Impact of timing differences in achieving emissions targets on global heatwaves

Achieving carbon neutrality is a great challenge, and the pathways to this goal are critical. However, it is still uncertain how the climate system will respond to different pathways for achieving carbon neutrality, including the timing of achieving the goal, whether quickly or slowly. Here, we analyze the mean and extreme climate responses under fast (SSP5-8.5) and slow (SSP1-2.6) achievement of the Paris Agreement target (2.0C), based on a linear relationship between cumulative CO₂ emissions and global mean surface temperature. Results from CMIP6 multi-model simulations show a difference of about 20 years between the two scenarios, with insignificant differences in global mean surface warming between the fast scenario (SSP5-8.5) and the slow scenario (SSP1-2.6). However, there are significant regional differences, particularly in land temperature. Furthermore, these differences in achieving timing have also affected the degree of exposure to heat waves, with clear regional differences in heat wave exposure. We will discuss the physical mechanisms involved, as well as the differences in regional climate responses to extremes and averages.