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Detection and Attribution of Climate-Driven Extremes in Net Biome Productivity from 1850 through 2100

Presentation Date
Tuesday, December 8, 2020 at 4:00am



Terrestrial ecosystems take up about one-third of total anthropogenic carbon emissions, providing a check on rising atmospheric CO2 concentration. While increases in CO2 fertilization and water use efficiency increase vegetation productivity under rising atmospheric CO2 levels, rising surface temperature often leads to a reduction in available soil moisture and an increase in plant respiration. This results in varying spatial and temporal responses of net biome production (NBP) and the strength of the land carbon sink. The latest generation of Earth system models and observations have shown that the increase in vegetation productivity could reach a tipping point beyond which the respiration losses could be higher than photosynthetic capacity, as the surface temperatures get higher than the optimum growing temperature of plants. However, the impacts of future climate on extremes in NBP is unknown. We investigated NBP extremes in the Community Earth System Model (CESM2) from 1850 through 2100 and attributed the NBP extremes to individual and compound effects of climate drivers. Preliminary results showed a net increase in the frequency of negative extremes in NBP, with anomalous reductions in soil moisture as the most dominant climate driver. We found increased variability in vegetation growth due to rising CO2 emissions through the study of extremes in NBP. A larger increase in the frequency and intensity of negative extremes in NBP than positive extremes in NBP indicates persistent extremes-driven reductions in vegetation growth in the future, and this imbalance could lead to a net reduction in terrestrial carbon uptake capacity and carbon storage when ecosystem respiration exceeds photosynthesis. The consequences of declining NBP and increasing negative extremes in NBP may result in global reduction in plant productivity and crop yield, even as the demand for vegetation is increasing due to rising demand for food, fiber, fuel, and building material.

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