Detection and Attribution of Climate-Driven Changes in Terrestrial Soils

Globally, soils store two to three times as much carbon as currently resides in the atmosphere, and it is critical to understand and predict how soils will respond to ongoing climate change. Our ability to detect and confidently attribute changes in soil carbon fluxes such as soil respiration is uncertain, however: such fluxes cannot be observed by satellites, and can only be measured at small spatial scales subject to significant spatial, temporal, and measurement uncertainty. We examine the probability of observing climate-driven changes in heterotrophic soil respiration (R_H), and show that the probably of detecting an R_H change at a random spot on the Earth's surface is very low, given current data record lengths. Is it more important to extend the existing R_H data record in time or in space? We situate these analyses within the context of ongoing changes in the global carbon cycle, discussing the implications for ecosystems' carbon balance as well as the benchmarking of Earth System Models.