Wednesday, December 18, 2019

Economic growth: the engine of collapse

Economists and environmental scientists are working to develop strategies that forestall our worst visions of the future,  so we can maintain a healthy environment alongside a robust growing economy that meets development goals. The hope is that, 
with astute academic guidance and sufficiently powerful doses of political will, we can safely navigate our way through the Anthropocene. 

But there are physical limits to what is possible. The human world is as much part of the natural universe as anything else. If we readily accept that the complex motions of the earth’s climate march to physical laws, it's hard to see how society should somehow be divorced from the rest of the universe. 

To be sure, many of us see treating people as physical systems seems a bit abhorrent, somehow an abnegation of the essence of what it means to be human. The music of J.S. Bach surely is proof that we are not mere automatons! We're different. And if we truly want to triumph against profound societal challenges, then surely we can.

But - sigh - even music appears to obey simple mathematical laws seen throughout nature. Perhaps if we really want to address our 21st century existential crises we should start trying to think more broadly about what it means to be human. 

To get a sense of any physical limits, it helps to look at how physical systems function. A useful concept here is a thermodynamic “heat engine” where available energy powers cyclical motions thereby enabling work’’ to be done to move something else while giving off waste heat. This process is as familiar as burning gasoline in a car to power its pistons and propel it forward.

What is less recognized is how this basic idea from physics can be extended to living systems. Organisms take high potential chemical energy (food and oxygen) and release it in an unavailable chemical state (mostly heat radiation, water and carbon dioxide). The interesting part is that organisms employ a selfish self-propagating twist. Unlike a car, if conditions are right, living things can use the energy and matter in food to grow, allowing themselves the opportunity to consume more energy in the future.

So, for example, people use the energy in fats, proteins, and carbohydrates, along with the matter in oxygen, water, vitamins and minerals, to sustain their daily motions and metabolic processes. Whenever we manage to consume more than our daily metabolic needs, we get bigger, and usually our appetite grows too, meeting our newly larger metabolic demands. 

Groups of organisms take this self-reinforcing cycle to the next level. A lioness expends energy to hunt gazelles so that she can feed herself and her pride. With enough extra food, her fertility allows her to reproduce and support cubs, so increasing the  predatory population.

The global economy is just a natural extension of these thermodynamic concepts, what has been termed by some a “superorganism”. Collectively, we bootstrap ourselves to greater heights by extracting energy and material resources from our environment in order to sustain interactions among the accumulated fruits of our prior labours. Growth happens only when there is a remainder of raw resources available to make more people and new  stuff. 

Suppose for a moment that we were offered the opportunity to look down at our growing civilization from afar. We might see, for example, the back-and-forth of people and their vehicles as they move over the land, sea, and air. Looking even closer, we could measure the activities of human brains and notice that, as part of a larger whole, these brains use some combination of past experiences and new information to make estimates of economic and societal market value, acquired through Google searches, social gatherings, travel, and trade. 

All these activities that form our judgments require a continual consumption of food and fuel. Going a step further, we could hypothesize that there is some connection between total market value and energy. Indeed, quantitative analysis reveals that in any given year, the historical accumulation of past global economic production has had a fixed ratio to the current rate of global energy consumption, give or take a couple of percent. In each year between 1970 and 2016, each additional one thousand U.S. dollars of net worth that we collectively added to civilization through the global inflation-adjusted GDP has required an additional 5.6 Watts of continuous power production capacity.

This existence of a mathematical “constant” tying society to physics offers a critical piece of the human puzzle: economic wealth is inseparable from energy consumption; any diminished capacity to recover the energy necessary to maintain the steady hive of civilization must lead to economic collapse. If for whatever reason we fail to adequately fuel ourselves, we can expect the cyclic motions of our machines and ourselves to slowly grind to a halt. Our interest in crypto-currency or the auction price of a self-destructing Banksy will be replaced by more primal values like having a tool for opening a can of Spam. In the logical extreme, with an absence of food, we will wither and die, with all our perceptions of economic worth buried along with us. 

Of course, macro-economists would call linking wealth to energy through a constant absurd, even those that acknowledge the key role of energy in economic production. They would likely point out that the global GDP has been rising faster than energy consumption, and offer the utopian dream of “decoupling”  the economy from its basic environmental needs. 

