energy limit

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According to the US Energy Administration , the annual growth rate of US energy consumption from 1650 to 2009 was 2.9%.

[Image description] The red line of energy consumption in the United States is 2.9% per year.

You might think that 2.9% is not a very high growth rate. To a certain extent, this is true. In the seventy years from 1949 to 2019, China’s electricity consumption increased by 1978 times, which is equivalent to an annual growth rate of 11.5%.

The 2.9% growth, then, seems modest.

But a physicist at the University of California thinks otherwise. He asks a question no one has asked: What will happen if humans continue to produce and consume energy at this rate?

Below, I present his calculation results . I don’t know if his calculations are correct, but I think his thinking is correct.

He later wrote a book called “Energy and Human Desires on a Finite Planet” (
Energy and Human Ambitions on a Finite Planet), a free download online. There is a detailed calculation process in the book, and interested friends can read it.


He first assumed that the world’s energy growth rate is 2.3% per year. This is easier to calculate, and this rate is exactly equal to a 10-fold increase every 100 years.

At this rate, one hundred years from now, in 2122, the world’s energy will be ten times what it is today; two hundred years later, in 2222, it will be 100 times what it is today.

Then, here comes the problem. How can human beings expand energy to 100 times today’s energy in two hundred years?

Fossil energy is impossible, solar energy is possible. According to Wikipedia , more solar energy reaches Earth in one hour than humans consume in the current year.

If we take full advantage of solar energy, it is indeed possible to expand energy to 100 times what it is today. But in that case, every inch of the earth’s land would have to be covered with solar panels.

Calculations show that if the growth rate of 2.3% is maintained for 400 years, all surfaces of the earth (including the ocean) must be covered with solar panels; for 1350 years, the energy required by mankind will be equal to the energy of the entire sun; for 2500 years, it is equal to the energy of the entire galaxy .

[Image description] A 2.3% energy growth rate will lead to the need for the energy of the entire galaxy in more than 2,000 years.

This is obviously not possible. But even ignoring the distant future, maintaining only a 2.3% energy growth rate in the next few decades, humanity will encounter a serious problem: heat dissipation.


Physics tells us that as long as energy does work, it must produce heat.

As humans consume more and more energy, more heat will inevitably be generated, and the problem of heat dissipation on the earth will become more and more serious.

The earth mainly radiates heat to the universe through infrared rays. However, the growth of greenhouse gases prevents infrared rays from leaving the atmosphere, so more and more heat remains on the surface of the earth, causing global warming.

The more heat humans generate, the more heat remains on the Earth’s surface, a problem that is compounded by greenhouse gases. Therefore, the degree of global warming is positively related to human energy consumption.

In 2020, the global average temperature is about 14.9°C. If the energy growth rate is maintained at 2.3%, after 350 years, the global average temperature will reach body temperature of 37°C, after 450 years, it will reach the boiling point of water at 100°C, after 750 years, it will reach the melting point of steel at 1500°C, and after 950 years, it will reach the temperature of the surface of the sun at 5500°C. °C.

[Image description] If the energy growth rate of 2.3% is maintained, the surface temperature will be the same as the surface of the sun within a thousand years.

This makes perfect sense: if humans produce the same amount of energy on Earth as the Sun, then the Earth’s surface must also have the temperature of the Sun’s surface, not to mention that the Earth is much smaller than the Sun.


The United Nations predicts that if the global average temperature rises by 4.5 degrees, half of the species are at risk of extinction. As temperatures continue to rise, humans may also become extinct.

Therefore, if the energy growth rate of 2.3% is maintained for another one or two hundred years, the heat dissipation problem of the earth will make human beings face a crisis of survival.

You can think of it this way, the current energy consumption of human beings has caused the summer temperature to rise to 40 degrees. If energy consumption becomes 10 times as high in 100 years, how much will the temperature rise at that time?

The obvious conclusion is that energy cannot sustain a growth rate of 2.3% for long. According to the current energy growth rate, there is very little time left for human beings. It is very likely that within a hundred years, human beings will have to stop the growth of energy in order to alleviate the heat dissipation problem of the earth.

Energy growth is strongly correlated with economic growth. Thus, within a hundred years, human economic growth may also stagnate.

Ideally, by that time, the world’s population has already started to shrink, so there will be no need for as much energy, and living standards won’t drop significantly.


The ideal is ideal, but the reality is that the world currently has an urgent need for energy, and there are signs of acceleration.

A Harvard study this year estimated how many more air conditioners the world needs.

They found that there are 2.8 billion people living in the hottest regions in the world, and as temperatures rise, these people need air conditioning. However, only about 8% of them currently have air conditioning in their homes, and the rest are looking forward to using it as soon as possible.

[Image description] Air conditioners are the most desired household appliances by Indians.

Harvard estimates that by 2050, 92 percent of the population will need air conditioning in Germany, 96 percent in the United States, and 99 percent in India and Indonesia.

The current penetration rate of air conditioners in the United States is 90%, so it is enough to install air conditioners for 6% of the people. However, the penetration rate of air conditioners in India and Indonesia is now 5% and 9% respectively, which means that more than 90% of people need to be equipped with air conditioners.

Both countries are populous, with 270 million in Indonesia and 1.4 billion in India, and air conditioning for all of them would require an astronomical amount of energy.

Therefore, in the coming decades, global energy will surely grow rapidly to meet the demand for air conditioning. The government has to increase the energy supply, because air conditioning is no longer a luxury, but a necessary equipment for survival, otherwise the high temperature will kill people.


This is the grim situation faced by mankind: the increase in energy leads to an increase in temperature; the increase in temperature requires more energy to cool down, thus forming a vicious circle.

As mentioned above, the energy growth period of human beings may only be left in the next hundred years. How human society can withstand global warming while achieving economic transformation and reducing energy consumption in such a short period of time is really an unoptimistic unknown road.


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  • Date of publication: July 27, 2022

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