claim: Continued greenhouse gas emissions at or above current rates would cause further warming and induce many changes in the global climate system during the 21st century that would very likely be larger than those observed during the 20th century.
evidence: Climate model projections summarized in the report indicated that during the 21st century the global surface temperature is likely to rise a further 0.3 to 1.7 °C ( 0.5 to 3.1 °F ) in a moderate scenario, or as much as 2.6 to 4.8 °C ( 4.7 to 8.6 °F ) in an extreme scenario, depending on the rate of future greenhouse gas emissions and on climate feedback effects.