Humans tend to obsessively keep
track of basically everything on earth, therefore, it’s not particularly surprising that humans have
been constantly recording the earth’s temperature for the last hundred years.
A great example of this is the “British East India Company”. At its peak at the beginning of the 19th century, it had approximately
around 450 total ships in service over the timescale of about 40 years.
During this time these ships were repeatedly travelling
across the Atlantic and Indian oceans. During this time, most (if not all) of these ships would take daily
logs of their exact position, wind speed, air pressure and temperature.
From the data entries of these boats, we have managed to
amass around 273,000 different climate records from 1789 to 1834.
Overall, what humans found from our measuring of the planet was that over the course of the last one hundred years
the temperature has been seemingly getting significantly hotter.
As can be seen in this graph.
In other words, if you look at this graph going back in
time, it looks like the temperature on average was getting colder. Whereas when
we go forward in time it looks as if on average the temperature has been getting
hotter.
The problem is how do we know what the reason of this is? And in order to work this out it is good to look at the different things
that can cause temperature change on earth. The most obvious one of these is the sun.
So how do we know the sun isn’t just getting warmer? Well, this graph below shows the amount of energy we have been receiving from the sun.
NASA have been using satellites to measure the amount of
energy form the sun since the late 1970s.
Whereas before then the energy was determined
by the number of black spots on the sun which are cooler areas
allowing us to accurately estimate the current amount of energy received from
the sun (the more the colder, the less the hotter) and has been accurately been
measured for over a hundred years.
This graph also tells us that we haven’t seen an overall
increase in energy from the sun since the 1950s.
If we place the changes to the earth’s temperature over the
same amount of time beside this graph, we see the average temperature of the
earth has steadily increased, while the energy from the sun has steadily
decreased.
So, another possible reason why the earth could be getting
hotter is that the earth is warming up due to its natural cycle and therefore
we are now at a time in which the earth should just be getting hotter.
Therefore, here is a graph of the earth’s temperature change over
the course of the last 800,000 years.
If you are wondering how that was worked out:
A while ago archeologists found that 5000-year-old man buried
in ice called "Oezti". By looking at “Oezti” we found out loads about what humans were
like 5000 years ago and we can do a similar thing with the earth’s temperature
by looking at the incredibly old ice in Greenland and Antarctica.
If we could find ice
that was 800,000 years old, we could determine what the temperature on earth
was like when that ice froze. The ice in Greenland and Antarctica are great for
this because their ice goes down for miles and miles and as we go down,
different layers of ice appear indicating the different years the ice formed,
similarly to that of rings on a tree stump showing the tree’s age.
To go back even 100,000 years you would have
to dig into the ice for many, many miles, and obviously that’s what they did.
We can also do something similar by looking at very old
shells of animals in the layers of sediment under the sea.
This has left us with an accurate idea of what the earth’s
temperature was like for the past 800,000 years. And it is clearly all over the
place because surprisingly, the earth doesn’t like to remain the same
temperature at all.
It wasn’t humans creating the large spikes in
temperature 800,000 years ago. So, the spike in temperature we are seeing right
now could just be one of those spikes the earth has seen many times before happening
again. To see if that is the case lets investigate the reasons for the big
changes in temperature in the past.
And to answer that we need to investigate the “Milankovitch
Cycles”. Which were invented by “Milutin Milankovitch”
In order to talk about this, let's zoom in a bit and
focus on a graph that specialises in the earth’s temperature over the course of
the last 400,000 years.
If we look closely at this graph, we can see that the
earth’s temperature follows a pattern every 100,000 years or so.
It starts at the sort of temperature we are currently at now, before
getting colder for around 90,000 years called a “Glacial period” and becoming
hotter again for another 10,000 years called an “Interglacial period”. This is
where we are now.
