Forests are major drivers of biophysical land-atmosphere feedbacks, the global carbon and water cycles, and thus overall planetary climate regulation. However, large uncertainties and substantial debate persist regarding ongoing and potential changes in the capacity of forests carbon sinks under anticipated future climate change. In this talk, I will first present the paradigm of ‘faster growth, faster mortality and shorter carbon turnover time’ in forests, thus challenging the traditional view of increased forest carbon storage in a future CO2 enriched atmosphere. Then I will show how the field-based tree mortality data can be used to reduce the uncertainty of model-projected forest carbon sinks in a future climate. Lastly I will demonstrate how the tree size vs density relationship can be linked with forest demography (growth and mortality) and carbon accumulation rates at ecosystem scales.