text: There are also several uncertainties and limitations. Firstly, there is no unified understanding of how to cal- 
  culate the temperature rise of 1.5 °C and 2.0 °C relative to pre-industrial levels in the worldwide. At present the 
  research on climate prediction and impact assessment under global warming 1.5 °C and 2.0 °C usually adopts 
  multi-mode ensemble average methods61,62, which could obtain the warming response under the condition of 
  instantaneous change, rather than the warming process under the stable state expected by the long-term goal. If 
  we expect to obtain the accurate results, the model prediction test should be estimated to form proprietary sce- 
  narios for global warming by 1.5 °C and 2.0 °C63,64, which could support for the impacts assessment on different 
  sectors. Some institutions are carrying out climate change predictions under the lower emission scenarios (global 
  warming 1.5 °C or 2.0 °C). At the same time, in order to achieve the goal of controlling temperature by 1.5 °C at 
  the end of the twenty-first century, it is urgent to take actions to reduce emissions and develop along the track 
  of low energy consumption65,66; but it is a great challenge for human society to achieve this goal. 