Things then tend to repeat themselves and this is just how
the earth works. This is rather baffling as most of the time the earth is
actually 5°c
to 10°c
lower in temperature than it is normally today. Especially since modern human
civilisation has entirely developed during this hotter period of time. For
example, for 90,000 years until roughly 10,000 years ago Canada was effectively
completely covered in ice.
Why these cycles happen, is where the Milankovitch cycles
come into play.
The Milankovitch cycles are about the earth and its orbit as
it travels around the sun.
If you look at the earth from the outside you would see that
the earth has something called “Obliquity” which effectively means the earth is
in a perpetual tilt.
You see the earth is slightly tilted on its axis, so instead
of the top and bottom of the earth getting the same amount of sun at any one
time, it instead varies across the course of a year.
For example, in July the top half of the earth is facing
towards the sun giving the top half of the planet much more energy from the
sun, causing it to be summer. While the opposite is true for the bottom half of the
earth which is why Australia has its winter in July.
So, the earths tilt isn’t always the same. The
earth instead tilts from 22.1° to 24.5° and back again.
This happens in a cycle, tilting to its maximum and back again,
each time taking 41,000 years.
The reason why the earth tilts like this (back and forth) is
because the other planets that travel around the solar system tug on the earth
with their gravity as they orbit around the sun, causing the tilt of the earth
to wobble up and down.
This is significant because at the earths maximum tilt it
makes things much hotter during each of the hemisphere’s summers. This
situation of high earth tilt is what causes the planet to get warmer and
warmer, ending glacial periods and causing the large spiky increases in
temperature we have seen in the past. An example of this was around 10,000
years ago. This was at the end of the glacial period, making the world much
hotter and allowing human civilisation to thrive.
There are a few other things about our orbit that change and
result in these sorts of events, however Obliquity is generally the most
significant.
Based on this theory its sensible to say that perhaps we are
getting warmer because we are tilting more towards the sun. However, the issue
with this is that we just had our maximum tilt around 10,000 years ago when
that glacial period ended and are now beginning to tilt away from the sun,
explaining the decrease in energy received from the sun.
The biggest lesson from this is that our tilt changes
very slowly with a change of just 2° over the course of 20,000 years. This shows
that changes in the earth’s temperature normally change very slowly. As the
earth goes into an interglacial period it increases in temperature by around 4°c to 7°c over
the course of around 5,000 years.
But in the past 100 years on earth we have seen our
temperature rise by about 1.1°c which is roughly 10 times faster than in the past. On average there would be an increase of 0.11°c every 100
years, at the beginning of an interglacial period.
While simultaneously we are at a point in time that our global
temperature should on average be getting colder.
Despite looking into the temperature changes in the past
there isn’t anything definitive to explain the sudden increase in global
temperature we have experienced over the last 100 years. As a result, the next
big theory we can talk about relates to the amount of CO2 in our atmosphere.
This theory starts with the sun. The sun keeps us rather
warm, however it isn’t enough to keep the earth going. Without an atmosphere the
earths average temperature would likely be around -18°c because we would
constantly, during the night where the earth faces away from the sun, lose all
our heat to the depths of space and freeze.
The reason why we remain warm is because there are certain
gasses surrounding us called “Greenhouse Gasses” keeping the earth warm. The
main gasses are H2O
(water, and yes, I know it’s not a gas), CO2 (Carbon Dioxide) and CH4 (Methane).
While you would be right in thinking that these gasses should
also just be lost to the depths of space, however, the earth is very big. And
because the earth is so big it has the gravitational force to hold all these
gasses in so they can’t escape, creating the earth’s atmosphere.
These gasses then absorb heat energy from the sun, more
energy than the earth itself gives off, like that of a sponge. Then after a
while they shoot this energy out in all directions and the earth then absorbs
the additional energy from both the sun and the gasses… like a sponge.
This means that the earth gets much more heat energy fired
at it and the earth is much hotter than it normally would be without these
gasses. As a result, the earth’s temperature is around 15°c and
we can survive on it. Without these gasses the earth would most
likely be an icy ball floating around in the vacuum of space… or in other words
like Mars.
