Today’s Solutions: December 17, 2025

When the Paris Agreement was signed four years ago, a major focus was on the role that cities would play in cutting emissions. After all, urbanization means more people are living in cities than in rural areas, and that trend will only continue in the coming years. And while progress has been a bit uneven around the world (with some cities only seeing rising emissions), there have been 30 major cities around the world, representing some 58 million urban citizens, that have seen a major decline in emissions.

According to a new analysis published by a coalition of cities known as C40, 30 cities of the global north have hit their “peak” emissions before 2015, meaning they have since reduced their greenhouse gas emissions by at least 10 percent. These cities make up a third of C40’s members, which are spread out across all continents (excluding Antartica).  A few smaller member cities in China and in lower-income countries have also hit peaks, though a thorough analysis of those won’t come out for a few years.

On average, the 30 cities identified by C40 have curbed emissions by 22 percent. Some of the most significant reductions came from London, Berlin, and Madrid, which averaged around 30 percent reductions, while Copenhagen lowered emissions by a dramatic 61 percent (although the city hit peak emissions in 1991). Among the 30 cities, Tokyo stands out, not only for being the only non-Western city, but also for the fluctuations in its yearly emission levels.

As for the US, the cities of Austin, Boston, Chicago, Los Angeles, New Orleans, Philadelphia, Portland, San Francisco, and Washington DC made the list. That’s quite a lot of cities for a country that pulled out of the Paris Agreement.

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