What do the CAT, UNFCCC Synthesis Report and the UNEP 2015 Emissions Gap report say about the prospects of limiting warming to below 2°C and 1.5°C from INDC levels for 2025 and 2030?

Summary

• The Climate Action Tracker (CAT), the UNFCCC Synthesis Report and the UNEP 2015 Emissions Gap Report (to which the CAT had an input) estimate global emission levels by 2025 and 2030 from Intended Nationally Determined Contributions (INDCs) submitted as of 1 October 2015, and compare these to levels required to hold warming below 2°C in the long term, and, in the case of UNEP and CAT, to below 1.5°C by 2100. The UNFCCC report does not assess the gap to achieve a 1.5°C warming limit.
• The three analyses essentially come to very similar and comparable results for 2025 and 2030 global emissions projections based on INDCs submitted as of 1 October 2015, the emissions gap between these levels and what is needed for emissions pathways likely to hold warming below 2°C.
• Within uncertainties the CAT and UNEP 2015 EGR estimate similar levels of warming using very different methodologies. The UNEP 2015 Emissions Gap Report estimates the INDCs would put the world on track to a temperature rise of around 3°C by 2100. As previously reported the CAT estimated that the INDCs submitted as of 1 October 2015 (if fully implemented) will result in 21st century likely below 3°C with a central estimate of 2.7°C and a 90% chance of warming above 2°C.
• Both CAT and the UNEP 2015 EGR estimate the gap between INDCs and emission levels for 1.5°C, finding the gaps in 2025 and 2030 somewhat larger than for 2°C. The principal divergence between 1.5°C and 2°C emission pathways emerges in the 2030-2050 period, during which time the scaling up of deep-reduction technologies and options must take place at a much larger scale and more rapidly to achieve 1.5°C.
• For 2025, all three studies agree that the gap between INDCs submitted as 1 October 2015 and the likely below 2°C emission paths is substantial. The UNFCCC synthesis report shows that the INDC levels for 2025 are significantly above the least-cost emission pathways for likely below 2°C. The most optimistic estimates of INDC emission levels in 2025 are not far above maximum levels that might still lead to below 2°C, or below 1.5°C by 2100, pathways.
• All three reports indicate that an increase in ambition for 2025 would be needed to close emissions gap safely for likely below 2°C pathways and to keep open the option of limiting warming below 1.5°C by 2100.
• The CAT concludes that 2025 INDC levels are just above the current “edge of feasibility” estimates for limiting warming below 2°C, or below 1.5°C by 2100.
• The CAT tries to address the question of whether it is possible to catch up if global emissions by 2025 are not further reduced from the presently estimated INDC levels, finding that this may be possible, but will require significantly faster rates of emission reduction and significantly higher cost than would otherwise be necessary.
• By 2030, all studies agree the gap grows very rapidly, and becomes very large, prompting all three studies to bring into question the feasibility of holding warming below 2°C with a likely probability from the presently estimated 2030 INDC levels. The UNFCCC observes that “much greater emission reductions effort than those associated with the INDCs will be required in the period after 2025 and 2030 to hold the temperature rise below 2 °C above pre-industrial levels“.
  - The CAT concluded that there is major risk that if current INDCs are locked in for 2030 and not reviewed and strengthened every five years, starting in 2020, achievement of the likely below 2°C limit is fundamentally threatened, and the 1.5°C limit may be locked out
  - The UNFCCC conclusion that “…the possibility of keeping the temperature increase below 2°C still remains” from current INDC 2030 emission levels applies only to limiting warming below 2°C with a probability of around 50%.
• The CAT finds that the UNEP EGR and UNFCCC Synthesis Report results lead to a conclusion that to hold warming below 2°C with a likely or greater probability, and to keep open limiting to below 1.5°C by 2100, INDCs for 2030 must be substantially stronger than those currently on the table.
• The UNFCCC Synthesis Report and CAT recognise the importance of five-year cycles for improving INDCs, and all three studies emphasise the INDCs’ need to be seen as a platform for increasing ambition, including for 2025 and 2030.

Full briefing available here.