Dream on. How much is your home worth in an uninhabitable city where there the fuel supply and electrical power are shut off for the foreseeable future? GDP represents the accumulated production of worth over an arbitrary period of just one year; meanwhile, energy is required to sustain the activities of a healthy civilization that has been steadfastly built up over all of history. Current energy consumption is far more tied to maintaining the fruits of centuries of collective effort than to the national vagaries of a single prior year. We cannot erase the past; it is always with us, and it must be fed. 

So if we want growth over and above repairing decay of everything we have previously built, requires us to extract and transform wood, copper, iron, and crops sufficiently fast. Rust never sleeps. Only when energy is sufficiently plentiful that the material balance between extraction and decay can be tipped in our favour is it possible for civilization to gain weight. 

Admittedly, we're pretty good at this! Recently, total net worth and energy consumption, the size of civilization, has been expanding by up to 2.3% each year and the GDP slightly faster. Ever since the end of the last ice age with the innovation of agriculture, we have collectively grown by leaps and bounds, from global populations of millions to billions, and from comparative poverty to extraordinary total wealth. It took 10,000 years to learn how to achieve 200 Quadrillion Btu’s of annual energy consumption in 1970s; we doubled that rate just 30 years later.

Feats of innovation have enabled us to accomplish not just exponential growth – e.g. growth at a fixed rate of 1% per year -- but the incredible mathematical feat of super-exponential growth: a growth rate that has increased with time. Humanity has been uncovering and exploiting ever newer and richer fuel resources – from wood, to coal, to oil – and ever more exotic raw materials – from wood, to copper, to niobium – and each has done its part to amplify the pace of expansion into the terrestrial buffet.

Unfortunately, we have become so consumptive that our future success is competing with the ongoing resource demands of a growing unchangeable past. The larger we get, the more energy and raw materials we require simply to sustain ourselves, forcing us to deplete the finite resource larder faster than ever before.

In the two decades following World War II, a remarkable period of rapid gas and oil discovery created an epoch of super-exponential growth. More recently, new extraction technologies and discoveries of fossil fuel reserves have only barely kept up with previously created demand. GDP growth is stagnating and individuals, professions, and nations are increasingly competing for their share.

Inevitably, there will come a point where collectively we can no longer access sufficient resources to sustain the current period of expansion. The question is not whether civilization is ultimately in trouble, but instead whether we will gradually subside or crash like a wave on the beach.

The negative impacts of past growth are already clear with accelerating climate change and environmental degradation. They will become particularly pronounced when resource depletion makes it challenging to self-repair, as flooded cities and drought-stricken farmland is abandoned. In biological and physical systems, when growth stagnates, fragility sets in. Following even small crises, recovery times slow, and there arrives a tendency for larger-scale collapse.

Of course, predicting the future is hard. But there are always going to be basic physical limits to what can and cannot happen. We can say with confidence that if civilization maintains current rates of economic growth over the next 30 years, within just one generation sustenance will mean doubling the current rate of energy consumption, extracting as much total energy from the environment as it has since the beginnings of the industrial revolution.

Can we really do this? Perhaps. Maybe we will continue to find the energy and raw materials on our finite planet to accomplish this extraordinary feat, but with the trade-off that sustaining “economic health” now means more potentially catastrophic consequences of global climate change later. Absent an extraordinarily rapid metabolic shift away from carbon based fuels, persistence of growth implies that we will face a likely 4 °C to 9 °C temperature rise within the lifetimes of those born today.

To all but Nobel Prize winning climate economists, such warming seems impossible to survive. Smaller civilizations have succumbed to much less. Looking to history may provide lessons for what actions are required to avoid the worst of what is to come.


  1. It seems embarrassing to have to say humans are subject to physics. Thanks for not throwing up your hands and giving up.

  2. Nothing like a dose of Reality to set the mood for this Christmas Day. Thanks, Tim....

  3. Great scientists who can communicate with the rest of the world are rare and valuable. Your writing is getting better and better.

    1. Writing is torture. Others are so fluent. But thanks.

  4. Dr. Garrett, your work is fascinating and more than a little disturbing, because I can't find a flaw in your logic. As I'm absorbing these ideas, I'm dying to know what you make of two results from the IEA report recently released:

    1. Even with the global economy expanding almost 3%, global emissions held steady in 2019.

    2. By 2050, energy-related carbon emissions will be only 4% lower than 2019 levels largely because energy demand will "outweigh improvements in efficiency". - This seems like an acknowledgement of the Jevons paradox.

    Thank you for all your hard work.