Climate-Relation Control of Tropical Carbon Balance

Abstract:

The humid tropics contain vast stores of carbon and dominate terrestrial-atmspheric carbon exchange. They are difficult to observe, whether in situ or from the atmosphere for logistical, climatic and ecological reasons, leading to persistent uncertainty about their quantitative role in the current carbon cycle, and how they might change in the future. In addition, as recent work has shown, the tropics have fast turnover times and short response times. As a result, they are the most likely focus of rapid change to terrestrial carbon-climate feedbacks. I will review what is known, and what remains controversial, about carbon fluxes in the tropics, and particularly in the Amazon. Current tropical carbon budgets suggest both high emissions, from land use, and high uptake from a combination of regrowth and carbon dioxide fertilization. Recent analyses also suggest significant trends in both these terms. We will propose a hypothesis to explain the current budget and a strategy for reducing uncertainty combining the OCO-2 satellite XCO2 observations in conjunction with other space-based measurememts.