Antarctic ... In some projections, Arctic late-summer sea ice disappears almost entirely by the latter part of the 21st century." Scenario-specific projections are based on analysis of multiple runs by multiple climate models, using the various SRES Scenarios. "Low scenario" refers to B1, the most optimistic scenario family. "High scenario" refers to A1FI, the most pessimistic scenario family. Temperature and sea level rise in the various scenarios There are six families of SRES scenarios, and AR4 provides projected temperature and sea level rises (excluding future rapid dynamical changes in ice flow) for each scenario family. Scenario B1 Best estimate temperature rise of 1.8 °C with a likely range of 1.1 to 2.9 °C (3.2 °F with a likely range of 2.0 to 5.2 °F) Sea level rise likely range [18 to 38 cm] (7 to 15 inches) Scenario A1T Best estimate temperature rise of 2.4 °C with a likely range of 1.4 to 3.8 °C (4.3 °F with a likely range of 2.5 to 6.8 °F) Sea level rise likely range [20 to 45 cm] (8 to 18 inches) Scenario B2 Best estimate temperature rise of 2.4 °C with a likely range of 1.4 to 3.8 °C (4.3 °F with a likely range of 2.5 to 6.8 °F) Sea level rise likely range [20 to 43 cm] (8 to 17 inches) Scenario A1B Best estimate temperature rise of 2.8 °C with a likely range of 1.7 to 4.4 °C (5.0 °F with a likely range of 3.1 to 7.9 °F) Sea level rise likely range [21 to 48 cm] (8 to 19 inches) Scenario A2 Best estimate temperature rise of 3.4 °C with a likely range of 2.0 to 5.4 °C (6.1 °F with a likely range of 3.6 to 9.7 °F) Sea level rise likely range [23 to 51 cm] (9 to 20 inches) Scenario A1FI Best estimate temperature rise of 4.0 °C with a likely range of 2.4 to 6.4 °C (7.2 °F with a likely range of 4.3 to 11.5 °F) Sea level rise likely range [26 to 59 cm] (10 to 23 inches) Selected quotes from the Working Group I Summary for Policymakers "Both past and future anthropogenic carbon dioxide emissions will continue to contribute to warming and sea level rise for more than a millennium, due to the timescales required for removal of this gas from the atmosphere." Reaction to Working Group I In the