Paradoxical effects of altruism on efforts to mitigate climate change

Abstract

It is common wisdom that altruism is a crucial element in addressing climate change and other public good issues. If individuals care about the welfare of others (including future generations) they can be expected to unilaterally adapt their behaviour to preserve the common good thus enhancing the wellbeing of all. We introduce a network game model featuring both altruism and a public good (e.g. climate) whose degradation affects all players. As expected, in an idealistic fully connected society where all players care about each other, increasing altruism results in a better protection of the public good. However, in more realistic networks where people are not all related to each other, we highlight an intrinsic trade-off between the effects of altruism on reducing inequality and the preservation of a global public good: the consumption redistribution generated by a higher altruism is partly achieved by lowering income transfers towards protection of the public good. Therefore, it increases overall consumption and is thereby detrimental to the public good. These results suggest that altruism, although good from a welfarist point of view, is not in itself sufficient to simultaneously solve public good and inequality issues.

Figure 1

Average per capita $C{O}_2$ emissions produced in each country over the 2000–2015 period (source: world bank data) and “income inequalities”, measured using the well-known GINI coefficient of each country, averaged over the period 2000–2015 (source: World Wealth and Income Database). The figure displays a negative correlation $(-0.39)$ for 153 countries over the period.

Figure 2

Phase diagram for a complete network of 100 players, among which a single rich one. In blue the set of Nash equilibria—for all players, to consume their initial income is optimal having considered the decisions of other players. All other initial conditions lead to a Nash equilibrium on the boundary, following the arrows (equidistributed consumption in green, no overconsumption in red).

Figure 3

Impact of the altruism coefficient on the size of the set of Nash equilibria. Incrementing $\alpha$ shrinks the Nash equilibria region not only in terms of area; it also limits both the maximum overconsumption and the Gini coefficient.

Figure 4

Overconsumption and Gini coefficient as a function of the altruism coefficient, for 5-regular trees of heights 1 (green), 2 (blue), 3 (black), 4 (red), and higher (cyan).

Figure 5

Critical values for the altruism coefficient with respect to tree height: the best altruism coefficient allowing for a simultaneous reduction of overconsumption and inequalities in the Nash equilibrium. Pushing $\alpha$ past this value increases overconsumption while still decreasing inequalities.