Biogeochemical Consequences of Climate Extremes: A Framework for Future Research.

Climate extremes, such as severe drought, heat waves and periods of heavy rainfall, can have profound consequences for ecological systems and for human welfare. Global climate change is expected to increase both the frequency and intensity of climate extremes and there is an urgent need to understand their consequences for biogeochemical cycling and feedbacks. Major challenges for advancing our understanding of the ecosystem consequences of climate extremes include setting a climatic baseline to facilitate the statistical determination of when climate conditions are extreme, having sufficient knowledge of systems so that extreme ecosystem responses can be identified, and finally, being able to attribute a climate extreme as the driver of an extreme response, defined as an extreme climatic event (ECE).  Although the occurrence of ECEs may be common in observational studies, studies in which climate extremes have been experimentally imposed often do not result in ecosystem responses outside the bounds of normal variability of a system. Thus, ECEs occur much less frequently than their potential drivers and even less frequently than observational studies suggest. Future research is needed to identify the types and timescales of climate extremes that result in ECEs and the potential for interactions among different types of climate changes and extremes. These research priorities require the development of alternative research approaches to impose realistic climate extremes on a broad range of ecosystems.