The hidden warming challenge in climate action
Science China Press
Over the past two decades, global warming has continued to accelerate. In response to the climate crisis, the 2015 Paris Agreement established a global consensus to limit global temperature rise to well below 2 °C by the end of the century. Compared to the initial Nationally Determined Contributions (NDCs), most parties have submitted updated second-round NDCs since 2020. Against this backdrop, a critical scientific question has emerged: will the accelerating trend of global warming be effectively curbed by current climate actions?
This study, based on a global emissions scenario consistent with China’s net-zero pathway and the 2 °C target, employed the widely used Community Earth System Model version 2 (CESM2) to conduct more policy-relevant climate change projections. The results indicate that even if all parties fully implement the decarbonization targets outlined in the second-round NDCs, the current acceleration of global warming may still not be effectively curbed over the next two decades. The primary reason is the significant decline in atmospheric aerosol burdens co-emitted with greenhouse gases. Aerosols exert a cooling effect by reflecting solar radiation. A reduction in their emissions weakens this “umbrella” effect, thereby allowing the warming effect of accumulated greenhouse gases—previously partially masked—to become increasingly apparent. The warming acceleration induced by aerosol reduction is particularly pronounced in the Arctic and Eurasia during the Northern Hemisphere winter.
Climate action is crucial for achieving long-term sustainable development: reducing greenhouse gases emissions not only mitigates global warming but also decreases the frequency and intensity of extreme climate events, thereby reducing associated economic losses. Simultaneously, aerosol reduction helps improve air quality and has positive impacts on public health. However, in the process of advancing the net-zero transition, it is essential to consider the additional climate effect owing to co-reduced aerosols and the resulting risks. The study recommends integrating this factor into comprehensive climate policy assessments to more fully capture the long-term benefits and overall climate effectiveness of emission reduction actions.
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