Human Population, Power, and CO2 Dynamics: The Positive Feedback Loop of Unsustainability

Population growth is the most basic component of the physical production of a human society, driven by energetic throughput that feeds back to further growth. The expansion of our population and energy systems has significantly altered the climate system that enables human activities. The objective of this study is to show that the changes in the human population and atmospheric CO2, over the last 220 years, can be understood through a sigmoid S-shaped dynamic model fueled by global power and its growth rate. This study analyzed the time series of population size and atmospheric concentration from 1800 to 2020 using a sigmoid model influenced by the power dynamics. Population growth was driven by two forces: the long-term increase in power use and the faster interdecadal changes in power growth rates, while the increase in atmospheric CO2 concentration growth rate is driven by the long-term increase in global power. Our expansionary population dynamic is starting to reach its limits. Population size, atmospheric CO2 concentration, and power (energy/time) were engaged in a positive feedback loop that explained the dynamics of our population system, making our present human societies increasingly vulnerable to collapse.