Lawrence Livermore National Laboratory (LLNL) plays a key role in detecting discernible human influence in various aspects of the climate and hydroclimate systems. To extend the Laboratory's detection and attribution (D&A) efforts to climate-driven impacts that are directly related to human systems, we sought to perform a feasibility study in which the LLNL D&A toolkit would be applied to detect a climate-change impact on the recent modifications in California’s specialty-crop productivity. Though circumstances precluded completion of the task as planned, we were able to pursue development of a cutting-edge research pathway focusing on the notion of flash droughts. This avenue may help LLNL develop new research capabilities related to the science and effects of drought, reflecting the Laboratory’s mission to support innovative science.
For the past 20 years, scientists have developed and applied D&A techniques to understand the contribution of human activity in the climate system. Scientists at LLNL pioneered and continue to contribute to the detection of discernible human influence on observed changes in surface temperature (Santer et al. 2006) and the thermal structure of the atmosphere (Santer et al. 2013). In addition, LLNL scientists have contributed to identifying human impacts on various aspects of the hydroclimate, such as global-scale rainfall (Marvel et al. 2013) and water vapor (Santer et al. 2009), as well as in snowpack depth and river runoff of the western U.S. (Barnett et al. 2008, Bonfils et al. 2008). An area where LLNL could extend its D&A efforts is to focus on climate-driven effects that are directly related to human systems. For instance, pervasive human-induced changes in temperature and precipitation can alter the water balance in California, affecting water availability. An increase in drought risk can change the timing of future runoff and affect reservoir storage and the amount of water available for irrigation and hydropower generation, unless innovative technologies are introduced. An expected increase in food demand from a rising population combined with the increasing vulnerability of agricultural systems under pressure from human-induced climate change could lead to food insecurity.
In our initial task (Task 1), we proposed to conduct a feasibility study in which LLNL D&A techniques would be applied to climate-change effects on recent modifications in California’s specialty-crop productivity. The main research goal was to investigate the relative effects on crop yields of the externally forced climate-change signal versus internal climate-variability noise, assuming that adaptation practices and technological advances remain unchanged. For this task, we needed to define and gather required observations and model data to initiate the D&A study, if feasible. This task relied on trends averaged over California or on the identification of a fingerprint (Bonfils et al. 2008, Moore et al. 2015), i.e., a geographical pattern in yield changes one would expect a priori from the climate trends, before examining the observed pattern. Because obstacles deterred the completion of Task 1, we followed another opportunity (Task 2) to explore the notion of flash droughts. Due to their sudden nature, flash droughts can trigger an emergency response by farmers and, ultimately, long-term vulnerability of food security. This task built stronger links between our current research on the nature and causes of the historical change in droughts and the climate-impact community. This research will likely lead to an article in a high-ranking journal.
If completed, Task 1 would apply directly to LLNL's climate security mission by improving our understanding of the effect of climate change on California’s economy and food security and by informing decisions for adaptation policies. Detecting a human signal in the noisy regional climate-crop systems is not guaranteed, a risk inherent in any D&A study. The introduction of innovative technologies can also obscure the detection of a climate signal in crop yields. The feasibility of this work, however, is reinforced by a recent study (Lobell et al. 2014) focusing on global yields of wheat and maize.
Task 2 is leading to very productive outcomes. In addition to creating new collaborations with renowned scientists, a summary publication of the Aspen Global Change Institute (AGCI) workshop will likely lead to an article in a highly ranked journal. The AGCI receives the support of the DOE's Biological and Environmental Research (BER) program, and it is conceivable that BER could support research ideas related to flash droughts in the near future. By contrasting specific sets of climate simulations, we could also investigate the model's ability to reproduce the onset and life cycle of existing historical flash floods in the western U.S. This new research pathway could lead to new LLNL research capabilities related to the science and impact of droughts.
This project enabled the exploration of new research avenues that would not have been possible otherwise. We developed a conceptual idea to detect climate-change effects on recent modifications in California’s specialty-crop productivity and developed a new partnership that includes climate scientists, economists, and farmers. LLNL became involved in cutting-edge science around the concept of flash droughts. These tasks have the potential to help LLNL deploy new research capabilities related to the science and impact of droughts, reflecting the Laboratory’s mission to support creative science.
Barnett, T. P., et al 2008. "Human-Induced Changes in the Hydrology of the Western United States." Science 319, 1080–1083. doi: 10.1126/science.1152538.
Bonfils, C., et al. 2008. "Detection and Attribution of Temperature Changes in the Mountainous Western United States." Journal of Climate 21, 6404–6424. doi: 10.1175/2008JCLI2397.1.
Lobell, D. B., et al. 2014. "Getting Caught with Our Plants Down: The Risks of a Global Crop Yield Slowdown from Climate Trends in the Next Two Decades." Environmental Research Letters 9. doi: 10.1088/1748-9326/9/7/074003.
Marvel, K., et al. 2013. "Identifying external influences on global precipitation." Proceedings of the National Academy of Sciences of the United States of America 110, 19301–19306, doi: 10.1073/pnas.1314382110.
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