Explanation of different emission scenarios used
The projections of the IPCC are based on a set of plausible scenarios for global emissions of greenhouse gases through the 21st century (Emission Scenario Explanations). These were identified in the Special Report on Emissions Scenarios (SRES) and are therefore called the "SRES" scenarios. It should be noted that these are "business as usual" scenarios without any implicit strategies for the mitigation of greenhouse gases.
The decision-support tool provides projections of sea-level rise based on three SRES scenarios: high (A1FI), medium (A1B) and low (B1) ones. Present global emissions are following a path in the vicinity of the A1FI and A1B emission scenarios (Global Carbon Project).
In addition, a multiplying factor (1.5 ) may be selected to account for the fact that the projections of the AR4 may be underestimates.