Carbon Pricing as a Tool of Deep Decarbonization

The latest news from the Intergovernmental Panel on Climate Change is not encouraging. A recent release of documents gives a preview of its forthcoming Sixth Assessment Report on the state of the global climate. Among the items released are a summary for policymakers based on the findings of a working group on the physical-science basis of climate change and a draft version of more detailed scientific analyses.

The findings include estimates of carbon budgets — the additional cumulative emissions that can be allowed until warming reaches specified temperature thresholds above the preindustrial global average. The estimate likely to get the most attention is that keeping emissions within 500 billion tons (500 Gt) of CO2, or the equivalent in other greenhouse gasses, would give a 50–50 chance of staying at or below the 1.5o C threshold relative to preindustrial temperatures (p. SPM-38, Table SPM-2). That 500 Gt is less than 15 years’ worth of emissions at current rates.

Although estimates such as those given by the IPCC are stated probabilistically, they serve as cautionary benchmarks. If worrisome outcomes are to be avoided, net emissions of CO2 and other greenhouse gasses would have to cease entirely before the critical carbon budget is exceeded. The goal of achieving net-zero emissions goes by the name of deep decarbonization.