Countries, worldwide, have agreed that international efforts should be aimed at keeping the global mean temperature increase below 2 °C, compared to pre-industrial levels. In order to achieve the 2 °C climate target with a likely probability (>67%), cumulative global CO2 emissions over in the 2010–2100 period need to be constrained to about 1000 GtCO2. An assessment of current policies shows that these lead to emissions that are much higher than those of the least-cost mitigation scenarios consistent with a likely chance of achieving the 2 °C target.
Model analysis suggests that it is possible to achieve the 2 °C climate target with a likely chance, global emissions need to peak in the 2020–2030 period, and 2030 emission levels need to be near the current level, followed by rapid reductions thereafter. This requires an average annual global decarbonisation rate of 4% to 6% for the period from 2020 to 2050. Further delay in reducing emissions beyond 2020, i.e. continuing current and planned policies until 2030, will make it increasingly more difficult to achieve the 2 °C target; global emission reduction rates will need to be much higher, mitigation costs are also expected to be higher, the risk of overshooting the 2 °C target n becomes greater and so will the dependence on technologies that often meet with public resistance.
Overall, the results show that achieving the 2 °C target critically depends on well organised international policies, in the short term, to realise stringent reductions during the 2020–2030 period.