Anyway, that’s how greenhouse gasses work, and as stated
before, humans just can’t stop measuring things.
So, here is a graph showing the earth’s concentration of CO2 in its atmosphere going back
to 803,719 BCE (going back 800,000 years)
If you were wondering how that was figured out, let's go
back to the ice found miles and miles under the Arctic and Greenland, basically
that ice, like all ice has small pockets of gas trapped inside it. Therefore,
the older the ice, the older the air trapped inside it would be. This allows us to
extract the air from these pockets in the ice, giving us a snapshot of what the
atmosphere was like thousands of years ago and allowing us to make an accurate
estimation of the amount of CO
2
in the atmosphere by measuring the amount of CO
2 within the incredibly old air.
Rather interestingly, when you line up the temperature of
the earth to the amount of CO2
in the atmosphere over the last 800,000 years it becomes incredibly clear that
the amount of CO2 in the
atmosphere and the earth’s overall temperature are very closely related.
Generally, whenever the global temperature goes up, so does
the amount of CO2 in the
atmosphere and vice versa. Overlapping these two graphs further shows their
similarity and link towards each other with large influxes of temperature
leading to more CO2.
Below is a graph of the temperature increase that happened
at the end of the last Glacial Period but significantly zoomed in.
When the earth began to warm up 20,000 years ago, we can see
that first it got warmer before the CO2 started to rise.
You can see a similar thing in this graph going back 400,000
years which shows multiple instances where the temperature first started to
rise and so did the CO2. Then at other parts of the graph, first the temperature started to drop,
followed by the CO2
concentration starting to drop.
What this appears to mean is that CO2 itself isn't
particularly seen to drive the earth to getting hotter or colder. However, if
you look at what is happening today (graph below) it seems as if the
concentration of CO2 started to increase around the late 1800s and then there
was an increase in the earth’s temperature shortly afterwards.
To understand what is going on here let’s investigate the
rise in temperature at the end of the last glacial period again. As discussed, this was likely caused by the Milankovitch
cycle making the summers on earth significantly hotter.
And if you want to know what this has to do with CO2, well the answer can be
explained with 2 separate cans of Coca-Cola. To explain why, basically
gasses can be dissolved in water effectively the same way that salt can. Coke
is pretty much just flavoured water with lots of CO2 dissolved within it, and
when you open the can, CO2
comes out of the liquid and escapes as a gas. Ultimately the colder a
liquid is, the more gas can be dissolved into it. This effect is explained in
a branch of chemistry called physical chemistry.
If you take a cold can of coke (representing the earth in a
glacial period) and a warm can of coke (representing the earth in an
interglacial period), when you open the colder can much less gas escapes compared
to when you open the warm can, which releases notably more gas.
What I’m demonstrating with this is is that after the Milankovitch
cycle warmed up the earth, the seas would have had to start releasing much more
of the gas dissolved within them because warmer liquids can’t hold on to as
much gas as cold liquids.
This explains why we see an increase in CO2 levels shortly after we see
an increase in global temperature. This is relevant because kick starting the
end of a glacial period needs significantly more heat than what we would get with the earth tilting a few more degrees towards the sun.
Each of the glacial periods lasted around 90,000 years each
and coming out of them required a much more significant increase in temperature
than what the Milankovitch cycle gives the earth by itself.
As a result, what seems to have happened is that the world is
warmed slightly by the Milankovitch cycle causing the seas to release
significantly more CO2. This then amplifies the greenhouse effect causing the earth to get even warmer,
which in turn causes more CO2
to be released and things very quickly get significantly hotter.
This is demonstrated on this graph.
The graph shows the earth getting warmer at the end of the
last glacial period similar to the one we saw before, however, this graph is
significantly more detailed and uses the global estimated amount of CO2 in the atmosphere using every
method we have available to estimate the earth’s average temperature as
accurately as possible.
