J. Geophys. Res. Biogeosci. http://doi.org/nrb (2013)

Terrestrial ecosystems constitute a significant CO2 sink, removing about 25% of anthropogenic CO2 emitted to the atmosphere. This land sink is responsive to climatic conditions, creating the potential for feedback loops that could reinforce or counteract anthropogenic climate change. An understanding of how the land sink responds to climate variability and change is therefore crucial in estimating the degree of climate change that can be expected in the future.

Ana Bastos from the Universidade de Lisboa, Portugal, and co-workers investigated the influence of the El Niño/Southern Oscillation (ENSO) on net primary productivity (NPP) — a measure of carbon uptake by plants — using satellite data and historical records of the strength of the land carbon sink.

They find that ENSO explains more than 40% of global NPP variability, mainly owing to the response of southern hemisphere ecosystems — particularly in tropical and subtropical regions. Water availability, controlled by temperature and precipitation anomalies, seems to be the main mechanism through which ENSO drives the regional changes in NPP