Quantifying uncertainty in future carbon cycle feedbacks

点击翻译按钮获取中文摘要

Predicting future climate change is subject to layers of uncertainty in our understanding of how the climate system will respond to continued human emissions of greenhouse gases.  An important component of the puzzle is how natural cycles in the earth system regulate levels of atmospheric greenhouse gases.  In particular, the global carbon cycle currently absorbs about half of human carbon dioxide emissions in natural carbon sinks, but there is substantial uncertainty in estimates of how these carbon sinks will persist over the next century. This uncertainty is particularly large with respect to land carbon sinks, and propagates directly to uncertainty in projected future climate changes and climate impacts.In order to predict how much climate warming will occur over the next century, it is essential that we understand how carbon that is currently absorbed and stored in vegetation and soils will respond to future changes in temperature and precipitation.  Will land carbon sinks persist in the face of continued climate warming?  How well do global models simulate current land carbon uptake?  How might the availability of growth-limiting nutrients (e.g. nitrogen and phosphorus) change in the future and affect carbon uptake?  How will continued changes in human land-use affect the flows of carbon between the atmosphere and the biosphere?  Can we understand how structural differences between models affect future projections, and which model processes are critical to include in simulations of future climate change?  Can we use available data-sets to constrain probabilistically the range of future predictions that are consistent with current observations?  In this research, I plan to address each of these questions using an approach which combines global earth system modelling with recent observational and experimental information about global climate and ecosystem processes.  Through analysis and quantification of carbon cycle uncertainties, I hope to both improve our understanding of how carbon flows through the natural climate system, and sharpen predictions of how the climate system will respond to continued human greenhouse gas emissions.