Scenarios of Greenhouse Gas Emissions and Atmospheric Concentrations; and Review of Integrated Scenario Development and Application

In the reference scenarios, economic and energy growth, combined with continued fossil fuel use, lead to changes in the Earth’s radiation balance that are three to four times that already experienced since the beginning of the industrial age. By 2100, primary energy consumption increases from over three to nearly four times 2000 levels as economic growth outpaces improvements in the efficiency of energy use. Non-fossil energy use grows from over four to almost nine times over the century, but this growth is insufficient to supplant fossil fuels as the major source of energy. As a result, global CO2 emissions more than triple between 2000 and 2100, and emissions are rising at the end of the twenty-first century in all three reference scenarios. Combined with the effects of non-CO2 GHGs, the increase in anthropogenic radiative forcing from preindustrial levels is substantial. T EC H N IC A L SU M M A R Y