As an environmental issue, climate change is characterized both by irreversibilities and time lags. Greenhouse gases (GHGs) currently entering the atmosphere will remain there for centuries. The global warming experienced today thus traces back in part to emissions released decades ago. Moreover, those GHG emissions may themselves be the result of infrastructure and investment decisions made even longer ago. It is for this reason that decarbonizing the global economy is likened to piloting a supertanker. For a supertanker to avoid an obstacle in its path, turning procedures must be initiated far in advance.