Uncertainty of temperature rise under nationally determined contributions and carbon neutral policies

Nationally determined contributions raised by Paris Agreement aim to control the temperature rise below 2 °C or even 1.5 °C at the end of the 21st century, compared to pre-industrial levels. However, the climate response of the Nationally Determined Contributions (NDCs) remains uncertain due to unstable policies and their credibility. In this study, we calculated the uncertainty of global temperature rise caused by uncertain NDCs and carbon-neutral policies and discussed the difficulty of policy implementation. The results show that there will be 8 GtC uncertainty in emission at the end of the 21st century, responsible for the temperature rise of 0.37 °C (1.73–2.10 °C). A delayed policy in emission reduction by major emitters would result in a temperature rise of over 2 °C, while under non-delay policy, the 2 °C target will be possibly achieved. Besides, low-emission countries would introduce a 30 GtC cumulative emission uncertainty at the end of the 21st century if there are no restrictions, leading to a 0.3 °C global warming uncertainty. Developed countries need more substantial reductions in carbon intensity to achieve their climate policies while developing countries are under less pressure. The reduction of carbon intensity requires the strengthening of technical and economic methods. This study provides a reference for the realization of emission policies and temperature rise targets.