We study the interactions between climate change and biogeochemical cycles, and focus on the processes that maintain and alter the composition of the atmosphere, and hence the climate. A question driving my research is how will atmospheric CO2 and climate co-evolve, and what we can do about it. We continue to analyze atmospheric, land and ocean observations pertinent to the carbon cycle, and to synthesize them in atmospheric transport models to infer how CO2 sources and sinks have been changing. We are also using the coupled carbon-climate model at NCAR to project how land and ocean carbon sinks will change with accelerating global warming and with human activities. A not surprising finding is that the droughts have diminished, and will continue to diminish, the land uptake of CO2.