China could greenhouse gas emissions peak a decade sooner than its Paris Agreement target is aiming for, according to a new peer-reviewed study released on Monday.

The world's highest emitting nation has pledged to peak its emissions by 2030 or sooner under the international climate accord, but research published in the journal Nature Sustainability suggests China could in fact reach its CO2 peak between 2021-2025, due to urban dwellers shifting to lower carbon lifestyles as they become wealthier.

Examining CO2 from 50 Chinese cities, researchers drew a close link between per capita emissions and per capita GDP, and found carbon emissions peak for most cities at a per capita GDP of around $21,000 (US).

And with the Chinese economy rapidly growing, the study projects many cities are likely to hit that level of per capita GDP between 2021-2025, at which point per capita emissions may also peak, thereby having have a major impact on the level of emissions from the country as a whole.

The climate impact of China's cities are of critical importance to its ability to decarbonise, as almost half of the population are expected to live in cities by 2025, with another 280 million moving from rural to urban areas over the next five years, according to Carbon Brief, which reported the findings.