The Tipping Point
This year we enjoyed the greatest summer of all time! It was so nice that I started wondering if this was still normal. Are we Scots supposed to have a summer, with moderate amount of rain and nice warm weather? Will this have an effect on the general vibe of our cities? Or even on our identities?
10th of October 2018 it was 18ᶛC and sunny! This is not normal! This is not what our lives are supposed to be like.
However, this nice weather might convince you of the fact that climate change is actually a nice thing. I have to admit that somewhere deep in my heart, I would like to keep having summers like the last one.
The first blog post explains in an easy to understand language how climate change works, what causes it and why not stopping it could have devastating consequences for our planet and our species.
Climate Change, how does it work?
The best starting point to understand the mechanism of climate change is to ask yourself the following four questions.
How does the atmosphere of a planet get “warm”?
What do greenhouse gases have to with it?
What are the main greenhouse gases?
What is humanities business with greenhouse gases?
What would be the consequence of to many greenhouse gases in the atmosphere?
The sun emits solar radiation (light) which happily travels through space, until some lucky light rays happen to hit our planet (Earth). When they hit a surface which is non-reflective or transparent — this could be anything, you, me, a house, a rock the Atlantic Ocean — the material absorbs the energy from the light ray and gets “warmer”. That’s why sitting in the sun makes you feel nice and ‘warm’. I write ’warm’ in quotation marks because, when sitting in the sun, you actually gain thermal energy. This means that the atoms on your skin starts to move quicker.
At this stage, this blog post gets a tiny bit nerdy; however, stick with me for the following six sentences and you will leave with some new scientific information and some bragging rights.
Every particle in the universe (including all of the ones that make you) which has a temperature above absolute zero (-273ᶛC) emits “light”. Invisible light to be precise, and this invisible light is commonly called electromagnetic waves. These are formed, because your body is made of billions of fast moving atoms, all of which have an electrical charge. This leads to you, and every other thing with a temperature to emit radiation. For comparatively cold object such as yourself and most objects around you these wavelength will be in the infrared spectrum. This is invisible for humans, but bees and bumblebees can actually see it.
Long story short, warm objects emit infrared radiation to lose some of the energy they just acquired. If earth didn’t have an atmosphere the energy would disappear into space, never to be seen again and earth would be freezing cold. The moon doesn’t have an atmosphere and is very cold. Poor moon L
What do greenhouse gases do with it?
Actually, in the last statement I gave the atmosphere a bit too much credit. It’s not the atmosphere that keeps our planet nice and cosy. It’s the greenhouse gases! They have a fascinating property. They can absorb infrared radiation, which increases their kinetic energy and vibrate quicker. The boring molecules in their proximity are now infected by the hot vibe of the greenhouse gas molecules and start moving faster as well. This increases the temperature of the entire gas mix. Alas! Greenhouse gases are a good thing!
If there weren’t any greenhouse gases in the atmosphere, it would be very cold on earth. The mean temperature would be -18ᶛC. And if the mean temperature was -18ᶛC, there would be snow everywhere, and snow is white, and white surfaces reflect the majority of light back into space, so it would get even colder and colder and colder until we lived on an ice ball. The “whiteness” or more accurate the ability to reflect light of a surface is called its “albedo”. An albedo of one means that 100% of the light hitting an objected are reflected, and one of 0 means that 0% of the light is reflected. Fresh snow has an albedo of 0.9, and this piece of information will be important later on.
So, up to this point, we have established that greenhouse gases keep us nice and warm and that we should be glad for having them in the atmosphere. Probably you are very excited about GHG now and really want to get to know these fellows a little bit better. I guess that you have heard of the big celebrity in the realm of greenhouse gases — CO2. But besides CO2 there are a few others, the most prominent being Methane, NiO2 and water vapour. All four gases have the ability to absorb infrared radiation and heat up during the process.
Let’s look a bit closer, so we can appreciate their full diversity and beauty. Here is the ultimate list of the four greatest greenhouse gases and their properties.
