A new study published in the journal Frontiers in Sustainable Cities presents the first global balance of greenhouse gases (GHG) emitted by the main cities of the world. The objective was to investigate and monitor the effectiveness of historical GHG reduction policies implemented by 167 cities distributed globally that are in different stages of development.
In 2015, 170 countries around the world adopted the Paris Agreement, aiming to limit the average rise in global temperature to 1.5 ° C. Following the agreement, many countries and cities proposed targets for greenhouse gas mitigation. However, the 2020 Emissions Gap Report from the United Nations Environment Program shows that, without drastic and strict actions to mitigate the climate crisis, we are still heading for a temperature increase of more than 3 ° C by the end of the year. of the XXI century.
Cities, large GHG emitters
While they only cover 2% of the Earth’s surface, cities are major contributors to the climate crisis. But current urban GHG mitigation targets are not enough to meet global climate change targets by the end of this century. ” Today, more than 50% of the world’s population resides in cities. These are responsible for more than 70% of GHG emissions and share a great responsibility in the decarbonization of the world economy. The current inventory methods used by cities vary globally, making it difficult to assess and compare the progress of emissions mitigation over time and space, “explains co-author Dr. Shaoqing Chen of Sun Yat-sen University, China.
Main results of the work
As we have already mentioned, the results revealed that only 25 cities accounted for 52% of urban GHG emissions. In addition, taking the emission data as a function of the number of inhabitants, it was observed that cities in Europe, Asia and the United States have significantly higher per capita emissions than those in developing areas.
The main emission sources that contribute to climate change in cities are transport and so-called ‘stationary energy’, including emissions from burning fuel and the use of electricity in residential and institutional buildings, commercial buildings and industrial buildings, and that it contributed to between 60 and 80% of the total emissions in the cities of North America and Europe. In a third of cities, more than 30% of total GHG emissions came from road transport. Meanwhile, less than 15% of total emissions came from railways, waterways, and aviation.
Actions to mitigate climate change
Of the forty-two cities that had traceable time series data, thirty decreased their annual GHG emissions during the study period. Although in several cities, on the contrary, an increase in emissions was detected.
Of the total of the cities analyzed, 113 established some type of emission reduction objective, while only 40 have carbon neutrality as their goal.
The most polluting
The results showed that both developed and developing countries have cities with high total GHG emissions, but that megacities in Asia (such as Shanghai in China and Tokyo in Japan) were especially important emitters. The per capita emissions inventory showed that cities in Europe, the US, and Australia had significantly higher emissions than most cities in developing countries. China, classified here as a developing country, also had several cities where per capita emissions matched those of developed countries. It is important to note that many developed countries outsource high-carbon production chains to China, increasing emissions related to the latter’s exports.
The top four cities with the highest per capita reduction were Oslo, Houston, Seattle, and Bogotá. By contrast, Rio de Janeiro, Curitiba, Johannesburg, and Venice saw the largest increase in emissions per capita.
Referencia: Wei et al. 2021. Keeping Track of Greenhouse Gas Emission Reduction Progress and Targets in 167 Cities Worldwide Front. Sustain. Cities, 12 July 2021 | https://doi.org/10.3389/frsc.2021.696381