In this graph the CO2 levels of the atmosphere was initially led by the earth’s global
temperature, but 90% of the earths warming only happened after there was a
large increase in the atmosphere’s concentration of CO2 which would have been caused by the seas
releasing more gas after the initial warming of the earth.
And after this happened, CO2 became what led the earth’s rise in temperature.
Temperature and CO2 do seem to be closely related as one has always affected the
other. And if you look at the earth’s CO2 concentration over the last 800,000 years you would
see that the total concentration has never properly exceeded 300ppm (parts per
million) which is basically a measure of concentration. However, in just the last
100 years we have seen a jump in CO2 concentration to around 400ppm which is practically 33% higher
than it has ever been before.
Shortly after this CO2 increase, we have seen an increase in temperature around
1.1°c
which, again, is roughly 5 to 10 times faster than any other temperature
increase we have ever recorded.
This change to our temperature is happening even though we
are now slowly tilting away from the sun and the amount of solar energy hitting
the earth is steadily decreasing.
But are greenhouse gasses the only thing that could possibly
be making the earth’s temperature rise?
Below are a series of graphs explaining the different
possible global activities that could possibly be affecting the global
temperature.
(The global temperature increase we have
observed over the last 100 or so years)
Here is the heating and cooling effect that volcanos have had
on our planet for the last 100 years.
Here are the heating and cooling effects that the sun has
had on our planet for the last 100 years.
And here is the effect human activity has had on the global
temperature over the last 100 years.
What these graphs show is that greenhouse gasses are the
only possible explanation for the rapid growth in the earth’s temperature, with
many having very little to no effect while others are actively cooling the
earth.
Based on the knowledge we know about CO2, the effect that it has had
on our temperature in the past and the lack of any other possible causes, CO2 has been deemed the most
likely cause for the increase in temperature over the last 100 years.
In that case it is important to understand where all this CO2 is coming from and to do
that we need to talk about Fossil Fuels.
Fossil fuels are basically just plants and animals that died
a very, very long time ago and over time these animals sank into the ground
eventually becoming coal and oil.
This happens because coal and oil are mostly just made from carbon. And plants and animals too are mainly carbon. This is what we mean when
we say we are “carbon-based lifeforms”.
When we burn these carbon-based fuels for energy the carbon
in the coal and oil reacts with oxygen and creates CO2.
One of the main reasons why CO2 is believed to be the most contributing factor to
the global temperature rise is because we started burning fossil fuels around
the late 1800s during the industrial revolution and almost immediately
afterwards we saw a rise in CO2
in the atmosphere, followed by a rise in temperature we are still seeing today.
But how do we know that this was caused by the burning of
fossil fuels that caused this increase in CO2.
Well, interestingly when air floats into the atmosphere it
absorbs cosmic rays from space causing a very small amount of carbon in the air
around us to become radioactive.
This is call Carbon-14 and all the air around us holds a
very tiny amount. However, the carbon in fossil fuels has been trapped under
ground for millions of years and hasn’t been exposed to the cosmic rays in a
very long time. This means when we burn fossil fuels we release carbon that has
very little to no Carbon-14.
To better convey my point here is a graph showing the
average amount of Carbon-14 in our atmosphere since the 1800s.
Over time we see the amount of Carbon-14 in our atmosphere
steadily reduce since the industrial revolution. This indicates that the
atmosphere is being filled with CO2 that has very little Carbon-14 and the most likely cause of this
CO2 is fossil fuels.
Unfortunately, we stopped being able to record the number of Carbon-14 as a reliable measurement of CO2 from fossil fuels after the 1950s.
This is because we began testing the atomic bombs,
releasing large numbers of eradiated Carbon-14 into the atmosphere.
However, there are also atoms called Carbon-13 which tell us
similar things to Carbon-14 but aren’t radioactive and don’t get affected using
atomic bombs.