Where does it come from? Farting cows! Landfill sides! Siberian permafrost! Swamps and methane hydrate (Mega Cool)
How much is in the atmosphere? Very little, less than 2 ppm (ppm = parts per million)
How long does it remain in the atmosphere? 9–15 years
How much heat does it absorb? 25 times as much as CO2 (that’s because it can very effectively absorb infrared of wavelength from 3.3–7 micrometres)
Where does it come from? Animal farming and fertilisation
How much is in the atmosphere? Very little, less than 322 ppb (ppb = parts per billion)
How long does it remain in the atmosphere? 114 years (on average)
How much heat does it absorb? 298 times as much as CO2
Where does it come from? The combustion of fossil fuels (cars, power plants, heating), your breathing, and photosynthesis (at night)
How much is in the atmosphere? Quite a bit, 400ppm (keep in mind, this one that continuously increases)
How long does it remain in the atmosphere? Very long (Hundreds to ten thousands of years)
How much heat does it absorb? 1 CO2 equivalent is the base unit that we will be using.
What is humanities business with greenhouse gases?
Over the last 200 years, humanity has developed a couple of — let’s say — bad habits. Firstly, we have started to burn fossil fuels in ridiculously large quantities, annually pumping billions of tons of carbon dioxide into the atmosphere. From 1750 until today the carbon dioxide concentration in the atmosphere has increased from 280–400 parts per million. Secondly, we have started to extensively farm animals, such as cows, that emit large quantities of methane as result of their digestive process. Finally, we have cleared large forest areas that used to absorb carbon dioxide and turn it into biomass. There are a couple of other things humanity did, but the three points on the top are the most important ones.
To cut a long story short, humanity has misbehaved, was greedy, and now we have to face the consequences. Payback time!
What would be the consequence of too many greenhouse gases in the atmosphere?
The summer was absolutely fantastic, don’t be so negative! Climate change is the best thing ever! How could it be bad for us?
Oh boy / girl, it is going to be bad. Very bad. But let’s start with the classic answer first, before I introduce you to the tipping point.
The classic. Everybody knows that increasing earth’s mean temperature will result in melting arctic ice and rising sea levels. This is a big problem, because many of our biggest city are located at low elevations close to the sea — for example, Shanghai, New York City, London. If you combine this with the drying of large areas in the tropics and sub-tropics this will result in the displacement of many people.
Despite that pathetic management of the current refuge crisis, I am sure that humanity, faced with a self-inflicted disaster of this scale would overcome selfishness and find a new home for these people.
Additional to this, many ecosystems will be flooded or otherwise destroyed, and a large amount of species, from plants, to beetles, to worms, to mammals and fish will go extinct. But as scientists already estimate that 150–200 species go extinct every 24 hours, who cares? (I actually do, this might be a great topic for its own blog post)
However, there are consequences that are even worse. Because at some point we will reach “the tipping point”. At that point, nature will take over and a positive feedback loop will set in, heating earth further and further.
The tipping point
There are four natural mechanisms, each of which has its own threshold that would cause the temperatures to increase further.
· The melting of arctic ice and glaciers
· The increase of water vapour in the atmosphere
· The defrosting of permafrost soils
· The melting of subsea methane hydrate
For each of them, it is unclear where the threshold lies; however, the mechanisms through which they would push the greenhouse effect further are very plausible.
1. Melting Ice
Earlier in this post I mentioned the albedo, the ability of a surface to reflect light. White surfaces have the highest reflectivity. On earth, there are two areas that are very white. Antarctica in the South, and the Arctic in the North. When sunlight hits these mainly white surfaces, the majority of the light and with it the energy of these light rays gets reflected back into space. This has a cooling effect on the planet. However, as the global temperatures increase, the ice melts. This is a particular problem in summer, as very large areas of the arctic become ice free. These areas are replaced by comparatively dark sea water. Dark sea water has a very low albedo of 0.05 to 0.22. This means, that the majority of the light gets absorbed and heats the water, which in turn emits infrared radiation, which is absorbed by the greenhouse gases in the atmosphere. Now the atmosphere is warmer than before, and more ice melts.
Tada! Our first positive feedback mechanism. That wasn’t so hard was it!
But this is not just theory. The melting of the ice has started. Since 1979, the Arctic’s minimum average sea ice surface area has been continuously decreasing. Around 1979, the minimum ice surface area has covered about 8.000.000 km2. From 2008 until 2018, the ice has been struggling to stay above 5.000.000 km2. (Check out the depressing graphic from NASA below).
