Inertia and the growth of civilization



For questions related to climate change or the long-term value of financial accounts, a link between economics and physics means that we can anticipate inertia in global consumption and economic growth. Our current consumption and wealth are inextricably tied to past production, where the past is unchangeable. Absent some sort of severe external shock (e.g. a meteorite), near-term reductions in energy consumption and wealth are implausible because they would somehow require civilization to “forget” its past.

Assuming that economic consumption and growth will persist in the near term may seem rather obvious to some. But what may be less well recognized is that there are mathematical and physical constraints to growth. For those who study the evolution of physical systems, a term that is often used here is “reddening”. This is a convenient way of expressing that large systems have accumulated a large amount inertia; or, the most slowly varying, low frequency and “red” (rather than blue) components of past variability in a system are the ones that most strongly influence its present behavior.

Predicting the weather next week can be almost impossible. But forecasting northern hemisphere average temperatures this coming winter is actually quite easy: history is an excellent guide. 20 years of growth through childhood and adolescence tends to have a greater influence on our daily food consumption than how much we ate yesterday. It is very difficult to predict a small company’s stock value next week; but extrapolating trends in globally-aggregated wealth can plausibly be done for as much as a decade hence. Surprises can happen, of course. Still, the natural tendency for growth is that it is predictably slow and steady.

The global economy’s current capacity to consume and grow has evolved from thousands of years of human development, through the creation of subsequent generations, as well as the construction of farms, towns, communication networks and machines. While everything does slowly decay or die, the past can never be entirely erased. Even our most distant ancestors have played a role in our current economic and social well-being. By now, civilization has enjoyed a rather lengthy past, and we can count on this accumulated inertia to carry us into the future.

Certainly, individual countries will continue to rise and fall, but globally aggregated economic wealth, defined as the accumulated inflation-adjusted GDP over all time and countries, should continue to enjoy recent inflation-adjusted rates of return for the next couple of decades. Even in 2009, during the depths of the Great Recession, 2.14% was added to total real generalized global wealth, only slightly down from the historical high of 2.26% in 2007. And we continue to grow our power production at similar rates. It is probably a safe bet to assume that similarly high rates of return will persist for some time. The mechanisms we put in place through centuries of innovation are unlikely to disappear in a hurry.

While we always need to be careful, persistence in trends is a highly effective tool for forecasting, particularly for highly “reddened” systems that are highly aggregated over time and space. It is always easier to make forecasts provided that we are willing to sacrifice temporal and spatial resolution.

The discouraging aspect to this is that global generalized wealth and energy consumption are linked through a fixed constant of 7.1 ± 0.1 milliwatts per inflation-adjusted 2005 dollar. If wealth grows at 2.2%/yr, i.e. with a doubling time of about 30 years, then we can expect our global energy demands to double over that time too. And given that inertia applies to our mix of energy needs as well, it is hard to see how our carbon dioxide emissions will not also do something close to a doubling over the same time period.

Naturally, the details dynamics of growth are more complicated than pure inertia, but the broad-brush aspects are probably not, at least not in a “near-term” of a couple of decades. Eventually carbon dioxide emissions and resource depletion will catch up with us, but my expectation is that globally aggregated economic growth will continue to persist for a few decades yet before the burden of our waste products and resource depletion becomes to great.