So, with that in mind, we can see in this graph that the
amount of Carbon-13 in the atmosphere drops steadily in the same way Carbon-14
did.
Judging from the evidence,
the temperature rise is the fault of fossil fuels releasing CO2 into the atmosphere.
The earth warming a few degrees (as
it is currently set in motion to do) based on the current amount of CO2 we are
producing will bring a variety of different issues across the world. A few
examples include: widespread flooding due to the icecaps melting and large areas
will become too hot to live in or grow food and forest fires will become
significantly more frequent.
So, in order to figure out what we
can do right now to slow or lower the amount of greenhouse gasses we release
into the atmosphere, first we need to know where all the human produced CO2 is coming from. Therefore, to
break this down here is a graph showing different emission percentages produced
by humans.
The main thing to see here is that
72% of all CO2 emissions produced from humans come from energy use. This is
because much of the energy that we use comes from burning fossil fuels.
If we were to expand this, we can see that 43% of this is
due to the production of electricity and the burning of fuels such as natural
gas, which is also a type of fossil fuel for heating and cooking. Another 17% is
from transport which comes from cars and planes and boats etc…
These are the things we need to focus on first simply
because it is the largest slice. In order to do this, we must first start using
less fossil fuels and instead use more renewable energy.
Renewable energy is effectively biofuels, wind
turbines and solar panels. These are called renewable sources of energy because
once it is set up it can make energy basically forever.
We take energy from places like the sun and the wind and use
it to make power, so we no longer need to dig giant holes in the ocean or
desert to mine coal or oil when we have an endless source of low cost energy
available.
In 2016 the fossil fuel industry was subsidised $360 Billion
to keep it on the path it’s on compared to renewable energy which was
subsidised $140 Billion. Renewable energy was subsidised less than half of what
fossil fuels were even though renewable energy is the fastest growing energy
resource in America and Solar energy is the fastest growing in the world.
However, because it makes economic sense, the transition from
fossil fuels to renewable energy is already happening.
In 2016, 26.5% of the worlds electrical energy came from
renewables. This is partly because 146 of 197 countries set green electricity
targets (targets to increase renewable energy for electricity). But this is
only for electricity, not including the natural gas required in heating and
cooking.
Only 10.3% of the energy we use to produce heat is from
renewable sources and only 48 of 197 countries have set green gas targets
(targets to increase renewable gas for heating and cooking). This is similarly true for transport, only 0.3% of our cars,
planes and boats/other use renewable energy.
It’s mostly down to politicians and governments to choose to
start building more renewable energy sources, to stop subsidising fossil fuels
so much and instead start subsidising renewable energy more.
Simply, one thing you can do is just vote for whatever
political party sets the most renewable energy targets. Most
political parties release a document outlining all of their claims. You could use
these documents and search for terms you care about such as the term
“renewable” and find out what party has the most results corresponding to the
term you search.
Another thing you can do is switch to a renewable energy
provider. To switch you can search “100% green energy provider” and try to find
some websites or a comparison page of different energy providers listed by how
much their energy is sourced from renewables. The best of which would be one
that provides both 100% green energy and gas.
Finally, let’s bring up the agricultural side of climate change.
The next biggest cause of CO2/greenhouse gas emissions is agriculture as
this graph shows.
Therefore, it begs the question as to what foods produce the
most CO2?
Well, here is a graph showing a selection of foods compared
to the amount of CO2 equivalent
in emissions per kilogram of said foods.
So cows clearly produce the most amount of CO2.
This is because cows mostly eat grass (which is pretty much inedible) and which
requires to be fermented within the cow’s stomach in order to digest. This creates methane gas which is then burped or farted out by the cow.
This is incredibly troublesome because methane is 84 times more effective at warming
the earth than CO2, which is why everything related to cows has such a high percentage
on the chart.
Generally, animals produce a significantly higher amount of
CO2 compared to plants because animals tend to fart a lot and need a lot of food.
