All activity requires an energy source, from plants growing in the ground, to animals walking on the ground, to rockets flying off the ground, and to all things happening in the vast expanse of the universe around us. Energy is the universal currency. It can assume various forms, with an exchange rate between them which is fixed, constant, and absolute.
Throughout the ages, people have sought to harness energy in its various forms to power evermore ambitious projects. First, simply using fire for warmth. Later, using wind to push ships across the oceans. And now, using refined fuels to fly high above the world to nearly any destination within a matter of hours, and communicating via a global electronic web choreographed by undersea cables and satellites.
Sun, wind, water, chemical, nuclear - the means by which we now tap into the grand energy flow are varied. But certain resources are finite or constrained, the world population is rising, and with it so too is a greater desire for energy to power the lifestyles and economies we have developed so far, and to develop them further still. And all is not even, with this story having played out differently for different people in different places.
Note: All data are from the "BP Statistical Review of World Energy 2019"  unless otherwise stated. Note: The "regions" are defined as follows:
Algeria, Egypt, Morocco, South Africa, Eastern Africa, Middle Africa, Western Africa, Other
Australia, Bangladesh, China, China Hong Kong SAR, India, Indonesia, Japan, Malaysia, New Zealand, Pakistan, Philippines, Singapore, South Korea, Sri Lanka, Taiwan, Thailand, Vietnam, Other
CIS (Commonwealth of Independent States)
Azerbaijan, Belarus, Kazakhstan, Russian Federation, Turkmenistan, USSR, Uzbekistan, Other
Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Netherlands, North Macedonia, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey, Ukraine, United Kingdom, Other
Iran, Iraq, Israel, Kuwait, Oman, Qatar, Saudi Arabia, United Arab Emirates, Other
Canada, Mexico, US
S. & Cent. America
Argentina, Brazil, Chile, Colombia, Ecuador, Peru, Trinidad & Tobago, Venezuela, Central America, Other
MTOE = Millions of Tonnes of Oil Equivalent. This means the amount of energy from all sources (fossil fuels, nuclear, hydro, wind, solar, geothermal, biomass, other) considered as the equivalent amount of energy that would be given just by burning the stated amount of crude oil .
Oil is less dense than water, so a certain mass of oil takes up about 10 - 20% more volume than the same mass of water, depending on its exact makeup . But cubic metres are simple to visualise, and the properties of water  are such that:
1 tonne is the mass of a cube of water 1m long on each side
1 million tonnes is the mass of a cube of water 100m long on each side
1 billion tonnes is the mass of a cube of water 1000m long on each side
From the above data, we have that in 2018 the world used approximately 13.9 billion tonnes of oil equivalent energy (13,865 MTOE). From the above conversions, that mass of oil is equivalent to the mass of 13.9 cubic kilometres of water, and so a 10 - 20% larger volume in terms of oil itself, equating to something in the range of 15 - 16.5 cubic kilometres. That works out to more than one cubic kilometre of oil equivalent energy use per month, in other words.
For comparison, the global average human body mass is currently about 62 kg , and as of mid-2020 there are approximately 7.8 billion people in the world . The total mass of humanity at this time is therefore about 484 million tonnes, equivalent to just less than half the mass of a cubic kilometre of water. So:
we are using more than double the combined current
mass of humanity in oil equivalent energy use each month.
We can extend this thought experiment a bit further, by considering that our species has been in its approximate form for about 50,000 years, and calculations estimate that there have been approximately 108.8 billion people in total over this period, including those alive today (which make up about 7% of the total figure) . Using the current average body mass of about 62 kg, the total mass of humanity from all time is then about 6.746 billion tonnes, although the average body mass over this period is sure to be a bit lower, but let's take this calculation as an upper limit. That's equivalent to the mass of 6.746 cubic kilometres of water. So:
we are using more than double the combined all-time
mass of humanity in oil equivalent energy use each year.
However you look at it, that's no small amount. But let's now make some further comparisons to get a better idea of relative scale. Adult humans in economically developed countries eat around 1.3 kg of food per day, so around 40 kg per month . That's much less than the average human body mass. So, on average, every month we each use less than our body mass in food, but we each use more than double our body mass in oil equivalent energy. Keeping our bodies running requires far fewer resources than keeping our economies and lifestyles running, in other words. And globally that assessment is far from being evenly balanced amongst all people.
