice has a very high albedo while the ocean has a low albedo as it absorbs a lot of radiation by being a dark surface. Overall, the earth has an albedo of about 0.3, which means that it reflects about 30% and absorbs about 70% of the radiation which reaches it. Without the greenhouse gases in our atmosphere and only with that 70% absorbtion rate, the average temperature on earth would be -18 degrees celsius. Thus, these gases are crucial for life on earth to exist. Only when human activity tips the balance between them and non-greenhouse gases in the atmosphere do they become dangerous. This was something I did not have any idea of previously to the course and it was really interesting to find out about the role the right amount of greenhouse gases plays in making life possible. Also, it has shown me how dangerous it is that sea ice is melting as this is turning into a vicious cycle: less sea ice -> more of the earth´s surface is dark blue ocean -> lower albedo (more absorbtion of heat radiation) -> warmer temperatures -> less sea ice…
The greenhouse gases I was introduced to in the online course are water vapour, carbon dioxide, methane, nitrous oxide and ozone. I was surprised to find out that carbon dioxide makes up “only” about 0.04% (400 parts per million) of the earth´s atmosphere. The other greenhouse gases beside it are present in even smaller amounts. The majority of the atmosphere is made up of Nitrogen (78%) and Oxygen (21%).
However, this most certainly does not mean that we do not have to worry about the amount of greenhouse gases present in our atmosphere today. Carbon dioxide is released naturally through the carbon cycle but it is also a very long lived gas, which is why it is so important to maintain the fine balance between it and the non-greenhouse gases. Sadly, human acitvity is tipping that balance. The online course taught me that human activity has increased the concentration of atmospheric carbon dioxide by more than a third since the Industrial Revolution.
Another long-lived gas which is added to the atmosphere by human activity is nitrous oxide. It makes up only a small fraction of the atmosphere, but is about 300 times more potent than carbon dioxide. Human activity, like the increased fertilisation of farm fields with nitrogen, has increased the atmospheric concentration of the gas by about 15%.
Methane and ozone are more short-lived gases. However, methane is about 25 times more potent than carbon dioxide and has increased almost 3-fold due to human activity and ozone, even though it is not only short-lived but also quite scarce as a greenhouse gas, is about 1000 times more potent than carbon dioxide. I thought it was very interesting to find out that this ozone is different to that which makes up the protective layer around the earth, protecting life from ultraviolet radiation from the sun. The greenhouse gas ozone is formed near the surface of the earth when vehicle emissions react in the sunlight.
Furthermore, it was completely new to me to hear of water vapour as a greenhouse gas. I was told that it is the most abundant one in the atmosphere and that its increasing presence there is caused indirectly by human activity. The reason for this is that the thicker blanket of greenhouse gases like carbon dioxide, emitted because of human activity, makes for higher temperatures which cause more water to evaporate.
What I took from this was that it is absolutely crucial to dramatically reduce the amount of greenhouse gases which we emit. In my opinion, we will not achieve this solely through technology like electric cars or solarpanels. These changes have to go hand in hand with changes to the lifestyle of excess of so many people. I am planning on writing a post about “green-growth vs. de-growth” in the future, but let me already spoiler you here: I do not think that green-growth is going to solve the environmental problems facing us today. If we want the earth´s temperature to support the wonderful variety of life we know in the future, we cannot go on with our neverending consumption.
Difference between weather and climate
This is a pretty straightforward one but I still feel like weather and climate get mixed up way too often. Donald Trump´s tweet “Wouldn´t be bad to have a little of that good old fashioned Global Warming right now!” when there were quite severe snow storms in the U.S. during winter is only one example. Many people question climate change because they believe that it is not possible to have some colder days or even snow during the year if the climate is warming. However, this is not true and only shows how important it is to understand the difference between weather and climate. This difference was explained very well in the online course. They said that weather is the elements we see daily and something that can change very quickly, whereas changes in climate are usually measured over a period of 30 years.
Moreover, I was shown a map and reminded of the different climate zones there are. The blue on the map shows the polar zones, the green the temperate, the yellow the arid, the red the tropical, the orange the meditarranean and the black the mountain zones.
Feedbacks and self-regulation
Lastly, I was taught to see the climate as a system encompassing the atmosphere, the biosphere, the hydrosphere, the cryosphere and the lithosphere. Moreover, the course reminded me that there are a series of cycles that link these different components together and that are very important to the earth´s climate. These cycles include so-called feedbacks. The three feedbacks I was introduced to are the water-vapour-feedback, the ice-albedo-feedback and the radiation-feedback. The first two are positive feedbacks, the last one is a negative feedback (positive & negative in the mathematical sense).
Water vapour feedback: increased temperature -> increased evaporation of water -> increased amount of water vapour in the atmosphere -> increased amount of radiation re-emitted to earth´s surface -> increased temperature…
Ice albedo feedback: increased temperature -> ice melting -> more surface made up of dark blue ocean -> lower albedo (more absorption of heat radiation) -> increased temperature -> ice melting…
Radiation feedback: the hotter a body the more heat it radiates, the more heat a body radiates the colder it gets
Something this part of the online course definitely taught me is how important it is not to disrupt the earth´s natural systems on a grand scale, as this can result in a global vicious cycle. And soon, we may not be able to reverse the damage done by this vicious cycle anymore. An article on the UN´s website that a friend brought to my attention recently underlines this point very well and really shows how scary and how real this scenario is.
Thank you so much for taking the time to read this blog post! It took me much longer than I thought it would `:) . I want to repeat how much I like this online course and how much of a professional impression it has already made on me. I recommend you check out futurelearn.com if you have not already. This blog post probably shows you how much you can learn on that website in only a couple of hours. And again: Do not feel discouraged by how big of a challenge climate change is. You CAN make a difference. Because remember: You may be a small part of this world, but you are not insignificant!