Many people don’t want to go vegetarian or vegan and
honestly, I don’t blame them (as I am one of those people too). I also think
that nothing puts people off this topic more than some random stranger telling
them what they can and can’t eat.
Instead all I want to do is show you the statistics and let
you make up your own mind on what you want to do.
The easiest starting point for someone who would want to get
involved in lowering their personal CO2 emissions, could try to stop eating as much beef related
products in favour of less polluting foods.
Interestingly, Poultry (chicken/turkey) doesn’t have much of
an impact on the levels of CO2,
so it would be understandable to eat less beef in favour of more chicken.
Here are the references used (in order):
East India trading company measuring climate: https://cp.copernicus.org/articles/8/1551/2012/cp-8-1551-2012.html
Earth temperature last 100 years graph: https://ourworldindata.org/co2-and-other-greenhouse-gas-emissions
Sun’s solar activity and amount of radiance hitting the
earth: https://climate.nasa.gov/faq/14/is-the-sun-causing-global-warming/
Earth’s temperature over the last 800,000 years: https://earthobservatory.nasa.gov/features/GlobalWarming/page3.php
Ice core records used to measure the Earth’s temperature and
CO2 levels going back: https://earthobservatory.nasa.gov/features/GlobalWarming/page3.php
Earth’s temperature over the last 400,000 years: https://saylordotorg.github.io/text_general-chemistry-principles-patterns-and-applications-v1.0/s09-05-energy-sources-and-the-environ.html
Glacial periods, mainly the most recent one: https://en.wikipedia.org/wiki/Last_Glacial_Period
Glacial and interglacial cycles: https://www.ncdc.noaa.gov/abrupt-climate-change/Glacial-Interglacial%20Cycles
Milankovitch cycles and Obliquity: https://climate.nasa.gov/news/2948/milankovitch-orbital-cycles-and-their-role-in-earths-climate/
Rate of Earth’s temperature changes in the past: https://earthobservatory.nasa.gov/features/GlobalWarming/page3.php
Greenhouse gasses and how they
work: https://www.epa.gov/ghgemissions/overview-greenhouse-gases
Earth’s CO2 concentration over the last 800,000 years: https://www.epa.gov/ghgemissions/overview-greenhouse-gases
Measuring the Earth’s CO2 levels in ice cores: https://www.bas.ac.uk/data/our-data/publication/ice-cores-and-climate-change/
Earth’s temperature VS CO2 concentration during the last
glacial period (references are below their video): https://www.youtube.com/watch?v=dHozjOYHQdE
The Earth’s temperature changes, then its CO2 concentration
follows: https://skepticalscience.com/co2-lags-temperature.htm
Gasses absorb different amounts as the temperature changes: https://antoine.frostburg.edu/chem/senese/101/solutions/faq/temperature-gas-solubility.shtml
Milankovitch cycles may cause the Earth to release CO2,
which drives the temperature change: https://skepticalscience.com/co2-lags-temperature-intermediate.htm
Bloomberg graphs of how different things affect the Earth’s
temperature: https://www.bloomberg.com/graphics/2015-whats-warming-the-world/
Changes to Carbon-13 and Carbon-14 levels in Earth’s
atmosphere: https://www.skepticalscience.com/co2-increase-is-natural-not-human-caused.htm
How the Earth’s temperature will change based on the amount
of CO2 we are currently producing: https://climateactiontracker.org/global/temperatures/
Breakdown of all human produced CO2: https://www.youtube.com/watch?v=GkbuV_a-rvs
Information for some of the graphs used, subsidy amounts for
fossil fuels and renewable energy: https://www.ren21.net/wp-content/uploads/2019/08/Full-Report-2018.pdf
Renewable energy and it’s growth: https://www.c2es.org/content/renewable-energy/
Breakdown of CO2 produced by food manufacturing (references
below the video): https://www.youtube.com/watch?v=mmNcOCwtFeg