That brings the situation into perspective in human-scale terms, but what about in Earth-scale terms? Let's take precipitation as another example. If all the precipitation in one year were to sit on the Earth's surface and not sink in, it would cover the globe in a shell about 1 metre thick . The Earth has a surface area of about 510,072 billion square metres , so with water having a density of 1 tonne per cubic metre, that gives us 510,072 billion tonnes of precipitation per year, which would occupy a volume of 510,072 cubic kilometres, equivalent to a cube of 79.9 km side length. To put that into perspective, the average depth of the world's oceans is only about 3.7 km, and about 11 km at the deepest point . That mass of water is approximately 37,000 times more than the mass of 2018 oil equivalent energy use. So in this measure of planetary scale activity, our actions may seem small. However, as discussed later, the potency of the byproducts of our current fuel mix means this nonetheless has a big effect.
GJ = Giga Joules = billion Joules. 1 GJ is the amount of energy needed to keep a single 32 Watt lightbulb on continuously for 1 year. The number of GJ per capita is therefore equivalent to the number of 32 Watt lightbulbs on continuously per capita. MTOE is too large a unit for per capita use, so instead GJ is typically used, hence the different scales seen in the above graphs.
From the above data, we have that in 2018 the energy use attributed to the average person in north America (the highest use of all the regions) was 240 GJ, while for the average person in Asia (the most populated of all the regions) this figure was 60 GJ. So in terms of continuous use of 32 Watt lightbulbs, that's 240 lightbulbs and 60 lightbulbs, respectively.
It should be noted that these figures are for energy use of society as a whole, including all industrial and domestic use, simply divided up amongst the people of the various territories. These figures are then representative of what the various territories use in all their activities, and the actual use for any given individual could be very different. Even so, the typical usage for individuals in different regions does indeed still vary greatly. Numerous factors add up to make the difference, such as methods and scale of both industry and agriculture, home and office heating and cooling, commute methods and distances, personal travel, personal devices ... the list goes on.
Oil is the dominant source overall, accounting for 34% of 2018 global energy use, followed by coal at 27% and natural gas at 24%. All the non-fossil fuel sources together (hydro, nuclear, renewables) account for the remaining 15%.
This non-fossil 15% of the 2018 global energy use of 13,865 MTOE works out at 2,121 MTOE, when the exact figures are used. When compared with the 2018 energy use of the various territories, we see that this amount just covers Europe's use of 2,051 MTOE, but falls short of North America's use of 2,832 MTOE, and is less than half of Asia's use of 5,986 MTOE.
Looking just at the renewables (wind, solar, geothermal, biomass, and others), their use has only come to noticeably register since the turn of the new millennium, having increased from a combined total of 49 MTOE in 2000 to 561 MTOE in 2018. In absolute terms, this increase of 512 MTOE is much less than the increase of any of the fossil fuels over this same period: oil grew by 960 MTOE, coal grew by 1,414 MTOE, and gas grew by 1,247 MTOE. These larger values reflect the already established fossil fuel industry, in which even small fractions of adjustment translate in to large absolute measures. And the fractions of adjustment in the fossil fuel industry were not even trivial over this period, with the absolute variations representing a 1.3 times increase in oil, a 1.6 times increase in coal, and a 1.6 times increase in gas. However, the absolute variation in the renewables represents an 11.4 times increase, which does show a real push for growth in this area. Indeed, if such rates of change hold over the next 20 years or so, then the renewables will actually come to dominate the fossil fuels. As to whether or not the renewables will be able to maintain such rapid growth, and whether or not the use of fossil fuels will actually decline, remains to be seen.
For the time being, it is readily apparent that the global energy supply is very much dominated by fossil fuels. To further give a sense of scale of the operations involved from any one location, grown over many decades of development:
by itself the US, the current biggest oil producer, extracted
0.75 cubic kilometres of oil from its wells in 2018,
1.4 times the current mass of all humanity.
However, given the current proved oil reserves, the US could only maintain that extraction rate (which has been lower in the recent past) for about another decade. The greatest proved oil reserves are by far in the Middle East, with approximately 130 cubic kilometres of oil left in the ground (a cube of about 5 km side length), 36% of which is in Saudi Arabia, the greatest share of any one country in that region. At Saudi Arabia's 2018 extraction rate, second only to that of the US, its proved reserves would run dry in about 70 years. But the demand for Saudi oil will likely increase as other sources run dry quicker, not to mention increasing energy demand regardless of source, so without further discovery the actual time limit will be much shorter.
