Working group report How should the uncertainties in the results of scaling be investigated and decreased?

Abstract

This chapter presents a report on the uncertainties in the results of scaling being investigated and decreased and discusses specific examples of a gas that is long-lived in the atmosphere—such as CO 2 —and one that is reactive and short-lived—such as NO—as chemical end points. For a well-mixed and long-lived trace gas, uncertainties in trace gas fluxes to ecosystems are greatest at the regional scale. This is true of the main greenhouse gases: CO 2 , methane (CH 4 ), and nitrous oxide (N 2 O). From the bottom-up approach, uncertainty would be anticipated to be highest at the global scale. This is not always the case because for some trace gases, the global-scale ecosystem flux is tightly constrained by the global trace gas budget. For a relatively short-lifetime trace gas, a different picture emerges. Such trace gases have markedly heterogeneous spatial distributions, and it is not possible to constrain global budgets with enough accuracy to reduce the uncertainty in trace gas budgets. Uncertainty in trace gas fluxes, therefore, continues to grow with increasing spatial scale, from the point scale to the global scale.