There is growing concern that trajectories of greenhouse gas emissions and feedbacks will generate a “four degree world”, far above the previously recognized dangerous threshold.¹  Activism by citizens, non-governmental organizations and even some scientists is increasing; however, global subsidies for fossil fuels still far exceed those for renewable energy, while many policies stress adaptation, even at the expense of mitigation.

Climate change, interacting with other aspects of limits to growth, may already be contributing to the apparent plateauing of average global living standards. Persistently high energy prices have slowed economic growth and elevated unemployment, especially in Europe.²  There is flattening growth in grain yields in many countries;³  compounded by the difficulty of expanding agriculture to new fertile land, due to its scarcity and the need to conserve other ecosystem services. In 2008, food prices reached a record, largely due to the high price of oil and fertilizer. But a second food price spike since then has been influenced by the extreme climatic events, including the 2010 Russo-Ukrainian heatwave and the US drought of 2011-12. It is plausible that these events are related to anthropogenic climate change.⁴

A four degree world entails major risks for the human enterprise, through interacting systemic factors, including regional food insecurity, large-scale migration and conflict.⁵  Adverse social responses, causally related to the proximity or passing of these thresholds threaten to magnify the harm wrought by ecological and environmental tipping points.

Successful adaptation to these risks could be a mirage. Rather than test human ingenuity and global co-operation beyond breaking point, we instead need to prioritise mitigation, and to develop economies that are based on integrative sustainability science and reduced inequality, rather than wishful thinking.