How much does civilization weigh?

[GliderGuider]

The weight of our global civilization is the cumulative total weight of all the structural materials that we use to build our structures, machinery, implements and artifacts of all kinds.

This idea occurred to me as I was searching for a better proxy variable to represent the "PAT" side of the I=PAT equation. The criteria for acceptable proxy variables include:

• It must be a measurable material quantity;
• It must be produced and used throughout modern civilization;
• It must have been used in its current form for a significant period of time;
• It must not vary in composition or use over time;
• Its role in human environmental impact should be intuitively obvious;
• It should represent a significant proportion of human activity;
• It must scale up as a consequence of population and economic growth;
• It must have a close connection with energy use; and
• It should incorporate increasing energy efficiency over time, in such a way that a parallel energy and technology analysis is not required.

Based on these criteria, I believe that the weight of human artifacts (97% of which comes from cement and steel) is is a far more accurate way of estimating the impact we are having on the biosphere than either GDP or energy consumption.

The total weight of civilization is about 125 billion tonnes today, up from about 1 billion tonnes at the beginning of the last century. In other words, the weight of human construction and artifacts has increased by a factor of 125 over the last century, while world population has only increased by a factor of 4. This increase implies that human impact of the planet's biosphere has also increased by about 125 times over the last century.

I'm now contemplating how this finding changes my perspective on the "Overpopulation vs. Overconsumption" debate.