Greenhouse gas emissions in a dynamics-as-usual scenario of economic and energy development

This article describes two greenhouse gas (GHG) emission scenarios covering the period 1990-2100. The first of these, the B2 scenario, is a successful attempt to provide an internally consistent quantification-checked by the computer models Scenario Generator (SG), MESSAGE, MACRO, and MAGICC-of key variables describing a plausible but unremarkable "storyline" that compleme nts the other storylines discussed in this special issue of Technological F orecasting and Social Change. In the B2 scenario global carbon emissions from energy use and industrial s ources rise from 6.5 gigatons of carbon (GtC) in 1990 to 14.2 GtC in 2100. Primary energy use climbs from 350 exajoules (EJ) to 1360 EJ. The global pr imary energy structure shifts away from gas and oil (28% in 2100 compared t o 55% in 1990) and toward non-fossil energy sources (50% in 2100 compared i n 18% in 1990). The share of coal is 22% in 2100, only four percentage poin ts lower than in 1990. Among regions there are significant variations in th e primary energy structure. Synthetic liquid fuel production grows to 330 E J in 2100, driven largely by assumptions about the long-term decline of oil and a continuation in current trends towards increasingly flexible, conven ient, and cleaner forms of final energy. On the global level sulfur emissions decline from 63 megatons of sulfur (Mt S) in 1990 to 43 MtS in 2100. Radiative forcing grows by approximately 1% p er year from 1990 through 2100. The ''best guess" temperature change (assum ed climate sensitivity = 2.5 degrees C) associated with this increase in ra diative forcing is 2 degrees C in 2100. The B2S550 scenario is a variation of the B2 scenario constrained to stabil ize the atmospheric carbon concentration below 550 parts per million by vol ume (ppmv). Carbon emissions in the B2S550 scenario peak in 2040 at 10.7 Gt C, before dropping to 5.5 GtC by 2100. Roughly 40% of the 8.7 GtC differenc e in 2100 between the B2 scenario and the B2S550 scenario is due to fuel sw itching, primarily away from coal. 32% is from carbon scrubbing, 14% is due to price-induced energy demand reductions, and 12% is from hydrogen inject ion into the natural gas system. The B2S550 scenario's radiative forcing in 2100 is 8% lower than that of the B2 scenario, and its best guess temperat ure change is 0.2 degrees C lower. (C) 2000 Elsevier Science Inc.