In climate-based neo-Malthusianism (Fig. 4.4), climatic stress (ƒ1) is understood in terms of atmospheric concentrations of greenhouse gases, most notably CO2. Climatic resilience (ƒ2) is almost impossible to measure, but it is usually understood as the ability of the climate system to absorb stresses without exceeding an envelope of change deemed acceptable to human society, such as a maximum global warming
Fig. 4.5 Energy-based neo-Malthusianism
of 2 °C. To the extent that, at the global level, greenhouse gas emissions are an unavoidable collateral of economic growth (Peters et al. 2012), climatic stresses are destined to outpace climatic resilience. Despite considerable time lags in the climate system, climate-based neo-Malthusians warn that the erosion of climatic resilience is destined to operate as a constraint on tolerable levels of climatic stress. When unchecked, climate change is expected to lead to a variety of social and political disasters that may eventually force a concomitant reduction of climatic stress (Dyer 2010; Welzer 2011).
Energy-based neo-Malthusians (Fig. 4.5) emphasize, first, that energy consumption (ƒ1) is a fundamental precondition for economic growth. Second, they point out that energy consumption is constrained by the availability of energy reserves (ƒ2). They further claim that energy reserves are unavoidably depleted due to their finite nature. Therefore, energy consumption has an inherent tendency to outpace the ability to extract declining energy reserves, with the latter ultimately constraining the former. Insofar as economic growth and human subsistence are tightly linked with energy consumption, energy scarcity will ultimately reverse the growth trajectory and lead to the demise of industrial civilization. This in turn will lead to all sorts of social and political calamities while at the same time constraining future energy consumption (Hubbert 1993; Heinberg 2003; Kunstler 2005).
Critique of Simple Neo-Malthusianism
Simple neo-Malthusian theories are problematic precisely because they are so simple. For example, it is only a half-truth that economic growth and CO2 emissions, as well as economic growth and energy consumption, are inextricably linked, as technological innovation can weaken that link by reducing the carbon and energy intensity of GDP. Similarly, it is only a half-truth that energy production is inextricably linked to CO2 emissions and resource depletion: this appears to be true in the case of nonrenewable but not renewable sources of energy. Expanding the share of renewable energy such as solar and wind can weaken the link between economic growth, resource depletion, and climate change.
-  As indicated by the dashed arrow, however, climate change itself may tragically reinforce climatic stress due to feedback mechanisms (Lenton et al. 2008)