Are there basic physical constraints on future anthropogenic emissions of carbon dioxide?

TL;DR

This paper demonstrates that human energy consumption growth is fundamentally constrained by thermodynamic principles, which can significantly narrow future CO2 emissions scenarios used in climate models.

Contribution

It introduces a simple thermodynamic framework showing that population and standard of living are unnecessary to model explicitly for emissions projections.

Findings

Human energy consumption growth is tied to historical economic production.

Energy efficiency and carbonization have historically varied slowly.

Thermodynamic constraints can reduce uncertainty in future emissions scenarios.

Abstract

Global Climate Models (GCMs) provide forecasts of future climate warming using a wide variety of highly sophisticated anthropogenic CO2 emissions models as input, each based on the evolution of four emissions "drivers": population p, standard of living g, energy productivity (or efficiency) f and energy carbonization c. The range of scenarios considered is extremely broad, however, and this is a primary source of forecast uncertainty. Here, it is shown both theoretically and observationally how the evolution of the human system can be considered from a surprisingly simple thermodynamic perspective in which it is unnecessary to explicitly model two of the emissions drivers: population and standard of living. Specifically, the human system grows through a self-perpetuating feedback loop in which the consumption rate of primary energy resources stays tied to the historical accumulation of global economic production - or p times g - through a time-independent factor of 9.7 +/- 0.3 milliwatts per inflation-adjusted 1990 US dollar. This important constraint, and the fact that f and c have historically varied rather slowly, points towards substantially narrowed visions of future emissions scenarios for implementation in GCMs.