4. Stabilization of Atmospheric CO₂: Prospects and Implications

In the face of ever-increasing amounts of anthropogenic CO₂ emissions, there have been attempts to estimate the “safe” limits of atmospheric CO₂ concentrations in terms of the global mean temperature rise. The notion of “acceptable risk” is directly linked to the “acceptable” global temperature change that would ensure the survival of humankind for the foreseeable future. Large uncertainties in climate sensitivity, i.e., amount of warming expected at different atmospheric CO₂ concentrations, can be attributed to the great number and complexity of the factors that shape climate. Currently, based on the overwhelming body of evidence including modeling studies and paleoclimate data, the majority of climate experts agree on the 2 °C change (above the preindustrial level) as an acceptable global mean temperature change target, which would require the stabilization of atmospheric GHG at about 450 ppm CO₂-equivalent level. Different CO₂ stabilization scenarios and roadmaps, as well as the implications of these scenarios for energy supply, GHG emissions, industry, transportation, and energy security, are discussed in this chapter.