GC053-0001
O3-related marginal damages to crop revenues driven by methane pulses

Thursday, 10 December 2020
Poster
Jon Sampedro, Pacific Northwest National Laboratory, Richland, WA, United States, Marcus C Sarofim, U.S. EPA - Climate Change Division, Washington, DC, United States, Stephanie Waldhoff, Pacific Northwest National Laboratory, College Park, MD, United States and Rita Van Dingenen, European Commission Joint Research Centre, Directorate for Energy, Transport and Climate, Ispra, Italy
Abstract:
Existing literature has demonstrated that ozone is the most hazardous pollutant for crop yields. While other environmental impacts, such as global mean temperature increase or CO2 fertilization effect may generate some positive effects to crops depending on the period and/or region, impacts of the exposure to high ozone levels are always negative. Several studies show that methane (CH4) and nitrogen oxide (NOx) are the most influential species for O3 formation. Moreover, due to the long equilibration time, O3 variations driven by changes in CH4 emissions are independent of the location of those emissions, so regional changes in CH4 emissions would have a direct impact to crops all over the world. In this context, the aim of this study is to estimate O3 -related marginal damages to crop revenues attributable to different shocks in CH4 emissions in USA. For that purpose, we combine a human-Earth system model (GCAM) with an air quality model (TM5-FASST) in order to obtain long-term projection of GHGs and air pollutant emissions, the resulting O3 concentration levels and the subsequent relative yield losses. Due to the atmospheric lifetime of CH4, to estimate O3 concentration levels, we adjust the air quality model to apply a transient approach (instead of the default steady-state), which follows the timeline of the CH4 emissions and more accurately captures the effects of the different shocks. Given the future uncertainty, we calculate the marginal damages for a range of scenarios based on different socioeconomic narratives (SSPs), pulse sizes and periods, and discount rates. We find that in the central scenario -which follows the SSP2 narrative, uses a discount rate of 3% and where the shock is a 10% increase of methane emissions in 2020- marginal damages account for 450$/ton, distributed as 98$/ton in USA and 352$/ton in the rest of the world. Regarding the uncertainty range, the higher discount rate (5%) would determine the lower bound of the total marginal damages (395$/ton) while setting the PulseYear to 2040 would set the upper bound of the damages (506$/ton). Focusing on USA, a high discount rate (5%) and setting the pulse to 2040 would also represent the lower and upper bounds of the uncertainty range of the marginal damages, which account for 76$/ton and 113$/ton, respectively.
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