Intergovernmental Panel on Climate Change
Uploaded by: Knoema
Accessed On: 02 March, 2016
Six alternative IPCC scenarios (IS92a to f) were published in the 1992 Supplementary Report to the IPCC Assessment. These scenarios embodied a wide array of assumptions affecting how future greenhouse gas emissions might evolve in the absence of climate policies beyond those already adopted. The different worlds that the scenarios imply, in terms of economic, social and environmental conditions, vary widely and the resulting range of possible greenhouse gas futures spans almost an order of magnitude. The assumptions for the IS92 scenarios came mostly from the published forecasts of major international organisations or from published expert analyses. Most of these were subject to extensive review. The premises for the IS92a and IS92b scenarios most closely resemble and update those underpinning the original SA90 scenario used in the First Assessment Report of the IPCC in 1990. IS92a has been widely adopted as a standard scenario for use in impact assessments, although the original IPCC recommendation was that all six IS92 emissions scenarios be used to represent the range of uncertainty in emissions. Population rises to 11.3 billion by 2100 and economic growth averages 2.3 % per annum between 1990 and 2100, with a mix of conventional and renewable energy sources being used. The highest greenhouse gas emissions result from the IS92e scenario that combines, among other assumptions, moderate population growth, high economic growth, high fossil fuel availability and eventual phase out of nuclear power. At the other extreme, IS92c has a CO2 emissions path that eventually falls below its 1990 starting level. It assumes that population first grows, then declines by the middle of next century, that economic growth is low, and that there are severe constraints on fossil fuel supply.