Limits to economic growth

Article author: 
Thomas W. Murphy Jr
Article publisher: 
Nature Physics
Article date: 
22 July 2022
Article category: 
Our American Future
Article Body: 

Across the world, decisions on investment and policy are made under the assumption of continuous economic expansion. Fundamental physical limits may soon put an end to this phase of development, as foreshadowed by the 1972 report The Limits to Growth.

Quantitative economic growth, in which inflation-adjusted wealth continues to rise, has been reasonably reliable for generations and is deeply woven into modern societal structure. The promise of a tomorrow that is "bigger" than today fuels investment, innovation and dreams. Growth is imagined to offer a solution to inequality between developed and developing nations: redistribution today is unnecessary if growth will eventually address the problem by growing the pie. Interest rates, bank loans, home mortgages and pension plans rest on the assumption of growth. The funding of social safety nets such as Social Security and Medicare in the United States is predicated upon both economic growth and growth of the labour pool...

Physical limits

A finite world of finite resources will not support indefinite growth in the extraction of those resources. In the case of non-renewable resources such as mined minerals and fossil fuels, whose stocks are finite, we obviously cannot continue extraction indefinitely: we simply run out of materials. But even for renewable resources such as solar power, the rate of replenishment is set by nature and cannot grow arbitrarily large, not to mention that building the technology to harvest such flows also requires consumption of non-renewable resources....

Because Earth has never hosted 8 billion humans with an unprecedented and continuously growing per-capita demand, we cannot base projections for future resources on the fact that they have not yet failed us....

In a continued progression, we would exceed the total solar power incident on Earth in just over 400 years, the entire output of the Sun in all directions 1,300 years from now, and that of all 100 billion stars in the Milky Way galaxy 1,100 years after that. This last jump is made impossible by the fact that even light cannot cross the galaxy in fewer than 100,000 years. Thus, physics puts a hard limit on how long our energy growth enterprise could possibly continue....

At present, the waste heat term is about four orders of magnitude smaller than the solar term. But at a growth factor of ten per century, they would reach parity in roughly 400 years. Indeed, the surface temperature of Earth would reach the boiling point of water (373 K) in just over 400 years under this relentless prescription....


An end to quantitative economic growth need not translate to an end to innovation or other forms of qualitative development and improvement. But growth as we have known it will no longer be able to drive the way civilization operates....

Thomas W. Murphy Jr. is a professor of physics at UC San Diego in La Jolla, California.


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