Projections of when temperature change will exceed 2 °C above pre-industrial levels

Manoj Joshi,

Ed Hawkins,

Rowan Sutton,

Jason Lowe and

David Frame

Abstract

Climate change projections are usually presented as 'snapshots' of change at a particular time in the future. Instead, we consider the key question 'when will specific temperature thresholds be exceeded?' Framing the question as 'when might something happen (either permanently or temporarily)?' rather than 'what might happen?' demonstrates that lowering future emissions will delay the crossing of temperature thresholds and buy valuable time for planning adaptation. For example, in higher greenhouse-gas emission scenarios, a global average 2 °C warming threshold is likely to be crossed by 2060, whereas in a lower emissions scenario, the crossing of this threshold is delayed by up to several decades. On regional scales, however, the 2 °C threshold will probably be exceeded over large parts of Eurasia, North Africa and Canada by 2040 if emissions continue to increase — well within the lifetime of many people living now.