CO2 – carbon dioxide – is a chemical compound made up of 1 Carbon atom and 2 Oxygen atoms.
Carbon (atomic number = 6) makes up only about 0.025% of the Earth’s crust, making it the 15th most abundant element (in the Earth’s crust) – it is however the fourth most abundant element by mass, after oxygen, helium and hydrogen.
The word carbon itself is speculated to derive from the Latin carbo aka “coal” or “charcoal” and its atomic version predominantly exists as amorphous carbon, graphite and diamond (the hardest naturally occurring substance known to us).
Oxygen (atomic number = 8), the 3rd most abundant element by mass, is a highly reactive non-metal which readily forms oxides with most elements and compounds – and oxides make up almost half of the Earth’s crust!
Too chemically reactive to exist as a free element in air, at standard temperature and pressure oxygen exists as dioxygen (O2) which is a colourless and odorless gas, constituting approx 21% of the Earth’s atmosphere. Another form is Ozone (O3) which strongly absorbs UVB radiation which is beneficial at high altitude layers (hence the global drive to protect the Ozone layer) though at surface level ozone is actually considered a pollutant.
O2 provides the energy released during combustion, aerobic cellular respiration (Oxygen -> ATP reactions) and oxygen itself is a component of many major organic and inorganic molecules (proteins, carbohydrates, fats, bone etc).
And now onto CO2 – an acidic, colourless gas which occurs naturally in the Earth’s atmosphere as a trace gas with a concentration of approx 0.04% by volume (or 415ppm [parts per million]) / 0.06% by mass (or 630ppm) as of end-2020. It is estimated that there is about 50x as much CO2 dissolved in our oceans than exists in the atmosphere.
Natural sources of CO2
Carbon dioxide is the primary carbon source for life on Earth, primarily naturally regulated by aerobic organisms and geological processes.
An example of a natural geological process is freeing of CO2 from carbonate rocks by dissolution in water and acids.
Natural geological sources include volcanoes, hot springs, and geysers.
Being soluble in water, it also occurs naturally “trapped” in groundwater, seawater, rivers, lakes, ice caps and glaciers.
It is produced by all aerobic organisms when they metabolize organic compounds to produce energy by respiration e.g. when plants use it to produce carbohydrates via photosynthesis. It is also produced during decay of organic matter and fermentation of sugars (carbohydrates).
Our own bodies produce approx 1kg (2.2lbs) of CO2 per day!
Man made sources of CO2
This is where human ingenuity inevitably clashes with mother nature’s plans for atmospheric CO2 levels, and the Industrial Revolution is deemed as the turning point for significant acceleration of our atmospheric CO2 contributions, its emissions sharply rising from the 1800s.
Fossil fuel-dependent energy systems are blamed for the majority of man made CO2 emissions. As is cement production, deforestation and burning of biomass.
Here’s some quick stats:
- Modern day human activity is estimated to emit over 30 billion tonnes of CO2 per year
- Oceans absorb approx 1/3rd of CO2 emissions
- Approx half of CO2 released from burning fossil fuels goes unabsorbed by vegetation and the oceans
- Pre-industrial (last 10,000 years) atmospheric levels of CO2 were estimated to be fairly stable, oscillating at around 280ppm
- Today they are at 415ppm
Change over the years
Whilst it is estimated that 500 million years ago CO2 concentrations were 20x greater than today, life on Earth looked much different back then. In fact, that’s well before the dinosaur age and the only lifeforms that have been traced back as far as 500m years ago were simple marine organisms.
Not saying that this was the result of CO2 concentrations but I think we can all agree that we don’t want to accelerate our planet’s return to such a landscape.
Sidenote: check out the cool interactive map at https://dinosaurpictures.org/ancient-earth#500 to see where your city of choice was located X years ago! Here’s where London, UK used to be:
Ok, what happened 500m years ago probably isn’t as relevant and/or relatable to us today hence here’s a more recent CO2 emissions chart:
If you’re like me, then I’m sure at some point you’ve wondered how it’s even possible to obtain such data going back 100s of thousands of years. From the above chart “concentrations can be measured at high-resolution using preserved air samples from ice cores”. I’ve also always wondered what kind of work research scientists carry out at North/South Poles. Now we know!
And whether you are a climate change believer or denier, from the chart we can clearly see the indisputable ~50+% increase in atmospheric CO2 concentration compared to the previous 100s of thousands of years avg. baseline.
CO2 as a Greenhouse Gas – or why is this even a problem?
By now you’re probably thinking “why are rising atmospheric CO2 levels even a problem”?
And it all has to do with CO2’s greenhouse gas potential.
A greenhouse gas [GHG] is a gas that absorbs infrared radiation (from the Sun) and contributes to the greenhouse effect which is illustrated below:
In addition to CO2 there are other greenhouse gases though unfortunately CO2 is by far the largest contributor in terms of both amount and rate of increase.
For completeness and awareness, other primary greenhouse gases in our atmosphere are water vapour, methane, nitrous oxide and ozone.
Back to the greenhouse effect, the process of infrared radiation being absorbed and re-radiated by the GHGs results in an increasing temperature of the Earth (aka global warming).
It is estimated that at current GHG emission rates the average global temperature increase could easily exceed 2°C – a level which is deemed by the UN as the upper limit to avoid “dangerous” levels.
Now whilst 2°C may not seem as much of an increase given that local clime variations can very easily and commonly exceed 2°C given weather seasonal patterns, the devil as always is in the details.
You see, what the 2°C UN upper boundary refers to is the global average temperature increase.
Let’s take a look at 2019 temperature data relative to 1951-1980 averages:
From the data used to compile then map we can tell that:
- The average temperature over land increased by 1.32±0.04°C
- The average ocean temperature increased by only 0.59±0.06°C
But let’s take a closer look at the map itself and go beyond the averaged data. We can readily see that in some regions the temperature change has been much more extreme.
Pretty much the entirety of Europe and large parts of Asia as well as parts of every other continent looks to have experienced temperature increases beyond the reported average of 1.32°C.
At very high latitudes (Polar region) warming can be seen to be upwards of 3°C, in some cases exceeding 5°C. These icy, permafrost regions could experience significant glacial melt as a result of rising temperatures – and as we’ve found out earlier, significant levels of CO2 are trapped within the ice. A chain reaction could start once a critical temperature is reached.
I hope that one of the takeaways from this brief primer on CO2 is that monitoring the global average temperature change is important, but some regions are much (much!) more extremely impacted than others.
The other significant takeaway is that together as a human race we should move fast towards lowering emissions from our energy systems and the way we do things in our “business as usual” way – first to achieve overall net zero global emissions, and subsequently to achieve a negative emissions profile.
Seeing a markedly increasing awareness of the world’s CO2 problem underpinned by rapidly growing support from policymakers and the business community we can be optimistic as pledges are being made, targets being set, and projects agreed & underway.
But we know that we need to go faster.
Hence, the Carbon Thesis was created – where we explore the technological landscape, evaluate the pros/cons as well as the opportunities presented by promising emission reduction technologies.
We cannot afford to sit on the sidelines anymore.
- A Short Introduction to Climate Change book by Tony Eggleton
- Our World in Data – CO2 and other GHG Emissions
- EPA – Global GHG Emissions Data
- Wikipedia – Carbon Dioxide
- Wikipedia – GHG
- Wikipedia – Climate Change
- Wikipedia – Oxygen
- Wikipedia – Carbon
- Britannica – Carbon
- National Oceanic and Atmospheric Administration
- University of Birmingham – Life 500 million years ago