Chapter 2: What emission levels will comply with temperature limits?

Abstract

The world is moving towards a crucial new climate agreement in 2015, which could provide the longneeded global plan to slow down climate change and enable humanity to adapt to the unavoidable part of a changing climate. While recognizing that some climate change is unavoidable, global leaders at the 2010 Cancun Climate Conference agreed to limit global warming to 2 °C in this century, relative to the pre-industrial period. They also decided to review this limit to see if it should be further lowered to 1.5 °C. Given the aim to limit global temperature, the critical question has now become what level of global emissions would make this possible? The United Nations Environment Programme (UNEP) has tackled this question since 2010 by convening a large group of knowledgeable scientists to prepare the Emissions Gap reports. These reports have examined the gap in 2020 between emission levels consistent with the 2 °C limit, and levels expected if country pledges/commitments are met. In earlier reports the scientists conveyed the message that indeed a large gap exists, but also that there were many promising opportunities for bridging the gap.