Global Warming Breakeven Times for Infrastructure Construction Emissions Are Underestimated

To achieve reductions in global warming, technology switching, such as converting to renewables or to lower carbon emitting fuels, must overcome the impact of infrastructure construction emissions. Current approaches for assessing construction emission impacts distribute emissions over the life of the infrastructure for the new technology or calculate a greenhouse gas payback time using a single global warming potential (e.g., GWP(20) or GWP(100)) for greenhouse gases other than carbon dioxide. More realistic approaches account for the temporal evolution of the radiative forcing of short-lived climate forcing species, such as methane, and the timing of the construction emissions. These more realistic approaches lead to longer breakeven times than current approaches. For a case study of switching from coal-fired electricity generation to liquefied natural gas-fired electricity generation in China, an approach accounting for the timing of construction emissions and the temporal evolution of radiative forcing leads to payback times that are 4 times longer than estimated using current practices. The differences in the payback times will depend on factors that include the composition and duration of the construction emissions, but this case study demonstrates that the temporal features of construction emissions should be addressed in assessing the short-term climate benefits of technology switching.

Automated summary

To reduce global warming, the impact of construction emissions from infrastructure must be addressed in technology switching. Current assessment methods are not realistic, and more realistic approaches should consider the temporal evolution of short-lived climate forcing species and the timing of construction emissions.