The period in which Limits to Growth first appeared came at the end of a decade that included Rachel Carson’s Silent Spring and Paul Ehrlich’s The Population Bomb. It was a period that saw the birth of the modern environmental movement, the passage of the Clean Air Act, the founding of the EPA, and large numbers of dystopian novels and films warning of an over-crowded, over-polluted, resource-poor future. In 1970, Ehrlich made the first of several appearances on The Tonight Show, then hosted by Johnny Carson,  where he talked about the need for programs of mass sterilization and birth permits to an audience with a reach that no modern show can match.

Both for people who lived through that period and those born after, the idea that we made it to 2021—and a world population of just under 8 billion—without falling into a global conflict over diminishing supplies of oil, or seeing the population drastically reduced from famine and disease, seems like a clear signal that all those old books were exaggerated. On further review, Ehrlich made a lot of bad assumptions in The Population Bomb—mostly because he was deeply enmeshed in a privileged white, Western culture that made him reject the idea that everyone would want anything other than to live like him. He also populated his work with a number of racial stereotypes, making academics and the public increasingly leery of his work. As for Silent Spring, well, we banned DDT, the eagle made a comeback, so … all good now.

The number of people on Earth has doubled since Limits to Growth was first published. There seem to be few signs of the kind of resource-shortage declines that the work predicted in a world where the amount of material each person consumes—from food, to electronics, to automobiles—is still trending up on a global basis. That makes it easy to believe that all of these old tomes, LTG included, can be safely ignored.

But earlier this year economist Gaya Herrington from international accounting and consultancy firm KPMG took a new look at the old book. With decades of new data and much more detailed information available than the original MIT team, Herrington found that the scenarios outlined in the 1972 work still “aligned closely with observed global data.” In particular, two possible futures matched up with what she collected in 2020.

One of those scenarios indicates a slowing, and eventual halt, of economic and technological growth over the next two decades. The second scenario is one in which pollution, chiefly in the form of greenhouse gases driving the climate crisis, brings population and economic growth to a halt over the same period.

In the first scenario, the end of growth is followed by a gradual decline in both average wealth, and in the size of the sustainable population. In the second, there is a devastating collapse. The likelihood of both of these scenarios seemed nearly even, and any better outcome failed to match Herrington’s data so well. “This suggests,” she writes, “that it’s almost, but not yet, too late for society to change course.”

This isn’t as bad as it could be. Previous analysis had suggested the world would continue on a “business as usual” course until right about … now. A steep and irreversible decline would then begin over the next decade. But resource scarcity (much of it related to metals and rare elements that have been heavily mined over the last century) seems less of a threat in Herrington’s evaluation. Instead, it’s greenhouse gases that act as the greatest threat, That leads Herrington toward a scenario that isn’t too far off from past predictions, just shifted about a decade down the line.

However, the paper is not all doom. There is another scenario called “stabilized world” or SW. That scenario involves rapid worldwide adoption of technologies like renewable energy, as well as shifting social priorities that encourage lower family sizes, paired with prioritizing individual health and education. That’s a pattern that’s been seen in country after country. Unfortunately, it’s not happening fast enough, and it’s not happening without pushback, especially in some authoritarian regimes. 

The best thing about that SW model isn’t just that it represents a world that’s become “stable.” It’s also a world that becomes stable at a high level, where every person has access to health care and education, and the relative wealth of every individual is high compared to today. That scenario could come by the middle of the next century.

But to get there means passing through the bottleneck of the next two decades.

Note: I shouldn’t end this without mentioning that many scientists, economists, and sociologists have found the models and principles endorsed by the Club of Rome in LTG to be short-sighted, simplistic, ethnically-biased, or all of the above. Many researchers have been dismissive of the model’s results from the beginning, and having to rejigger the inputs frequently (as has happened several times) hasn’t made the project seem any more capable of predicting the future. But it is an interesting exercise to check in on these predictions, and there are genuine limits on every system.