The Middle East has maintained its stance of having about 50% of the world's proved oil reserves for at least the last 40 years, showing that both discovery and extraction in this region alone have been occurring at similar rates to all other regions combined. Not only that, but discovery in the Middle East is steadily continuous, whereas in many other regions there are typically long periods of virtual flatlining between significant findings.
It's perhaps not surprising then, with a clear lack of immediate concern for domestic supply, that the Middle East has one of the lowest installation levels of renewable energy sources. Continuing with Saudi Arabia as an example, at the end of 2018 it had a solar generating capacity just 0.16% that of the US, and zero generating capacity from all other non-fossil sources. Even catering for the population difference of the two countries, with Saudi Arabia having about 10% the population of the US [29 - 30], that difference is extreme. Given the geographic location, available desert land and weather, the Middle East is a prime site for solar farms. It's not unfeasible for the region to maintain its position as a prime global energy source via exported solar electricity, which could be a wise investment plan. But according to the data, the political and business will to make that happen seems not to be there, at present.
Note: Historical data for coal reserves are not given in the reference , only those for oil and gas, hence only two sets of graphs shown above.
With energy use dominated by fossil fuels, it's no surprise that global CO2 emissions data follows global energy use data, region by region. The most significant increase in 21st century fossil fuel use has come from the Asia Pacific region, in particular from China in terms of all three oil, coal, and gas, but particularly coal, with a surge in use beginning around the year 2002. As seen in the previous section, coal is the most abundant of the fossil fuels, but has the greatest ratio of CO2 to energy output from combustion . It is therefore a double edged sword. On the one hand, it affords us more time to shift away from fossil fuel use in general, but on the other hand it has a greater impact on our atmosphere and environment.
It is well known that average global temperatures have generally been rising for over a century, in correlation with industrialisation, over and above any natural fluctuations . There is strong scientific consensus that human activities aren't simply correlated with these temperature measurements, but are indeed their underlying cause . In 2018 the world CO2 emissions were about 34 billion tonnes, equivalent to the mass of 34 cubic kilometres of water. Even though this is a huge number in everyday terms, the mass of the entire atmosphere is much greater at around 5,148,000 billion tonnes . The CO2 emissions from 2018 are therefore around 6.6 millionths of the mass of the entire atmosphere, so a small fraction of the whole. But CO2 is a minor component of the atmosphere, with a concentration in early 2019 of only about 411 parts-per-million , which equates to a total mass of about 3,211 billion tonnes , and the CO2 emissions from 2018 are around 1% of that value. That is the real measure of significance here, and it is not small. Humans affecting an Earth-scale value at the percentile level on a yearly basis is far from trivial.
The rate of CO2 absorption, in the oceans and the biosphere, does not match the rate of CO2 production from human activities, and so there is a continual increase in its atmospheric presence. The potency of CO2 as a greenhouse gas (GHG) is so great that even a minor change can have a huge impact, as is apparent in the above temperature data. To reduce the likelihood of severe climate change, the sooner we can move away from a fossil fuel based society, the better the chances of maintaining the kind of climate that we, and the biosphere as a whole, are presently used to.
The 1997 Kyoto climate conference saw many nations acknowledge and agree to address the climate crisis by reducing GHG emissions [37 - 39]. As the above data show, the 20 years that followed saw anything but meaningful global progress in this area. Importantly, China, the state with the second largest GHG emissions after the US at the time of the Kyoto conference, was not bound to that agreement due to being classed as a developing country , and its surge of fossil fuel use to power its development over the last few decades is clear. In absolute terms it overtook the US as the most significant CO2 source in 2005, a few years before the Kyoto protocol's first commitment period even began. Furthermore, the US ultimately refused to ratify the Kyoto protocol in order to protect the fossil fuel basis of its already developed economy . So regardless of being classed as developing or developed, immediate local economic concerns clearly won out over any longer term issues of global impact. Between 1997 and 2018, global CO2 emissions rose by around 50%.
Climate pledges were next significantly reviewed and renewed 18 years after the Kyoto event, at the 2015 Paris climate conference [40 - 42]. Crucially, both China and the US became ratified members of the agreement. However, with a subsequent change of presidential administration, the US made a swift move to renege its pledge. But ratified state or not, the agreement is non-punitive for failure to achieve its stated goals, and it remains to be seen if the necessary actions will be taken to curb GHG emissions in real-world, tonnes-in-the-sky terms. Talk is cheap, actions speak louder than words, and data are the messengers of the real story.
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