Almost all nations in the world agreed to take measures to restrict the average increase in worldwide surface temperature to within 2°C, or preferably 1.5°C than preindustrial levels, in accordance with the Paris Agreement.
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But from the time the Agreement was signed, concerns about global warming propose that nations should aim for the 1.5°C 'preferable' warming limit.
For China, what are the consequences of making attempts to achieve this lower limit?
Professor Hongbo Duan from the University of Chinese Academy of Sciences and Professor Shouyang Wang from the Academy of Mathematics and Systems Science of the Chinese Academy of Sciences and their colleagues have tried to find a solution to this question.
The findings of the study were reported in an article titled “Assessing China’s efforts to pursue the 1.5°C warming limit,” published on April 22nd, in the journal Science.
Nine different integrated assessment models (IAMs) were used by the researchers to assess China’s measures to realize the warming limit of 1.5°C.
The different IAMs exhibit different emission trajectories for noncarbon and carbon emissions. Most of the IAMs will achieve negative or near-zero carbon emissions by about 2050, ranging from −0.13 billion tonnes of CO2 (GtCO2) to 2.34 GtCO2 across various models.
But a highly consistent result among all models is that the 1.5°C warming limit needs a steep decline in carbon emissions after 2020.
The team found that a sharp and early fall in carbon emissions minimizes the reliance on negative emission technologies (NETs)—technologies involving carbon capture and sequestration.
One significance of this result is that there occurs a trade-off between considerable early mitigation of carbon emissions and the dependence on NETs, which may have unpredictable performance.
Meanwhile, the model that displayed the lowest carbon emissions by 2050 exhibits the highest dependence on carbon capture and storage (CCS) technology—indicating that NETs play a crucial role in minimizing carbon emissions.
Carbon emissions formed a significant point of focus for the study, but the team also observed that minimizing noncarbon emissions is essential to maintain well below the warming limit.
Carbon emissions must particularly be decreased by 90%, N2O emissions by nearly 52%, and CH4 emissions by around 71% to achieve the goal of 1.5°C.
The researchers demonstrated that difficulties in mitigation vary across sectors, for example, residential and commercial, industry, electricity, transportation, and 'other.' Of these sectors, industry has a huge role in end-use energy consumption.
Thus, considerable variations in industrial energy use must take place to achieve deep decarbonization of the whole economy and achieving the specified climate goals. In fact, a more constant result across all models is that the major proportion of emission reduction will arise from a major decline in energy consumption.
The research also emphasizes the significance of substituting fossil fuels with renewables, an approach that has the next most crucial role in reducing emissions after energy consumption reduction.
The study proposes that China must bring down its fossil energy consumption (as quantified by standard coal equivalent, or Gtce) by nearly 74% in 2050 when compared to the no-policy scenario.
The team predicts that realizing the 1.5°C goal will incur a GDP loss in 2050 of about 2.3% to 10.9%, caused by reduced energy consumption and other factors.
The research also observed that China’s latest plan to turn carbon neutral by 2060 considerably agrees with the 1.5°C warming limit. But realizing the latter goal is very difficult.
Duan, H., et al. (2021) Assessing China’s efforts to pursue the 1.5°C warming limit. Science. doi.org/10.1126/science.aba8767.