The interannual variability of atmospheric CO2 shows remarkable correlation with the ENSO, punctuated by volcanic eruptions, midlatitude drought episodes, and likely influenced by many other modes of climate variability such as PDO and NAM. In this talk, I will describe how a 'conspiracy' between climate anomalies and plant/soil physiology work together to produce such tight carbon-climate linkage, and how such variability can help to understand future climate-carbon feedbacks. I will also discuss the prospect for prediction of ecosystem and carbon cycle on seasonal-interannual timescales.