Shrinking window of climate mitigation
Journal paper, in review
Climate change poses a significant threat to global economic development, prosperity and wellbeing. Action on climate change can take the form of reducing emissions (particularly from energy and industrial processes) and sequestering carbon on land. These two options can be considered as axes defining a space of potential mitigation, where action on one axis can be traded off against the other to achieve an equivalent outcome.
On the bio-mitigation axis, there are biophysical limits to the amount of carbon that can be sequestered. On the industrial emissions axis, mitigation involves a reallocation of economic resources and activities as a result of imposing a price on carbon or through equivalent policies, thereby reducing GWP (Gross World Product). However, in the absence of emissions reductions, climate change will reduce economic production and also reduce GWP. The reduction in GWP caused by the impacts of climate change can be used to define a 'no regrets' level of climate mitigation, where the cost of mitigation policy is no greater than the cost of climate impacts.
Using the Global Integrated Assessment Model (GIAM), we explore these trade-offs between reductions in industrial emissions and biosequestration, and evaluate the potential to achieve the four IPCC Representative Concentration Pathways (RCPs). Our analysis shows that is possible to move from the RCP8.5 scenario, which we treat as the reference case, to the three mitigation scenarios (RCP6.0, RCP4.5 and RCP2.6) through a mix of bio-mitigation and reductions in industrial emissions at a range of carbon prices. These ranges, which shrink as we go from RCP6.0 to RCP2.6, define the space in which welfare outcomes can be explored.
However, achieving the most stringent emissions target (RCP2.6) through reduction of industrial emissions alone requires an apparently implausibly high carbon price, given the technologies represented in the current GIAM model. The inclusion of new technologies such as bio-energy with carbon capture and storage, which allows negative emissions, can increase the range of effective carbon prices to some degree but if biofuel production is limited to levels that are sustainable in the long term, these increases are not substantial.
David Newth, Yiyong Cai, John J. Finnigan, Ian N. Harman, and Nicky Grigg, Steve Hatfield-Dodds