Global climate change is a defining challenge of the 21st century and efforts to address it have many dimensions. Reducing greenhouse gas (GHG) emissions through higher energy efficiency, using solar, wind and nuclear energy, deploying carbon capture and storage (CCS), reducing deforestation, reducing methane emissions and minimizing other causes of excessive radiative forcing are all important. No one option will suffice and it is crucial to integrate technology solutions with policy drivers.
Because the carbon dioxide (CO2) emitted by fossil fuel use is the largest source of anthropogenic GHG emissions, the climate challenge is often characterized as the need to "decarbonize" the economy by eliminating fossil fuels. However, carbon is literally the fuel of life; the natural carbon cycle annually circulates twenty times as much carbon as released from fossil fuels and the majority is biogenic carbon fixed through photosynthesis. Although rapid release of fossil carbon is the primary cause of rising atmospheric CO2 concentrations, the real problem is an imbalance in the carbon cycle rather than fossil fuel use per se. Thus, the real need is to bring the carbon cycle into balance and eventually restore a global net carbon sink.