This might come as a shock, but water vapour is a greenhouse gas as well. Most likely, you have experienced this effect first hand. Imagine a bright sunny day where it was nice and warm. The sky is clear and you spend the day doing your favourite outdoor activity. As it gets dark — the sky is still clear — it will get cold very quickly.
Now imagine the same day. However, now there is cloud cover. Again you spend your day enjoying you favourite outdoor activity. As it gets dark — the sky is cloudy — it will still be warm.
There are two reasons why climate change will increase the amount of water vapour in the atmosphere. First: because the atmosphere gets warmer, the water will get warmer. How long this will take depends on the properties of the water body. A small lake or river heats up rather quickly, while it can take a thousand years for the oceans temperatures to increase significantly. Warm water evaporates quicker than cold water.
This is closely linked to the second effect. Warm air can “transport” more water vapour than cold air. This is why the air is very dry on cold winter days and can be very humid on hot summer days. Long story short, as the atmosphere gets warmer, more water evaporates, which makes the temperature increase further, which leads to more water evaporating.
How powerful this effect will be is unclear at this stage. However according to Wikipedia the average residence time of a water molecule in the atmosphere 9 days. I hope that I am wrong here, but I conclude that it will rain even more. L L L
2. Defrosting of the permafrost
Finally it’s time to move away from the rather intuitive feedback mechanisms and to progress to the really crazy stuff. The crazy stuff has got a name: permafrost. Permafrost is ground (soil or rocks) that has been continuously frozen for at least two successive years. You can find it at very high latitudes, close to the north or south poles, or at very high elevations (e.g. the Alps, Himalayas, and Andes). 24% of the landmass in the Northern Hemisphere is covered by permafrost! It contains a large amount of methane (how large exactly nobody knows), a greenhouse gas 25 times as potent as CO2. It was formed thousands of years ago when these areas were covered by vegetation, which forms methane during decomposition.
Great news! Up to 530 billion tonnes of methane are estimated to be safely stored within frozen peat in Siberia and cause no harm.
Oh wait — the peat is frozen! What happens to frozen things when they warm up again? Oh shit — bad news coming! They melt and the gases stored within those soils will gradually be released to the atmosphere.
By now you should know the drill. The atmosphere gets warmer, the permafrost thaws and starts to release the super potent greenhouse gas methane (25x CO2), the atmosphere heats up even more, more permafrost defrosts, more methane is released ….
However, don’t panic, there is some hope! Perhaps (a very big perhaps), global warming might dry wetlands in southern regions, a natural methane source, which would reduce the methanogenesis (production of methane) in those regions. If we are lucky, this will lead to a less dramatic increase in atmospheric methane.
I wrote the last paragraph to rebuild your confidence. But now, it’s time to introduce you to the final level of insanity! Brace yourself, as you are about to meet the end boss.
3. Methane Hydrates
Welcome to the most unknown, but potentially most dangerous climate feedback mechanism. But first things first — what are methane hydrates? Methane hydrate refers to methane which is trapped within the crystal structure of frozen water (ice). Specific temperature and pressure conditions are required to form stable carbon hydrate. These are found in the deep sea, or more specifically in the regions of the oceans, where the rather shallow sea close to the continents dips into the deep sea. We know little about it, because it forms in depth between 500 -1000 meters. However, the estimated amounts of methane hydrate in our oceans range from 2,000 -8,000 billion tons. If the upper threshold was to hold true, there would be more carbon stored in subsea methane hydrate than in the entirety of the world’s coal deposits.
So far so good. Nothing to be scared off! The carbon is safely stored in frozen methane hydrates! There is nothing to worry about!
I think, you can make the feedback cycle up by yourself.
If you actually read this blog post up to this point — well done. I will finally leave you with a quote from Mario Molina (a Nobel prize winner) on the IPCC report from Monday.
“The IPCC report demonstrates that it is still possible to keep the climate relatively safe, provided we muster an unprecedented level of cooperation, extraordinary speed and heroic scale of action. But even with its description of the increasing impacts that lie ahead, the IPCC understates a key risk: that self-reinforcing feedback loops could push the climate system into chaos before we have time to tame our energy system, and the other sources of climate pollution.”
The actions and changes required by every single one of us, the global society and economic system will be the main focus of future blog entries.
Have a nice day!
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