... if the decline continues and further intensifies it can have a significant impact.
The 18 peak-and-decline countries also played a part in the stalling of global emissions between 2014 and 2016 while the global economy continued to grow, a combination that showed, briefly and for the first time, what accelerated decarbonisation would look like. While China did not have 10 years of continuous declining emissions (and hence it was not part of the group of 18 countries), it was the biggest contributor during this stalling.
There is no guarantee that the declining trends will continue over the coming decades. In fact, our global 2018 carbon budget report showed that some of the more recent country trends are fragile and require further policy and actions to strengthen the decreases and support long-term robust decarbonisation trends. [Source]