It falls below the long-term 1998 UN High projection of 18 billion. All scenarios describe futures that are generally more affluent than today . The scenarios span a wide range of future levels of economic activity, with gross world product rising to 10 times today s values by 2100 in the lowest to 26-fold in the highest scenarios. A narrowing of income differences among world regions is assumed in many of the SRES scenarios. Two of the scenario families, A1 and B1, explicitly explore alternative pathways that gradually close existing income gaps in relative terms.
Technology is at least as important a driving force as demographic change and economic development.
These driving forces are related. The SRES scenarios cover a wider range of energy structures than the IS92 scenarios. This reflects uncertainties about future fossil resources and technological change. The scenarios cover virtually all the possible directions of change, from high shares of fossil fuels, oil and gas or coal, to high shares of non-fossils. In most scenarios, global forest area continues to decrease for some decades, primarily because of increasing population and income growth.